Intestinal Helminth Species Research Articles

Levels of infection of intestinal helminth species in the golden jackal Canis aureus from Serbia

During the past decade, golden jackal populations have substantially increased, yet little is known of their potential for transmitting parasites within animal and human hosts. In the present study, between 2005 and 2010, 447 jackals from six localities in Serbia were examined for intestinal parasites. Two species of trematodes (Alaria alata, Pseudamphistomum truncatum), three nematodes (Toxocara canis, Ancylostoma caninum, Gongylonema sp.), and seven cestodes (Taenia pisiformis, Taenia hydatigena, Multiceps multiceps, Multiceps serialis, Mesocestoides lineatus, Mesocestoides litteratus, Dipylidium caninum) were identified. Pseudamphistomum truncatum and M. serialis species were recorded for the first time. The overall prevalence of parasitic infection was 10.3%. No significant differences were found in the prevalence of infection between males and females (P>0.817), between localities (P>0.502), or with regard to annual cycles (P>0.502). In the infected jackal population, 65% harboured multiple infections and one individual was a host to five different types of parasite species, the highest number of parasites we recorded in a single host. These findings indicate that although the prevalence of gastrointestinal helminths in the jackal population in Serbia is significantly lower than expected from earlier studies, further monitoring is required given the jackal's rapid population increase.

Trematodes Recovered in the Small Intestine of Stray Cats in the Republic of Korea

In 2005, we reported the infection status of 438 stray cats with various species of intestinal helminths, including nematodes (4 species), trematodes (23 species), and cestodes (5 species) in the Republic of Korea. However, morphologic details of each helminth species have not been provided. In the present study, we intended to describe morphologic details of 13 trematode species which were either new fauna of cats (10 species) or new fauna of not only cats but also all animal hosts (3 species). The worms were fixed in 10% neutral buffered formalin under a cover slip pressure, stained with Semichon's acetocarmine, and then observed using a light microscope equipped with a micrometer. The 13 subjected species included members of the Heterophyidae (Stellantchasmus falcatus, Stictodora fuscata, Stictodora lari, Centrocestus armatus, Procerovum varium, and Cryptocotyle concava), Echinostomatidae (Echinostoma hortense, Echinostoma revolutum, Echinochasmus japonicus, and Stephanoprora sp.), Diplostomidae (Neodiplostomum seoulense), Plagiorchiidae (Plagiorchis muris), and Dicrocoeliidae (Eurytrema pancreaticum). By the present study, Cryptocotyle sp. and Neodiplostomum sp. recored in our previous study were identified as C. concava and N. seoulense, respectively. Three species, P. varium, C. concava, and Stephanoprora sp., are new trematode fauna in Korea.

The association between multiple intestinal helminth infections and blood group, anaemia and nutritional status in human populations from Dore Bafeno, southern Ethiopia

In this cross-sectional study, the associations between helminth infections and ABO blood group, anaemia and undernutrition were investigated in 480 febrile outpatients who visited Dore Bafeno Health Centre, southern Ethiopia, in December 2010. Stool specimens were processed using the Kato-Katz method and examined for intestinal helminth infections. Haemoglobin level was measured using a HemoCue machine and blood group was determined using an antisera haemagglutination test. Nutritional status of the study participants was assessed using height and weight measurements. Among the study participants, 50.2% were infected with intestinal helminths. Ascaris lumbricoides (32.7%), Trichuris trichiura (12.7%), Schistosoma mansoni (11.9%) and hookworm (11.0%) were the most frequently diagnosed helminths. The odds of infection and mean eggs per gram of different intestinal helminth species were comparable between the various blood groups. Among individuals who were infected with intestinal helminth(s), the mean haemoglobin level was significantly lower in individuals harbouring three or more helminth species and blood type AB compared to cases with double or single helminth infection and blood type O, respectively. The odds of being underweight was significantly higher in A. lumbricoides and T. trichiura infected individuals of age ≤ 5 and ≥ 20 years, respectively, when compared to individuals of the matching age group without intestinal helminths. In conclusion, infection with multiple intestinal helminths was associated with lower haemoglobin level, which was more severe in individuals with blood type AB. Future studies should focus on mechanisms by which blood group AB exacerbates the helminth-related reduction in mean haemoglobin level.

