Larval Burden Research Articles

Vaccines against Trichinellaspiralis: Progress, challenges and future prospects.

Trichinellaspiralis, the causative agent of trichinellosis, is able to infect a wide range of carnivores and omnivores including human beings. In the past 30years, a mass of vaccination efforts has been performed to control T.spiralis infection with the purpose of reduction in worm fecundity or decrease in muscle larval and adult burdens. Here, we summarize the development of veterinary vaccines against T.spiralis infection. During recent years, increasing numbers of new vaccine candidates have been developed on the protective immunity against T.spiralis infection in murine model. The vaccine candidates were not only selected from excretory-secretory (ES) antigens, but also from the recombinant functional proteins, such as proteases and some other antigens participated in T.spiralis intracellular processes. However, immunization with a single antigen generally revealed lower protective effects against T.spiralis infection in mice compared to that with the inactivated whole worms or crude extraction and ES productions. Future study of T.spiralis vaccines should focus on evaluation of the protective efficacy of antigens and/or ligands delivered by nanoparticles that could elicit Th2-type immune response on experimental pigs.

Epidemiology of gastrointestinal parasites and impact of two anthelmintic treatment systems in sheep flocks of arid and semi-arid Rajasthan

Comparative epidemiology of gastrointestinal (GI) parasites and economic impact of two anthelmintic treatment systems (conventional and modified) in naturally infected sheep flocks were studied in arid and semi-arid Rajasthan. From April 2004 to March 2016, sheep flocks (376) were evaluated for GI parasites by examining 79311 faecal samples and monitored for performance in two anthelmintic treatment systems. Period from July to mid-September in arid and from early-June to mid-September in semi-arid Rajasthan was found suitable for translation of predominant GI nematode (Haemonchus contortus). The monthly incidence of strongyle nematodes showed almost similar trend among flocks given either modified (1 drench/yr) or conventional (2–3 drenches/yr) anthelmintic treatment. Significantly (P < 0.001) higher pasture larval burden was recorded during July to September in both the regions. Among other GI parasites, only infection with amphistomes was found endemic particularly in semi-arid region. The economic appraisal showed that reduced anthelmintic frequency in modified system as against conventional system had no adverse effect on flock performance. It was concluded that modified anthelmintic intervention provides better opportunities for gainful interaction between epidemiology, weather and management of flocks for worm control and prevent unwanted expenditure incurred by farmer on anthelmintics.

Time- and dose-dependent development of humoral immune responses to Ascaridia galli in experimentally and naturally infected chickens

Factors affecting the development of Ascaridia galli–specific humoral responses and their protective roles are largely unknown. We investigated the effects of time and infection dose on A. galli–specific IgY antibody levels following experimental infection. The acquisition and development of new infections and reinfections were also monitored by using tracer birds. Relationships between the retrospective IgY and the final worm burden of the birds were investigated to determine whether humoral immune responses generated during infection provide protection to the host animal.Young chickens were infected (+) with either 100 or 1000 embryonated eggs of A. galli (100+: n = 45; 1000+: n = 45) or kept as uninfected controls (CON: n = 10). Uninfected birds were also added to each infection group as tracer (T) birds (T100+; n = 5 and T1000+; n = 5). Faecal egg counts and IgY antibody concentrations in plasma and egg yolk were determined at selected intervals. Final worm burdens were quantified at 28 weeks post infection (wpi).The plasma antibody (PAB) and egg yolk antibody (EAB) levels of experimentally infected birds were compared to those of control and tracer birds throughout the study period, and PAB levels were found to depend initially on the infection dose but thereafter mainly on reinfections. Starting at wpi 2, 1000+ had consistently higher PAB levels than CON did (P < 0.05). With exceptions at wpi 0, 2 and 12, PAB levels were also higher (P < 0.05) or tended to be higher (P < 0.10) in 100+ than in CON. An earlier and higher increase was observed in the PAB levels of T1000+ than in those of T100+, implying that (re-)infection occurrence depended on the infection dose. Although 1000+ showed higher (P < 0.05) EAB levels than CON did at both wpi 14 and 18, EAB levels were higher in 100+ than in CON only at wpi 28 (P < 0.05). The total worm burdens in the initial experimentally infected birds were similar (P = 0.257); they were also highly comparable between experimentally and naturally infected birds, indicating that final worm burden was mainly determined by the naturally occurring infections resulting from continuous exposure. When all available information on the retrospective plasma and egg yolk IgY levels was collectively evaluated to estimate the larval or total worm burdens of the experimentally infected birds, both PAB and EAB levels at particular wpi were significantly associated with worm burden, especially with larval count. In conclusion, our data support the hypothesis that the number of larvae, rather than the number of mature worms, affects the antibody levels in both plasma and egg yolk. Despite the increased levels of A. galli–specific antibodies in plasma and egg yolk throughout the study period, only a weak indication was found that antibodies might be directly associated with protection.

