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Introduction: Hemotoxicity is common following rattlesnake envenomation. Published experiences with equine-derived crotalidae immune F(ab')2 antivenom have characterized hemotoxicity as delayed, recurrent, or persistent. This study investigated recovery of hypofibrinogenemia following rattlesnake envenomation treated with equine-derived crotalidae immune F(ab')2 antivenom. Methods: This is a retrospective analysis of human rattlesnake envenomations reported to the Arizona Poison and Drug Information Center over four years. We included rattlesnake-envenomated patients who developed hypofibrinogenemia (<1,500 mg/L) and were treated with equine-derived crotalidae immune F(ab')2 antivenom. The primary outcomes were recovery period (h) and recovery rate (mg/L/h) of hypofibrinogenemia following equine-derived crotalidae immune F(ab')2 antivenom administration. Collected data included demographics, laboratory values, and antivenom administered. Statistics used were percentages, medians, and Kruskall-Wallis test. Results: There were 527 rattlesnake envenomations treated with antivenom, of which 80 met the inclusion criteria. Patients receiving treatment with F(ab')2 antivenom and had a median fibrinogen concentration recovery rate of 62.3 mg/L/h (IQR: 42.0–74.3 mg/L/h) and median recovery period of 19.2 h (IQR: 13.8–26.2 h). There were statistically significant differences between categories for time to antivenom for the median recovery period (P = 0.0154). Discussion: Hypofibrinogenemia is a common laboratory finding following rattlesnake envenomation in Arizona. This study investigated rattlesnake envenomated patients treated with F(ab')2 antivenom and monitored fibrinogen concentrations as a surrogate marker of venom toxicity. Additionally, time to administration of F(ab')2 antivenom was a statistical significant marker of the recovery period from hypofibrinogenemia. Limitations of this study included the geographic coverage of the poison center and exclusion of patients with insufficient laboratory monitoring or those who received another antivenom. Conclusions: Following rattlesnake envenomation in Arizona, recovery from hypofibrinogenemia was able characterized in a rate (mg/L/h) and period (h) with the quantity and time to administration of antivenom. More studies are needed to assess this finding with other antivenoms and its clinical significance. [ABSTRACT FROM AUTHOR]

Background: The snake genera Atropoides, Cerrophidion, and Metlapilcoatlus form a clade of neotropical pit vipers distributed across Mexico and Central America. This study evaluated the myotoxic and neurotoxic effects of nine species of Atropoides, Cerrophidion, and Metlapilcoatlus, and the neutralising efficacy of the ICP antivenom from Costa Rica against these effects, in the chick biventer cervicis nerve-muscle preparation. Given the prominence of PLA2s within the venom proteomes of these species, we also aimed to determine the neutralising potency of the PLA2 inhibitor, varespladib. Results: All venoms showed myotoxic and potential neurotoxic effects, with differential intra-genera and inter-genera potency. This variation was also seen in the antivenom ability to neutralise the muscle damaging pathophysiological effects observed. Variation was also seen in the relative response to the PLA2 inhibitor varespladib. While the myotoxic effects of M. mexicanus and M. nummifer venoms were effectively neutralised by varespladib, indicating myotoxicity is PLA2 mediated, those of C. godmani and M. olmec venoms were not, revealing that the myotoxicity is driven by non-PLA2 toxin types. Conclusions: This study characterises the myotoxic and neurotoxic venom activity, as well as neutralisation of venom effects from the Atropoides, Cerrophidion, and Metlapilcoatlus clade of American crotalids. Our findings contribute significant clinical and evolutionary knowledge to a clade of poorly researched snakes. In addition, these results provide a platform for future research into the reciprocal interaction between ecological niche specialisation and venom evolution, as well as highlighting the need to test purified toxins to accurately evaluate the potential effects observed in these venoms. [ABSTRACT FROM AUTHOR]

Green pit viper bites induce mild toxicity with painful local swelling, blistering, cellulitis, necrosis, ecchymosis and consumptive coagulopathy. Several bite cases of green pit vipers have been reported in several south-east Asian countries including the north-eastern region of India. The present study describes isolation and characterization of a haemostatically active protein from Trimeresurus erythrurus venom responsible for coagulopathy. Using a two-step chromatographic method, a snake venom serine protease erythrofibrase was purified to homogeneity. SDS-PAGE of erythrofibrase showed a single band of ~30 kDa in both reducing and non-reducing conditions. The primary structure of erythrofibrase was determined by ESI LC-MS/MS, and the partial sequence obtained showed 77% sequence similarity with other snake venom thrombin-like enzymes (SVTLEs). The partial sequence obtained had the typical 12 conserved cysteine residues, as well as the active site residues (His57, Asp102 and Ser195). Functionally, erythrofibrase showed direct fibrinogenolytic activity by degrading the Aα chain of bovine fibrinogen at a slow rate, which might be responsible for causing hypofibrinogenemia and incoagulable blood for several days in envenomated patients. Moreover, the inability of Indian polyvalent antivenom (manufactured by Premium Serum Pvt. Ltd., Maharashtra, India) to neutralize the thrombin-like and plasmin-like activity of erythrofibrase can be correlated with the clinical inefficacy of antivenom therapy. This is the first study reporting an α-fibrinogenase enzyme erythrofibrase from T. erythrurus venom, which is crucial for the pathophysiological manifestations observed in envenomated victims. [ABSTRACT FROM AUTHOR]

Crotalidae immune F(ab')2 [equine] was approved for the treatment of North American rattlesnake envenomation in 2015 and Agkistrodon envenomation in 2021 after a phase 3 trial demonstrated lower rates of late hemotoxicity compared to crotalidae polyvalent immune fab-ovine (Fab) in a population of primarily rattlesnake envenomations. Currently, there are limited data on the use of this new antivenom in controlling tissue damage associated with Agkistrodon envenomations. We describe four cases of Agkistrodon contortrix envenomation in which edema continued to progress despite standard doses of F(ab')2, necessitating administration of additional antivenom. In three cases, control was achieved only after a switch to Fab. As F(ab')2 use in envenomations by the primarily cytotoxic Agkistrodons increases, further research is needed to evaluate its ability to control tissue damage. [ABSTRACT FROM AUTHOR]

Snakebite envenoming is a life threatening neglected tropical disease that represents a considerable public health concern in the tropics. Viperid snakes of the genus Bothrops are among those of greatest medical importance in Latin America, and they frequently cause severe systemic haemotoxicity and local tissue destructive effects in human victims. Although snakebite antivenoms can be effective therapeutics, their efficacy is undermined by venom toxin variation among snake species. In this study we investigated the extent of paraspecific venom cross-reactivity exhibited by three distinct anti-Bothrops antivenoms (Soro antibotrópico-crotálico, BothroFav and PoliVal-ICP) against seven different Bothrops pit viper venoms from across Latin America. We applied a range of in vitro assays to assess the immunological binding and recognition of venom toxins by the antivenoms and their inhibitory activities against specific venom functionalities. Our findings demonstrated that, despite some variations, the monovalent antivenom BothroFav and the polyvalent antivenoms Soro antibotrópico-crotálico and PoliVap-ICP exhibited extensive immunological recognition of the distinct toxins found in the different Bothrops venoms, with Soro antibotrópico-crotálico generally outperformed by the other two products. In vitro functional assays revealed outcomes largely consistent with the immunological binding data, with PoliVap-ICP and BothroFav exhibiting the greatest inhibitory potencies against procoagulant and fibrinogen-depleting venom activities, though Soro antibotrópico-crotálico exhibited potent inhibition of venom metalloproteinase activities. Overall, our findings demonstrate broad levels of antivenom paraspecificity, with in vitro immunological binding and functional inhibition often highly comparable between venoms used to manufacture the antivenoms and those from related species, even in the case of the monovalent antivenom BothroFav. Our findings suggest that the current clinical utility of these antivenoms could possibly be expanded to other parts of Latin America that currently suffer from a lack of specific snakebite therapies. [ABSTRACT FROM AUTHOR]

Objectives: North American pit viper, or crotalid bites, remain a low-incidence and potentially high-consequence medical event. Although the venom of these snakes is known to cause tissue, hematologic, and neurologic toxicity, the published literature on North American crotalid bites remains limited. The National Poison Data System, the data repository for the 55 poison control centers in the United States, offers a unique opportunity to examine nationwide trends involving venomous snake bites.Methods: National Poison Data System cases involving North American crotalids from 2006 to 2020 were analyzed. Data collected included age and type of snake, date, geographic location, pertinent clinical characteristics, treatments administered, and medical outcomes including incidence of "dry" bites and death.Results: A total of 55,914 cases were identified during the 15-year study period. Cases, especially those involving copperheads, increased during the study period. Most of the cases were reported in July. Cases were reported in all 50 states and Washington, DC, with Texas having the most cases (n = 9115). North Carolina had the largest increase in bites during the study period. Moderate or major medical outcomes were documented in 58% (n = 32,584) of cases, with 25% (n = 14,195) being admitted to a critical care unit. Puncture wound, edema, and pain were the most commonly documented symptoms. Antivenom was documented as being administered in 25% (n = 14,151) of cases. Dry bites were reported in <1.5% of cases. Thirty-two deaths were reported, 23 involving rattlesnakes.Conclusions: This study demonstrates that reported North American crotalid bites appear to be increasing over time and are associated with potentially significant morbidity. Mortality, however, remains low. [ABSTRACT FROM AUTHOR]

