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microRNAs are small non-coding RNAs that are important regulators of gene expression in a range of animals, including nematodes. We have analysed a cluster of four miRNAs from the pathogenic nematode species Haemonchus contortus that are closely linked in the genome. We find that the cluster is conserved only in clade V parasitic nematodes and in some ascarids, but not in other clade III species nor in clade V free-living nematodes. Members of the cluster are present in parasite excretory-secretory products and can be detected in the abomasum and draining lymph nodes of infected sheep, indicating their release in vitro and in vivo. As observed for other parasitic nematodes, H. contortus adult worms release extracellular vesicles (EV). Small RNA libraries were prepared from vesicle-enriched and vesicle-depleted supernatants from both adult worms and L4 stage larvae. Comparison of the miRNA species in the different fractions indicated that specific miRNAs are packaged within vesicles, while others are more abundant in vesicle-depleted supernatant. Hierarchical clustering analysis indicated that the gut is the likely source of vesicle-associated miRNAs in the L4 stage, but not in the adult worm. These findings add to the growing body of work demonstrating that miRNAs released from parasitic helminths may play an important role in host-parasite interactions.

The structure of sensory organs situated on palps and inside the cheliceral stylet of the quill mite Sringophilopsis fringilla (Fritsch, 1958) was examined in scanning and transmitting electron microscopes. Eight sensilla of 3 types were revealed on palptarsus, including two contact chemo-mechanosensory sensilla, a single distant chemosensory (probably olfactory) sensillum, and 5 tactile mechanosensitive sensilla. All other sensilla situated on basas parts of the palp and on the outer surface of gnathosoma are represented by tactile mechanoreceptors. A proprioceptor sensillum was revealed in the movable digit of the chelicera; modified cilia of dendrites of 5 sensory neurons run in the inner non-sclerotized core of the stylet, ending at different levels as electron-dense rods connected with the sclerotized wall of the stylet. The authors assume that the proprioceptor sensillum of the stylet detects the pressing force of the movable digit on the inner wall of the quill during piercing process, while papal sensilla determine the optimal place for piercing.

Background: Molecular methods have great potential for sensitive parasite detection in the diagnosis of human African trypanosomiasis (HAT), but the requirements in terms of laboratory infrastructure limit their use to reference centres. A recently developed assay detects the Trypanozoon repetitive insertion mobile element (RIME) DNA under isothermal amplification conditions and has been transformed into a ready-to-use kit format, the Loopamp Trypanosoma brucei. In this study, we have evaluated the diagnostic performance of the Loopamp Trypanosoma brucei assay (hereafter called LAMP) in confirmed T.b. gambiense HAT patients, HAT suspects and healthy endemic controls from the Democratic Republic of the Congo (DRC)., Methodology/principal Findings: 142 T.b. gambiense HAT patients, 111 healthy endemic controls and 97 HAT suspects with unconfirmed status were included in this retrospective evaluation. Reference standard tests were parasite detection in blood, lymph or cerebrospinal fluid. Archived DNA from blood of all study participants was analysed in duplicate with LAMP. Sensitivity of LAMP in parasitologically confirmed cases was 87.3% (95% CI 80.9-91.8%) in the first run and 93.0% (95% CI 87.5-96.1%) in the second run. Specificity in healthy controls was 92.8% (95% CI 86.4-96.3%) in the first run and 96.4% (95% CI 91.1-98.6%) in the second run. Reproducibility was excellent with a kappa value of 0.81., Conclusions/significance: In this laboratory-based study, the Loopamp Trypanosoma brucei Detection Kit showed good diagnostic accuracy and excellent reproducibility. Further studies are needed to assess the feasibility of its routine use for diagnosis of HAT under field conditions.

