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We identified a Thelazia callipaeda eyeworm in an American black bear in Pennsylvania, USA, on the basis of its morphological features and molecular analysis. Our finding highlights emergence of a T. callipaeda worm sylvatic transmission cycle in the United States.

Intestinal parasites, including cestodes like Dipylidium caninum, are common in dogs in the United States of America (USA), but fecal flotation consistently, and, at times, dramatically, fails to identify many of these infections. To determine the extent to which including coproantigen testing for D. caninum would improve the identification of dogs infected with this cestode, we evaluated fecal samples from 877 dogs (589 pet and 288 from municipal shelters) from six USA states using zinc sulfate (specific gravity 1.24) fecal flotation with centrifugation along with coproantigen detection for Giardia sp., hookworms, ascarids, and Trichuris vulpis. For D. caninum, PCR of perianal swabs was included. Intestinal parasite infections were identified, using centrifugal fecal flotation or coproantigen, in 265 dogs (13.2 % pet, 64.9 % shelter). Dipylidium caninum infection was detected in 5.6 % of dogs with the combination of coproantigen and centrifugal fecal flotation, and 7.3 % of dogs when perianal swab results were included; prevalence varied by diagnostic method, population, and geographic region. In pet dogs, D. caninum infection was identified by fecal flotation (0), coproantigen (2.2 %), or perianal swabs (1.2 %). The same methods revealed infection in 0.3 %, 12.5 %, and 11.1 % of shelter dogs, respectively. Frequent use of praziquantel in shelter dogs (116/288; 40.3 %) may have reduced prevalence. Positive and negative agreement of D. caninum coproantigen with perianal swab PCR in pet dogs was 85.7 % and 98.8 %, respectively. Multiple logistic regression analysis accounting for region, population, and age found D. caninum infection to be more common in shelter dogs relative to pet (adjusted OR 4.91 [2.48, 10.24]) and in the Southcentral and Southeast regions relative to North (adjusted OR 9.59 [1.92, 174.13] and 17.69 [3.67, 318.09] respectively). Coproantigen testing also enhanced the detection of other intestinal parasites over fecal flotation alone, including Giardia sp. (14.7 % vs 3.3 %), hookworms (13.8 % vs 8.4 %), ascarids (2.9 % vs 2.2 %), and T. vulpis (2.9 % vs 1.4 %). Together, these data indicate that the coproantigen assay employed increases detection of D. caninum infections several fold, supporting the use of this test in clinical practice, and add to a growing body of research documenting enhanced diagnosis through implementation of multiple laboratory-based methods., Competing Interests: Declaration of Competing Interest As employees of IDEXX Laboratories, Inc., JB, DE, RH, JH, PT, and MB have an affiliation to the commercial funders of this research. The other authors declare no conflict of interest., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Purpose: The clinical progression of Leishmania (Leishmania) amazonensis infection depends on multiple factors, including immunological status of the host and their genotypic interaction. Several immunological processes depend directly on minerals for an efficient performance. Therefore, this study used an experimental model to investigate the alterations of trace metals in L. amazonensis infection associate with clinical outcome, parasite load, and histopathological lesions, and the effect of CD4 + T cells depletion on these parameters., Methods: A total of 28 BALB/c mice were divided into 4 groups: 1-non-infected; 2-treated with anti-CD4 antibody; 3-infected with L. amazonensis; and 4-treated with anti-CD4 antibody and infected with L. amazonensis. After 24 weeks post-infection, levels of calcium (Ca), iron (Fe), magnesium (Mg), manganese (Mn), Cu, and Zn were determined by inductively coupled plasma optical emission spectroscopy using tissue samples of the spleen, liver, and kidneys. Additionally, parasite burdens were determined in the infected footpad (inoculation site) and samples of inguinal lymph node, spleen, liver, and kidneys were submitted to histopathological analysis., Results: Despite no significant difference was observed between groups 3 and 4, L. amazonensis-infected mice had a significant reduction of Zn (65.68-68.32%) and Mn (65.98 to 82.17%) levels. Presence of L. amazonensis amastigotes was also detected in the inguinal lymph node, spleen, and liver samples in all infected animals., Conclusion: The results showed that significant alterations in micro-elements levels occur in BALB/c mice experimentally infected with L. amazonensis and may increase the susceptibility of individuals to the infection., (© 2023. The Author(s) under exclusive licence to Witold Stefański Institute of Parasitology, Polish Academy of Sciences.)

