Parasitology

Parasites of the genus Hepatocystis are close relatives of Plasmodium that frequently infect epauletted fruit bats across West and East Africa. Our understanding of susceptible hosts and prevalence of infection of Hepatocystis remains fragmented. Non-invasive sampling of bat assemblages in representative habitats critically contribute to haemosporidian parasite distribution maps. Here, we report on a survey of Hepatocystis parasite infections in bats undertaken over two consecutive years in a protected area in Nigeria, where prevalence and diversity of bat-infecting haemosporidian parasites have not been studied. Microscopic examination of blood films in combination with PCR detection and sequencing revealed Hepatocystis infections with prevalences of 25% and 42% in the closely related epauletted fruit bats Epomophorus sp. and Micropteropus pusillus. For the first time, mature Hepatocystis gametocytes were identified in one Egyptian fruit bat (Rousettus aegyptiacus). This novel host record was confirmed by parasite and host genotyping and suggests that Hepatocystis parasites have a broader host distribution in African fruit bats than currently known.

Antigenicity of adult Opisthorchis viverrini, metacercariae and eggs was investigated by radio-immunoprecipitation and polyacrylamide gel electrophoresis using sera from patients with opisthorchiasis and from hamsters experimentally infected with 0. viverrini metacercariae. ¹²⁵I-labelled aqueous somatic extract and in vitro metabolic products of adult worms, and the extracts of metacercariae and eggs were immunoprecipitated, electrophoresed and autoradiographed and major antigens were characterized. Although components with M_r of > 116, 89, 78 and 20 kD appeared to be specifically associated with the somatic extract of adult fluke, the 89 kD protein was the most prominent component found in the in vitro culture fluid of adult worms and the metacercarial extract. Hamsters, experimentally infected with 0. viverrini, also showed the presence of antibody reactive with the 89 kD component within 15 days of infection. The potential of this antigen in immunodiagnosis is discussed.

Bovine besnoitiosis is caused by the largely unexplored apicomplexan parasiteBesnoitia besnoiti. In cows, infection during pregnancy often results in abortion, and chronically infected bulls become infertile. Similar to other apicomplexansB. besnoitihas acquired a largely intracellular lifestyle, but its complete life cycle is still unknown, modes of transmission have not been entirely resolved and the definitive host has not been identified. Outbreaks of bovine besnoitiosis in cattle were described in the 1990s in Portugal and Spain, and later several cases were also detected in France. More cases have been reported recently in hitherto unaffected countries, including Italy, Germany, Switzerland, Hungary and Croatia. To date, there is still no effective pharmaceutical compound available for the treatment of besnoitiosis in cattle, and progress in the identification of novel targets for intervention through pharmacological or immunological means is hampered by the lack of molecular data on the genomic and transcriptomic level. In addition, the lack of an appropriate small animal laboratory model, and wide gaps in our knowledge on the host-parasite interplay during the life cycle of this parasite, renders vaccine and drug development a cost- and labour-intensive undertaking.

Toxoplasmosis is a significant public health threat for Inuit in the Canadian Arctic. This study aimed to investigate arctic seals as a possible food-borne source of infection. Blood samples collected from 828 seals in 7 Canadian Arctic communities from 1999 to 2006 were tested for Toxoplasma gondii antibodies using a direct agglutination test. Polymerase chain reaction (PCR) was used to detect T. gondii DNA in tissues of a subsample of seals. Associations between seal age, sex, species, diet, community and year of capture, and serological test results were investigated by logistic regression. Overall seroprevalence was 10·4% (86/828). All tissues tested were negative by PCR. In ringed seals, seroprevalence was significantly higher in juveniles than in adults (odds ratio=2·44). Overall, seroprevalence varied amongst communities (P=0·0119) and by capture year (P=0·0001). Our study supports the hypothesis that consumption of raw seal meat is a significant source of infection for Inuit. This work raises many questions about the mechanism of transfer of this terrestrial parasite to the marine environment, the preponderance of infection in younger animals and the natural course of infection in seals. Further studies to address these questions are essential to fully understand the health risks for Inuit communities.