Malaria and related outcomes in patients with intestinal helminths: a cross-sectional study

BackgroundThe effects of helminth co-infection on malaria in humans remain uncertain. This study aimed to evaluate the nature of association of intestinal helminths with prevalence and clinical outcomes of Plasmodium infection.MethodsA cross-sectional study involving 1,065 malaria suspected febrile patients was conducted at Dore Bafeno Health Center, Southern Ethiopia, from December 2010 to February 2011. Plasmodium and intestinal helminth infections were diagnosed using Giemsa-stained blood films and Kato-Katz technique, respectively. Haemoglobin level was determined using a haemocue machine.ResultsAmong 1,065 malaria suspected febrile patients, 28.8% were positive for Plasmodium parasites (P. falciparum =13.0%, P. vivax =14.5%, P. falciparum and P. vivax =1.3%). Among 702 patients who provided stool samples, 53.8%, 31.6% and 19.4% were infected with intestinal helminths, Plasmodium alone and with both Plasmodium and intestinal helminths, respectively. The prevalence of infections with Ascaris lumbricoides (A. lumbricoides), Trichuris trichiura (T. trichiura), Schistosoma mansoni (S. mansoni) and hookworm (9.8%) were 35.9%, 15.8%, 11.7% and 9.8%, respectively. Out of the 222 (31.6%) Plasmodium infected cases, 9 (4.1%) had severe malaria. P. falciparum infection was more common in febrile patients infected with A. lumbricoides alone (21.3%), T. trichiura alone (23.1%) and S. mansoni alone (23.1%) compared to those without intestinal helminth infections (9.3%) (p<0.001 for all). Prevalence of non-severe malaria was significantly higher in individuals infected with intestinal helminths than in those who were not infected with intestinal helminths (adjusted OR=1.58, 95% CI=1.13-2.22). The chance of developing non-severe P. falciparum malaria were 2.6, 2.8 and 3.3 times higher in individuals infected with A. lumbricoides alone, T. trichiura alone and S. mansoni alone, respectively, compared to intestinal helminth-free individuals (p<0.05 for all). The odds ratio for being infected with non-severe P. falciparum increased with the number of intestinal helminth species (p<0.001). Mean Plasmodium density among intestinal helminth infected individuals was significantly increased with the number of intestinal helminths species (p=0.027). Individuals who were co-infected with different species of intestinal helminths and Plasmodium showed lower mean haemoglobin concentration than individuals who were infected only with Plasmodium.ConclusionsInfections with A. lumbricoides, T. trichiura and S. mansoni were positively associated with P. falciparum infection. However, further studies are required to investigate how these helminths could contribute to increased prevalence of P. falciparum infection.

High prevalence of intestinal infections and ectoparasites in dogs, Minas Gerais State (southeast Brazil)

In the present study, 155 dogs euthanized by the Zoonotic Disease Unit of Uberlândia in Minas Gerais State (Southeast Brazil) were autopsied. Ectoparasites were collected, and the intestinal content of dogs was systematically examined for the presence of helminthic parasites. In total, we isolated 5,155 metazoan parasites of eight species (three intestinal helminth species, five ectoparasite species). The cestode Dipylidium caninum was present in 57 dogs (36.8 %), the nematodes Ancylostoma caninum in 30 (19.4 %) and Toxocara canis in 24 (15.5 %), respectively. Among the ectoparasites, 139 (89.7 %) dogs were infested with Rhipicephalus sanguineus, 115 (74.2 %) with Ctenocephalides felis, 5 (3.2 %) with Tunga penetrans and one specimen (0.7 %) with Amblyomma cajennense, while myiasis was found in one dog (0.7 %). In logistic regression analysis, young age (adjusted odds ratio 5.74; 95 % confidence interval 1.18-27.85) and male sex (3.60; 1.24-10.40) were significantly associated with toxocariasis, and crossbreed dogs (8.20; 1.52-44.31), with dipylidiasis. Male (2.23; 1.12-4.43) and crossbreed dogs (5.17; 1.17-22.83) had also a significant higher number of concomitant parasitoses. Spatial distribution of dogs by neighbourhood identified high-risk areas. Our systematic study shows that dogs in Uberlândia carry a high number of parasites which may cause zoonotic diseases in humans; therefore, further specific evidence-based intervention measures are needed.