Calloselasma rhodostoma (Malayan pit viper) is a medically important snake species that is widely distributed across Southeast Asia. Systemic coagulopathy causing severe haemorrhage and local tissue injury is commonly observed following C. rhodostoma envenoming. However, nephrotoxicity and congestive heart failure were previously reported in a patient who had a long length of hospital stay. In this study, we determined the effect of C. rhodostoma envenoming on cardiovascular disturbances and the associated morphological changes in the liver, heart and kidneys using animal models. We also evaluated the efficacy of Hemato polyvalent antivenom (HPAV; Queen Saovabha Memorial Institute (QSMI) of the Thai Red Cross Society, Thailand) in neutralising the histopathological effects of C. rhodostoma venom. The intravenous (i.v.) administration of C. rhodostoma venom (1000 µg/kg) caused a rapid decrease in mean arterial pressure (MAP) followed by complete cardiac collapse in anaesthetized rats. Moreover, the intraperitoneal (i.p.) administration of C. rhodostoma venom (11.1 mg/kg; 3 × LD50) for 24 h caused cellular lesions in the liver and heart tissues. C. rhodostoma venom also induced nephrotoxicity, as indicated by the presence of tubular injury, interstitial vascular congestion and inflammatory infiltration in the whole area of the kidney. The administration of HPAV, at manufacturer-recommended doses, 15 min prior to or after the addition of C. rhodostoma venom reduced the extent of the morphological changes in the liver, heart and kidneys. This study found that experimental C. rhodostoma envenoming induced cardiovascular disturbances, hepatotoxicity and nephrotoxicity. We also highlighted the potential broad utility of HPAV to neutralise the histopathological effects of C. rhodostoma venom. The early delivery of antivenom appears capable of preventing envenoming outcomes. [ABSTRACT FROM AUTHOR]

We present the first published case of Tamaulipan Rock Rattlesnake (Crotalus morulus) envenoming. A 54-year-old male professional herpetologist was bitten on the left thumb by a captive C. morulus. Pain, swelling, bruising, and pressure in the thumb were experienced within minutes. On presentation, he reported 7/10 pain and had firm edema in his thumb and thenar eminence. Initial laboratory studies showed normal platelet count, PT, PTT, and creatine kinase. He was treated with pain medication and 10 vials of crotalidae immune F(ab') 2 (equine) antivenom approximately 3 h post envenoming. Lymphangitic streaking and axillary lymphadenopathy developed, followed by progression of edema, emergence of a hemorrhagic bulla, and declining platelets, prompting treatment with two additional 10-vial antivenom doses. His platelet count declined to 125 × 103/μL 24 hours post envenoming and he developed numbness in his thumb. Following antivenom therapy completion no further decline in platelets occurred and thrombocytopenia improved to 131 × 103/μL prior to discharge 46 hours post envenoming; fibrinogen, PT, PTT, and CK remained normal. He had no residual signs or symptoms 5 months later. C. morulus venom includes proteolytic venom enzymes that induce local soft tissue destruction, pain, and edema with ecchymosis and blister formation. Although C. morulus venom contains a unique disintegrin, morulustatin, no fibrinogenolytic activity was observed. [Display omitted] • Tamaulipan Rock Rattlesnake envenoming is previously unreported. • Crotalus morulus is an uncommon Mexican species maintained in a few USA zoos and private collections. • Rapid local tissue effects resulted after envenoming by a juvenile Crotalus morulus. • F (ab')2 antivenom was effective in halting progression of local and systemic effects. [ABSTRACT FROM AUTHOR]

Late hemotoxicity is common following rattlesnake envenomation treated with crotalidae immune polyvalent Fab (ovine) (FabAV). Initial clinical trials showed crotalidae immune F(ab')2 (equine) (Fab2AV) to be superior to FabAV in preventing late hemotoxicity, but this effect has not been demonstrated in broader populations. This study investigated late hemotoxicity in patients receiving Fab2AV or FabAV after rattlesnake envenomation. This is a retrospective analysis of prospectively collected data from patients with snakebite reported to the ToxIC North American Snakebite Registry (NASBR) between January 1, 2019, and December 31, 2020. Inclusion criteria were rattlesnake envenomation and administration of antivenom. Patients were excluded if they received more than one type of antivenom. The primary outcome was occurrence of late hemotoxicity (platelets ≤120 k/mm3 or fibrinogen ≤170 mg/dL) in patients receiving Fab2AV and FabAV. Data collected included demographics, envenomation characteristics, laboratory values, and treatment administered. Statistics including t-test and Fisher's exact test were used. A total of 201 rattlesnake envenomated patients receiving antivenom were reported to the NASBR in the study period; 144 were included. 49 received Fab2AV alone, 45 received FabAV alone and 50 received both antivenoms. Baseline patient and envenomation characteristics were similar between the groups. Late hemotoxicity occurred in 2/49 patients in the Fab2AV group (4% (95% CI 0.7–12.6)) and in 19/45 patients in the FabAV group (42% (95% CI 28.4–59.0); absolute risk reduction 39.1% (95% CI 21.2–46.2) (p = 0.001). On follow up, 0 patients (0%) receiving Fab2AV were retreated with antivenom; 4 patients (9%) receiving FabAV were retreated (p = 0.049). In the North American Snakebite Registry, late hemotoxicity was less common in rattlesnake envenomated patients treated with Fab2AV compared to FabAV. [ABSTRACT FROM AUTHOR]

This case report presents an exotic envenomation by a Chinese snake, Protobothrops mangshanensis. Its venom exhibited potent activity against plasma and fibrinogen, among other enzymatic activities. The patient initially presented with edema of the right upper limb, without tissue necrosis. There were no signs of bleeding; however, severe hypofibrinogenemia was observed (nadir value at 0.4 g/L), with a marked increase in fibrinogen degradation products and D-dimers, without any other coagulation disturbances. In the absence of a specific antivenom available against Asian Crotalinae venoms, the patient was treated at the 29th hour after bite with six vials of Antivipmyn™ TRI (Instituto Bioclon, Mexico, Mexico), a Mexican antivenom initially intended for American Crotalinae venoms, i.e., Bothrops asper , Lachesis muta and Crotalus durissus. Fibrinogen began to rise 6 hours after the antivenom infusion and was within the normal range 38 hours later. The report also underscores the utility of ClotPro® (Haemonetics ®USA), a viscoelastic test, for real-time monitoring of the snakebite-related coagulopathy. The clotting time was extended to 188 seconds on the EX-test while the MCF was decreased to 31 mm on the EX-test and the AP-test and was not measurable on the FIB-test, confirming severe hypofibrinogenemia. In order to confirm the paraspecificity of antivenom on the venom of P. mangshanensis , we studied the experimental neutralization of the venom procoagulant effect by Antivipmyn TRI and Green Pit Viper antivenom, which has been used in previous published clinical cases of P. mangshanensis envenomation. Both Antivipmyn™ TRI and Green Pit Viper antivenom corrected the procoagulant effect induced by P. mangshanensis venom. These findings suggest that Antivipmyn™ TRI cross-reacts with Protobothrops mangshanensis venom. In the absence of antivenom covering Asian Crotalinae, Antivipmyn TRI should be considered to treat an envenomation by Protobothrops spp. [Display omitted] • Envenoming by the Chinese species Protobothrops mangshanensis causes local edema and coagulopathy by direct fibrinogenolysis. • ClotPro® test enables real-time monitoring of snakebite-induced coagulopathy. • Mexican Antivipmyn TRI antivenom is effective in neutralizing this fibrinogenolysis. • Paraspecificity of Antivipmyn TRI antivenom: confirmed in experimental conditions with the neutralization assay. • In the absence of specific antivenom, Antivipmyn TRI should be considered to treat an envenomation by Protobothrops spp. [ABSTRACT FROM AUTHOR]

Green pit vipers, a name that can refer to several unrelated species, comprise a large group of venomous snakes found across the humid areas of tropical and sub-tropical Asia, and are responsible for most of the bite cases across this region. In India, green pit vipers belonging to several genera are prevalent in the northern and north-eastern hilly region, unrelated to species present in the peninsular region. In the present study, crude venom of representative species of green pit vipers present in the north and north-eastern hilly region of India (Trimeresurus erythrurus , T. septentrionalis, Viridovipera medoensis , and Popiea popieorum) were characterized to elucidate venom composition and venom variation. Profiling of crude venoms using SDS-PAGE and RP-HPLC methods revealed quantitative differences among the species. Further, in vitro biochemical assays reveal variable levels of phospholipase activity, coagulation activity, thrombin-like activity, fibrinogenolytic and haemolytic activity. This correlates with the pseudo-procoagulant effects on the haemostatic system of victims, which causes consumptive coagulopathy, frequently observed in patients bitten by green pit vipers. The immunoreactivity of Indian polyvalent antivenom and Thai green pit viper antivenom towards crude venoms were also evaluated by western blotting and inhibition of biochemical activities. The results exhibited poor efficacy of Indian polyvalent antivenom in neutralizing the venom toxins of crude venoms; however, Thai green pit viper antivenin (raised against the venom of Trimeresurus allbolabris , not present in India) showed higher immunoreactivity towards congeneric venoms tested. Analysis of green pit viper bite patients records from a community health centre in Assam, India, further revealed the inability of Indian polyvalent antivenom to reverse the extended coagulopathy featured. [Display omitted] • Green pit vipers from north-east and northern India showed considerable differences in venom profiles. • Variation in biochemical activities causing pathophysiological effects were observed. • Thai green pit viper monovalent antivenom showed better neutralization potency than Indian Polyvalent Antivenom. [ABSTRACT FROM AUTHOR]

