Familial aggregation of human susceptibility to co- and multiple helminth infections in a population from the Poyang Lake region, China

Human helminthiases are common in China, especially in rural areas where sanitation conditions are poor. Co- and multiple infections with helminths are strikingly frequent. A cross-sectional parasitological and questionnaire survey was carried out in a population of 3205 individuals belonging to 498 families from five villages in the Poyang Lake region, Jiangxi Province, China, to assess their helminth infection status and to collect information on risk factors for infection. The prevalences for Ascaris lumbricoides, Schistosoma japonicum and Trichuris trichiura were 30.9%, 15.7% and 47%, respectively. Hookworm infection prevalence was low (0.7%). A significant association was observed between A. lumbricoides and T. trichiura infection, and also between S. japonicum and T. trichiura infection. Variance components analysis was undertaken to investigate the aggregation of S. japonicum and the soil-transmitted helminths, A. lumbricoides and T. trichiura. While A. lumbricoides was found to aggregate only at a household level, T. trichiura was shown to cluster predominantly in families. Both genetic and household effects were found to be important in determining the risk of infection with S. japonicum. Variance components analysis for A. lumbricoides/T. trichiura co-infections indicated a significant domestic environmental effect, attributable for 32.7% of the co-infection risk. Aggregation of S. japonicum/T. trichiura co-infection was also observed at a household level. The risk of infection with multiple helminth species, although mainly environmentally influenced, was also shown to have significant involvement of genetic and household components. The results of this study indicate that a shared household is a major contributing risk factor for helminth co-infections and emphasises the need for increased standards of sanitation and hygiene to prevent parasite transmission. Further, the results suggest that susceptibility to one helminth infection is not completely independent of another, and that there exist common genetic factors underlying infection with multiple helminth species.     

Comparison of the Kato-Katz and FLOTAC techniques for the diagnosis of soil-transmitted helminth infections

Decisions on individual or community treatment and evaluation of chemotherapy based control programs depend on parasitological diagnostic techniques. The aim of this study was to compare the accuracy of a single Kato-Katz thick smear and a single FLOTAC for the determination of the prevalence and intensity of soil-transmitted helminth infections. A total of 271 faecal specimens were collected from schoolchildren in Ethiopia, and microscopically examined using the Kato-Katz method (41.7 mg stool per slide) and the FLOTAC technique. The combined results from the Kato-Katz and FLOTAC methods were used as diagnostic 'gold' standard for reference in the analysis. Agreement between the two methods showed kappa values of 0.74, 0.73 and 0.28 for Ascaris lumbricoides, Trichuris trichiura and hookworm, respectively. A single FLOTAC revealed significantly more infections than a single Kato-Katz for each of the three soil-transmitted helminths (p<0.01). The sensitivities of a single Kato-Katz for diagnosis of T. trichiura, A. lumbricoides and hookworm infections were 76.6%, 67.8% and 19.6%, respectively, while the sensitivity of FLOTAC was 100% for all the three soil-transmitted helminth species. A single Kato-Katz yielded considerably higher mean faecal egg counts (FECs) (729.1, 145.2 and 60.7 eggs per gram of stool (EPG) for A. lumbricoides, T. trichiura and hookworm, respectively) compared with a single FLOTAC (142.5, 54.5 and 14.6 EPG, respectively) (p<0.05). Our study confirms that a single FLOTAC is more sensitive than a single Kato-Katz for the diagnosis of soil-transmitted helminth infections, but results in lower FECs. Further standardization and validation are still required in different epidemiological settings with varying levels of intensity of infections before recommending FLOTAC for large-scale community diagnosis.     