Tongue has higher larval burden of Trichinella spp. than diaphragm in wolverines (Gulo gulo)

Trichinella is an important zoonotic parasite found in a range of wildlife species harvested for food and fur in Canada. We compared larval intensity from tongue and diaphragm, the best predilection sites in other animal species, from naturally infected, wild wolverines (Gulo gulo) (n = 95). Muscle larvae of Trichinella spp. were recovered by the pepsin/HCl artificial digestion method (gold standard) using double separatory funnels, and species were identified using multiplex PCR. Prevalence was 83% (79/95). Of those positive for Trichinella spp. (n = 79), 76 (96.2%) were detected in both tissues, 2 (2.5%) were positive only on diaphragm, and 1 (1.3%) only on tongue. A total of 62 of 79 wolverines (78.5%) had higher larval burden in tongue than in diaphragm, whereas 17 wolverines (21.5%) had higher larval burden in diaphragm. The predilection site (higher larval burden) of Trichinella spp. larvae did not vary significantly between juvenile and adult wolverines (P = 0.2), between male and female wolverines (P = 0.9), and among wolverines classified as having low and high larval intensities overall (P = 0.2). Trichinella T6 was the predominant genotype (63 of 79; 80%), followed by T. nativa (T2) (6 of 79; 8%). Mixed infections of T2 and T6 were observed in 9 of 79 (12%) wolverines. Larval intensity of Trichinella T6 was higher in tongues than diaphragms. No statement can be made for T2 due to insufficient T2 positive samples. In conclusion, tongues are a better site for sampling than diaphragms in future surveys of Trichinella larval intensity in wolverines; however, either tissue is suitable for prevalence studies.

Clinicohistopathological And Immunological Alterations in Egyptian Donkeys Infested by Rhinoestrus Spp. During the Winter Season

Little information is available about the homeostasis and alterations appeared against infestation by nasal myiasis caused by Rhinoestrus spp. larvae in Egyptian donkeys. Therefore, the present work aimed to investigate the hematological and biochemical profiles associated with histopathological features and immunological response developed against Rhinoestrus spp. larvae infestation in donkeys in the winter season. The results revealed that 40 out of 80 examined donkeys were infested by nasal myiasis. IgG values were higher (P< 0.01) in infested donkeys (IND) than non-infested ones all over the winter months while the highest mean larval burden was observed in December (11.6 larvae/animal). Neutrophils% in (IND) increased (P<0.01) during December and February. However, an elevation in lymphocytes% (P<0.05) was observed in (IND) during December and January while eosinophils% increased (P<0.01) in all winter months. These results paralleled to the nasal fluid cytological profile in which lymphocytes%, neutrophils% and eosinophils% in (IND) increased (P< 0.05) in December, January and February. Glutathione peroxidase, superoxide dismutase and catalase activities in (IND) were declined (P<0.01) in all winter months. Interleukin-2 (IL-2) and tumor necrosis factor- α (TNF-α) elevated (P<0.05) in December and January. The histopathological picture of turbinate bones, olfactory bulb and meninges reflected the blood and nasal fluid cytological picture as there was lymphocytes infiltration, meningitis and satellitosis. The results indicated that Rhinoestrus spp. infestation in donkeys might affect the vital and immunological processes. In addition, Rhinoestrus spp. infestation in donkeys could linked to oxidative stress and shifting the immune response polarization towards Th2 cytokines.