Background: Venomous snakebites are a common clinical scenario in the Southeastern United States. CroFab® (Crotalidae Polyvalent Immune Fab (Ovine), BTG, Wales, UK) antivenom is indicated in cases involving pit vipers and is known to be expensive. The treatment protocol for snakebites is based on clinically subjective measures triggering the application, or escalation of, antivenom administration. The purpose of this study is to characterize the use of CroFab at our institution and to evaluate the impact of its use regarding cost and overall outcomes. We suspect that it is often used but potentially less often needed. We hypothesized that CroFab use was associated with increased length of stay (LOS) without an observed difference in patient outcomes.Materials and Methods: A retrospective chart review of snakebite patients at our level-1 trauma center from 2000 to 2016 was performed. Snakebite location, snake species, number of vials of CroFab administered, hospital LOS, intensive care unit (ICU) LOS, and complications were identified for each patient. Patients were divided into CroFab (C) and no CroFab (NC) groups.Results: One hundred ninety patients with venomous snakebites were included. 53.7% of patients received CroFab. There was no difference in the complication rate of C versus NC groups, (P = .1118). CroFab use was associated with longer hospital LOS (P < .0001) and ICU LOS (P < .0001).Discussion: CroFab use was associated with increased LOS in our patient population. There was no difference in observed outcomes between the C and NC groups. These findings imply that CroFab is potentially over-used in our patient population. [ABSTRACT FROM AUTHOR]

The venom of the Brazilian pit viper Bothrops jararaca (BjV) is a complex mixture of molecules, and snake venom metalloproteinases (SVMP) and serine proteinases (SVSP) are the most abundant protein families found therein. Toxins present in BjV trigger most of the deleterious disturbances in hemostasis observed in snakebites, i.e., thrombocytopenia, hypofibrinogenemia and bleedings. The treatment of patients bitten by snakes still poses challenges and the bioflavonoid rutin has already been shown to improve hemostasis in an experimental model of snakebite envenomation. However, rutin is poorly soluble in water; in this study, it was succinylated to generate its water-soluble form, rutin succinate (RS), which was analyzed comparatively regarding the chemical structure and characteristic features of rutin. Biological activities of rutin and RS were compared on hemostatic parameters, and against toxic activities of crude BjV in vitro. In vivo , C57BL/6 mice were injected i.p. with either BjV alone or pre-incubated with rutin, RS or 1,10-phenanthroline (o-phe, an SVMP inhibitor), and the survival rates and hemostatic parameters were analyzed 48 h after envenomation. RS showed the characteristic activities described for rutin – i.e., antioxidant and inhibitor of protein disulfide isomerase – but also prolonged the clotting time of fibrinogen and plasma in vitro. Differently from rutin, RS inhibited typical proteolytic activities of SVMP, as well as the coagulant activity of BjV. Importantly, both rutin and RS completely abrogated the lethal activity of BjV, in the same degree as o-phe. BjV induced hemorrhages, falls in RBC counts, thrombocytopenia and hypofibrinogenemia in mice. Rutin and RS also improved the recovery of platelet counts and fibrinogen levels, and the development of hemorrhages was totally blocked in mice injected with BjV incubated with RS. In conclusion, RS has anticoagulant properties and is a novel SVMP inhibitor. Rutin and RS showed different mechanisms of action on hemostasis. Only RS inhibited directly BjV biological activities, even though both flavonoids neutralized B. jararaca toxicity in vivo. Our results showed clearly that rutin and RS show a great potential to be used as therapeutic compounds for snakebite envenomation. [ABSTRACT FROM AUTHOR]

Background: Green pit vipers (GPVs), namely Trimeresurus albolabris and Trimeresurus stejnegeri accounts for most snakebites in Southern China. Green pit viper venom contains thrombin-like enzymes, resulting in defibrination syndrome. Using of clotting factor replacement after antivenom administration is controversial. The objective of this study was to investigate the effects of clotting factor replacement in coagulopathic patients with T. albolabris and T. stejnegeri bites after antivenom administration.Methods: We retrospectively reviewed 123 patients who were bitten by T. albolabris and T. stejnegeri and were admitted to the Emergency Department of a hospital in Guangzhou, Southern China, from 2013 to 2019. Recovery of prothrombin time (PT) and fibrinogen level were compared among (1) fresh-frozen plasma (FFP) group; (2) cryoprecipitate (cryo) group; (3) FFP and cryo group; and (4) control group after antivenom administration.Results: The incidence of coagulopathy was 31%. Persistent and late coagulopathy were the most common patterns among four groups. The median reduction in PT was 20.1 ± 31.2 s for FFP and cryo group. The median increase in fibrinogen level was very small: 0.05 ± 0.20 g/L for FFP group, 0.09 ± 0.37 g/L for cryo group and 0.07 ± 0.31 g/L for FFP and cryo group, respectively. The percentage of unimproved PT was markedly higher in the FFP and cryo group than the control group (P = 0.01 by log-rank test, P = 0.02 by Gehan-Breslow-Wilcoxon test). The percentage of unimproved fibrinogen level tended to be worse in the FFP and cryo group than the control group, but the different was marginal (P = 0.05 by Gehan-Breslow-Wilcoxon test, P = 0.07 by log-rank test). A total of 7.8% (7/90) of the patients in the clotting factor replacement groups developed anaphylaxis and heart failure.Conclusion: There is no improvement in coagulopathy profile in patients with T. albolabris and T. stejnegeri bites who received clotting factor replacement after antivenom administration. But the results from GPVs may not be generalized to other species of venomous snakes. [ABSTRACT FROM AUTHOR]

Introduction: Crotalidae immune F(ab')2 (Fab2AV) became available in the USA in 2019 for treatment of rattlesnake envenomation. In the clinical trial comparing Fab2AV to crotalidae immune polyvalent fab (FabAV), Fab2AV was associated with less late hemotoxicity. The purpose of this study was to describe outcomes following use of Fab2AV in patients with rattlesnake envenomation in Arizona. Methods: This is an observational study of patients admitted to a medical toxicology service at two hospitals in Arizona between January 1, 2019 and December 31, 2020. Patients with rattlesnake envenomation who received Fab2AV were included. Patients who received FabAV, alone or in combination with Fab2AV, were excluded. The main outcomes of interest were antivenom dose, adverse reactions, late hemotoxicity, and hospital readmission or retreatment. Results: Forty-six patients were included. The mean age was 40 years, with 15% under 12 years of age. All exhibited swelling, 20% thrombocytopenia, and 35% coagulopathy. Median time to treatment was 3 h and median total Fab2AV dose was 20 vials. Three patients had an acute reaction to Fab2AV which was non-life-threatening and resolved with antihistamines and/or steroids. In the follow-up period, one case of delayed thrombocytopenia (platelets = 108 K/mm3) and one case of recurrent thrombocytopenia (platelets = 111 K/mm3) were identified. There was no late coagulopathy. Five patients reported symptoms consistent with mild serum sickness. Conclusions: In this series of patients with rattlesnake envenomation in Arizona who were treated with Fab2AV, there were no cases of clinically significant late hemotoxicity, and no patients required late retreatment with antivenom. Acute and delayed reactions did occur in some patients but were mild and easily treated. [ABSTRACT FROM AUTHOR]

Treatment of pit viper envenomated puppies (≤6 months old) with antivenom was well tolerated, similar to adult dogs. However, therapeutic guidelines should be established to direct use and prove efficacy in this population. [ABSTRACT FROM AUTHOR]