Intestinal Helminthiasis among School Children in Ilie, Osun State, Southwest, Nigeria

A cross sectional study of intestinal helminthiasis among school pupils was undertaken in three primary schools in Ilie in Olorunda Local Government Area of Osun state in order to determine the prevalence and intensity of helminthic infections. The relationship between intestinal helminths and anthropometric indices and the factors that could favour the infection were also studied. Faecal samples from three hundred and four (304) randomly selected out of the four hundred and seven (407) school children in the study area were collected and analysed with the semi-quantitative Kato Katz technique and concentrated method. The intensity of infection was classified into light, moderate or high according to World Health Organisation (WHO) thresholds. The overall prevalence rate was 52.0% while five species of intestinal helminths were identified. Ascaris lumbricoides (36.2%) was the most common, followed by Hookworm (10.5%), Schistosoma mansoni (4%), Strongyloides stercoralis (0.7%) and Hymenolepis nana (0.7%). Multiple helminthic infection were recorded with Ascaris –Hookworm (6.58%) having the highest prevalence among the children. Female (56.6%) were more infected than male (46.4%) and the difference was statistically significant (P=0.0019). Seventeen percent (17%) of the children were below the third percentile for weight (wasted) while fourteen percent (14%) were below the third percentile for height (stunted). There was a relationship between intensity of infection and wasting since there were fewer underweight pupils (13%) with normal stool than those moderately infected (35%) (P

Intenstinal Parasitic Infections in Primary School in Pulau Panggang and Pulau Pramuka, Kepulauan Seribu

Stool samples were collected and examined for soil-transmitted helminthic and protozoal infection in the first grade of three primary schools, located on Pulau Panggang and Pulau Pramuka, which are parts of a group of islands not far from the north coast of Jakarta. The stool examinations were part of activities during a control program on soil-transmitted helminthic infections. The schools have never participated with control programs on soil-transmitted helminthiases. For the examination of the samples a semi-quantitative Kato thick smear method was used and the direct smear with a 2% iodine solution. Four intestinal helminth species and five protozoa species were found in a total of 101 stool samples. Ascaris and Trichuris infections were found in 68.8% or more. Hookworm infection was only found in one school (2.9%). Eggs of Hymenolepis nana were detected in one sample. Cysts of Entamoeba histolytica and Entamoeba coli were both found in 5.0% of the samples, whereas Endolimax nana was recovered from 2.0% of the samples. High prevalence rates were detected for Blastocystis hominis (36.0%) and for Giardia lamblia it was 30.0%. Most of the Ascaris infections were categorized as light infections at School I (69.0%) and not a single heavy infection were found in this school. In School II and III most of the infections were moderate i.e. respectively 51.4 and 81.8%. Also in Schools II and III heavy infections were detected, respectively 11.4 and 5.8%. Fertilized Ascaris eggs were detected in 93.1%, 100% and 95.5% at School I, II and III respectively. As a whole among 86 positive samples 96.5% were recorded as samples with fertilized eggs, whereas 3.5% contained unfertilized eggs. The high prevalences of Ascaris and Trichuris infections in this area could be expected due to the low level of environmental hygiene and sanitation. Among the protozoal infections B. hominis and G. lamblia were the dominant species.

Principal intestinal parasites of dogs in Tirana, Albania

From 2004 to 2009, the digestive tracts of 111 dogs from suburban areas around Tirana, Albania, were examined for intestinal helminths. In addition, rectal faecal samples of all dogs were examined for protozoan infections and 48 faecal samples from dogs >6 months of age were processed with the Baermann technique to test for the excretion of lungworm larvae. The heart and pulmonary arteries of 30 dogs >6 months of age also were examined for nematode parasites. The intestinal parasite fauna of the dogs included three protozoan species (Cystoisospora canis, Cystoisospora ohioensis/burrowsi, Sarcocystis spp.), three cestode species (Dipylidium caninum, Taenia hydatigena, Echinococcus granulosus), five nematode species (Ancylostoma caninum, Uncinaria stenocephala, Toxocara canis, Toxascaris leonina, Trichuris vulpis) and one acanthocephalan (Centrorhynchus buteonis). Rates of infection were: 15.3% for C. canis, 31.5% for C. ohioensis/burrowsi, 1.8% for Sarcocystis spp., 65.8% for D. caninum, 16.2% for T. hydatigena, 2.7% for E. granulosus (genotype G1), 13.5% for A. caninum, 64.9% for U. stenocephala, 75.7% for T. canis, 0.9% for T. leonina, 21.6% for T. vulpis and 0.9% for C. buteonis. Up to six species of gastrointestinal parasites were found per dog. The 63 ≤ 6-month-old dogs harboured significantly (p<0.001) fewer gastrointestinal parasite species concurrently (mean 2.65 ± 1.25 species per animal) than the 48 older animals (mean 3.77 ± 1.45 species per animal). Dogs >6 months of age harboured significantly (p<0.05) more D. caninum, T. hydatigena, A. caninum, U. stenocephala and T. vulpis compared to younger dogs. Conversely, the younger dogs harboured significantly (p<0.001) more T. canis than the older ones. There was no difference in the male and female dogs' counts of individual intestinal helminth species apart from T. hydatigena in dogs >6 months of age: Male dogs harboured significantly (p<0.05) more tapeworms than female dogs. Based on faecal examination, there was no indication for lungworm infection; however, two adult heartworms (Dirofilaria immitis) were found in the right ventricle of one dog.