Intestinal helminthiases and schistosomiasis among school children in an urban center and some rural communities in southwest Nigeria

Intestinal helminths and schistosomiasis among school children were investigated in an urban and some rural communities of Ogun State, southwest Nigeria. Fecal samples of 1,059 subjects (524 males, 535 females) aged 3-18 years were examined using direct smear and brine concentration methods between June 2005 and November 2006. The pooled prevalence of infection was 66.2%. Ascaris lumbricoides showed the highest prevalence (53.4%) (P < 0.001) followed by hookworms (17.8%), Trichuris trichiura (10.4%), Taenia sp. (9.6%), Schistosoma mansoni (2.3%), Strongyloides stercoralis (0.7%), Schistosoma haematobium (0.6%), and Enterobius vermicularis (0.3%). The prevalences of A. lumbricoides, hookworms, Taenia sp., S. mansoni, and S. stercoralis in the urban centre were similar (P > 0.05) to those in the rural communities. The fertile and infertile egg ratios of A. lumbricoides in the urban centre and the rural communities were 13: 1 and 3.7: 1, respectively. Each helminth had similar prevalences among both genders (P > 0.05). The prevalence of A. lumbricoides increased significantly with age (P < 0.001). The commonest double infections were Ascaris and hookworms, while the commonest triple infections were Ascaris, hookworms, and Trichuris. The study demonstrates the need for urgent intervention programmes against intestinal helminthiases and schistosomiasis in the study area.     

Immunity acquired by sheep from an experimental infection with haemonchus contortus

Adams D.B. and Beh K.J. 1981. Immunity acquired by sheep from an experimental infection with Haemonchus contortus. International Journal for Parasitology11: 381–386. A primary infection of sheep with a single dose of Haemonchus contortus larvae was traced by faecal egg counts until it had substantially declined after 55 weeks. These primed sheep were then given a sequence of two reinfections with the parasite. Comparison of faecal egg counts in primed sheep and in two separate groups of previously worm-free sheep showed that primary infection conferred significant immunity. This, however, was not sufficiently protective to prevent the development of further anaemia and faecal egg counts indicative of clinical haemonchosis. It is suggested that an adaptation in the host-parasite relationship which promotes the longevity of primary infection with H. contortus may also moderate the induction of acquired immunity.The titre of haemagglutinating antibody specific for H. contortus rose in serum during the course of primary infection, but the two reinfections did not stimulate a rise in titre. Titres of haemagglutinating antibody before reinfection did not correlate with subsequent faecal egg counts.     

A comparative study of different albendazole and mebendazole regimens for the treatment of intestinal infections in school children of Usigu Division, western Kenya

A clinical trial to compare the effectiveness of 4- and 6-mo repeated treatment with albendazole 600 mg (Zentel, SmithKline Beecham) or mebendazole 600 mg (Vermox, Janssen) on geohelminth infections was carried out on children in 6 primary schools; the study included 1,186 children, ages 4 to 19 yr. Kato-Katz examination was performed on stool samples before and after treatment. Overall, albendazole produced better cure rates and egg reduction rates for geohelminths. The cure rates for albendazole were 92.4% for hookworm infection, 83.5% for Ascaris lumbricoides, and 67.8% for Trichuris trichiura. Mebendazole given either 2 or 3 times in a year had cure rates of 50 and 55.0% (respectively) for hookworm, 79.6 and 97.5% for A. lumbricoides, and 60.6 and 68.3% for T. trichiura infection. The geometric mean intensity of hookworm eggs per gram (epg) of stool decreased by 96.7% after albendazole treatment compared with 66.3 and 85.1%, respectively, for 2 or 3 doses of mebendazole (P < 0.05) over the same period. Reductions in epg for A. lumbricoides and T. trichiura were comparable for both drugs. Our results indicate that treatment with albendazole at a 6-mo interval was more effective than mebendazole regimens and may be the best choice for use in the control of the 3 geohelminths.     