Background: Gastrointestinal nematode (GIN) infections are the predominant cause of economic losses in sheep. Infections are controlled almost exclusively by the use of anthelmintics which has lead to the selection of drug resistant nematode strains. An alternative control approach would be the induction of protective immunity to these parasites. This study exploits an ovine microarray biased towards immune genes, an artificially induced immunity model and the use of pseudo-afferent lymphatic cannulation to sample immune cells draining from the intestine, to investigate possible mechanisms involved in the development of immunity., Results: During the development of immunity to, and a subsequent challenge infection with Trichostrongylus colubriformis, the transcript levels of 2603 genes of cells trafficking in afferent intestinal lymph were significantly modulated (P < 0.05). Of these, 188 genes were modulated more than 1.3-fold and involved in immune function. Overall, there was a clear trend for down-regulation of many genes involved in immune functions including antigen presentation, caveolar-mediated endocytosis and protein ubiquitination. The transcript levels of TNF receptor associated factor 5 (TRAF5), hemopexin (HPX), cysteine dioxygenase (CDO1), the major histocompatability complex Class II protein (HLA-DMA), interleukin-18 binding protein (IL-18BP), ephrin A1 (EFNA1) and selenoprotein S (SELS) were modulated to the greatest degree., Conclusions: This report describes gene expression profiles of afferent lymph cells in sheep developing immunity to nematode infection. Results presented show a global down-regulation of the expression of immune genes which may be reflective of the natural temporal response to nematode infections in livestock.

Theileria parva causes an acute lympho-proliferative disease in cattle, which can result in death of susceptible animals within 2-3 weeks of infection. Analyses of the cellular response in the lymph node draining the site of infection demonstrated an early T cell response, with the appearance of large numbers of uninfected lymphoblasts between 6 and 9 days p.i., coinciding with initial detection of parasitised cells. There was a marked increase in the representation of CD8(+) T cells and the emergence of a sizable sub-population of CD2(-) CD8(+) alpha/beta T cells during this period. Analysis of T cell receptor beta chain variable (TCR BV) gene expression did not reveal any evidence for the involvement of a superantigen in stimulating the response. Responding lymph node cells were found to produce increased quantities of IFNgamma and IL-10, and both the CD2(+) CD8(+) and CD2(-) CD8(+) populations expressed IFNgamma transcripts. Purified CD2(+) CD8(+) cells proliferated when stimulated in vitro with autologous parasitised cells or non-specific mitogens, whereas CD2(-) CD8(+) cells were refractory to these stimuli. In contrast to the parasite-specific cytotoxic activity associated with T cell responses in immune cattle, the responses to primary infection exhibited variable levels of non-specific cytotoxic activity. Stimulation of purified CD2(+) CD8(+) T cells in vitro with autologous parasitised cells also failed to reveal evidence of specific cytotoxic activity. These findings indicate that primary infection with T. parva induces an aberrant T cell response that lacks appropriate effector activity.

Lymph node cannulation allows the collection of lymph draining from a defined anatomical region. Proteomic analysis of that lymph offers a potentially valuable insight into the immunoinflammatory response of that particular region. In this study, ovine gastric lymph has been used to monitor the proteomic changes occurring in the tissue fluid of the abomasum, in response to infection with the parasitic nematode, Teladorsagia circumcincta. Lymph, collected temporally over an experimental infection period, was analysed by means of 2-DE and subsequent gel analysis using densitometry software. In addition, the composition of the lymphatic proteome was further explored by means of MALDI-TOF and MS/MS analyses. The concentration of gelsolin, alpha-1 beta glycoprotein and haemopexin were altered significantly (p<0.05) with infection.

Canine leishmaniosis (CanL) caused by Leishmania spp. is a zoonotic protozoon disease. It is widespread in most parts of the world including the Mediterranean basin. The present study was carried out in order to determine the prevalence of CanL in dogs in Kayseri and vicinity by nested-PCR. A total of 300 asymptomatic dogs were sampled randomly. Blood samples taken from the vena cephalica antebrachii were collected into tubes containing EDTA. Furthermore, lymph samples were taken from 14 dogs while bone marrow, spleen and liver biopsies were taken from three dogs. The DNA's obtained from these samples were examined for the presence of Leishmania spp. by nested-PCR which amplified the small subunit ribosomal RNA (ssr RNA) gene. According to the results of the nested-PCR, none of the 300 dogs were Leishmania spp. DNA positive.