Snakebite is an important problem in Myanmar. Regionally, bites by Eastern Russell's vipers, Daboia siamensis (Viperidae, Viperinae), and monocled cobras, Naja kaouthia are considered medically important, but those categorised as "green snake" bites are not. However, these may include bites by green pit vipers, Trimeresurus spp. (Viperidae, Crotalinae) for which no antivenom is available in Myanmar. Elsewhere in Southeast Asia, these snakes are reported to cause local and systemic envenoming. As part of the Myanmar Snakebite Project, prospective case data were collected over 3 years from five hospitals in the Mandalay region. These included 3803 snakebite cases reported from Mandalay region. Of these, 355 were listed as bites by a witnessed green-coloured snake. In 22 cases, the snakes responsible were retained and preserved, then expertly identified; 21 were medically important white-lipped pit vipers (Trimeresurus albolabris), and one as an Asian vine snake, Ahaetulla prasina (Colubridae, Ahaetuliinae) which is not of medical importance. Among confirmed Trimeresurus albolabris bites, 15/21 developed swelling of the bitten limb, and 3/21 coagulopathy, defined as a positive 20-min whole blood clotting test (20WBCT). None developed necrosis, blistering, thrombocytopenia or acute kidney injury (AKI). Of the remaining 333 patients bitten by green snakes that were not specifically identified, 241 (72%) developed swelling of the bitten limb, and 62 (19%) coagulopathy. AKI occurred in 21/333 patients, but only one required dialysis. At least 10/21 of the cases with AKI in this study were more likely to represent bites from Trimeresurus spp. than D. siamensis because the snake responsible was brought into the hospital, examined and described by the treating physician as "green-coloured". This study describes a previously unpublished case of AKI from envenoming by T. erythrurus in Yangon, and reviews cases of AKI following bites by this species and T. albolabris in Myanmar. This confirms that, at least on rare occasions, Trimeresurus spp. envenoming can cause AKI. This has important implications for snakebite management in Myanmar as the finding of local swelling, coagulopathy and AKI is generally considered pathognomonic of D. siamensis envenoming. Further collection of confirmed Trimeresurus spp. bites is required in Myanmar in order better to define the syndrome of envenoming and to assess the possible need for antivenom against Trimeresurus spp. in this country. • 3/21 patients envenomed by Trimeresurus albolabris developed coagulopathy. • Trimeresurus spp. envenoming can cause acute kidney injury occasionally requiring haemodialysis. • Verified identification of snakes presented with bitten patients prevents unnecessary antivenom use. [ABSTRACT FROM AUTHOR]

Snake venoms are mixtures of proteins whose physicochemical features confer them toxicity and immunogenicity. Animals (e.g., horses or sheep) immunized with snake venoms produce antibodies towards the venom proteins. Since these antibodies can neutralize the venom toxicity, they have been used to formulate snake antivenoms. The efficacy of the antivenoms is widely accepted, and standard venoms are expected to be representative of the snake's population that inhabit in the region where the antivenom is intended to be used. The representativeness of a single venom collected from a Crotalus simus snake, and its usefulness as standard venom to produce an antivenom is evaluated. The use of an "average venom" might be as representative of the population intended to be used, as the standard venom composed by many venom samples. Variations in the relative abundance concentration of crotoxin in the C. simus leads to different clinical manifestations, as well as differences in the neutralization efficacy of the antivenoms. A monovalent anti-Cs antivenom was produced from a single venom C. simus specimen, and its efficacy in neutralizing the lethal activity of 30 C. simus snakes was tested. Despite the variations in the relative abundance content of crotoxin found in the proteomes, the monovalent anti-Cs antivenom was successful in neutralize the toxicity caused by the variations on the venom composition of three different snake population used. Interestingly, it seems that the sex is not a key factor in the lethality of the venoms tested. The concept of representative venom mixtures for immunization should be revised for the case of C. simus on the populations found in Costa Rica, since it might use as less as one representative individual whose venom covers the mainly toxic enzymes. • The representativeness of a single Crotalus simus snake venom as an "average venom" should be considered. • The sex as a variable in the venom toxicity may not be a key factor in Crotalus simus venoms from Costa Rica. • The concept of representative venom mixture for antivenom production, in the case of Crotalus simus , should be revised. • The antivenom design should integrate a knowledge-base analysis of the snake venoms used. [ABSTRACT FROM AUTHOR]

Crotamine is a paralyzing toxin (MW: ~5 kDa) found in different proportions in some rattlesnake venoms (up to 62%). Mexican pit viper antivenoms have shown low immunoreactivity against crotamine, which is an urgent quality to be improved. The objective of this work was to evaluate the ability of a novel recombinant fusion protein composed of sphingomyelinase D and crotamine, and two whole venoms from Crotalus molossus nigrescens and C. oreganus helleri to produce neutralizing antibodies against crotamine. These immunogens were separately used for immunization procedures in rabbits. Then, we generated three experimental antivenoms to test their cross-reactivity via western-blot against crotamine from 7 species (C. m. nigrescens , C. o. helleri , C. durissus terrificus , C. scutulatus salvini , C. basiliscus , C. culminatus and C. tzabcan). We also performed pre-incubation neutralization experiments in mice to measure the neutralizing potency of each antivenom against crotamine induced hind limb paralysis. Our antivenoms showed broad recognition across crotamine from most of the tested species. Also, neutralization against crotamine paralysis symptom was successfully achieved by our three antivenoms, albeit with different efficiencies. Our results highlight the use of crotamine enriched venoms and our novel recombinant fusion protein as promising immunogens to improve the neutralizing potency against crotamine for the improvement of Mexican antivenoms. [Display omitted] • We expressed in Escherichia coli a novel recombinant fusion protein composed of sphingomyelinase D and crotamine. • Our recombinant fusion protein generated antibodies which cross-reacted to crotamine from seven rattlesnake species. • Antibodies against the recombinant fusion protein prevented crotamine hind limb paralysis in mice. • Two rattlesnake venoms also generated neutralizing antibodies against crotamine paralysis. [ABSTRACT FROM AUTHOR]

Green pit vipers are one of the most widely distributed group of venomous snakes in south-east Asia. In Indian, green pit vipers are found in the Northern and North-eastern states spreading across eastern and central India and one of the lesser studied venoms. High morphological similarity among them has been a long-established challenge for species identification, however, a total of six species of Indian green pit viper belonging to genus Trimeresurus , Popeia and Viridovipera has been reported from North-east India. Biochemical and biological studies have revealed that venom exhibits substantial variation in protein expression level along with functional variability. The symptoms of envenomation are painful swelling at bite site, bleeding, necrosis along with systemic toxicity such as prolonged coagulopathy. Clinical data of green pit viper envenomated patients from Demow community health centre, Assam advocated against the use of Indian polyvalent antivenom pressing the need for a suitable antivenom for the treatment of green pit viper envenomation. To design effective and specific antivenom for green pit vipers, unveiling the proteome profile of these snakes is needed. In this study, a comparative venomic of green pit vipers of Northern and North-eastern India, their clinical manifestation as well as treatment protocol has been reviewed. [Display omitted] • Green pit vipers from north-eastern and northern India shows high morphological similarity among each other. • They exhibit substantial variation in protein expression as well as functional variability. • The clinical manifestation of Trimeresurus erythrurus from Assam, India include incoagulable blood for several days. • Indian Polyvalent antivenom shows poor efficacy in reversing incoagulable blood, posing the need for a suitable antivenom. [ABSTRACT FROM AUTHOR]

Bothrops atrox is the most clinically relevant snake species within the Amazon region, which includes Ecuadorian territories. It comprises a large distribution, which could contribute to the genetic and venomic variation identified in the species. The high variability and protein isoform diversity of its venom are of medical interest, since it can influence the clinical manifestations caused by envenomation and its treatment. However, in Ecuador there is insufficient information on the diversity of venomic phenotypes, even of relevant species such as B. atrox. Here, we characterized the biochemical and toxicological profiles of the venom of six B. atrox individuals from the Ecuadorian Amazon. Differences in catalytic activities of toxins, elution profiles in liquid chromatography, electrophoretic patterns, and toxic effects among the analyzed samples were identified. Nonetheless, in the preclinical testing of antivenom, two samples from Mera (Pastaza) required a higher dose to achieve total neutralization of lethality and hemorrhage. Taken together, these data highlight the importance of analyzing individual venoms in studies focused on the outcomes of envenoming. Image 1 • Ecuadorian Bothrops atrox venoms possess a variability in abundance of metalloenzymes isoforms. • Enzymatic profiles evidenced variations in proteolytic and phospholipase A 2 activities at an individual level. • Significant differences were observed in myotoxicity and hemorrhage damage induced by samples. • Certain samples required higher proportion of antivenom for the complete neutralization of hemorrhagic and lethal effects. [ABSTRACT FROM AUTHOR]

Scorpions are arthropods covered with a thick layer of chitin, whose adult individuals have a length between 11.5 and 220 mm. Since they cause situations of poisoning and due to their predatory nature, humans usually fear them. In scorpion envenomation, it is necessary to apply anti-venom especially for patients with severe symptoms. Turkey is a suitable country for scorpion life in terms of climate. Today, it is reported in the world that there are 2512 species of scorpions in terms of 21 families and 195 genera. In addition, when the recent increase is taken into account, it is reported that the number of Scorpion species in Turkey has reached 50 and will continue to increase. Although the most venomous scorpion species known in Turkey is Leirus abdullahbayrami, scorpion anti-venom is obtained from Androctonus crassicauda. The studies show that the antivenom from A. crassicauda in Turkey which had been produced in a continuous manner since 1942 gave better results than other anti-venoms. A. crassicauda, which is shown as one of the five most poisonous scorpions in the world, is about 90 to 100 mm in length, has dark brown or black color, and has claws which are very chunky and a very curved tail. It is one of the most important species regarding medical terms in Turkey. A. crassicauda is mainly found in the regions of Southeastern Anatolia and in the areas of the cities of Iğdır and Kars which have low altitude levels, located in Eastern Anatolia in Turkey. It is stated that the responsible scorpion is the A. crassicauda with respect to the majority of patients who are admitted to the hospital with complaints of scorpion stings especially in the Southeastern Anatolia Region. Scorpion sting events, occurring mostly during the summer period still continues to be a major problem both in Turkey and the world's other countries. The scorpion anti-venom produced from A. crassicauda has taken its place as a national monograph of the Turkish Pharmacopoeia, which was prepared for the first time after many years. This review aims to provide detailed information on the history of anti-venom preparations in Turkey, starting from the foundation of the Turkish Republic up until the present day. [ABSTRACT FROM AUTHOR]