A novel antigenic cathepsin B protease induces protective immunity in Trichinella-infected mice

Trichinellosis is a foodborne disease that remains a public health hazard and an economic problem in food safety. Vaccines against the parasite can be an effective way to control this disease; however, commercial vaccines against Trichinella infection are not yet available. Trichinella cathepsin B proteins appear to be promising targets for vaccine development. Here, we reported for the first time the characterization of a novel cDNA that encodes Trichinella spiralis (T. spiralis) cathepsin B-like protease 2 gene (TsCPB2). The recombinant mature TsCPB2 protein was successfully expressed in E. coli system and purified with Ni-affinity chromatography. TsCPB2 expression was detected at all the developmental stages of T. spiralis and it was expressed as an excretory–secretory protein of T. spiralis muscle larvae. Immunization with TsCPB2 antigen induced a combination of humoral and cellular immune responses, which manifested as a mixed Th1/Th2 response, as well as remarkably elevated IgE level. Moreover, vaccination of mice with TsCPB2 that were subsequently challenged with T. spiralis larvae resulted in a 52.3% (P < .001) reduction in worm burden and a 51.2% (P < .001) reduction in muscle larval burden. Our results suggest that TsCPB2 induces protective immunity in Trichinella-infected mice and might be a novel vaccine candidate against trichinellosis.

Trichinella spp. biomass has increased in raccoon dogs (Nyctereutes procyonoides) and red foxes (Vulpes vulpes) in Estonia

BackgroundRaccoon dogs and red foxes are well-adapted hosts for Trichinella spp. The aims of this study were to estimate Trichinella infection prevalence and biomass and to investigate which Trichinella species circulated in these indicator hosts in Estonia.MethodsFrom material collected for evaluating the effectiveness of oral vaccination program for rabies eradication in wildlife, samples from 113 raccoon dogs and 87 red foxes were included in this study. From each animal, 20 g of masseter muscle tissue was tested for the presence of Trichinella larvae using an artificial digestion method. The Trichinella larvae were identified to species level by multiplex polymerase chain reaction method.ResultsThe majority of tested animals were infected with Trichinella spp. The parasite species identified were T. nativa and T. britovi. The apparent infection prevalence was 57.5% in raccoon dogs and 69.0% in red foxes, which were higher than previous estimates. In addition, the larval burden had also increased in both hosts. We estimated that in 2011–2012, the Trichinella spp. biomass was more than 15 times higher in raccoon dogs and almost two times higher in red foxes than in 1992–2000 (based on mean larval burden), and almost 20 times higher in raccoon dogs and almost five times higher in red foxes than in 2000–2002 (based on median larval burden).ConclusionsRaccoon dogs and red foxes are relevant reservoirs for Trichinella spp. in Estonia. The biomass of Trichinella circulating in sylvatic cycles was substantial and had increased: there is substantial infection pressure in the sylvatic cycle.

Prevalence and intensity of Oestrus ovis in sheep and goats in south-eastern part of Turkey

Oestrosis is a parasitic disease which is prevalent among sheep and goats in Mediterranean region. Slaughter house surveys to determine the prevalence and intensity of infestation by Oestrus ovis Linnaeus (Diptera: Oestridae) in sheep and goats, were conducted monthly for one year in south-eastern region of Turkey. A total of 804 heads belonging to 724 sheep and 80 goats were examined for Oestrus ovis larvae between May 2014 and April 2015. 72.75% of sheep heads and 50% of goat heads were seen to be infested with Oestrus ovis larvae. Of a total of 4723 larvae found in sheep heads, 2245 were detected to be first instars larva, 1231 second instars larva, 1247 third instars larva. Of a total of 259 larvae detected in goats, 150 were first instars larva, 79 second instars larva, 30 third instars larva. The mean of larval burden per infested animal was significantly higher in sheep (8.8±5.9) than in goat (6.5±5.0) (P less than 0.05). Monthly distribution of first, second and third instars larvae indicate that adult flies are active between April and end of September, first instars larvae enter hypobiotic period in October. In conclusion, it was revealed that to use an effective drug against Oestrus ovis that will be done during reproductive period of flies should start in April and continue until the end of summer due to high rates of oestrosis, parasite treatment that will be done when reproductive period ends should be done in October and November in the southeast part of Turkey.