A survey was conducted in a low-endemic and in a non-endemic area of Sudan to evaluate the specificity and efficiency of different serological antibody detection techniques for Trypanosoma brucei gambiense. Comparisons were made of the card agglutination test for trypanosomiasis (CATT) on diluted blood, on diluted plasma and on eluates from blood dried on filter paper, the LATEX test on diluted plasma and an ELISA on diluted plasma and filter paper. The specificities of all the serological tests were not significantly different from CATT on diluted blood (99.5%). The specificity of CATT on diluted blood was similar (99.3%). The highest sensitivities (100%) were observed with CATT on diluted blood and with CATT and LATEX on diluted plasma. CATT on diluted blood was more cost-efficient than the classic test, CATT on whole blood.

The expression of interleukin (IL)-4, IL-5, IL-10, IL-13, TNF-alpha and IFN-gamma genes, and parasite-specific IgM, IgG1, IgG2, IgA and total IgE levels, were monitored daily in intestinal lymph of sheep infected repeatedly with the nematode parasite Trichostrongylus colubriformis. Host genotype had a significant influence on IL-13 gene activity, with resistant-line (R) sheep consistently expressing higher levels of mRNA than susceptible-line (S) sheep. Mean gene expression of IL-13, IL-4 and IFN-gamma did not differ significantly between the first and second nematode challenge. Field-primed R and S as well as field-primed R and naïve S sheep had lower mean gene expression of IL-5 and IL-10, respectively, during the second when compared to primary challenge. Genes for IL-13 and IL-5 were transiently and strongly up-regulated after nematode infection, particularly in animals with previous exposure to nematodes. Genes for TNF-alpha and IFN-gamma were also transiently up-regulated, but to a lesser extent and more typically after primary challenge. Naïve sheep of both genotypes produced relatively little antibody response after primary challenge. A second nematode challenge resulted in large increases in the lymphatic levels of all antibody sub-classes which were significant for adult antigen-specific IgA and larval antigen-specific IgG1. In naïve S line sheep, the larval-specific IgA and IgG2 response appeared delayed when compared to the R line animals. Field-primed R and S line sheep had relatively high lymphatic IgG1 levels prior to experimental infection and these did not change significantly afterwards. These results demonstrate that during nematode infections, the intestinal micro-environment of sheep is transiently skewed towards Th2 cytokine dominance, although IFN-gamma gene expression continues. This response is accompanied by increases of nematode-specific IgG1, IgA, IgG2 and IgM, as well as of total IgE in lymph plasma.

Objective: To illustrate the cytomorphologic features of Leishmania lymphadenitis associated with visceral leishmaniasis (V/L) and post-kala-azar dermal leishmaniasis (PKDL) and to highlight the fact that Leishmania lymphadenitis must he included in the differential diagnosis of patients presenting with lymphadenopathy, particularly in areas endemic for the disease., Study Design: Fine needle aspiration (FNA) was routinely done in 21 cases of lymphadenopathy in VL (18 cases) and PKDL (3 cases), and the detailed cytomorphologic features were correlated with the respective histopathologic findings., Results: Amastigote forms of Leishman-Donovan (LD) bodies were seen in 19 cases both intracellularly, in histiocytes and multinucleate giant cells, and extracellularly. The FNA smears revealed a polymorphous population of cells composed of lymphocytes, histiocytes, plasma cells, giant cells and tingible body macrophages. In a few cases, epithelioid cell granulomas were also seen. The cytomorphologic features were confirmed and correlated on histopathology., Conclusion: Not all lymphadenopathy in VL and PKDL is due to Leishmania lymphadenitis. Demonstration of LD bodies on FNA smears helps with the early diagnosis of VL and PKDL with lymphadenopathy where the diseases are endemic.

