Abstract
BackgroundAlthough the detection of Toxoplasma gondii in bovine tissues is rare, beef might be an important source of human infection. The use of molecular techniques, such as magnetic capture qPCR (MC-qPCR), in combination with the gold standard method for isolating the parasite (mouse bioassay), may increase the sensitivity of T. gondii detection in infected cattle. The risk of transmission of the parasite to humans from undercooked/raw beef is not fully known and further knowledge about the predilection sites of T. gondii within cattle is needed. In the current study, six Holstein Friesian calves (Bos taurus) were experimentally infected with 106 T. gondii oocysts of the M4 strain and, following euthanasia (42 dpi), pooled tissues were tested for presence of the parasite by mouse bioassay and MC-qPCR.ResultsToxoplasma gondii was detected by both MC-qPCR and mouse bioassay from distinct pools (100 g) of tissues comprising: liver, tongue, heart, diaphragm, semitendinosus (hindlimb), longissimus dorsi muscle (sirloin) and psoas major muscle (fillet). When a selection of individual tissues which had been used for mouse bioassay were examined by MC-qPCR, parasite DNA could only be detected from two animals, despite all calves showing seroconversion after infection.ConclusionsIt is apparent that one individual test will not provide an answer as to whether a calf harbours T. gondii tissue cysts. Although the calves received a known number of infectious oocysts and highly sensitive methods for the detection of the parasite within bovine tissues were applied (mouse bioassay and MC-qPCR), the results confirm previous studies which report low presence of viable T. gondii in cattle and no clear predilection site within bovine tissues.
Highlights
The detection of Toxoplasma gondii in bovine tissues is rare, beef might be an important source of human infection
Toxoplasma gondii serology in calves as tested by modified agglutination test (MAT) All calves were seronegative for T. gondii by MAT at the start of the experiment
In conclusion, the results from this study demonstrate that viable T. gondii and Deoxyribonucleic acid (DNA) can be detected in several different calf tissues including meat cuts six weeks after oral inoculation with 106 oocysts
Summary
The detection of Toxoplasma gondii in bovine tissues is rare, beef might be an important source of human infection. The risk of transmission of the parasite to humans from undercooked/raw beef is not fully known and further knowledge about the predilection sites of T. gondii within cattle is needed. (n = 504) in southern Spain [4], 45.6% (n = 406) in Switzerland [5], 33.8% (n = 74) in eastern Poland [6], and 25.0% (n = 995) in cattle over 12 months old from the Netherlands [7] In contrast to these figures, a much lower seroprevalence of 7.5% (n = 161) was reported for cattle from North Portugal [8]. Despite the high seroprevalence observed in the majority of studies, T. gondii parasites are rarely detected in seropositive animals
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