Human helminth co-infection: No evidence of common genetic control of hookworm and Schistosoma mansoni infection intensity in a Brazilian community

Strong statistical associations between soil-transmitted helminths and schistosomes are frequently observed in co-endemic human populations, although the underlying explanations remain poorly understood. This study investigates the contribution of host genetics and domestic environment to hookworm and Schistosoma mansoni infection intensity and evaluates the role of genetic and non-genetic factors in co-variation of infection intensity. Detailed genealogical information allowed assignment of 1303 individuals living in the Brazilian community of Americaninhas, Minas Gerais state, to 25 pedigrees (containing between two and 1159 members) residing in 303 households. The prevalence of co-infection with both hookworms and schistosomes was high (38.5%), with significant correlation between Necator americanus and S. mansoni faecal egg counts. Bivariate variance component analysis demonstrated a modest but significant species-specific heritability for intensity of N. americanus (h² = 0.196) and S. mansoni infection (h² = 0.230). However, after accounting for demographic, socio-economic and household risk factors, no evidence for common genetic control of intensity of hookworm and schistosome infection was observed. There was some evidence for residual clustering within households but the majority (63%) of the covariance between N. americanus and S. mansoni infection intensity remained specific to the individual and could not be explained by shared genes, shared environment or other shared demographic, socio-economic or environmental risk factors. Our results emphasize the importance of exposure to hookworm and schistosome infection in driving the association between levels of infection with these species in hosts resident in areas of high transmission and suggest that much of this common exposure occurs outside the home.     

Trichuris vulpis (Froelich, 1789) infection in a child: a case report

We present a human infection with the canine whipworm, Trichuris vulpis, in a child suffering from rhinitis with a diagnosis of rhinitis. T. vulpis eggs resemble those of T. trichiura but they can be differentiated based on their morphological features and egg size, using micrometry with an ocular micrometer. T. vulpis eggs measured an average of 90 μm by 44 μm (range 86-99 μm by 38-47 μm). Prevalence of hookworms (28.1%), Toxocara canis (11.8%), and Trichuris vulpis (3.5%) was found in 292 fecal samples of dogs collected at the peri-domicile, which showed that the risk of infection was not only fortuitous. The treatment of canine whipworm infections is similar to that of T. trichiura infection. We recommend differentiation of the 2 species for their epidemiological and prevention implications.     

Prevalence and intensity of infections of Ascaris lumbricoides and Trichuris trichiura and associated socio-demographic variables in four rural Honduran communities

Between January and March 1998, a cross-sectional survey was carried out in four rural communities in Honduras, Central America. We examined the prevalence and intensity of Ascaris lumbricoides and Trichuris trichiura infections among 240 fecal specimens, and the association between selected socio-demographic variables and infection for 62 households. The overall prevalence of A. lumbricoides and T. trichiura was 45% (95% CI 39.0-51.9) and 38% (95% CI 31.8-44.4) respectively. The most intense infections for Ascaris and Trichuris were found in children aged 2-12 years old. By univariate analysis variables associated with infections of A. lumbricoides were: number of children 2-5 years old (p=0.001), level of formal education of respondents (p=0.01), reported site of defecation of children in households (p=0.02), households with children who had a recent history of diarrhea (p=0.002), and the location of households (p=0.03). Variables associated with both A. lumbricoides and T. trichiura infection included: number of children 6-14 years old (p=0.01, p=0.04, respectively), ownership of a latrine (p=0.04, p=0.03, respectively) and coinfection with either helminth (p=0.001, p=0.001, respectively). By multivariate analysis the number of children 2-5 years living in the household, (p=0.01, odds ratio (OR)=22.2), children with a recent history of diarrhea (p=0.0, OR=39.8), and infection of household members with T. trichiura (p=0.02, OR=16.0) were associated with A. lumbricoides infection. The number of children 6-14 years old in the household was associated with both A. lumbricoides and T. trichiura infection (p=0.04, p=0.01, OR=19.2, OR=5.2, respectively).     