This case documents envenomation by a Green pit viper (Cryptelytrops sp.), a species found in South and Southeast Asia that causes the majority of venomous snakebites among Southeast Asian pit vipers. The proven life-threatening cases described in published literature, however, are sparse. We report a case of noticeable envenomation due to confirmed Green pit viper, Cryptelytrops sp. bite in Jajarkot. This is the first known reported case of such a bite from Jajarkot in Nepal. This case highlights the urgent need to improve diagnosis, monitoring, and supportive care for snakebite victims in Nepal. [ABSTRACT FROM AUTHOR]

Objectives: To describe 2 cases of boomslang (Dispholidus typus) envenomation in dogs, with thromboelastographic evaluation performed both pre‐ and postadministration of monovalent antivenom, and to contrast the clinical application of thromboelastography (TEG) with that of conventional coagulation testing in 1 of these cases for monitoring coagulation status in dogs suffering from such envenomation. Case Series Summary: Two dogs, a Weimeraner and a Dachshund, were referred, on separate occasions, for stabilization and treatment following observed boomslang envenomation. Initial physical examination revealed minor bleeding from the bite wound site in both dogs, along with mild swelling of the surrounding tissue. The Weimeraner also demonstrated bleeding from the gingival margin and had pale mucous membranes at time of presentation. Findings consistent with a diagnosis of disseminated intravascular coagulation (DIC) were noted on conventional coagulation testing. TEG tracings in both dogs revealed a hypocoagulable state preadministration of monovalent antivenom, followed by return to a normocoagulable state immediately postadministration, along with resolution of clinical bleeding. Both dogs were successfully discharged from the hospital, with no adverse reactions, either acute or delayed being noted. New or Unique Information Provided: Boomslang envenomation (hemotoxic snake venom) in dogs is rare, with currently only 3 cases in the literature. Herein, we document a further 2 cases and contrast changes on TEG with that noted on a routine hemostatic testing profile in 1 of these cases, to assess overall coagulation status both pre‐ and postadministration of antivenom. [ABSTRACT FROM AUTHOR]

Repurposing small molecule drugs and drug candidates is considered as a promising approach to revolutionise the treatment of snakebite envenoming. In this study, we investigated the inhibiting effects of the small molecules varespladib (nonspecific phospholipase A 2 inhibitor), marimastat (broad spectrum matrix metalloprotease inhibitor) and dimercaprol (metal ion chelator) against coagulopathic toxins found in Crotalinae (pit vipers) snake venoms. Venoms from Bothrops asper , Bothrops jararaca , Calloselasma rhodostoma and Deinagkistrodon acutus were separated by liquid chromatography, followed by nanofractionation and mass spectrometry identification undertaken in parallel. Nanofractions of the venom toxins were then subjected to a high-throughput coagulation assay in the presence of different concentrations of the small molecules under study. Anticoagulant venom toxins were mostly identified as phospholipases A 2 , while procoagulant venom activities were mainly associated with snake venom metalloproteinases and snake venom serine proteases. Varespladib was found to effectively inhibit most anticoagulant venom effects, and also showed some inhibition against procoagulant toxins. Contrastingly, marimastat and dimercaprol were both effective inhibitors of procoagulant venom activities but showed little inhibitory capability against anticoagulant toxins. The information obtained from this study aids our understanding of the mechanisms of action of toxin inhibitor drug candidates, and highlights their potential as future snakebite treatments. This study investigated the small molecule inhibitors varespladib, marimastat and dimercaprol in neutralising coagulopathic Crotalinae (pit vipers) snake venom toxins by using nanofractionation analytics which combines bioassays, liquid chromatography and mass spectrometry in parallel. Results obtained highlight their potential as future snakebite treatments. Image 1 [ABSTRACT FROM AUTHOR]

A 15‐month‐old, male neutered Staffordshire Bull Terrier cross was presented to its referring veterinarian collapsed and agonal. He was immediately intubated, manually ventilated, and treatment commenced for presumptive snake envenomation with two vials of Tiger/Multi‐Brown Snake Antivenom (minimum 7000 units/vial). The dog was transferred to a referral hospital intubated. Additional diagnostics performed following arrival at the referral hospital included a urine snake venom detection kit test, which was positive for brown snake immunotype. Three additional vials of Tiger/Multi‐Brown Snake Antivenom (minimum 7000 units/vial) were administered until the dog was extubated and able to stand. Venom‐induced consumptive coagulopathy (VICC) was diagnosed based on prolonged clotting times and scleral haemorrhage. Paroxysms of right ventricular outflow tract (RVOT) origin ventricular arrhythmias were treated with lignocaine and sotalol. Four days after presentation, a new‐grade IV/VI systolic heart murmur was auscultated, prompting an echocardiogram. An anechoic and compartmentalised mass measuring 43 mm × 19 mm was visualized within the right ventricular wall at the RVOT, immediately adjacent to the pulmonic valve. The mass was causing a RVOT obstruction. Its appearance was suggestive of an intramyocardial haematoma, most likely secondary to VICC. The dog remained cardiovascularly stable, and treatment consisted of supportive care. Recheck echocardiograms at 2 and 7 weeks after discharge revealed progressive improvement of the intramyocardial mass and resolution of the associated heart murmur. Although intramyocardial haematomas are rare, it should be considered as a differential in dogs that develop a newly diagnosed heart murmur and/or cardiac arrhythmia following brown snake envenomation. [ABSTRACT FROM AUTHOR]

• Trimeresurus species of viperid snakes are differentially coagulotoxic. • These species may produce significant clinical effects. • Variations in venom function results in differential antivenom efficacy. Snake envenomation globally is attributed to an ever-increasing human population encroaching into snake territories. Responsible for many bites in Asia is the widespread genus Trimeresurus. While bites lead to haemorrhage, only a few species have had their venoms examined in detail. We found that Trimeresurus venom causes haemorrhaging by cleaving fibrinogen in a pseudo-procoagulation manner to produce weak, unstable, short-lived fibrin clots ultimately resulting in an overall anticoagulant effect due to fibrinogen depletion. The monovalent antivenom 'Thai Red Cross Green Pit Viper antivenin', varied in efficacy ranging from excellent neutralisation of T. albolabris venom through to T. gumprechti and T. mcgregori being poorly neutralised and T. hageni being unrecognised by the antivenom. While the results showing excellent neutralisation of some non- T. albolabris venoms (such as T. flavomaculaturs , T. fucatus , and T. macrops) needs to be confirmed with in vivo tests, conversely the antivenom failure T. hageni, and the very poor results against T. gumprechti and T. mcgregori, despite being conducted in the ideal scenario of preincubation of antivenom:venom, indicates that the likelihood of clinically relevant cross-reactivity for these species is low (T. gumprechti and T. mcgregori) to non-existent (T. hageni). These same latter three species were also not inhibited by the serine protease inhibitor AEBSF, suggesting that the toxins leading to a coagulotoxic effect in these species are non-serine proteases while in contrast T. albolabris coagulotoxicity was completely impeded by AEBSF, and thus driven by kallikrein-type serine proteases. There was a conspicuous lack of phylogenetic pattern in venom variation, with the most potent venoms (T. albolabris and T. hageni) being distant to each other on the organismal tree, and with the three most divergent and poorly neutralised venoms (T. gumprechti, T. hageni, and T. mcgregori) were also not each others closest relatives. This reinforces the paradigm that the fundamental dynamic evolution of venom results in organismal phylogeny being a poor predictor of venom potency or antivenom efficacy. This study provides a robust investigation on the differential venom effects from a wide range of Trimeresurus species on coagulation, highlighting differential fibrinogenolytic effects, while also investigating the relative antivenom neutralisation capabilities of the widely available Thai Red Cross Green Pit Viper antivenom. These results therefore have immediate, real-world implications for patients envenomed by Trimeresurus species. [ABSTRACT FROM AUTHOR]

The intraspecific geographical venom variations of Calloselasma rhodostoma from Malaysia (CR-M), Indonesia (CR-I), Thailand (CR-T) and Vietnam (CR-V) were investigated through 1D SDS-PAGE and nano-ESI-LCMS/MS. The venom antigenicity, procoagulant activities and neutralization using Thai C. rhodostoma Monovalent Antivenom (CRMAV) were also investigated. SDS-PAGE patterns of the venoms were relatively similar with minor variations. Proteomic analysis revealed that snake venom metalloproteinases (SVMPs, particularly P–I class), serine proteases (SVSPs) and snaclecs dominated the venom protein composition (68.96–81.80%), followed by L-amino acid oxidase (LAAO) and phospholipase A 2 (PLA 2) (7.37–11.08% and 5.18–13.81%, respectively), corroborating C. rhodostoma envenoming effects (hemorrhage, consumptive coagulopathy, thrombocytopenia and local tissue necrosis). Other proteins of lower abundances (2.82–9.13%) identified include cysteine-rich secretory proteins (CRISP), phospholipase B, phosphodiesterase, nerve growth factor, 5′-nucleotidase, aminopeptidase and hyaluronidase. All four venoms exhibited strong procoagulant effects which were neutralized by CRMAV to different extents. CRMAV immunoreactivity was high toward venoms of CR-M, CR-I and CR-T but relatively low for CR-V venom. Among the venom samples from different locales, CR-V venom proteome has the smallest SVMP composition while SVSP, PLA 2 and phosphodiesterase were more abundant in the venom. These variations in C. rhodostoma venom protein composition could partly explain the differences seen in immunoreactivity. (198 words). Image 1 • Geographical variations of Calloselasma rhodostoma venom were investigated. • Specimens were from Malaysia, Indonesia, Thailand and Vietnam. • Major protein families were commonly present among the different venoms. • Procoagulant effects of all venoms were neutralized by CRMAV to different extents. • CRMAV immunoreactivity was relatively lower toward the venom from Vietnam. [ABSTRACT FROM AUTHOR]