We report a case of Spirometra infection in a Samar cobra ( Naja samarensis ) imported from the Philippines, belonging to a zoological collection in the southern United States. Under a poor post-surgical prognosis, the snake was euthanized, and at necropsy plerocercoids of a Diphyllobotriidea were found in its subcutaneous tissues and musculature. Molecular and phylogenetic analyses of the complete cytochrome oxidase c subunit I ( cox1 ) gene of the mitochondrial DNA confirmed that the isolate belonged to the genus Spirometra and was closely related to Spirometra mansoni isolates from Asian countries (bootstrap support = 99.4%). Considering the origin and clinical history and handling of the animal, the snake probably arrived infected in America. We suggest the inclusion of diagnostic imaging in the investigation of sparganosis in research and disease surveillance protocols applied in the pre- and post-quarantine period to asymptomatic animals imported from endemic areas., Competing Interests: The authors declare no conflict of interest., (© 2023 The Authors.)

From June 2013 to January 2014, blood sera samples and ticks were collected from domestic dogs and wild small mammals, and ticks from the vegetation in a preservation area of the Atlantic Forest biome (Turvo State Park), and the rural area surrounding the Park in Derrubadas municipality, state of Rio Grande do Sul, southern Brazil. Dogs were infested by Amblyomma ovale and Amblyomma aureolatum adult ticks, whereas small mammals were infested by immature stages of A. ovale, Amblyomma yucumense, Amblyomma brasiliense, Ixodes loricatus, and adults of I. loricatus. Ticks collected on vegetation were A. brasiliense, A. ovale, A. yucumense, Amblyomma incisum, and Haemaphysalis juxtakochi. Three Rickettsia species were molecularly detected in ticks: Rickettsia bellii in I. loricatus (also isolated through cell culture inoculation), Rickettsia amblyommatis in A. brasiliense, and Rickettsia rhipicephali in A. yucumense. The latter two are tick-rickettsia associations reported for the first time. Seroreactivity to Rickettsia antigens were detected in 33.5% (55/164) small mammals and 8.3% (3/36) canine sera. The present study reveals a richness of ticks and associated-rickettsiae in the largest Atlantic Forest Reserve of the state of Rio Grande do Sul, which is characterized by a rich fauna of wild mammals, typical of more preserved areas of this biome. Noteworthy, none of the detected Rickettsia species have been associated to human or animal diseases. This result contrasts to other areas of this biome in Brazil, which are endemic for tick-borne spotted fever caused by Rickettsia rickettsii or Rickettsia parkeri., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background: The canine heartworm Dirofilaria immitis, a filarioid nematode of dogs and other carnivores, is widespread in the USA and the world. Over 20 different mosquito species serve as intermediate hosts of D. immitis, but their contribution to transmission varies according to factors like host feeding patterns, geographic locations and climatic conditions. The yellow fever mosquito, Aedes aegypti, is a competent vector of D. immitis but is often dismissed as a vector of veterinary relevance given its anthropophilic feeding behavior. We evaluated the prevalence of D. immitis in pet dogs along the USA-Mexico border and assessed whether Ae. aegypti in the area are naturally infected with heartworm and are potentially acting as a vector., Methods: A total of 200 whole blood samples collected from pet dogs in the Lower Rio Grande Valley in south Texas from 2016 to 2019 were included in this study. Canine serum samples for D. immitis were tested using the DiroCHEK® Canine Heartworm Antigen Test Kit pre- and post-immune complex dissociations (ICD) and blood samples were tested using high-resolution melt (HRM) quantitative PCR (qPCR) and a probe-based qPCR. Additionally, mosquito specimens were collected and identified, and Ae. aegypti heads, abdomens and pools were tested using conventional PCR (cPCR) and HRM qPCR., Results: Overall, heartworm prevalence in dogs aged > 6 months was 40.8% (64/157) when the results from all testing modalities were considered. Heartworm antigen was detected in 33.5% and 40.7% of the dogs using DiroCHEK® pre- and post-ICD, respectively. By molecular screening, 20.1% of dogs tested positive with probe-based qPCR, while only one tested positive with HRM qPCR. Of the Ae. aegypti abdomens from blood-fed Ae. aeygpti tested, 20 (21.7%) from mosquitoes that fed on dogs and four (7%) from those that fed on humans tested positive for heartworm. Among Ae. aegypti heads from blood-fed Ae. aeygpti, two (1.1%) were positive based on cPCR and four (2.5%) were positive based on HRM qPCR. No D. immitis DNA was detected in the 208 pools of whole bodies (358 individuals) of Ae. aegypti gravid females., Conclusions: Our study highlights a high prevalence of heartworm in dogs in south Texas and provides evidence that Ae. aegypti could be contributing to heartworm transmission in canine populations in this region., (© 2022. The Author(s).)