Total and antigen-specific IgE responses in afferent (AIL) and efferent (EIL) intestinal lymph of sheep with a nematode resistant (R) or susceptible (S) genotype during challenge infection with the intestinal nematode parasite Trichostrongylus colubriformis were examined. Within each sheep line, lambs with a nematode naive or nematode field-primed pre-challenge status were used. Total IgE level in AIL and EIL was dependent on nematode infection and was further influenced by genotype or the immune phenotype (nematode immune mean FEC+/-SDM=77+/-179 or non-immune mean FEC+/-SDM=4016+/-4318) of the animal. During T. colubriformis challenge immune animals had higher levels of total IgE in lymph than non-immune sheep, R line sheep had higher concentrations of total IgE than S line sheep, and field-primed animals had higher total IgE levels than nematode naive animals. Concentrations of total IgE were consistently higher in AIL than EIL or serum and were higher in lymph draining the proximal than the distal jejunum demonstrating that polyclonal IgE in AIL was largely derived from the intestinal mucosa of the anatomical compartment where the nematodes reside. The consistently higher concentration of total IgE in AIL was dependent on phenotype or genotype and in S genotype sheep also on the pre-challenge status. Concentrations of nematode specific IgE were significantly higher in EIL than AIL indicating a preference for the production of IgE reacting with excretory secretory products of the infective T. colubriformis larvae in the regional lymph node.

Immunization of cattle with in vitro propagated bovine mononuclear cells infected with Theileria annulata induces a protective immune response. Activation and effector function of T cells exiting the lymph node draining the site of cell line immunization were investigated to understand the mechanisms involved in the generation of immunity. Immunized animals exhibited a biphasic immune response in efferent lymph as well as peripheral blood. The first phase corresponded to allogenic responses against MHC antigens of the immunizing cell line and the second was associated with parasite specific responses. An increase in the output of CD2(+) cells and MHC class II(+) cells in efferent lymph was observed after cell line immunization with a corresponding decrease in WC1(+) cells. Although the percentage of CD4(+) T cells did not change significantly over the course of the experiment, they became activated. Both CD25 and MHC class II expressing CD4(+) T cells were detected from day 7 onwards, peaking around day 13. Efferent lymph leukocytes (ELL) exhibited sustained responses to IL-2 in vitro following cell line immunization. Antigen specific proliferation was also detected first to the immunizing cell line and then to parasite antigens. The two peaks of CD2(+) cells were observed, which corresponded to similar peaks of CD8(+) cells. The increase in CD8(+) cells was more pronounced during the second parasite specific phase than the first allogenic phase. Activated CD8(+) T cells mainly expressed MHC class II and some expressed CD25. Significantly the peak of activated CD4(+) T cells preceded the peak of activated CD8(+) T cells, highlighting the role of T. annulata specific CD4(+) T cells in inducing parasite specific CD8(+) cytotoxic responses. A biphasic cytotoxic response also appeared in efferent lymph and peripheral blood, the first directed against MHC antigens of the immunizing cell line followed by MHC class I restricted parasite specific cytotoxicity. The cytotoxic responses in efferent lymph appeared earlier than peripheral blood, suggesting that activated CD8(+) cells exiting the draining lymph node following immunization with T. annulata infected schizonts play an important role in the development of protective immune responses.

Hydatidosis or echinococcosis is a parasitic disease caused by Echinococcus granulosus or E. multilocularis, which forms cysts in the liver and lung after penetrating the duodenal mucosa and entering the portal circulation. The liver and lung act as a filter but some embryos enter the general circulation and disseminate throughout the body. Musculoskeletal involvement is a rare manifestation of hydatidosis, which is usually reported to affect a single muscle. We report here a rare case of a 68-year-old man with widespread hydatidosis of the retroperitoneum and the subcutaneous adipose tissue, and with multiple muscle involvement in the absence of liver, lung, and spleen involvement. The patient underwent surgical excision of a subcutaneous hydatid cyst 7 years earlier. It is likely that the large dissemination of parasites resulted from accidental rupture of the primary focus during surgery with consequent release and spreading of scolices via lymphatics.