Gastrointestinal and ectoparasites from urban stray dogs in Fortaleza (Brazil): high infection risk for humans?

Dogs are important definite or reservoir hosts for zoonotic parasites. However, only few studies on the prevalence of intestinal parasites in urban areas in Brazil are available. We performed a comprehensive study on parasites of stray dogs in a Brazilian metropolitan area. We included 46 stray dogs caught in the urban areas of Fortaleza (northeast Brazil). After euthanization, dogs were autopsied. Ectoparasites were collected, and the intestinal content of dogs were examined for the presence of parasites. Faecal samples were collected and analysed using merthiolate iodine formaldehyde concentration method. A total of nine different parasite species were found, including five endoparasite (one protozoan, one cestode and three nematode species) and four ectoparasite species (two flea, one louse and one tick species). In the intestinal content, 3,162 specimens of four helminth species were found: Ancylostoma caninum (prevalence, 95.7%), Dipylidium caninum (45.7%), Toxocara canis (8.7%) and Trichuris vulpis (4.3%). A total of 394 ectoparasite specimens were identified, including Rhipicephalus sanguineus (prevalence, 100.0%), Heterodoxus spiniger (67.4%), Ctenocephalides canis (39.1%) and Ctenocephalides felis (17.4%). In the faeces, intestinal parasites were detected in 38 stray dogs (82.6%), including oocysts of Giardia sp. (2.2%) and eggs of the nematode A. caninum (82.6%). Neither eggs nor larval stages of D. caninum, T. canis or T. vulpis were detected in dog faeces. Sensitivity of faecal examination for A. caninum was 86.4% (95% confidence interval, 72.0-94.3) but zero percentage for the other intestinal helminth species. Our data show that stray dogs in northeast Brazil carry a multitude of zoonotic ecto- and endoparasites, posing a considerable risk for humans. With the exception of A. caninum, sensitivity of faecal examination was negligible.

The impact of concomitant infections by Trypanosoma cruzi and intestinal helminths on the health of wild golden and golden-headed lion tamarins

A 4-year longitudinal epidemiological study was carried out to evaluate the effect of infection by Trypanosoma cruzi and three intestinal helminth species on the health of golden and golden-headed lion tamarins. We evaluated health using analysis of blood counts, serum proteins, electrophoretograms, electrocardiograms and a health ranking based on physiological parameters. Among the helminths, Trichostrongylidae was demonstrated as the most pathogenic, followed by Prosthenorchis sp.; concomitant infection by Spiruridae may exacerbate the negative effects of the other two helminths. T. cruzi infection was not highly detrimental to the health of the study animals and was correlated with increased resilience to helminths. Tamarins younger than 1-year of age or older than 4-years had lower health condition. Golden-headed lion tamarins were in lower health condition because of higher parasitic prevalence. Our data suggest that when parasite community pathogenicity and prevalence are high, natural selection will allow survival only of lion tamarins in the best health condition.