Background: Current recommendations for diagnosis of Dirofilaria immitis infection in dogs rely on the detection of antigen produced largely by adult females coupled with the visualization of microfilariae (mf) in the circulation via a microfilaria detection test (MFDT). It is hypothesized that qPCR assays used in parallel with antigen detection tests will perform better in detecting mf than modified Knott's test (MK), when combined with antigen detection. This study compares probe-based qPCR and MK techniques for mf detection used in parallel with the DiroCHEK ® antigen test to screen for heartworm infection in shelter dogs., Methods: Matching blood and serum samples were collected from 300 shelter dogs in Brazos and Harris counties, Texas, USA. Blood was assessed for the presence of mf via MK and the presence of D. immitis DNA by a species-specific probe-based qPCR assay. Serum samples were tested for the presence of heartworm antigen using DiroCHEK ® before and after immune complex dissociation (ICD) via heat treatment. In addition, the performance of each diagnostic test was evaluated via Chi-square test, Cochran's Q test, and post hoc analysis., Results: Qualitatively, MK detected mf in 22.0% (66/300) of samples, 55 of which were morphologically identified as D. immitis and 11 as Acanthocheilonema reconditum. The range of heartworm mf was 28 to 88,803 mf/ml (median: 6627.5). Real-time PCR detected D. immitis DNA in 20.7% (62/300) of samples. Heartworm antigen was detected in 24.7% (74/300) of samples pre-ICD, and in 29.3% (88/300) post-ICD. When comparing tests, the Chi-square and McNemar's tests showed that the difference between positive and negative proportions was statistically significant. The Cochran test showed the difference in the distributions of cases and non-cases was significant when individual tests were combined (χ 2  = 62.3, df = 3, P < 0.0001) and when parallel methods were combined (χ 2  = 43.1, df = 4, P < 0.0001)., Conclusion: Considering individual and combined test performances, practicality, and efficient use of bench time, this heartworm-specific probe-based qPCR method is a viable option as a mf detection test to be used in parallel with antigen tests for canine heartworm infection in diagnostic and research settings., (© 2022. The Author(s).)

Dictyocaulus is a globally distributed genus of lungworms of domestic and wild ungulates. Dictyocaulus adults inhabit the bronchi, frequently causing subclinical and clinical disease, and that impacts animal health and production. North American bison ( Bison bison ) and cattle ( Bos taurus ) share various parasitic nematode species, particularly in areas where co-grazing occurs. The current assumption is that North American bison share the lungworm D. viviparus with cattle, but this has not been confirmed on a molecular basis. The aim of this study was to molecularly characterize Dictyocaulus lungworm isolates from North American plains bison ( Bison bison bison ). Fecal samples were collected from 5 wild conservation bison herds located in Iowa, North Dakota, Oklahoma, Colorado, and Montana in 2019 and 2020, and from ranched and feedlot bison from 2 herds in Oklahoma and Texas. First-stage lungworm larvae (L1) were isolated via Baermann technique. Genomic DNA was extracted from L1s of up to 3 samples per herd and followed by PCR and sequencing targeting the internal transcribed spacer 2 (ITS2) region of the nuclear ribosomal DNA and the partial cytochrome oxidase c subunit 1 ( cox1 ) of mitochondrial DNA. Phylogenetic analyses were performed in MEGA X 10.1. Sequences of North American plains bison Dictyocaulus belong to a single, uncharacterized species, clustering in well-supported clades (100% and 100% bootstrap support for ITS2 and cox1 , respectively), differing from D. viviparus of cattle in North America and Europe, and European bison ( Bison bonasus ). Our results contradict previous assumptions regarding parasite identity, highlighting the need for characterization of this species through morphological and molecular methods, elucidating its biology and host range, and potential impact on host health. Further investigation into the biodiversity of Dictyocaulus species infecting bovids and cervids in North America is warranted., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors.)

In collaboration with the American College of Veterinary Pathologists.