The object of these experiments was to study the pathogenesis and kinetics of Theileria annulata infection in the efferent lymph of the draining lymph nodes of calves. Efferent lymphatics of calves were cannulated prior to infection with T. annulata sporozoite or an allogeneic schizont cell line. Potentially lethal sporozoite challenge induced cell shut-down from days 4-6 and then a massive increase in output of blasting cells (both infected and non-infected) in the efferent lymph. The rate of lymph flow and total cell output increased to 5 to 10-fold from day 6 onwards. Sporozoites were never isolated from the efferent lymph. However, large numbers of parasite-infected cells were seen in efferent lymph from the sixth day of infection. The animals inoculated with an allogeneic T. annulata-infected cell line exhibited only a small increase in flow rate and cell output. Parasite-infected cells of recipient origin were seen in efferent lymph from day 11 onwards. However, cells of donor origin were never isolated either from efferent lymph or peripheral blood. Thus the parasite transferred from the inoculated donor cell line to the cells of the recipient before schizonts appeared in efferent lymph.

Efferent lymphatic cannulation was used to study the dissemination of strain S48 of Toxoplasma gondii and the cell output from the prefemoral lymph node, after infection of both "naive" and vaccinated sheep. In the former the mean cell output decreased for 3 days before reaching a peak at 11 and 12 days, but in vaccinated ewes a similar drop in cell output and subsequent peak occurred significantly earlier, at 24 h and 5 days, respectively. The cellular response in both types of sheep was largely due to a marked increase in blast cells. The detection of live toxoplasms and parasite DNA by mouse inoculation and the polymerase chain reaction, respectively, gave similar results; the parasite was demonstrated in lymph from days 3 to 12 during a primary infection but with a sharp cut-off after day 9 coinciding with the peak blast cell response. Very little evidence of T. gondii was found in lymph of vaccinated sheep after challenge. Immunity, which is thought to be largely T-cell mediated and is sustained without continuous antigenic stimulation, suppresses dissemination of the parasite in the lymph and therefore to other sites, which might include the gravid uterus.

It has been reported that third stage larvae (L3) of Wuchereria bancrofti strain from Jakarta, molted to the fourth stage (L4) in vitro, in a simple culture medium supplemented with 10% human serum. In the present study, this culture medium has been used to examine the effects of some physico-chemical parameters on larval growth, development and molting of Wuchereria bancrofti from India. Lymph at 10% concentration enhanced the in vitro survival time of larvae. Molting of larvae from L3 to L4 stage has been obtained using human fetal lung cells in cellular co-culture and as a source of conditioned medium. Given these improvements in the medium supplementation, it has been observed that the age of L3s (duration of L3s maintenance within the mosquitos) is one of the most important parameters for the development of L3s in vitro. No molting was observed when one day L3s were used whereas, molting occurred with one or two weeks old L3s. On the contrary, when more than 3 weeks old L3s were used molting failed to occur even though duration of survival of L3s was improved and in this case, most of the larvae were degenerated.

The investigators carried out a comparative evaluation of twelve or parasitological techniques used nowadays in the diagnosis of human trypanosomiasis and parasite isolation in the lymph fluid, blood and cerebro-spinal fluid (CSF). The tests were performed on 64 seropositive suspects selected with TESTRYP-CATT among 661 attendants examined at the Projet de Recherches Cliniques sur la Trypanosomiase (PRCT), Daloa, Côte-d'Ivoire. The study showed that the sensitivity of the different techniques varies between 17.2% (for CSF inoculation to Mastomys) and 84.5% (for the anion exchange centrifugation technique-mAECT). The classical techniques, says lymph fluid examination, direct blood examination and thick blood have a sensitivity of 58.6, 22.4 and 34.5% respectively. The most sensitive methods are lymph fluid examination, mAECT and double centrifugation of CSF (69%). The sensitivity increases up to 98.3% with the combination of two or three techniques. The combination of lymph fluid examination/mAECT/double centrifugation of CSF is either the most sensitive and the most suitable one for use in the field. The combination of lymph fluid examination and mAECT which detects 91.4% of the infected subjects is the most efficient. The authors discussed the results and recommended that similar study be done in field conditions to assess methods which either demonstrated better sensitivity and are more suitable for field use.