Toxoplasma gondiiis largely transmitted to definitive felid hosts through predation. Not all prey species represent identical risks of infection for cats because of differences in prey susceptibility, exposure and/or lifespan. Previously published studies have shown that prevalence in rodent and lagomorph species is positively correlated with body mass. We tested the hypothesis that different prey species have different infection risks by comparing infection dynamics of feral cats at 4 sites in the sub-Antarctic Kerguelen archipelago which differed in prey availability. Cats were trapped from 1994 to 2004 and anti-T. gondiiIgG antibodies were detected using the modified agglutination test (⩾1:40). Overall seroprevalence was 51·09%. Antibody prevalence differed between sites, depending on diet and also on sex, after taking into account the effect of age. Males were more often infected than females and the difference between the sexes tended to be more pronounced in the site where more prey species were available. A difference in predation efficiency between male and female cats may explain this result. Overall, our results suggest that the composition of prey items in cat diet influences the risk ofT. gondiiinfection. Prey compositon should therefore be considered important in any understanding of infection dynamics ofT. gondii.

Polymerase chain reaction–ribosomal ITS-1 DNA (rDNA) restriction fragment length polymorphism (PCR–RFLP) analysis and sequencing of the mitochondrial cytochrome c oxidase subunit 1 (CO1) and NADH dehydrogenase 1 (ND1) genes were used to characterize 33 Echinococcus granulosus isolates collected from different regions and hosts in Argentina, and to determine which genotypes occurred in humans with cystic hydatid disease. The results of the study demonstrated the presence of at least 4 distinct genotypes; the common sheep strain (G1) in sheep from Chubut Province and in humans from Río Negro Province, the Tasmanian sheep strain (G2) in sheep and 1 human from Tucumán Province, the pig strain (G7) in pigs from Santa Fe Province and the camel strain (G6) in humans from Río Negro and Buenos Aires Provinces. The finding that pigs harboured the pig strain and the occurrence of the Tasmanian sheep strain has considerable implications for the implementation of hydatid control programmes due to the shorter maturation time of both strains in dogs compared with the common sheep strain. Furthermore, this is the first report of the presence of the G2 and G6 genotypes in humans which may also have important consequences for human health.

Many issues concerning the taxonomy ofEchinococcushave been resolved in recent years with the application of molecular tools. However, the status ofEchinococcusmaintained in transmission cycles involving cervid intermediate hosts remains to be determined. The recent characterization of the parasite from cervids in Finland has highlighted the paucity of data available, particularly that from North America. In this study, we have characterized a large number ofEchinococcusisolates from cervids from Western Canada on the basis of morphology and molecular genetic techniques. Our results support earlier studies suggesting thatEchinococcusof cervid origin is phenotypically and genetically distinct toEchinococcusmaintained in domestic host assemblages, and also confirms thatEchinococcusof cervid origin does not constitute a genetically homogeneous group. However, our data do not support the existence of 2 distinct genotypes (strains/subspecies) with separate geographical distributions. Our data appear to support the existence of only 1 species in cervids, but additional isolates from cervids and wolves in other endemic regions should be characterized before a final decision is made on the taxonomic status ofEchinococcusin cervids.

The mitochondrial genomes of the genus Echinococcus have already been sequenced for most species and genotypes to reconstruct their phylogeny. However, two important taxa, E. felidis and E. canadensis G10 genotype (Fennoscandian cervid strain), were lacking in the published phylogeny. In this study, the phylogeny based on mitochondrial genome sequences was completed with these taxa. The present phylogeny highly supports the previous one, with an additional topology showing sister relationships between E. felidis and E. granulosus sensu stricto and between E. canadensis G10 and E. canadensis G6/G7 (closely related genotypes referred to as camel and pig strains, respectively). The latter relationship has a crucial implication for the species status of E. canadensis. The cervid strain is composed of two genotypes (G8 and G10), but the present phylogeny clearly suggests that they are paraphyletic. The paraphyly was also demonstrated by analysing the complete nucleotide sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1) of E. canadensis genotypes from various localities. A haplotype network analysis using the short cox1 sequences from worldwide isolates clearly showed a close relatedness of G10 to G6/G7. Domestic and sylvatic life cycles based on the host specificity of E. canadensis strains have been important for epidemiological considerations. However, the taxonomic treatment of the strains as separate species or subspecies is invalid from a molecular cladistic viewpoint.