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OBJECTIVES/SPECIFIC AIMS: Trichuris trichiura, is a leading cause of chronic colitis worldwide, resulting in growth stunting, anemia, and cognitive deficits, predominately in children. Our long-term goal is to develop a vaccine against T. trichiura. Both T. trichiura and the closely related Trichuris muris release excretory/secretory (ES) macromolecules from the stichosome organ, which facilitates intracellular invasion into the cecum. We exploited the high degree of genetic sequence homology between T. trichiura and T. muris to evaluate T. muris stichosome proteins as vaccine candidates. METHODS/STUDY POPULATION: Through immunological screening of the T. muris stichosome cDNA library and T. muris ES macromolecules generated in culture, we identified, cloned, and expressed several vaccine candidates. In ranking these antigens, we selected the most promising recombinant proteins, WAP and CAP-1, and vaccinated AKR mice to evaluate the immunogenicity and efficacy of our candidate. In addition, we collected 240 serum samples in the T. trichiura endemic region of Honduras to measure the recognition of WAP and CAP-1 in naturally infected human. RESULTS/ANTICIPATED RESULTS: We measured a statistically significant reduction in larval worm burden in WAP and ES vaccinated mice, but not CAP-1, by microscopy and real-time PCR of T. muris DNA. We found a significant relationship between antigen-specific IgG1:IgG2a ratio in the mouse serum and degree of protection. Mouse splenocytes, vaccine-sensitized draining lymph nodes, and mesenteric lymph nodes were antigen-stimulated and their secreted Th1, Th2, and Th17 cytokines were measured by Luminex®. Stimulated mouse lymphoid cells were further analysed for T helper, T cytotoxic, and central/effector memory T cells by Flow Cytometry. Human IgG1, IgG2, and IgE antibody titers against WAP and CAP-1 were measured by ELISA. DISCUSSION/SIGNIFICANCE OF IMPACT: In our study, we describe the T cell dependent mechanism of humoral immunity of 2 promising ES-derived vaccines recombinant proteins, WAP and CAP-1. We evaluated the immune response, indicating a driving a Th2-induced humoral response necessary for protection. We further predict protection and allergenicity of WAP in humans using serum from a cohort in an T. trichiura endemic region.

Trichinella spiralis a new alien parasite in Italy and the increased risk of infection for domestic and wild swine

In Europe, Trichinella spiralis, the most dangerous species for humans of the genus Trichinella, has a patchy distribution with important foci in Eastern countries and Spain. This zoonotic pathogen was apparently not circulating among wild and domestic animals of Italy. In 2016, muscle larvae belonging to this nematode species were detected in a red fox (Vulpes vulpes) shot in the Piacenza province (Northern Italy). This parasite may have been introduced into northern Italy from eastern Europe by hunters, by a hunting dog, or by immigrants, who illegally carried infected meat in their personal baggage. In the same year, T. spiralis infected sausages illegally introduced by personal baggage into Italy from Romania, were inadequately disposed of in the garbage of a central Italian town. Even though these two episodes may not be connected in time and space, they represent an increased risk of infection for domestic and wild swine, which are highly susceptible to this pathogen. In these animals, T. spiralis shows a higher larval burden and a longer survival time than other Trichinella species. Since most of the Italian pig production plants are in northern Italy, the circulation of T. spiralis should be strictly monitored in wildlife living in these areas.

Cascading effects of predator activity on tick-borne disease risk.

Predators and competitors of vertebrates can in theory reduce the density of infected nymphs (DIN)—an often-used measure of tick-borne disease risk—by lowering the density of reservoir-competent hosts and/or the tick burden on reservoir-competent hosts. We investigated this possible indirect effect of predators by comparing data from 20 forest plots across the Netherlands that varied in predator abundance. In each plot, we measured the density of questing Ixodes ricinus nymphs (DON), DIN for three pathogens, rodent density, the tick burden on rodents and the activity of mammalian predators. We analysed whether rodent density and tick burden on rodents were correlated with predator activity, and how rodent density and tick burden predicted DON and DIN for the three pathogens. We found that larval burden on two rodent species decreased with activity of two predator species, while DON and DIN for all three pathogens increased with larval burden on rodents, as predicted. Path analyses supported an indirect negative correlation of activity of both predator species with DON and DIN. Our results suggest that predators can indeed lower the number of ticks feeding on reservoir-competent hosts, which implies that changes in predator abundance may have cascading effects on tick-borne disease risk.

Oral contraceptive pills: Risky or protective in case of Trichinella spiralis infection?