Prevalence and Associated Risk Factors of Toxocara vitulorum Infections in Buffalo and Cattle Calves in Three Provinces of Central Cambodia

The prevalence and associated risk factors of Toxocara vitulorum infection in buffalo and cattle calves was studied in 3 provinces in central Cambodia. Fecal samples were collected from 517 calves between the age of 1-15 weeks and processed for nematode egg counts by a modified McMaster method. A total of 64 calves were found to excrete T. vitulorum eggs in their feces (12.4%; 95% exact CI: 9.7-15.5). The mean fecal egg count was 2,798 EPG (SD=16,351; range=0-224,400). A multivariable generalized linear mixed model showed higher odds of T. vitulorum infection for buffalo versus cattle, for animals aged 4-8 weeks versus younger and older ones, and for animals with strongyle infection. There was no association with fecal consistency. Farmers should be aware of the potential impact of T. vitulorum, and treat their calves at the age of 2-3 weeks with anthelmintics such as benzimidazoles or pyrantel.     

The effects of host age and superparasitism by the parasitoid, Microplitis rufiventris on the cellular and humoral immune response of Spodoptera littoralis larvae

To study the dynamics of stage-dependent immune responses in Spodoptera littoralis (Boisd.) larvae (Lepidoptera: Noctuidae), single and superparasitism experiments were carried out using the parasitoid Microplitis rufiventris Kok. (Braconidae: Hymenoptera). Compared to younger (preferred) host larvae, the older (non-preferred) host larvae displayed a vigorous humoral response that often damaged and destroyed the single wasp egg or larva. Superparasitism and host age altered both the cellular and humoral immune responses. Younger host larvae showed a stronger encapsulation response compared to older host larvae. Moreover encapsulation rates in younger hosts (e.g., second instar) decreased with increasing numbers of parasitoid eggs deposited/larvae. In older larvae, the encapsulation rate was low in fourth, less in fifth and absent in sixth instar hosts. Conversely, the order and magnitude of the cellular immune response in S. littoralis hosts were highest in second instar larvae with the first instar larvae being a little lower. The immune response steadily decreased from the third through to the fifth instar and was least obvious in the sixth instar. In contrast, the general humoral immune response was most pronounced in sixth instar larvae and diminished towards younger stages. The results suggest that both cellular and humoral responses are stage-dependent. Wasp offspring in younger superparasitized host larvae fought for host supremacy with only one wasp surviving, while supernumerary wasp larvae generally survived in older superparasitized larvae, but were unable to complete development. Older instars seem to have a method for immobilizing/killing wasp larvae that is not operating in the younger instars.     

Relationships in the prevalence of geohelminth infections in humans from Venezuela]

By means of Kato-Katz technique 113,254 coprological samples of the human population belonging to 100 counties from Venezuela were analyzed. It was determined the following prevalences: Ascaris lumbricoides 26.8%, Trichuris trichiura 32.7% and hookworm 5.6%. It was found a strong correlation between A. lumbricoides and T. trichiura infection (p < 0.001), a significant correlation between T. trichiura and hookworm (p < 0.5) and no correlation between A. lumbricoides and hookworm.     

Phenotypic analysis of host-parasite interactions in lambs infected with Teladorsagia circumcincta

Female Blackface lambs expected to exhibit genetic variability for resistance to gastrointestinal nematodes, were either exposed to continuous experimental infections of Teladorsagia circumcincta or were sham-dosed to monitor phenotypic responses to infection. As a measure of parasitism and host response, worm-eggs in faeces (faecal egg count, FEC) were counted over a 3-month period and worm burdens were ascertained at post-mortem. The host response to the infection was also measured by differential counts of white blood cells, anti-T. circumcincta IgA antibody levels and body weight. Results suggest that nematode abundance (mean number of parasites per host) and prevalence (proportion of infected animals) were maximal shortly after the beginning of infection (21 days p.i.) when virtually all the infected animals were shedding worm eggs. Increasing anti-T. circumcincta IgA antibody and eosinophil concentrations were associated with a reduction in total numbers of adult worms and an increase in the frequency of early L4s. The data also suggest that genetic selection for an enhanced anti-T. circumcincta IgA response might complement selection based on a reduced FEC as a strategy to select for resistance to gastrointestinal nematodes.     