Efferent lymph and peripheral blood collected from sheep experimentally infected with Toxoplasma gondii strain S48 were analysed for parasite DNA by amplification of the B1 and P30 T. gondii genes by the polymerase chain reaction (PCR). The relative sensitivity of these two gene amplification methods was assessed and compared with parasite detection by mouse injection (MI). B1 PCR was consistently more sensitive than P30 PCR and the results agreed closely with those from MI. By contrast, P30 PCR gave more than twice as many false negatives results than B1 PCR. The few apparent false positive results given by either PCR method were probably due to the inability of MI to detect non-viable parasites. All specimens collected before infection with T. gondii gave negative results by PCR and MI. Parasite DNA was detected by both B1 and P30 PCR in the lymph node of a sheep 12 days after infection but not in other tissues. The results permit a direct comparison between T. gondii detection by P30 and B1 PCR. Moreover, they further confirm the value of PCR detection of toxoplasma as a sensitive, specific and reliable diagnostic and research tool.

Waking electroencephalograms (EEG) were recorded from 48 patients infected with Trypanosoma gambiense. The EEG of the 10 patients with blood-lymph involvement were indistinguishable from those of healthy controls but recordings from the 38 patients with the encephalitic phase of the disease showed three unusual profiles. One profile type, apparently indicative of early cerebral impairment, had a sustained low-voltage background similar to that seen during light sleep. A second profile type, seen in cases with acute cerebral involvement but without focal seizures, showed paroxystic waves. The third unusual EEG pattern was of various types of delta wave (similar to those seen in demyelinating encephalitis) and rapid, intermittent high-voltage delta bursts between periods of lower-voltage delta activity (as often seen in meningo-encephalitis); all types of delta wave were of higher voltage than the spike and wave complexes. Although no definite correlation has been established between the severity of the disease, the results of clinical tests, and waking EEG patterns, it appears that the three types of EEG profile are indicative of the degree of cerebral involvement.

Trypanosoma congolense infected tsetse were fed on the flanks of goats at sites drained by the prefemoral lymph node. The efferent lymphatic of this lymph node was surgically cannulated and the lymph was collected daily and examined for appearance of parasites, lymph flow and cells. Trypanosomes were detected in the lymph 4 days after infection, which was 2 days prior to the appearance of the local skin reaction or the presence of parasites in the blood. Once the animal became parasitaemic, trypanosomes were found to recirculate in the lymphatic system, appearing in the lymph of the contralateral lymph node 11 days after infection. In goats infected with T. congolense and superinfected 12 or 13 days later with a different tsetse-transmitted T. congolense serodeme, parasites belonging to the second serodeme were apparently delayed in their development in the skin and appeared up to 7 days later in the efferent lymph when compared to control animals. This delay in development might have implications for field situations where superinfections frequently occur; it might result in limiting the number of serodemes of T. congolense an animal can be infected with at any one time.

Mesenteric lymphadenectomy caused a marked reduction in the amounts of both parasite-specific and total IgE in the serum of Nippostrongylus brasiliensis infested rats. This was accompanied by reduced quantities of IgE in the thoracic duct lymph, showing that the mesenteric lymph node is of great importance in the generation of the elevated IgE levels which accompany this infestation. Conversely, the intestinal lamina propria and the Peyer's patches did not appear to be significant contributors to either thoracic duct lymph or serum IgE levels. Homocytotropic antibody-secreting cells specific for parasite antigens were detected in the thoracic duct lymph of lymphadenectomized rats and are believed to arise directly from the gut mucosa and possibly from Peyer's patches.