The aim of this study was to investigate how Trichinella spiralis infection can be affected by contraceptive pills in vivo. Methods included six groups of female Wistar rats; healthy, Trichinella infected, receiving combined contraceptive pills (COCPs), receiving progestin only pills (POPs), infected receiving COCPs and infected receiving POPs. Parasite burden was measured; adult worm counts, gravidity, larvae and reproductive capacity index). Histopathological examination, immunohistochemical detection of C-kit+ mast cells and Foxp3+ T-reg. cells in intestinal sections, eosinophils muscle infiltration and CPK level were performed. Rats infected and receiving COCPs showed a significant increase in parasitic burden, and infected receiving POPs showed a significant reduction compared to infected only, with a significant increase in nongravid females (Mean total worms=964.40±55.9, 742±52.63, 686±31.68, larvae/g=5030±198.75, 2490±143.18 and 4126±152,91, respectively). Intestinal sections from infected receiving COCPs showed intact mucosa (though the high inflammatory cells infiltrate), and significant increase in C-kit+ mast cells number and intensity (30.20±4.15 and 60.40±8.29), and Foxp3+ T-reg. cells (10±1.58). Infected receiving POPs showed a significantly less CPK (5886±574.40) and eosinophilic muscle infiltration (58±13.51). Oestrogen-containing pills established a favourable intestinal environment for Trichinella by enhancing Foxp+T-reg. cells and stabilizing C-kit+mast cells, while POPs gave a potential protection with less gravidity, larval burden and eosinophilic infiltrate.

Repeated inoculations with the lung and heartworm nematode Angiostrongylus vasorum result in increasing larval excretion and worm burden in the red fox (Vulpes vulpes).

The French heartworm Angiostongylus vasorum is found in European red fox (Vulpes vulpes) and dog populations, where it appears to be spreading geographically. Once introduced into new areas, it establishes in local fox populations, typically to over 50% prevalence in a few years. High susceptibility and constant excretion of first stage larvae (L1) by the definitive hosts are prerequisites for sustaining high parasite biomass in a particular habitat. The present study explores the hypothesis that repeated ingestion of gastropods in nature will result in accumulation of adult worms and elevated excretion of L1 in feces. Experimentally infected foxes were subsequently inoculated via stomach tube once (9 weeks post initial inoculation) or twice (9 and 13 weeks post inoculation (wpi)) with 100 third stage A. vasorum larvae (L3) previously isolated from aquatic snails infected with L1 from a naturally infected dog. Despite large variation in fecal larval excretion for the individual animals within the groups, excretion of L1 was significantly higher in foxes twice inoculated as compared to foxes inoculated only once. With an outlier in the once inoculated group removed, excretion became significantly higher in the three times inoculated group. Establishment of adult worms varied and only a trend to higher worm burdens was found in the group of foxes inoculated three times. However, this became significant with the same single outlier removed. Overall, it appears that protective immunity to A. vasorum does not appear to occur in V. vulpes with animals exhibiting high infection intensities without obvious clinical signs. The increasing larval excretion in foxes being repeatedly exposed to A. vasorum L3 support the hypothesis that foxes under natural conditions may repeatedly ingest infected gastropods and remain a source of environmental contamination for several months, potentially contributing to the establishment of endemic foci through increasing L1 excretion.

Studies on vertical transmission of Trichinella spiralis in experimentally infected guinea pigs (Cavia porcellus).

An experimental study to enhance knowledge on the capability of Trichenella spiralis to pass from guinea pigs to progeny at different periods of pregnancy or lactation was performed. For this purpose, 18 female adult guinea pigs were inoculated with 100 or 1000 T. spiralis muscle larvae (ML) during early, late gestation and during lactation period. The presence of T. spiralis (ML) in mothers and newborns was studied through enzymatic digestion from muscle samples. ML were observed in 9 of 42 newborn guinea pigs and levels of infection were significantly higher when infections of mothers were done during late gestation (p=0.0046) with the high infective dose (p=0.0043). T. spiralis ML were not recovered from any of the newborns from mothers infected in the lactation period. Ten out of 18 infected mothers presented larvae 1 in their mammary glands. Muscle samples from the tongue and the masseter showed the highest larval burdens. These observations confirm previous reports on that ML of T. spiralis are capable to pass through placental tissues to reach and encyst in striated muscle groups of newborn guinea pigs. This study may also reinforce the importance of preventive programs to control trichinellosis in those endemic areas where pregnant women would have high risk of infection.

Trichinella and polar bears: a limited risk for humans.

In this review, we identified 63 cases reported since World War II of human trichinellosis linked to the consumption of parasitized polar bear (Ursus maritimus) meat. This low number contrasts to the numerous cases of human trichinellosis related to consumption of the meat of black (U. americanus) or brown bears (U. arctos). The prevalence of Trichinella infection is high in bears, but larval muscular burden is usually lower in polar bears compared to other bear species. Polar bears, therefore, seem to play a limited role in the transmission of trichinellosis to humans, as native residents living in the Arctic traditionally consume well-cooked bear meat, and travellers and foreign hunters have only limited access to this protected species due to the declining polar bear population.