Comparative study on the effectiveness of modified Kato's cellophane thick smear and Stoll's dilution egg counting technique for quantitative fecal examination of helminth eggs]

A total of 197 fecal specimens was prepared for quantitative examination of helminth eggs by modified Kato's cellophane thick smear (M.C.T.S.) and Stoll's dilution egg counting technique (D.E.C.T.). The comparative effectiveness of two techniques was evaluated and conversion function was deduced. The average time required for the microscopic examination on one slide by M.C.T.S. was 12.6 minutes and that of D.E.C.T. was 14.6 minutes. M.C.T.S. showed lower false negative rate than D.E.C.T. in light worm burden cases. Functions to convert the counts obtained by M.C.T.S. to E.P.G. by Stoll's dilution egg counting technique were 47.86 x 10(0.87) logM.C.T.S. in A. lumbricoides, 41.69 x 10(0.82) logM.C.T.S. in T. trichiura and 63.10 x 10(0.85) logM.C.T.S. in C. sinensis. It was suggested M.C.T.S. be better than D.E.C.T. for the quantitative examination of intestinal helminthiases such as A. lumbricoides, T. trichiura, and C. sinensis infections even in the cases with low worm burden.     

Increased human IgE induced by killing Schistosoma mansoni in vivo is associated with pretreatment Th2 cytokine responsiveness to worm antigens

In schistosomiasis endemic areas, children are very susceptible to postchemotherapy reinfection, whereas adults are relatively resistant. Different studies have reported that schistosome-specific IL-4 and IL-5 responses, or posttreatment worm-IgE levels, correlate with subsequent low reinfection. Chemotherapy kills i.v. worms providing an in vivo Ag challenge. We measured anti-worm (soluble worm Ag (SWA) and recombinant tegumental Ag (rSm22.6)) and anti-egg (soluble egg Ag) Ab levels in 177 Ugandans (aged 7-50) in a high Schistosoma mansoni transmission area, both before and 7 wk posttreatment, and analyzed these data in relation to whole blood in vitro cytokine responses at the same time points. Soluble egg Ag-Ig levels were unaffected by treatment but worm-IgG1 and -IgG4 increased, whereas worm-IgE increased in many but not all individuals. An increase in worm-IgE was mainly seen in >15-year-olds and, unlike in children, was inversely correlated to pretreatment infection intensities, suggesting this response was associated both with resistance to pretreatment infection, as well as posttreatment reinfection. The increases in SWA-IgE and rSm22.6-IgE positively correlated with pretreatment Th2 cytokines, but not IFN-gamma, induced by SWA. These relationships remained significant after allowing for the confounding effects of pretreatment infection intensity, age, and pretreatment IgE levels, indicating a link between SWA-specific Th2 cytokine responsiveness and subsequent increases in worm-IgE. An exceptionally strong relationship between IL-5 and posttreatment worm-IgE levels in < 15-year-olds suggested that the failure of younger children to respond to in vivo Ag stimulation with increased levels of IgE, is related to their lack of pretreatment SWA Th2 cytokine responsiveness.     

Involvement of host recognition by oncomiracidia and post-larval survivability in the host specificity of Heterobothrium okamotoi (Monogenea: Diclidophoridae)

