Date: Tue 4 Apr 2017
Source: Parasites & Vectors [edited]
Klun I, Uzelac A, Villena I et al. The first isolation and molecular characterization of _Toxoplasma gondii_ from horses in Serbia. Parasit Vectors. 2017;10(1):167. doi: 10.1186/s13071-017-2104-x.
Consumption of undercooked or insufficiently cured meat is a major risk factor for human infection with _Toxoplasma gondii_. Although horsemeat is typically consumed rare or undercooked, information on the risk of _T. gondii_ from infected horse meat to humans is scarce. Here, we present the results of a study to determine the presence of _T. gondii_ infection in slaughter horses in Serbia, and to attempt to isolate viable parasites.
The study included horses from all regions of Serbia slaughtered at 2 abattoirs between June 2013 and June 2015. Blood sera were tested for the presence of specific IgG _T. gondii_ antibodies by the modified agglutination test (MAT), and samples of trypsin-digested heart tissue were bioassayed in mice. Cyst-positive mouse brain homogenates were subjected to DNA extraction and _T. gondii_ strains were genotyped using 15 microsatellite markers (MS).
A total of 105 slaughter horses were sampled. At the 1:6 cut-off 48.6 percent of the examined horses were seropositive, with the highest titre being 1:400. Viable parasites were isolated from 2 grade type mares; both parasite isolates (RS-Eq39 and RS-Eq40) were _T. gondii_ type III, and both displayed an increased lethality for mice with successive passages. These are the 1st cases of isolation of _T. gondii_ from horses in Serbia. When compared with a worldwide collection of 61 type III and type III-like strains, isolate RS-Eq39 showed a combination of MS lengths similar to a strain isolated from a duck in Iran, and isolate RS-Eq40 was identical in all markers to 3 strains isolated from a goat from Gabon, a sheep from France and a pig from Portugal. Interestingly, the source horses were 1 seronegative and 1 weakly seropositive.
The isolation of viable _T. gondii_ parasites from slaughter horses points to horsemeat as a potential source of human infection, but the fact that viable parasites were isolated from horses with only a serological trace of _T. gondii_ infection presents further evidence that serology may not be adequate to assess the risk of toxoplasmosis from horsemeat consumption. Presence of _T. gondii_ type III in Serbia sheds more light into the potential origin of this archetypal lineage in Europe.
[_Toxoplasma gondii_ are able to infect all mammals and birds. A very high infection rate which is reported in horses in this study. Horses are not carnivores and infection most probably comes from pastures contaminated with _T.gondii_ oocysts shed by felines. The study underlines the importance of eating meat which has been thoroughly cooked. - ProMED Mod.EP]
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