During the course of a lethal infection with Theileria parva in susceptible cattle, the dissemination of the parasite was examined in central lymph efferent from superficial lymph nodes in the thoracic duct. From the regional node, lymphocytes containing macroschizonts of T. parva were detected in efferent lymph 8 days after challenge where their appearance coincided with a dramatic increase in the output of lymphoblasts. The number of infected cells reached a maximum around Day 14, when 60-65% of efferent lymphocytes were parasitized. A severe reduction in the total cell output occurred after Day 14, at the time when widespread lymphocytosis was observed in the parent lymph node. A similar pattern of cellular kinetics was observed in the thoracic duct and in lymph efferent from lymph nodes distant from the site of challenge, although in the latter, the parasitosis reached only 10% of total cells. There was no selective depletion of parasitized cells from central lymph during the third week of infection, although the comparative parasitosis between lymph and lymph node cells indicated that infected cells entered central lymph less readily during this period. Macroschizonts appeared in cultures of lymphatic lymphocytes sampled between 5-9 days after challenge. These results, together with the failure of ablation of the regional lymph node 2, 3 or 5 days after challenge to delay the onset of the disease, indicated that dissemination of the infection from the site of challenge occurred within the first 2-3 days after the inoculation T. parva.

Localised skin reactions (chancres) occurred on the flanks of cattle at the sites of deposition by tsetse flies of metacyclic forms of Trypanosoma congolense. Marked enlargement of the draining prefemoral lymph nodes accompanied the development of the skin reactions. Lymph from these nodes was collected through polyethylene cannulae inserted into the efferent lymphatics, and examined for trypanosomes, cells and antibody content. Within 6-9 days after infected tsetse fly bite, trypanosomes were detected in the efferent lymph; this preceded their appearance in the blood by 3-6 days, indicating that the lymphatic system acted as a major route for the passage of trypanosomes from the skin into the bloodstream. Responses induced in the draining lymph node as a result of trypanosome migration included a 2-3-fold increase in the volume of lymph and up to a 10-fold increase in lymphocyte output, including blast lymphocytes and plasma cells. Neutralising antibodies to metacyclic trypanosomes were detected in lymph and serum by Day 14 after infection, although in 2 out of 4 animals investigated, they were not demonstrated in serum until Day 18. Trypanosomes were also found in small numbers in efferent lymph of the prefemoral lymph node on the flank contralateral to the infected tsetse bites after development of parasitaemia. Increases in lymph flow and cellular output occurred about the same time in the ipsilateral and the contralateral efferent lymphatics, but were significantly less in the latter. Homologous challenge of immunised calves with tsetse-transmitted parasites revealed that trypanosomes were eliminated at the level of the skin or within the draining lymph node, as no parasites were detected in efferent lymph.

In group I (15 monkeys) the infection time was less than 70 days with one exception and histologically 14 had trypanosomal pancarditis with morphological evidence of lymph stasis. Trypanosomes served as markers of the dilated cardiac lymphatics seen at apices, atrioventricular junctions, near the His bundle, at the base of cardiac valves and around the root of the aorta and pulmonary artery. 3 hearts had apical aneurysms. In group II (6 monkeys) the infection time exceeded 130 days and despite specific non-arsenical treatment all relapsed. Histologically focal cardiac fibrosis and extravascular trypanosomes within the brain were seen (encephalitis), the latter was absent in group I. The impairment of the cardiac lymph flow is contributory to the development of pericarditis, valvulitis, myocytolysis, apical aneurysm as well as fibrosis, and it may well be a common denominator in the pathogenesis for cardiopathies induced by various pathogenes .