Helminth species richness in wild wood mice,Apodemus sylvaticus, is enhanced by the presence of the intestinal nematodeHeligmosomoides polygyrus

We analysed 3 independently collected datasets of fully censused helminth burdens in wood mice, Apodemus sylvaticus, testing the a priori hypothesis of Behnke et al. (2005) that the presence of the intestinal nematode Heligmosomoides polygyrus predisposes wood mice to carrying other species of helminths. In Portugal, mice carrying H. polygyrus showed a higher prevalence of other helminths but the magnitude of the effect was seasonal. In Egham, mice with H. polygyrus showed a higher prevalence of other helminth species, not confounded by other factors. In Malham Tarn, mice carrying H. polygyrus were more likely to be infected with other species, but only among older mice. Allowing for other factors, heavy residual H. polygyrus infections carried more species of other helminths in both the Portugal and Egham data; species richness in Malham was too low to conduct a similar analysis, but as H. polygyrus worm burdens increased, so the prevalence of other helminths also increased. Our results support those of Behnke et al. (2005), providing firm evidence that at the level of species richness a highly predictable element of co-infections in wood mice has now been defined: infection with H. polygyrus has detectable consequences for the susceptibility of wood mice to other intestinal helminth species.

Why do Siberian chipmunks Tamias sibiricus (Sciuridae) introduced in French forests acquired so few intestinal helminth species from native sympatric Murids?

A lack of newly acquired species partly explains why introduced host species have poor specific parasite diversity. The intestinal helminth community from two native Murid host species, wood mice Apodemus sylvaticus [Murinae] (n=40), bank voles Clethrionomys glareolus [Arvicolinae] (n=42), and an introduced Sciurid, the Siberian chipmunk Tamias sibiricus (n=42), dominant in the rodent communities, was studied from three woody areas in the Ile-de-France region. Native gastrointestinal helminth fauna from mice and voles was formed by 12 taxa: ten nematodes, Aonchotheca murissylvatici, Aonchotheca annulosa, Aspiculuris tetraptera, Eucoleus sp., Heligmosomoides glareoli, Heligmosomoides polygyrus, Mastophorus muris, Syphacia frederici, Syphacia stroma, Trichuris muris, a Cestode and a Trematode. Two helminth taxa were imported by chipmunks from eastern Asia: Brevistriata skrjabini and Strongyloides callosciureus. Only A. annulosa was transferred to chipmunks from the native small rodent community. None of the 82 native murids harbored chipmunk helminths. The developmental ability of helminth according to host phylogenetic relatedness was the main driving force explaining the species composition of the helminth community between these sympatric native and introduced hosts.

Parasites of importance for human health in Nigerian dogs: high prevalence and limited knowledge of pet owners

BackgroundDogs are the most common pet animals worldwide. They may harbour a wide range of parasites with zoonotic potential, thus causing a health risk to humans. In Nigeria, epidemiological knowledge on these parasites is limited.MethodsIn a community-based study, we examined 396 dogs in urban and rural areas of Ilorin (Kwara State, Central Nigeria) for ectoparasites and intestinal helminths. In addition, a questionnaire regarding knowledge and practices was applied to pet owners.ResultsNine ectoparasite species belonging to four taxa and six intestinal helminth species were identified: fleas (Ctenocephalides canis, Pulex irritans, Tunga penetrans), mites (Demodex canis, Otodectes sp., Sarcoptes scabiei var. canis), ticks (Rhipicephalus sanguineus, Ixodes sp.), and lice (Trichodectes canis); and Toxocara canis, Ancylostoma sp., Trichuris vulpis, Dipylidium caninum, Taenidae and Strongyloides sp. Overall prevalence of ectoparasites was 60.4% and of intestinal helminths 68.4%. The occurrence of C. canis, R. sanguineus, T. canis, Ancylostoma sp. and T. vulpis was most common (prevalence 14.4% to 41.7%). Prevalence patterns in helminths were age-dependent, with T. canis showing a decreasing prevalence with age of host, and a reverse trend in other parasite species. Knowledge regarding zoonoses was very limited and the diseases not considered a major health problem. Treatment with antiparasitic drugs was more frequent in urban areas.ConclusionParasites of importance for human health were highly prevalent in Nigerian dogs. Interventions should include health education provided to dog owners and the establishment of a program focusing on zoonotic diseases.

Structure in parasite component communities in wild rodents: predictability, stability, associations and interactions .... or pure randomness?

