Wild and domestic animals as hosts of Toxoplasma gondii in Finland
Year: 2013
Type: dissertation
Abstract: Toxoplasma gondii is a widespread protozoan parasite of humans, domestic animals, and wildlife. In this work including nationwide epidemiological cross-sectional studies and descriptive case series studies, T. gondii was confirmed as endemic, common, and sometimes fatal in a selection of animal hosts in Finland. Antibodies against T. gondii were detected in all host species investigated, including hosts hunted or raised for human consumption. The samples were screened with a commercial direct agglutination test using a conservative cut-off for seropositivity. Specific anti-T. gondii IgG antibodies were detected in 9.6% of the 1215 moose (Alces alces), 26.7% of the 135 white-tailed deer (Odocoileus virginianus), and 17.6% of the 17 roe deer (Capreolus capreolus) examined. Seropositive animals were found in 76.3% of 97 sheep farms and 60.0% of 25 wild boar farms, while antibodies were detected in 24.6% of the 1940 individual sheep (Ovis aries) and 33.0% of the 197 farmed wild boars (Sus scrofa) examined. Both of the possible definitive hosts present in Finland had commonly encountered the parasite: 48.4% of the 490 domestic cats (Felis catus) and 86.1%, a significantly higher proportion, of the 337 Eurasian lynx (Lynx lynx) tested seropositive. Raw meat in the diet was a major risk factor (odds ratio 2.0) for the infection in domestic cats. Evidence of exposure to T. gondii followed a north-south gradient in several hosts. The prevalence data indicate an environment contaminated with oocysts. PCR-confirmed T. gondii oocysts were found in one (0.8%) of the fecal samples from domestic cats. None of the lynx shed oocysts. Cats also died of toxoplasmosis; the proportional mortality rate was 3.1% among the 193 domestic cats examined postmortem. The first local T. gondii isolates (FIN1 and FIN2) were obtained from two cats into cell culture. Toxoplasma gondii also caused deaths in species considered highly susceptible to clinical toxoplasmosis. The proportional mortality rates were 8.1% in 173 European brown hares (Lepus europaeus), 2.7% in 148 mountain hares (L. timidus), and 15.8% in a limited number of 19 Eurasian red squirrels (Sciurus vulgaris). Direct genotyping of T. gondii strains was based on analysis of length polymorphism at six microsatellite markers (B18, TUB2, TgM-A, W35, B17, and M33); one fingerprinting marker (M48) was included for further characterization. Both wild and domestic animals were infected with strains belonging to genotype II, which was also the genotype of the oocysts shed. Strains of genotype II had caused all 27 fatal cases investigated in detail. The observed fatality rates among apparently immunocompetent animals challenge the prevailing assumption of nonvirulence of genotype II strains. Toxoplasma gondii infections represent both a public health issue and a welfare issue for its hosts. The parasite thrives in Finland and should not be underestimated.
Source: Työväentutkimus Vuosikirja
Author: Jokelainen, Pikka
Language: English
Subfield: Parasitology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1584003222