The recirculation of Trichinella spiralis newborn larvae was studied in inbred AO rats. Newborn larvae collected after in vitro incubation of adult T. spiralis worms for 2 or 24 hr were injected into rats through the tail vein or hepatic portal vein. Blood samples from the femoral vein, hepatic portal vein, and abdominal aorta were collected at intervals from 1 min to 24 hr after larval injection. Newborn larvae of both ages (24 hr or 2 hr old) persisted in femoral vein blood for less than or equal to 5 hr after injection, but they could be detected in portal vein blood by 24 hr after injection. The injection of larvae into a tail vein or the portal vein did not influence the pattern of larval circulation, although there was a 1-5 min delay in newborn larval appearance time after injection into the portal vein. Transcapillary migration through tissue and back to the circulation was evident in the appearance of newborn larvae in the thoracic duct lymph up to 24 (occasionally 48) hr after tail vein injection of newborn larvae. During the course of a natural primary infection, no evidence for trapping of larvae in the mesenteric lymph node could be found despite direct larval migration through this organ. Injected newborn larvae were retained in the lungs, and small numbers could be recovered 24 hr after intravenous injection. We conclude that a proportion of newborn larvae recirculates within the vasculature for several hours; a smaller population extravasates but can reenter the circulatory system via the lymphatics. Furthermore, some newborn larvae are found in organs rich in capillaries up to 24 hr after their entry into the blood.

The thoracic lymph duct of rats infected with Trypanosoma brucei and with T. congolense was cannulated at different stages of infection. Trypanosomes were always present in the lymph of rats infected with T. brucei, wheras they were absent or very scarce in the lymph of rats infected with T. congolense. There were greater fluctuations in the numbers of trypanosomes in the blood than in the lymph. The intra- and extravascular populations of T. brucei differed: stumpy forms were present only in blood; dividing forms were usually more numerous in lymph.

The route by which Trichinella spiralis newborn larvae migrate from the small intestine to striated muscle was studied in inbred AO and random-bred Sprague-Dawley rats. Newborn larvae were quantitatively recovered from the thoracic duct lymph, peritoneal cavity, and hepatic portal vein blood during the course of a primary infection with 4000 muscle larvae. The total recovery of newborn larvae assessed in this manner was compared with the number of muscle larvae in control rats receiving the same infection. In both strains of rats, most of the newborn larvae were recovered from hepatic portal vein blood, fewer than 3% of newborn larvae were recovered from the thoracic duct lymph and peritoneal cavity combined. Long-term drainage of thoracic duct lymph (greater than 24 hr) significantly increased newborn larval recovery over short-term drainage (less than 24 hr). We conclude that there are several natural pathways of newborn larval migration that result in muscle larval establishment. These include direct invasion of capillaries and lymphatics in the intestine as well as migration through the intestinal serosa to the peritoneal cavity. In both AO and Sprague-Dawley rats, greater than or equal to 97% of newborn larvae migrate via the hepatic portal vein blood to the general circulation.

The lymph draining the prefemoral lymph node of a sheep infected with Trypanosoma congolense was examined over a period of 10 days. Only six trypanosomes were detected in 1500 ml of this fluid during this time, in spite of the animal having about 65,000 organisms/ml in its blood. It is concluded that the suggestion that T congolense is a strict plasma parasite is essentially proven for this specific situation.

Rates of lymph flow in cats were measured by calculating the disappearance of radioactive colloidal gold (198Au) from the feet of (1) uninfected cats, (2) cats infected for various periods after primary infection with Brugia pahangi, and (3) cats repeatedly challenged with B. pahangi infective larvae over long periods. The results of the study showed that (1) there is great variation in gold disappearance rates in different cats in all 3 groups above, (2) the cat lymphatic system is functionally highly efficient, and (3) in a cat with lymphoedema and early elephantiasis, there was a significant impairment of gold removal from the affected foot. The study proved useful in finding lymph drainage rates in the various animals but did not, as hoped, show any pattern of lymph flow decrease which might have enabled the use of the technique as a diagnostic tool for lymphatic pathology prior to the occurrence of external clinical manifestations of filariasis.