Experimental data establish that interactions exist between species of intestinal helminths during concurrent infections in rodents, the strongest effects being mediated through the host's immune responses. Detecting immune-mediated relationships in wild rodent populations has been fraught with problems and published data do not support a major role for interactions in structuring helminth communities. Helminths in wild rodents show predictable patterns of seasonal, host age-dependent and spatial variation in species richness and in abundance of core species. When these are controlled for, patterns of co-infection compatible with synergistic interactions can be demonstrated. At least one of these, the positive relationship between Heligmosomoides polygyrus and species richness of other helminths has been demonstrated in three totally independent data-sets. Collectively, they explain only a small percentage of the variance/deviance in abundance data and at this level are unlikely to play a major role in structuring helminth communities, although they may be important in the more heavily infected wood mice. Current worm burdens underestimate the possibility that earlier interactions through the immune system have taken place, and therefore interactions may have a greater role to play than is immediately evident from current worm burdens. Longitudinal studies are proposed to resolve this issue.

Intestinal helminthiases among rural and urban schoolchildren in south–western Nigeria

The prevalences and intensities of intestinal helminthic infection among primary schoolchildren were determined in rural and urban communities of the Ife Central local government area, in south-western Nigeria. After the schools in the study area had been stratified into urban and rural, a random sample from each stratum was selected for further study. In each study school, a single fresh stool specimen was obtained from each pupil in randomly selected classes and checked, using a quantitative method (Stoll's dilution egg-count technique), for helminth eggs and larvae. Overall, 366 rural and 383 urban schoolchildren were investigated and 30.0% of them (36.1% of the rural and 24.3% of the urban; P<0.001) were found to be harbouring at least one species of intestinal helminth. The mean intensities of infection, in terms of excreted eggs/g faeces of those infected, were 2371.4 for Ascaris, 1070.6 for hookworm, and 500 for Trichuris. Although the mean intensities of Ascaris infection were significantly lower among the infected rural children than among the infected urban (2025.7 v. 2791.4; P=0.014), the corresponding difference in the hookworm infections did not reach statistical significance (1458 v. 666.7; P=0.063). The means of the log-transformed egg outputs, in eggs/g faeces of those infected, also showed similar trends: a significant difference between the rural and urban Ascaris infections (3.1877 v. 3.3340; P=0.002) but not between the rural and urban hookworm infections (2.9667 v. 2.8027; P=0.453). Intestinal helminthiases still clearly represent a common childhood health problem in the study area, particularly in the rural communities.

The prevalence of intestinal helminthic infections and associated risk factors among school children in Babile town, eastern Ethiopia

Abstract Background: The effective prevention and control of intestinal helminthic infections requires the identification of local risk factors, particularly among high-risk groups. Objectives: To determine the prevalence and associated risk factors of intestinal helminthic infections among school children. Methods: A cross-sectional study, involving 415 schoolchildren, techniques was conducted between May and June of 2001. Interviews, observation, and anthropometric indices assessment were used to identify the risk factors. Stool specimens were examined using the formal ether concentration technique. Data were analysed done using the SPSS statistical software. Results: Nine species of intestinal helminths were identified with an overall prevalence of 27.2% (113 of 415 children). The predominant parasites involved were Hymenolepis nana 42 (10.1%) and hookworm 28 (6.7%). In this study, the prevalence of Schistosoma mansoni was determined to be 4.3%, which contrasts with the prevalence of 43% reported previously for schoolchildren in Babile town. Prevalence of intestinal helminthic infections was not related to the availability, type and usage of latrines (p>0.05). A higher prevalence of H. nana was found among children with poor personal hygiene (p

Leukocytosis and blood eosinophilia in a polyparasitised population in north-eastern Brazil

It has long been known that leukocytosis and blood eosinophilia are common in the tropical environment, but data derived from population-based studies are scarce. A study was undertaken in a fishing village in north-east Brazil where both intestinal helminthiases and parasitic skin diseases are common. Of 409 individuals studied, 128 (31.3%) were infected with one intestinal helminth or ectoparasite species, 93 (22.7%) with two, 61 (14.9%) with three, 25 (6.1%) with four and 11 (2.7%) with more than four species; no parasites were found in 91 (22.2%) individuals. Leukocyte counts ranged between 3,300 cells/microl and 16,100 cells/microl (median, 7,200 cells/microl) and eosinophil counts between 40 cells/microl and 5,460 cells/microl (median, 455 cells/microl). Eosinophilia (>500/microl) was detected in 44.7% of the individuals, and hypereosinophilia (>1,000/microl) in 12.9%. Thirty-six (8.8%) individuals showed leukocytosis. While 75% of individuals with normal eosinophil counts were considered parasite-free, only 14% with eosinophilia and 11% with hypereosinophilia did not have enteroparasites or ectoparasites. Multivariate regression showed that the probability of eosinophilia and hypereosinophilia, but not of leukocytosis, increased with the number of parasite species present. The data show that eosinophilia occurs in almost one-half of the individuals from a resource-poor setting and that it is significantly associated with the presence of intestinal helminths, but not with the presence of ectoparasites.