Heterobothrium okamotoi, a monogenean gill parasite, shows high host specificity for tiger puffer, Takifugu rubripes. In the present study, in vivo and in vitro experimental infections were conducted using various fish species, including T. rubripes, to understand the mechanisms of specificity. In in vivo experiments, T. rubripes, grass puffer, Takifugu niphobles, olive flounder, Paralichthys olivaceus, and red sea bream, Pagrus major, were exposed to oncomiracidia of H. okamotoi labelled with a fluorescent dye, 5- (and -6) carboxyfluorescein diacetate succinimidyl ester, and the numbers of parasites on the gills and skin were recorded at intervals. Oncomiracidia were attached to gills and skin of all the experimental fish species immediately after exposure, and the infection intensity on T. rubripes was higher than that on T. niphobles and much higher than those on the other two species. After 2 days, the attached parasites remained on the gills of T. rubripes, but disappeared from the other hosts. During in vitro experiments, gill filaments excised from seven different fish species (four fish species used in the in vivo experiments and panther puffer, Takifugu pardalis, southern flounder, Paralichthys lethostigma and spotted halibut, Verasper variegates) were exposed to oncomiracidia and the attachment to each fish species and subsequent larval behaviour was observed. The percentage of post-larvae that attached to T. rubripes was slightly higher than those which attached to congeneric fish species and much higher than those of non-tetraodontid fish species. In vivo and in vitro experiments demonstrated that oncomiracidia of H. okamotoi have an affinity for their natural host, T. rubripes, and congeneric fish species. The disappearance of attached post-larvae from 'alien' hosts within 2 days during in vivo experiments suggested that host recognition by oncomiracidia and subsequent post-larval survivability are involved in the host specificity of H. okamotoi.     

High prevalence of Opisthorchis viverrini infection in a riparian population in Takeo Province, Cambodia

Opisthorchis viverrini infection was found to be highly prevalent in 3 riverside villages (Ang Svay Chek A, B, and C) of the Prey Kabas District, Takeo Province. This area is located in the southern part of Cambodia, where the recovery of adult O. viverrini worms was recently reported. From May 2006 until May 2010, fecal examinations were performed on a total of 1,799 villagers using the Kato-Katz thick smear technique. In the 3 villages, the overall positive rate for helminth eggs ranged from 51.7 to 59.0% (av. 57.4%), and the percentage positive for O. viverrini was 46.4-50.6% (47.5%). Other helminths detected included hookworms (13.2%), echinostomes (2.9%), Trichuris trichiura (1.3%), Ascaris lumbricoides (0.6%), and Taenia spp. (0.06%). The prevalence of O. viverrini eggs appeared to reflect a lower infection in younger individuals (<20 years) than in the adult population (>20 years). Men (50.4%) revealed a significantly higher (P=0.02) prevalence than women (44.3%). The Ang Svay Chek villages of the Prey Kabas District, Takeo Province, Cambodia have been confirmed to be a highly endemic area for human O. viverrini infection.     

Identification and characterisation of an aspartyl protease inhibitor homologue as a major allergen of Trichostrongylus colubriformis

Allergens were identified from the gastrointestinal nematode of sheep, Trichostrongylus colubriformis, by probing Western blots of infective larvae (third stage) somatic antigen with IgE purified from the serum of sheep grazed on worm contaminated pasture. A 31 kDa allergen was frequently recognised by sera from immune sheep, particularly those deriving from a line that has been genetically selected over 23 years for parasite resistance. Using a proteomic approach, the 31 kDa allergen was identified as an aspartyl protease inhibitor homologue. The entire coding sequence of T. colubriformis aspartyl protease inhibitor (Tco-api-1) was obtained and the mature protein expressed in Escherichia coli. Anti-Tco-API-1 antibodies revealed that a commonly observed 21 kDa T. colubriformis allergen species is a truncated form of Tco-API-1. Specific IgE responses to T. colubriformis aspartyl protease inhibitor were significantly correlated with the degree of resistance to nematode infection as measured by faecal egg count in sheep. Surprisingly, IgE responses to Tco-API-1 were not correlated with breech soiling (dag score), which is thought to be caused, in part, by allergic hypersensitivity to worms. Therefore, a specific IgE response to this allergen may be a suitable marker for identifying lambs at an early age that will develop strong immunity to gastrointestinal nematodes.     