North Central Florida is the home to several venomous snakes. The most clinically significant pit vipers include the Eastern Diamondback Rattlesnake, the Water Moccasin, and less commonly the Timber Rattlesnake. Many of the dogs and cats that become envenomated by these particular snakes have moderate to severe clinical signs requiring the use of antivenom in doses that can range from 1 to 20 vials with the average case requiring two vials. Oftentimes, the pet owners' financial limitations restrict the amount of antivenom that can be administered initially to severely envenomed cases. Most of these patients will become clinically stable after the first 48 hours of treatment, but there are rare instances where some patients will follow this same initial course, and then revert back to the initial signs of envenomation associated with delayed absorption of redistributed venom from other tissue sites in addition to the bite site. This report describes three dogs that showed signs of persistent and/or recurrent envenomation requiring additional doses of antivenom. The medical records of three dogs showing signs of persistent envenomation were reviewed by the author who was available and provided assistance during the course of the dogs' respective hospitalizations. The dog's signalment, time of year of the envenomation, clinical signs, treatment, and outcome are provided in each case. Each of these three dogs showed severe signs of envenomation characterized by marked mental depression, prostration, hemorrhagic lymphedema, and evidence of prolonged coagulation times. Initial treatment in each consisted of intravenous crystalloid solution and polyvalent crotalid antivenom that exceeded the usual average dose as reported in the literature. After the coagulation test normalized during the first three days, all of them reverted to abnormal prolonged clotting times with signs of clinical deterioration requiring additional doses of antivenom. Clinical stability was eventually reached and all dogs survived to be discharged. The clinical course of the three dogs described in this study showed that veterinary patients can experience persistent envenomation in a similar manner as described in humans. It behooves the veterinary practitioner to be aware of this complication and to be prepared to extend antivenom treatment as deemed necessary. • Three cases of persistent envenomation in dog. • Clinical findings similar to those seen in man. • Persistent envenomation requires increased doses of antivenom. [ABSTRACT FROM AUTHOR]

Backgrounds: Snake antivenom (SAV) is the definitive treatment for snake envenomation. But SAVs are specific, expensive and limited in supply. SAVs also come with risk of adverse reactions. Hence, this study was conducted to assess the use of SAV, adverse reactions to SAV and its clinical outcomes in snakebite patients. Methods: This was a retrospective study. Medical records of snakebite patients for the period from January 2014 to September 2017 were reviewed and study data was extracted. Clinical outcomes were measured by mortality rate in those receiving SAV. Results: Among 165 subjects, only 9 patients (5%) were treated with SAV after presenting with envenomation symptoms in which five cases with identified snakes were given monovalent SAV namely pit viper (two cases), king cobra, sea snake and cobra with one case each. Meanwhile, three cases of unidentified snake received polyvalent SAV and one case received pit viper SAV. Most of the patients (8/9, 88.9%) received SAV within 24 hours after snakebite. The average time gap to first administration was 7.23 hours. In patients receiving SAV, six out of 9 cases required two to four vials of SAV. All the patients receiving SAV did not encounter any adverse effects except a child who had pyrogenic reaction. All patients survived without significant morbidity at discharge. The total cost of SAV for the 9 patients was US$ 24,082.68. Conclusion: From this study, the incidence of snakebites requiring SAV was low. Low incidence of adverse effects and no mortality were observed in patients receiving SAV. [ABSTRACT FROM AUTHOR]

Abstract Delayed or recurrent coagulopathy can occur up to 14 days after North American rattlesnake envenomation in patients that have been treated with Crotalidae Polyvalent Immune Fab (CroFab). There is little data in the literature characterizing the sequelae of North American rattlesnake envenomation in pregnancy and no previously published reports of recurrent coagulopathy in pregnancy. Case report We present 2 cases of first trimester pregnant women requiring readmission and retreatment with Crotalidae Polyvalent Immune Fab (CroFab) after developing recurrent/late coagulopathy following North American Rattlesnake Envenomation. Both patients were initially admitted and treated with CroFab following snakebite and discharged home without coagulopathy. One patient developed significant hypofibrinogenemia and subsequent hemorrhage after spontaneous abortion secondary to recurrent venom induced hypofibrinogenemia. Discussion Pregnant women with recurrent or late coagulopathy may be at higher risk for hemorrhage and spontaneous abortion and require more frequent laboratory monitoring after initial hospitalization and treatment with antivenom. A lower threshold for re-treatment with CroFab may be warranted in patients with fibrinogen less than 100mg/dL even in the setting of a normal platelet count. Highlights • Recurrent coagulopathy can occur up to 14 days after rattlesnake envenomation in patients treated with CroFab. • Pregnant women with coagulopathy after rattlesnake envenomation have increased risk of spontaneous abortion and hemorrhage. • Re-treatment with CroFab should be considered in pregnant patients with fibrinogen less than 100mg/dL. [ABSTRACT FROM AUTHOR]

Introduction: Studies of acute hypersensitivity reactions in pediatric populations receiving Crotalidae Polyvalent Immune Fab (CPIF) are complicated by small size, wide age ranges, and diverse definitions of such reactions. Methods: This is a retrospective chart review of patients aged 13 years or younger treated with CPIF for Crotalid envenomation from November 2006 to 2016. The primary outcome was the presence of an acute hypersensitivity reaction to CPIF and was defined as the development of any of the following symptoms within 3 hours of initiation of CPIF infusion: urticaria, wheezing or respiratory distress, angioedema, hypotension, nausea, and/or vomiting. Demographics, CPIF dose to control and total dose, bite location, level of care, and length of stay were also recorded. Results: Thirty-four patients were ultimately treated with CPIF. Ages ranged from 10 months to 13 years. Twenty-one patients (60%) were male, 24 (70.6%) were admitted to the ICU, and the median length of stay was 2 days with a range of 1–11 days. Zero patients developed an acute hypersensitivity reaction to CPIF. Conclusion: Acute hypersensitivity reactions to CPIF did not occur in this cohort. Such reactions are rare with the use of CPIF in pediatric patients. [ABSTRACT FROM AUTHOR]

Objective: To compare the incidence of hypersensitivity reactions following copperhead envenomation treated with Fab antivenom (FabAV) or placebo.Methods: Patients with copperhead snakebites received treatment and follow-up in a prospective, randomized, double-blind, placebo-controlled trial of FabAV or placebo. The treatment allocation ratio was 2:1 (FabAV:placebo). All of the included patients received at least one dose of study treatment. We reviewed all treatment-emergent adverse events (AEs) using a previously published scale to classify likely hypersensitivity reactions as mild, moderate, or severe.Results: We enrolled 74 patients at 13 sites. Forty-five patients received FabAV, and 29 patients received placebo. Five FabAV patients and 4 placebo patients had moderate envenomations; the rest were mild. Twenty-five FabAV patients and 8 placebo patients had at least 1 AE. Mild skin reactions occurred in 11 (24%) FabAV patients (pruritis, urticaria, rash, ecchymosis, erythema) and 1 (3%) placebo patient (pruritis). Moderate gastrointestinal AEs occurred in 7 (16%) FabAV patients (nausea, vomiting, constipation, diarrhea, oral paresthesia) and in 2 (7%) placebo patients (nausea). Respiratory AEs occurred in 3 (7%) FabAV patients (dyspnea, pulmonary embolism, nasal congestion, sneezing) and no placebo patients. Hypotension occurred in 1 patient in each group.Conclusions: In a randomized controlled trial of FabAV for copperhead bites, the incidence of hypersensitivity reactions was low. Most reactions were mild skin reactions. [ABSTRACT FROM AUTHOR]

Background: Crotalidae Polyvalent Immune Fab (Fab Antivenom) is the primary Viperid antivenom used in the United States since 2000. Adverse event data associated with its use are limited. The purpose of this study is to describe the prevalence of acute adverse events associated with the use of Fab antivenom. Methods: The American College of Medical Toxicology's Toxicology Investigators Consortium maintains a prospective case registry of poisoned and envenomated patients managed by medical toxicologists at the bedside. This registry includes the North American Snakebite sub-registry. We performed a review of 438 cases entered into the Snakebite sub-registry. Results: A total of 373 (85.2%) received at least one vial of Fab Antivenom. Forty percent were children. Adverse events occurred in 10 patients (2.7%) of whom six were adults. Rash was the most common adverse event. More severe adverse events (hypotension, bronchospasm, and/or angioedema) occurred in four (1.1%) patients. Prophylaxis was administered prior to Fab antivenom in 4.0%. Eight patients received various treatments for their adverse events. Neither the initial number of Fab antivenom vials, atopic history, nor prior envenomation correlated with the prevalence of adverse events. Discussion: This prevalence of adverse events was lower than in previous studies and in a meta-analysis of 11 studies. The types of adverse events and treatments used are consistent with those in previous reports. There were no prior reports of prophylaxis use with which to compare. Conclusion: The prevalence of Fab antivenom adverse events in the North American Snakebite Registry was 2.7%. [ABSTRACT FROM AUTHOR]