Comparison of targeted selective and whole flock treatment of periparturient ewes for controlling Haemonchus sp. on sheep farms in Ontario, Canada

Haemonchosis is commonly associated with late gestation and parturition in ewes during the spring in Ontario, Canada. Due to widespread anthelmintic resistance, targeted selective treatment (TST) of ewes with closantel, an anthelmintic not previously available in Canada, at lambing was investigated as a potential strategy to manage haemonchosis in both ewes and lambs, while also maintaining parasite refugia (i.e., a population of parasites not exposed to anthelmintic). In a longitudinal pilot study in 2013 and 2014, six client-owned farms were randomly assigned as either whole treatment (WT) farms (n=3), where all the ewes were treated with oral closantel (10mg/kg) at lambing, or TST farms (n=3), where ewes were treated with oral closantel (10mg/kg) at lambing only if they met at least one of four criteria: a) the last grazing season was their first grazing season; b) body condition score ≤2; c) FAMACHA© score ≥4; and/or d) three or more nursing lambs. Pasture samples to assess larval burdens and fecal samples from a minimum of 20 ewes and 20 lambs on every farm were collected monthly during the grazing season (May-October). Additional anthelmintic treatments given by producers (either fenbendazole or ivermectin) and deaths attributable to parasitism were also recorded. Pre-treatment arithmetic mean Haemonchus sp. fecal egg counts (FECs) on each farm at the beginning of the study in May 2013, ranged from 506 to 2738 eggs per gram of feces. The number of animals treated on TST farms was reduced by as much as 47% compared to WT farms, and there was no significant difference between TST and WT farms in the proportion of additional treatments given by producers throughout the grazing season or the percentage of parasitism deaths reported. In the first year of the study, Haemonchus sp. larval burdens on pasture were generally higher on TST than WT farms at the beginning of the grazing season, but were not significantly different at the end of the grazing season. In the second year, there were no significant differences in Haemonchus sp. larval burdens on pasture between TST and WT farms throughout the grazing season. This study suggests that, under Ontario conditions, when TST indicators are able to accurately identify animals with high Haemonchus sp. FECs, TST of ewes at lambing can be employed to control Haemonchus sp. FEC in the flock, thereby maintaining refugia and delaying the onset of anthelmintic resistance.

Gastrointestinal nematode larvae in the grazing land of cattle in Guwahati, Assam.

Aim:To know the prevalence of gastrointestinal nematode larvae (L3) in the grazing land of cattle in Guwahati, Kamrup district, Assam.Materials and Methods:Pastures were collected and examined for the presence of nematode larvae (L3) from six localities of Guwahati at monthly interval from August 2012 to July 2013. The counted larvae were then expressed as per kg dry matter of herbage (L3/kg DM).Results:Examination of pastures revealed presence of nematode larvae (L3) in pastures throughout the year which varied from 4.5 L3/kg DM in January to a maximum of 106.33 L3/kg DM in August. The L3 of Haemonchus contortus, Trichostrongylus spp., Oesophagostomum spp., Cooperia spp., and Mecistocirrus spp. were recovered from pastures. The average pasture larval burden (PLB) was 34.75±3.48 L3/kg DM. Season-wise PLB revealed the presence of 23.89±3.01, 67.54±5.41, 26.67±1.92, and 7.28±0.89 L3/kg DM during pre-monsoon, monsoon, post-monsoon, and winter seasons, respectively. Monsoon season has significant (p<0.05) effect on PLB. However, analysis of variance of different locations with respect to season revealed that there was no significant difference but season-wise it was highly significant (p<0.01). Pearson correlation of environmental variables (temperature, relative humidity, and rainfall) with PLB revealed correlation was statistically significant with rainfall (p<0.05).Conclusion:This study reveals the presence of five nematode larvae (L3) in the pastures of Guwahati, Assam throughout the year, statistically significant during monsoon season.

First Report of the Occurrence of Trichinella-Specific Antibodies in Domestic Pigs in Central and Eastern Uganda.