Wild canids serve as reservoir for various vector-borne pathogens of veterinary and medical importance, including the canine heartworm, Dirofilaria immitis . In North and Central America, coyotes ( Canis latrans ) may be a relevant reservoir host for heartworm transmission. The objective of this study was to determine the occurrence of D. immitis in coyotes across Texas using integrated antigen detection test and molecular assays. Matching whole blood and serum samples were collected from 122 coyotes from different locations across the state of Texas, United States, encompassing nine counties. Collections occurred from February to April 2016, and December 2016. Samples were assessed serologically using a commercial microtiter plate ELISA (DiroCHEK®), and molecularly by conventional PCR targeting the cytochrome oxidase c subunit 1 ( cox1 ) and NADH dehydrogenase subunit 5 ( nad5 ) of the mitochondrial DNA, and via a TaqMan© probe-based real-time PCR protocol, also targeting a fragment of the cox1 gene. Overall, 12 (9.83%) samples tested positive when serological and molecular results were combined. Seven of 122 samples (5.73%) were antigen-positive, 8 (6.55%) were qPCR-positive, and 4 (3.27%) were positive using conventional PCR. Of 12 positive samples, 4 tested antigen-positive by DiroCHEK® but were negative in all molecular tests, another 4 tested positive by at least one of the molecular assays but tested negative by DiroCHEK®, and 3 samples tested positive by both antigen test and at least one of the molecular assays. Two samples (16.67%) tested positive on both the antigen test and both conventional PCR and qPCR. Our study confirmed the presence of D. immitis infection in coyotes from southern and northern Texas. The combination of serologic and molecular diagnostic tests was proven synergistic for the identification of D. immitis infections, including occult dirofilariosis, and revealed a more accurate picture of heartworm occurrence in the sampled coyotes., Competing Interests: The authors declare no conflict of interest., (© 2022 Published by Elsevier Ltd on behalf of Australian Society for Parasitology.)

A single, male Dirofilaria immitis was found in the right ventricle of a captive, 10-month-old female Asian small-clawed otter (Aonyx cinereus) from East Feliciana parish in Louisiana, USA. Molecular analysis was performed for unequivocal species level identification using the cytochrome c oxidase subunit 1 (cox1) region of the mitochondrial DNA and comparing to known D. immitis cox1 sequences available on GenBank to which the specimen had a 99.54-100% pair wise identity. As there is no safe adulticidal treatment for D. immitis in mustelids, chemoprophylaxis using macrocyclic lactones is recommended to prevent infection. Further studies are needed to better characterize D. immitis infection and its propensity to cause disease in the Asian small-clawed otter., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Species of the genus Dipetalonema are parasitic nematodes of the family Onchocercidae (Nematoda; Filarioidea) which infect the peritoneal cavity of Neotropical primates. Of these, six species have been taxonomically described, two of these have been reported infecting the black-faced spider monkey ( Ateles chamek ): Dipetalonema gracile and Dipetalonema yatesi . Description of Dipetalonema species have been based on morphological characteristics, and their phylogenetic relationships remain unresolved. A few molecular studies have been carried out in Dipetalonema spp. infecting Neotropical primates. Seven filarioid nematodes (6 females and one male) recovered from one A. chamek in the Peruvian Amazon rainforest were morphologically identified as D. yatesi and molecularly characterized. A multi-locus genetic analysis of nuclear ribosomal region (18S) and mitochondrial ( cox1 , 12S, and nad5 ) gene sequences supported D. yatesi as a distinct lineage and yielded a highly resolved phylogenetic lineage tree for this filarioid genus of Neotropical primates. Our results highlighted that Dipetalonema species are divided in two well-supported clades, one containing D. yatesi and D. caudispina , and the second containing D. robini , D. gracile, and D. graciliformis . Due to sequence ambiguities from GenBank entries, relationships among isolates of D. gracile and D. graciliformis cannot be fully resolved, which requires further investigation. However, this suggests that these could represent a species complex. Our study confirms that D. yatesi is a valid species and constitutes the first molecular phylogenetic analysis of this parasite in black-faced spider monkeys., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors.)