Accidents involving venomous snakes are a public health problem worldwide, causing a large number of deaths per year. In Brazil, the majority of accidents are caused by the Bothrops and Crotalus genera, which are responsible for approximately 80% of severe envenoming cases. The cross-neutralization of snake venoms by antibodies is an important issue for development of more effective treatments. Our group has previously reported the construction of human monoclonal antibody fragments towards Bothrops jararacussu and Crotalus durissus terrificus ’ venoms. This study aimed to select human single-chain variable fragments (scFvs) that recognize both bothropic and crotalic crude venoms following venoms neutralizing capacity in vitro and in vivo . The cross-reactivity of Cro-Bothrumabs were demonstrated by ELISA and in vitro and in vivo experiments showed that a combination of scFvs neutralizes in vitro toxic activities ( e.g. indirect hemolysis and plasma-clotting) of crotalic and bothropic venoms as well as prolonged survival time of envenomed animals. Our results may contribute to the development of the first human polyvalent antivenom against Bothrops jararacussu and Crotalus durissus terrificus venoms, overcoming some undesirable effects caused by conventional serotherapy. [ABSTRACT FROM AUTHOR]

The medical records of 95 pit viper envenomations in client-owned dogs presented to an academic emergency hospital in the Southeastern United States during the period spanning 2018 and 2020 were retrospectively examined. This study's primary objectives were to record the clinical abnormalities and treatment responses associated with envenomation and their relation to outcome. Approximately 80% of the bites involved the head region associated with varying degrees of hemorrhagic lymphedema. Some of the most common additional symptoms observed were; hypotension (10%), cardiac dysrhythmias (17%), and coagulopathy (21%). Treatment in most cases consisted of intravenous fluids, antivenom, and analgesic drugs. Blood products were used as indicated for anemia and persistent bleeding. The average dose of the F('ab') 2 was 1–2 vials. Additional vials (3–22) were administered as needed to counteract persistent or recurrent coagulopathy and hemolysis. Only 3% of the dogs had mild clinical signs of Type 1 hypersensitivity during their treatment period. Antihistamine use at the tertiary hospital was restricted to the three dogs showing signs of a suspected allergic reaction in response to antivenom administration; these patients received diphenhydramine intramuscularly. A glucocorticoid drug was used in only one dog prior to referral but not subsequently. Ninety dogs had a good outcome, while five died. Historically, pit viper envenomation in dogs in the southeastern United States has been a potentially life-threatening problem. Most dogs will survive if treated promptly and appropriately with adequate amounts of intravenous fluids, and antivenom titrated on severity of clinical presentation. [Display omitted] • Four different types of venomous pit vipers in Northcentral Florida. • Hemolysis, coagulopathy, and cardiac arrhythmias occur. • F(ab) 2 antivenom is safe and effective. • Allergic reactions rare. • Intravenous crystalloid solutions and ample antivenom are essential for moderate and severe cases. [ABSTRACT FROM AUTHOR]

Although snakebites are uncommon, there are several species of medically important venomous snakes native to Singapore. We present a case of envenoming by the shore pit viper (Trimeresurus purpureomaculatus) that showed clinical improvement when treated with the Indian (Haffkine) polyvalent antivenom. A 40-year-old man was bitten on his right hand by a snake, which was identified through photos and his description to be a shore pit viper, which is native to the local mangrove area. Severe swelling and pain developed immediately after the bite, which progressed up the arm. Because of the progression of local swelling, antivenom was started. He was given a total of 6 vials (60 mL) of polyvalent antivenom, with the first vial started 3 hours after the bite. He showed clinical improvement within 24 hours. His subsequent recovery was uneventful, with no other complications as a result of envenomation or antivenom use. Severe envenoming by the shore pit viper can lead to marked local effects such as extensive swelling and tissue necrosis. Antivenom is indicated in the presence of severe local envenomation. Antivenom against the shore pit viper is however not available locally. The Indian (Haffkine) polyvalent antivenom contains antibodies against 4 common venomous snakes in India, namely the Indian cobra, common krait, Russell's viper, and sawscaled viper. The improvement seen in this patient suggests possible cross-neutralizing activity of the Indian vipers' antivenom against the local shore pit viper venom. Further in vivo and in vitro studies should be performed to verify this clinical case. [ABSTRACT FROM AUTHOR]

Over 14,000 copperhead (Agkistrodon contortrix) bites were reported to United States poison centers between 1983 and 2008, and 1809 cases were reported to poison centers in 2014. The copperhead is primarily found in the southeastern United States and belongs to the pit viper subfamily Crotalinae, which also includes the water moccasin (Agkistrodon piscivorus) and rattlesnakes (Crotalus and Sistrurus genera). Postmortem rattlesnakes have been reported to cause clinically significant envenomation; we report a case of a postmortem copperhead causing clinically significant envenomation after inadvertent puncture with the deceased copperhead fang. The copperhead was transected twice, leaving the snake in 3 separate pieces. While handling the snake head, an inadvertent puncture occurred on the right index finger followed by pain and swelling in the affected extremity necessitating antivenom administration. Care should be taken when handling deceased pit vipers due to the continued risk of envenomation. [ABSTRACT FROM AUTHOR]

We report 2 cases of catastrophic ischemic stroke after Crotalidae polyvalent immune Fab (ovine)-treated rattlesnake envenomation, 1 fatal and the other resulting in significant permanent disability. It is possible these serious adverse events may have been related to venom factor(s), an interaction between venom and antivenom, occult patient blood dyscrasia, or to random unrelated events. We present the rationale for each possibility, and submit the experiences to elicit alternate postulation and communication of similar presentations. [Copyright &y& Elsevier]

Abstract: An in vitro potency assay of antivenom against Malayan pit viper (Calloselasma rhodostoma, CR) has been developed. The assay is based on the neutralizing activity of the antivenom against the coagulant activity of the venom. The minimum coagulant dose (MCD) of CR venom was 22.12 ± 0.25 μg/ml. The coagulation time induced by 2MCD of the venom was used as the control for calculating the neutralizing activity of each batch of antivenom. The in vitro potency of antivenom, expressed as effective dose (ED), was the antivenom/venom ratio at which the coagulation time was increased three fold of that induced by 2MCD of the venom. Eleven batches of the antivenom were assayed for their lethality neutralizing activity (ED50) by the in vivo assay using mice as well as the developed in vitro assay. The correlation coefficient (r) between the in vitro neutralizing activities (ED) and in vivo neutralizing activities (ED50) was 0.957, (p value < 0.001). This simple and rapid in vitro assay of C. rhodostoma antivenom should be a good alternative method for the assessment of antivenom potency during the immunization program and fractionation process. The assay should be adaptable for use with antivenoms against other similar procoagulant venoms. [Copyright &y& Elsevier]

• Specific treatment for snakebites consists of administering animal-derived antivenoms. • Antivenom treatment resulted in 16.1% of early adverse reactions. • Early adverse reactions were mostly mild. • CXCL-8 and IL-2 levels are potential predictors of early adverse reactions. • CXCL-8 and IL-2 play a role in the onset of early adverse reactions. Snakebite envenomings are considered a global health problem. The specific therapy for these envenomings consists of administering animal-derived antivenoms aiming to neutralize the venom toxins. Antivenoms have been used effectively to treat snakebites for more than a century; however, their administration may result in early and/or late adverse reactions. The present study presents the prevalence of early adverse reactions (EARs) towards Bothrops antivenom therapy in a health tertiary unit in the Brazilian Amazon and explores if specific plasma cytokines and chemokines from envenomed patients could be used as predictors of EARs. A cohort of patients bitten by Bothrops atrox was followed-up at the Fundação de Medicina Tropical Dr. Heitor Vieira Dourado (FMT-HVD), from 2014 to 2016. Patients were treated with the Brazilian Bothrops antivenom and CXCL-8, CCL-5, CXCL-9, CCL-2, CXCL-10, IL-6, TNF, IL-2, IL-10, IFN-y, IL-4, and IL-17A were evaluated in patients' plasma samples before and after antivenom administration. From the total of patients (n = 186), mostly were male (82.3%), inhabiting rural areas (87.1%), with an average age of 35 years. Most of the patients (83.8%) were admitted to the hospital within 6 h after the accident, 26 (14%) reported having suffered a previous snakebite, and 97 (52.1%) received between 7 and 9 antivenom vials. The frequency of antivenom-induced EARs was 11.8% (22), resulting mostly of mild reactions. Urticaria was the major EAR manifestation (46.4%). Interestingly, CXCL-8 and IL-2 showed significantly lower levels in patients who progressed to EARs, although IL-2 levels might not represent biological relevance due the small magnitude difference between groups. This study reveals that CXCL-8 and IL-2 could play a role in the onset of EARs in pit viper envenomings. [ABSTRACT FROM AUTHOR]