Intestinal helminths of capybaras, Hydrochoerus hydrochaeris, from Venezuela

Quantitative parameters of intestinal helminth species and their potential relations to host characteristics in a population of capybaras (Hydrochoerus hydrochaeris) from Venezuela are reported for the first time. The intestines of 40 capybaras were collected during the 1992-annual harvest at Hato El Cedral. Six helminth species were found: 2 cestodes (Monoecocestus macrobursatum, M. hagmanni), 2 nematodes (Viannella hydrochoeri, Protozoophaga obesa), and 2 trematodes (Hippocrepis hippocrepis, Taxorchis schistocotyle). This is the first report for M. macrobursatum in Venezuela. Helminth abundance did not differ between sexes or age classes. Although patterns of distribution for all helminth species were overdispersed, the high prevalence found for all species (over 70%) and the high abundance observed for nematodes made it difficult to assess the effect that these helminths may produce on capybaras. Nevertheless, the negative associations found between the body condition of capybaras and helminth intensity for M. macrobursatum and V. hydrochoeri, might be pointing out potential host population regulatory role for these parasites which require further research.

Spatial variation in helminth community structure in the red-legged partridge (Alectoris rufa L.): effects of definitive host density.

Parasite community ecology has recently focused on understanding the forces structuring these communities. There are few surveys, however, designed to study the spatial repeatability and predictability of parasite communities at the local scale in one host. The purpose of our study was to address the relationship between infracommunity and component community richness, and to describe spatial variations on the local scale, of helminth parasite communities in an avian host, the red-legged partridge (Alectoris rufta). We sampled 235 wild partridges from 8 separate localities, with different partridge population densities, in the Ciudad Real and Toledo provinces of central Spain, and we determined their overall and intestinal helminth species. We found that habitat variables (mean temperature and land use) were not significantly associated with any component community. The partridge population abundance index was directly correlated with the prevalence and mean intensity of infection but not with component community species richness. There was a curvilinear relationship between infracommunity and component community species richness, as well as negative interspecific associations, for the helminth species assemblage parasitizing the intestine. A nestedness/anti-nestedness pattern, considered as part of a continuum, was associated with prevalence, mean intensity and partridge population abundance index, but not with component community richness. Increases in the partridge population abundance index and the prevalence and mean intensity of infection were associated with increases in helminth community nestedness. Although negative interactions between helminth species could not be ruled out as forces structuring helminth communities, our results suggest that parasite community structure in the red-legged partridge was primarily determined by the extrinsic influence of parasite habitat heterogeneity and its amplification of the differing probabilities of colonization of parasite species.

The impact of sexual selection on Corynosoma magdaleni (Acanthocephala) infrapopulations in Saimaa ringed seals (Phoca hispida saimensis).

In free-living animals sexual selection is a central force shaping the spatial distribution of individuals in a population as well as sexual size dimorphism. We studied the influence of sexual selection on spatial distribution, female-to-male body size ratio, and female mating success of acanthocephalans in a natural host population of Saimaa ringed seal (Phoca hispida saimensis) harbouring a single intestinal helminth species, Corynosoma magdaleni. The acanthocephalans were always found along the full length of the small intestine; however, the site selection varied among the individual seals according to the age of the infection. The distribution of male acanthocephalans was not random with respect to females, with larger males tending to aggregate around non-mated females. A higher proportion of C. magdaleni females had copulated in seals with relatively more male worms. Male-male competition for access to females can be intense in C. magdaleni infrapopulation and may select for large males. We found that the larger the infrapopulation size, the smaller the males compared to females. In addition, the greater the female bias in the infrapopulation, the smaller the testes of males. Our study shows that sexual selection may be an important determinant of spatial distribution, male body size and female mating success of C. magdaleni in Saimaa ringed seal.