A 4-year-old intact female Yorkshire Terrier presented an acute onset of hypersalivation and depressed mentation. The owner reported that the dog displayed tremors, right-sided torticollis, right-sided head tilt, and lifting of the left forelimb. The dog appeared restless and confused, and the condition progressed to lethargy and death on the way to an emergency hospital. At necropsy, a single 10 mm long x 1 mm wide, pale gray, botfly larva with black spines was found along the cerebral meninges. Areas of hemorrhage were noted in the right cerebral hemisphere. Microscopically, these areas also had evidence of necrosis and inflammation. Morphology of the larva allowed confirmation of subfamily-level identification as Cuterebrinae, and presumed genus-level identification of Cuterebra. Species-level identification of the larva as C. abdominalis was achieved through DNA extraction, PCR and sequencing at the cytochrome oxidase subunits 1 and 2 (COI and COII), followed by phylogenetic analysis. Aberrant cuterebrosis is a poorly documented condition in dogs that may cause neurologic signs and lead to death., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A 4-yr-old male intact lesser spot-nosed guenon ( Cercopithecus petaurista ), housed at a North American zoological facility, presented with acute lethargy, inappetence, and mild neurologic signs. Physical examination revealed hemorrhagic pleural effusion in the right hemithorax. This guenon's condition improved over several days but then deteriorated, and the guenon presented with lethargy and weakness. A hemorrhagic pleural effusion was identified within the left hemithorax. The guenon developed respiratory and cardiac arrest while anesthetized. Gross examination revealed tract formation in the liver, adhesions of the liver to the diaphragm, hemorrhagic thoracic and abdominal effusion, and a single trematode within the right hemithorax. Morphologic features and species identification by PCR confirmed that the parasite was Fascioloides magna . Histologic examination revealed tract formation in the liver associated with biliary hyperplasia, fibrosis and hepatic necrosis, severe bile peritonitis, and pleuritis. This is the first report of an infection by F. magna in a primate.

The Cuvier's beaked whale (CBW; Ziphius cavirostris ) is a cosmopolitan marine mammal found in deep tropical and temperate waters of all oceans. CBW strandings have been recorded sporadically in Brazil; however, there is lack of information available regarding their causes of stranding and/or death. Herein, we report the epidemiologic, pathologic, morphologic parasitologic features and molecular identification of arterial and renal crassicaudiasis by Crassicauda sp. in three geographically and chronologically distant CBW stranded off Brazil. CBW-1 was an adult male stranded dead in Rio Grande do Sul State. CBW-2 was an adult female that stranded alive in Sergipe State and died shortly after. CBW-3 was and adult male that stranded dead in Santa Catarina State. The most relevant pathologic findings in these three CBW were severe, chronic proliferative mesenteric and caudal aortic endarteritis and chronic granulomatous and fibrosing interstitial nephritis with renicular atrophy and loss, and numerous intralesional Crassicauda sp. nematodes. Furthermore, CBW-1 had concomitant gram-negative bacterial pneumonia and pulmonary and hepatic thromboembolism. Morphologic analysis of renal adult nematodes identified Crassicauda sp. in the three CBW. Molecular analyses targeting the 18S and ITS-2 ribosomal loci of renal nematodes in CBW-2 and CBW-3 identified C. anthonyi . It is believed that severe arterial and renal crassicaudiasis likely resulted or contributed significantly to morbidity and death of these animals. These results expand the known geographical range of occurrence of crassicaudiasis in CBW. Specifically, the present study provides the first accounts of arterial and renal crassicaudiasis in CBW off the southern hemisphere, specifically in CBW off Brazil, and to the authors' knowledge, it is the first record of C. anthonyi in the southern Atlantic Ocean., (© 2021 The Authors.)

We report the pathologic features, local inflammatory response immunophenotype, and molecular identification results of cerebral nematodiasis in a young sitatunga (Tragelaphus spekii) from Texas. To the authors' knowledge, this is the first report of cerebral nematodiasis by Parelaphostrongylus tenuis in a sitatunga, a bovid species introduced into the USA, and the first characterization of the local inflammatory response immunoprofile in this condition. A molecular identification method based on formalin-fixed and paraffin-embedded-polymerase chain reaction was described. These results contribute to knowledge on geographical distribution and host spectrum of P. tenuis, and highlight the relevance of this nematodiasis in naïve translocated or introduced bovid species into endemic areas.

Background: Companion animal endoparasites play a substantial role in both veterinary medicine and public health. Updated epidemiological studies are necessary to identify trends in occurrence and distribution of these parasites, and their associated risk factors. This study aimed to assess the occurrence of canine endoparasites  retrospectively, using fecal flotation  test data available through participating academic veterinary parasitology diagnostic laboratories across the United States of America (USA)., Methods: Canine fecal flotation records from ten veterinary diagnostic laboratories located in nine states in the USA acquired from January 1, 2018, to December 31, 2018, were included., Results: A total of 4692 fecal flotation test results were obtained, with a majority comprised of client-owned dogs (3262; 69.52%), followed by research dogs (375; 8.00%), and shelter dogs (122; 2.60%). Samples from 976 (20.80%) dogs were positive for at least one parasite, and co-infections of two or more parasites were found in 3.82% (179/4692) of the samples. The five most commonly detected parasites were: Giardia sp., (8.33%; 391/4692), Ancylostomatidae (5.63%; 264/4692), Cystoisospora spp. (4.35%; 204/4692), Toxocara canis (2.49%;117/4692), and Trichuris vulpis (2.43%; 114/4692). Various other internal parasites, including gastrointestinal and respiratory nematodes, cestodes, trematodes, and protozoans were detected in less than 1% of samples., Conclusions: These data illustrate the importance of parasite prevention, routine fecal screening, and treatment of pet dogs. Additionally, pet owners should be educated about general parasite prevalence, prevention, and anthelmintic treatment regimens to reduce the risks of environmental contamination and zoonotic transmission., (© 2021. The Author(s).)