Previous research on trichinellosis in Africa focused on isolating Trichinella from wildlife while the role of domestic pigs has remained highly under-researched. Pig keeping in Uganda is historically recent, and evidence on zoonotic pig diseases, including infection with Trichinella species, is scarce. A cross-sectional survey on Trichinella seroprevalence in pigs was conducted in three districts in Central and Eastern Uganda from April 2013 to January 2015. Serum from a random sample of 1125 pigs from 22 villages in Eastern and Central Uganda was examined to detect immunoglobulin G (IgG) against any Trichinella spp. using a commercially available ELISA based on excretory-secretory antigen. ELISA positive samples were confirmed using Western Blot based on somatic antigen of Trichinella spiralis as recommended in previous validation studies. Diaphragm pillar muscle samples (at least 5 g each) of 499 pigs from areas with high ELISA positivity were examined using the artificial digestion method. Overall, 78 of all 1125 animals (6.9%, 95% CI: 5.6–8.6%) tested positive for antibodies against Trichinella spp. in the ELISA at significantly higher levels in Kamuli district compared to Masaka and Mukono districts. Thirty-one percent of the ELISA positive samples were confirmed IgG positive by the Western Blot leading to an overall seroprevalence of 2.1% (95% CI: 1.4–3.2%). The large proportion of ELISA positive samples that could not be confirmed using Western blot may be the result of cross-reactivity with other gastrointestinal helminth infections or unknown host-specific immune response mechanisms in local pig breeds in Uganda. Attempts to isolate muscle larvae for species determination using the artificial digestion method were unsuccessful. Due to the large number of muscle samples examined we are confident that even if pigs are infected, the larval burden in pork is too low to pose a major risk to consumers of developing trichinellosis. This was the first large systematic field investigation of Trichinella infection in domestic pigs in Uganda and its results imply that further studies are needed to identify the Trichinella species involved, and to identify potential sources of infection for humans.

The larval development of Habronema muscae (Nematoda: Habronematidae) affects its intermediate host, Musca domestica (Diptera: Muscidae).

Although the life cycle of the equid stomach parasite Habronema muscae was disclosed more than 100years ago, little is known about the effect of the developing nematode larvae in its intermediate host, Musca domestica. In a series of experiments, freshly hatched M. domestica larvae were exposed to H. muscae eggs contained in a faecal sample of a naturally infected horse. In daily intervals, 50 fly larvae were removed and transferred on a parasite-free larval rearing medium where they completed their development. Hatched flies were examined for the presence of Habronema third-stage larvae. In two subsequent control groups, flies spend their entire larval life in contaminated horse faeces and in a parasite-free larval rearing medium, respectively. Out of the 700 fly larvae used in the infection experiments, 304 developed into adult flies of which 281 were infected. The average nematode larval burden rose from 3.6 in the group with the shortest exposure to more than 25 in the groups with the longest exposure. The proportion of larvae that developed into the adult insect fell from 82 % in the uninfected control group to 27 % in the positive control group. The pupae of the positive control group were smaller and lighter than those of the uninfected control group. Lower pupal size and weight in the positive control group as well as a lower insect developing rate might be attributed to the destruction of adipose cells in the maggots by Habronema larvae.

ABorrelia afzeliiInfection Increases Larval Tick Burden onMyodes glareolus(Rodentia: Cricetidae) and Nymphal Body Weight ofIxodes ricinus(Acari: Ixodidae)

Several microorganisms have been shown to manipulate their host or vector to enhance their own transmission. Here we examined whether an infection with Borrelia afzelii affects its transmission between its bank vole (Myodes glareolus, Schreber, 1780) host and tick vector. Captive-bred bank voles were inoculated with B. afzelii or control medium, after which host preference of Ixodes ricinus L. nymphs was determined in a Y-tube olfactometer. Thereafter, infected and uninfected bank voles were placed in a semifield arena containing questing larvae to measure larval tick attachment. Engorged larvae were collected from these bank voles, molted into nymphs, weighed, and analyzed for infection by PCR.Nymphs were attracted to the odors of a bank vole compared to ambient air and preferred the odors of an infected bank vole over that of an uninfected bank vole. In the semifield arena, infected male bank voles had greater larval tick burdens then uninfected males, while similar larval tick burdens were observed on females regardless of infection status. Nymphal ticks that acquired a B. afzelii infection had higher body weight than nymphs that did not acquire an infection regardless of the infection status of the vole. These results show that a B. afzelii infection in bank voles increases larval tick burden and that a B. afzelii infection in larvae increases nymphal body weight. This finding provides novel ecological insights into the enzootic cycle of B. afzelii.