Effects of the mermithid nematode Ovomermis sinensis on the hemocytes of its host Helicoverpa armigera

Little is known about the mechanism by which mermithid nematodes avoid encapsulation responses of insect hosts. In this study, we investigated the influence of the mermithid nematode Ovomermis sinensis on host Helicoverpa armigera hemocyte number, encapsulation activity, spreading behavior and cytoskeleton. Parasitism by O. sinensis caused a significant increase in the total hemocyte counts (THC) and plasmatocyte numbers of H. armigera. However, in vivo encapsulation assays revealed that hemocyte encapsulation abilities of H. armigera were suppressed by O. sinensis. Moreover, parasitism by O. sinensis changed the spreading behavior and cytoskeletons of the host hemocytes. The results suggested that O. sinensis could actively suppress the hemocyte immune response of its host, possibly by destroying the host hemocyte cytoskeleton. This is the first report of a possible mechanism by which mermithid nematodes suppress encapsulation responses of insect hosts.     

Spatial heterogeneity and temporal variations in Echinococcus multilocularis infections in wild hosts in a North American urban setting

Echinococcus multilocularis, the causative agent of human alveolar echinococcosis, has the potential to circulate in urban areas where wild host populations and humans coexist. The spatial and temporal distribution of infection in wild hosts locally affects the risk of transmission to humans. We investigated the spatial and temporal patterns of E. multilocularis infection in coyotes and rodent intermediate hosts within the city of Calgary, Canada, and the association between spatial variations in coyote infection and the relative composition of small mammal assemblages. Infection by E. multilocularis was examined in small mammals and coyote faeces collected monthly in five city parks from June 2012 to June 2013. Coyote faeces were analysed using a ZnCl₂ centrifugation and sedimentation protocol. Infection in intermediate hosts was assessed through lethal trapping and post-mortem analysis. Parasite eggs and metacestodes were morphologically identified and molecularly confirmed through species-specific PCR assays. Of 982 small mammals captured, infection was detected in 2/305 (0.66%) deer mice (Peromyscus maniculatus), 2/267 (0.75%) meadow voles (Microtus pennsylvanicus), and 1/71 (1.41%) southern red backed voles (Myodes gapperi). Overall faecal prevalence in coyotes was 21.42% (n = 385) and varied across sites, ranging from 5.34% to 61.48%. Differences in coyote faecal prevalence across sites were consistent with local variations in the relative abundance of intermediate hosts within the small mammal assemblages. Infections peaked in intermediate hosts during autumn (0.68%) and winter (3.33%), and in coyotes during spring (43.47%). Peaks of infections in coyote faeces up to 83.8% in autumn were detected in a hyper-endemic area. To the best of our knowledge, our findings represent the first evidence of a sylvatic life-cycle of E. multilocularis in a North American urban setting, and provide new insights into the complexity of the parasite transmission ecology.     

Impacts of an endoparasitic copepod, Ismaila belciki, on the reproduction,growth and survivorship of its nudibranch host, Janolus fuscus

Copepods from the genus Ismaila are large endoparasites that inhabit the main body cavity and/or cerata of opisthobranch molluscs. These parasites exhibit many life history characteristics typically found in parasitic castrators, yet the actual impact of infection on reproduction, growth or survivorship of the hosts are unknown. On the Oregon (USA) coast, Ismaila belciki can infect over 80% of their hermaphroditic hosts, Janolus fuscus. In laboratory mating experiments, we compared the reproductive output (egg mass weight, number of egg capsules, number of viable embryos) and the gonadal somatic index of infected versus uninfected J. fuscus. Infected J. fuscus could produce viable sperm and copulate. Mating with an infected individual did not limit a sea slug’s reproductive output. However, infected J. fuscus had significantly lower reproductive output (by 34–54%), producing smaller egg masses with fewer capsules and viable embryos. Infected hosts had significantly lower gonadal somatic index than their uninfected counterparts, although there was no significant difference in gonadal somatic index between hosts with single and double infections. By collecting the egg sacs produced by the copepod parasite during experiments, we estimated that 25–34% of the host’s reproductive output is usurped by the parasite and re-directed to the parasite’s own reproduction. In the laboratory, infection did not alter growth in J. fuscus. However, infection significantly decreased survivorship in mature (but not immature) nudibranch hosts. These results suggest that I. belciki is not a true castrator, but it does reduce the reproductive output of its host and may therefore limit the natural population size of J. fuscus.