Abstract: Background: Envenomation by pit vipers is associated with coagulation disorders including hypofibrinogenemia and thrombocytopenia. These abnormalities correct following antivenom treatment during the acute phase of the disease. Delayed or recurrent coagulation abnormalities have been reported following use of Fab antivenom, resulting in risk of hemorrhage or death. Methods: We hypothesized that the longer plasma persistence of F(ab′)2 antivenom, relative to Fab, in patients at risk of coagulopathy would result in decreased venonemia and coagulopathy one week after treatment. We conducted a Phase 2, randomized comparative clinical trial of rattlesnake bitten adults presenting for care in Tucson, Arizona, USA. Patients were randomly assigned to receive either Fab or F(ab′)2 antivenom using a predefined treatment schedule. Endpoints included platelet counts, fibrinogen levels, and venom and antivenom ELISAs. Measurements were conducted at baseline and at various times over the following two weeks. Results: Twelve patients were studied, with 6 randomly assigned to each treatment group. Early response of platelet counts, fibrinogen, and venom levels to acute treatment was similar in the two groups. One week following treatment, platelet counts and fibrinogen levels were lower in the Fab group than in the F(ab′)2 group, following a characteristic pattern that reached its lowest point approximately one week after initial treatment. Venom levels dropped below detection limits in all patients following initial treatment but subsequently rebounded into the measurable range in 4 of 6 Fab cases. F(ab′)2 antivenom levels demonstrated a longer plasma persistence than Fab levels, with a less rapid drop during the two days following treatment. Two patients in the Fab group had significant adverse events involving coagulation abnormalities, for which additional antivenom was administered following the initial treatment period. Conclusions: Following the acute phase of presentation and treatment for pit viper envenomation, there appears to be a roughly 2-week subacute phase of the disease during which ongoing presence of venom may result in serious delayed or recurrent coagulation defects. Late hypofibrinogenemia and thrombocytopenia are associated with recurrent venonemia and drop in antivenom levels. This pattern was apparent in patients treated with Fab antivenom but was not seen among F(ab′)2 recipients in this Phase 2 study, consistent with pharmacokinetic differences between the two products. Improved understanding of Fab pharmacokinetics is important for the management of coagulopathy-prone pit viper envenomation. Use of F(ab′)2 antivenom may prevent recurrent venom effects, but larger studies are necessary for statistical confirmation of this observation. [Copyright &y& Elsevier]

Abstract: Background: Reconstitution of CroFab® (Crotalidae Polyvalent Immune Fab [ovine]) lyophilized drug product was previously performed using 10 mL sterile water for injection followed by up to 36 min of gentle swirling of the vial. CroFab has been clinically demonstrated to be most effective when administered within 6 h of snake envenomation, and improved clinical outcomes are correlated with quicker timing of administration. An alternate reconstitution method was devised, using 18 mL 0.9% saline with manual inversion, with the goal of shortening reconstitution time while maintaining a high quality, efficacious product. Methods: An analytical study was designed to compare the physicochemical properties of 3 separate batches of CroFab when reconstituted using the standard procedure (10 mL WFI with gentle swirling) and a modified rapid procedure using 18 mL 0.9% saline and manual inversion. The physical and chemical characteristics of the same 3 batches were assessed using various analytic methodologies associated with routine quality control release testing. In addition further analytical methodologies were applied in order to elucidate possible structural changes that may be induced by the changed reconstitution procedure. Results: Batches A, B, and C required mean reconstitution times of 25 min 51 s using the label method and 3 min 07 s (a 88.0% mean decrease) using the modified method. Physicochemical characteristics (color and clarity, pH, purity, protein content, potency) were found to be highly comparable. Characterization assays (dynamic light scattering, analytical ultracentrifugation, LC–MS, SDS-PAGE and circular dichroism spectroscopy were also all found to be comparable between methods. Discussion: When comparing CroFab batches that were reconstituted using the labeled and modified methods, the physicochemical and biological (potency) characteristics of CroFab were not significantly changed when challenged by the various standard analytical methodologies applied in routine quality control analysis. Additionally, no changes in the CroFab molecule regarding degradation, aggregation, purity, structure, or mass were observed. Conclusion: The analyses performed validated the use of the more rapid reconstitution method using 18 mL 0.9% saline in order to allow a significantly reduced time to administration of CroFab to patients in need. [Copyright &y& Elsevier]

Abstract: Background: In patients bitten by North American rattlesnakes and treated with Crotalidae Polyvalent Immune Fab (Ovine) (FabAV), late hematologic abnormalities—persistent, recurrent, or late, new onset of hypofibrinogenemia, prolonged PT/INR, prolonged PTT, and/or thrombocytopenia beyond 48 h post-envenomation—are common, difficult to manage, and may result in morbidity and mortality are common, difficult to manage, and may result in morbidity and mortality. The optimal management of late hematologic abnormalities, particularly the use of further treatment with antivenom, has not been well defined. The current FabAV treatment regimen is to give antivenom as a bolus dose over a one-hour period. We describe our experience using a continuous intravenous infusion of FabAV for late hematologic effects and/or associated bleeding complications in rattlesnake envenomation. Methods: This is a retrospective, observational case series of patients envenomated by North American rattlesnakes at three medical centers managed with a continuous intravenous infusion of FabAV for late hematologic abnormalities and/or associated bleeding complications. Indications, dilution and infusion protocols, and duration of therapy were individualized. Results: Five cases were identified between July 2010 and September 2011. All patients had profound late hematologic abnormalities and/or were associated with bleeding complications. Several patients had received repeat bolus infusions of FabAV, with or without human blood products, with either inadequate or only transient beneficial response. All patients were then managed with a continuous intravenous infusion of FabAV and all appeared to respond to the continuous intravenous infusion of FabAV, titrated to effect, with cessation of progression and, in most cases, improvement in hematologic abnormalities. Rates of infusion varied from 2 to 4 vials per 24 h (mean = 3.1 ± 0.4 vials/day). The termination of FabAV infusion was between day 6 and day 14 from the time of envenomation (mean = 10 ± 3 days), after which hematologic values were normalized or were normalizing in all patients and continued to do so. Discussion: The use of FabAV as a continuous intravenous infusion, particularly after the acute phase of envenomation has passed, provides a continuous source of circulating antibodies to neutralize venom components reaching circulation from tissue stores and allows natural replenishment of hematologic factors such as platelets and/or fibrinogen. This method is an efficient use of FabAV, avoiding the wasteful excess of a bolus dose, may be more effective, eliminating the potential for destruction of hematologic factors when protective antivenom levels are lost between bolus FabAV doses, and appears to be safe. Further assessments of the stability and sterility of the product during infusion are needed. The need to continue hospitalization is the major drawback, but continued observation and inpatient care may be needed for other indications (e.g. bleeding) in this subset of patients. Conclusions: A continuous intravenous infusion of FabAV between 2 and 4 vials per day, titrated to effect, and continued for 6–14 days post-envenomation appeared to be associated with reversal of late hematologic effects of rattlesnake envenomation and, when combined with indicated human blood products, control of significant bleeding. Continuous intravenous infusion of FabAV may be safer, more efficacious, and more cost-effective than observation without FabAV treatment or as-needed bolus dosing in selected patients with late hematologic abnormalities. [Copyright &y& Elsevier]

Abstract: Total venom–antivenin immune complex formation and binding parameters relevant to antivenin protection against venom toxicity and lethality can be evaluated using size-exclusion high-performance liquid chromatography (SE-HPLC). Simple integration of regions within SE-HPLC elution profiles was used to compare binding characteristics of Crotalidae Polyvalent Immune Fab (Ovine) antivenin (FabAV) and Crotalus atrox (western diamondback rattlesnake; C. atrox), C. varidis varidis (prairie rattlesnake; C. v. v.), Agkistrodon contortrix contortrix (southern copperhead; A. c. c.), and A. piscivorus leukostoma (western cottonmouth; A. p. l.) venom. Areas associated with bound venom and antivenin ({Areabnd}) were evaluated using a logistic dose–response equation to estimate EC50 and {Areabnd}max. The relative magnitudes of EC50, which inversely reflect venom–antivenin binding affinity, were C. atrox > C. v. v. > A. c. c. > A. p. l. Less than 50% of FabAV appeared to be reactive with each of the venoms based on {Areabnd}max. Data was also consistent with FabAV binding to multiple sites on polyvalent antigens within the venoms. Evaluation of immune complex formation using SE-HPLC was compared to neutralization of phospholipase A2 (PLA2) activity of C. atrox, A. c. c., and A. p. l. venom by FabAV as reported in the literature. Maximum neutralization of PLA2 activity occurred, in general, prior to maximum immune complex formation. Venom–antivenin binding at EC50 determined via SE-HPLC appeared to be greater than binding associated with neutralization of venom lethality in mice based on LD50 and ED50 reported by others. SE-HPLC analysis of venom–antivenin binding could provide a priori information, relevant to reducing the use of animals in evaluating antivenin protection against venom-induced toxicity and lethality. [Copyright &y& Elsevier]