Background: Onchocerca lupi is an emerging, zoonotic filarioid nematode associated with ocular disease in companion animals in North America and the Old World. The areas where this parasite is assumed to be endemic in the USA comprise southwestern states. Thus far, all cases reported outside of the southwest are associated with travel or animal movement., Methods: An 11-year-old, castrated male Pitbull dog from McAllen, Hidalgo County, southern Texas, with no travel history, was diagnosed with a perforating corneal ulceration of the right eye. Enucleation was performed and tissues submitted for histopathology., Results: Histologically, sections of two filarioid nematodes were observed. DNA was extracted from formalin-fixed paraffin-embedded tissue using a commercial kit. We performed PCR targeting the cox1 gene of the mitochondrial DNA, followed by sequencing and phylogenetic analysis. Altogether, these results confirmed the identification of the nematode specimens as O. lupi, phylogenetically belonging to haplotype 1., Conclusion: We report the first autochthonous case of O. lupi in a dog from Hidalgo County, southern Texas, USA. Our finding suggests Texas as an additional state where this zoonotic nematode is endemic. Further investigations are required to understand the epidemiology of this parasite along the USA/Mexico border.

Thelazia californiensis is a spirurid nematode found in the conjunctival sac of domestic and wild animals, including humans, across the western United States of America. Herein, we report two cases of thelaziosis by T. californiensis in dogs from New Mexico, United States, based on integrated morphological and molecular approaches. Nematode specimens collected from the conjunctiva of both dogs were identified as T. californiensis based on morphology. Our study substantially expands the knowledge on morphometry of this nematode species. Therefore, these data will be useful for accurate diagnosis of thelaziosis in domestic animals, wildlife and humans in North America, using classical, microscopy-based methods. We characterized for the first time the mitochondrial cytochrome c-oxidase subunit 1 (COI) and 12S genes of T. californiensis. While these markers support the validity of T. californiensis, they were not very informative for elucidating the phylogenetic relationships among Thelazia species. Nevertheless, the characterization of these diagnostic markers for T. californiensis will be useful for studies on the epidemiology, molecular xenomonitoring of fanniid vectors, and population genetics of this multi-host, zoonotic parasite., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Antigen enzyme-linked immunosorbent assay tests are widely used for the diagnosis of heartworm infection in dogs. While commercially-available heartworm antigen tests have high sensitivity and specificity, false-negative test results can occur in dogs with low worm burdens, female-only infections, or prior to patency. The use of immune complex dissociation (ICD) methods have demonstrated increased sensitivity in the detection of Dirofilaria immitis antigens and the reversal of false-negative antigen results. However, there are concerns pertaining to false-positive antigen results due to infections of other nematode parasites, especially post-ICD. Therefore, this study evaluated the effect of heat-treatment on serum samples of dogs experimentally-infected with Dirofilaria repens during the course of infection, to assess for potential cross-reactivity on heartworm antigen tests. Archived serum samples from three dogs experimentally-infected with D. repens were utilized. All samples were tested for cross-reactivity pre- and post-heat-treatment using the DiroCHEK® Heartworm Antigen test kit throughout infection (day -9 through 404 days post-infection; dpi). All heat-treated samples tested false-positive starting at 164 dpi and continuing through 404 dpi, thereby testing positive prior to patency. No cross-reactivity was observed for any dog at any time point prior to heat-treatment. Our results suggest that the ICD method decreased the specificity of heartworm antigen tests and caused cross-reactivity of serum from dogs experimentally infected with D. repens. In conclusion, heat-treatment of serum in areas co-endemic for D. repens and D. immitis has limited clinical value, and should be used with caution., (Copyright © 2020 Elsevier B.V. All rights reserved.)