Natural Toxoplasma Gondii Infections in European Brown Hares and Mountain Hares in Finland: Proportional Mortality Rate, Antibody Prevalence, and Genetic Characterization

Abstract

ABSTRACT:In material examined postmortem in Finland from May 2006 to April 2009, acute generalized toxoplasmosis was the immunohistochemically confirmed cause of death in 14 (8.1%) of 173 European brown hares (Lepus europaeus) and four (2.7%) of 148 mountain hares (Lepus timidus). Sera from 116 of the European brown hares and 99 of the mountain hares were screened with a commercial direct agglutination test for Toxoplasma gondii-specific IgG antibodies at a dilution of 1:40. All sera from cases of fatal toxoplasmosis had high titers of antibodies reactive to T. gondii. In contrast, none of 107 European brown hares and four (4%) of 96 mountain hares that died of other causes were antibody-positive. The proportional mortality rates and the T. gondii antibody prevalences among noncases differed significantly between the two host species (P,0.05). Direct genetic characterization of the causative agent was performed on DNA extracted from formalin-fixed, paraffin-embedded tissue of the hares with fatal toxoplasmosis. Based on the results with six microsatellite markers (B18, TUB2, TgM-A, W35, B17, and M33; all six in 15 cases and four in three cases), all the cases were caused by T. gondii genotype II; the size of the PCR product at the seventh marker (M48) varied (213-229 base pairs). The presence of T. gondii genotype II, which is endemic in Europe, is now confirmed in Finnish wildlife: Natural infections with T. gondii parasites belonging to this widespread genotype caused fatal generalized toxoplasmosis in the two species of wild hares.

Free-Ranging Eurasian Lynx (Lynx Lynx) as Host of Toxoplasma Gondii in Finland

“…A similar north-south gradient in anti-T. gondii antibody prevalence was reported in Eurasian lynx in Sweden (Ryser-Degiorgis et al, 2006). No geographic gradient was demonstrable in the previous Finnish lynx study (Oksanen and Lindgren, 1995), whereas a clear gradient has been seen in other hosts in Finland (Jokelainen et al, 2010(Jokelainen et al, , 2011 and attributed to the likely presence of more domestic cats in the more densely populated southern part of the country. Furthermore, the division line for southwest and northeast in the present study (Fig.…”

“…In the northeastern area, the main prey species for lynx is mountain hare (Lepus timidus). Anti-T. gondii antibody prevalence was 25.7% in apparently healthy small cervids hunted in 2008-2009, whereas a significantly lower proportion (4.2%) of mountain hares examined postmortem in 2006-2009 and had died from some other cause than toxoplasmosis were antibody positive (Jokelainen et al, 2010(Jokelainen et al, , 2011. The size of prey animals affects the number of them eaten by the lynx, which probably partly balances this difference.…”

“…Underdiagnosis by veterinary pathologists is unlikely. Postmortem diagnosis of toxoplasmosis can be challenging because gross findings are typically nonspecific and scarce, but histopathologic examination reveals the typical lesions and parasite structures, and methods for confirming the diagnosis are available and routinely used in the Finnish laboratory (Dubey, 2010;Jokelainen et al, 2011Jokelainen et al, , 2012. The concomitant high antibody prevalence and undetectably low or zero incidence of clinical cases suggest that Eurasian lynx are not especially susceptible to clinical toxoplasmosis.…”

“…The same method and cutoff to define a sample antibody positive make the results of these three studies comparable. The method chosen has been widely used for several animal species (Dubey, 2010;Jokelainen et al, 2010Jokelainen et al, , 2011Jokelainen et al, , 2012. The cutoff chosen can be considered high, and only one antibody class was examined.…”

Acute Fatal Toxoplasmosis in a Great Spotted Woodpecker (Dendrocopos major)

“…The staining was performed according to Conley et al (1981) with Toxoplasma gondii Ab-1 Rabbit Polyclonal Antibody (Thermo Fisher Scientific, Runcorn, United Kingdom) as the primary antibody, and repeated in parallel according to Jokelainen et al (2011) with Toxoplasma gondii EpitopeSpecific Rabbit Antibody (Thermo Fisher Scientific). DNA was extracted from the formalin-fixed, paraffin-embedded tissue samples for direct genetic multilocus characterization of the causative parasite strain (Jokelainen et al 2011). DNA was extracted from frozen, cultivated T. gondii tachyzoites as positive control and from nuclease-free water as negative control.…”