The aim of study was to determine the seroprevalence of Toxoplasma gondii infection in stray cats and correlation with oocyst shedding and IFN-γ concentration. From April to August 2016, one hundred fifty nine stray cats were captured from various localities in Mashhad area. The blood and fecal samples were collected from each cat. The serum samples of stray cats were examined to detect antibodies against T. gondii infection by ELISA assay and the fecal samples were microscopically examined for T.gondii oocyst detection. In addition, the concentration changes of IFN-γ in serum samples of seropositive and seronegative cats were measured by ELISA kit. The results showed that 59.12% (94/159) of cats had antibodies against T. gondii infection. The seroprevalence of T. gondii infection in the adult cats above 3 years olds was higher than other age groups (p<0.05). The difference of seroprevalence of T.gondii infection was not significant by gender, month and region factors (p>0.05). In this study, the Toxoplasma/Hammondia like oocyst (THLO) were detected in 2.5% (4/156) in fecal samples of one seropositive and three seronegative cats. Results also showed that the mean of IFN-γ concentration in the seropositive cats was significantly higher than the seronegative cats (P<0.007). Based on the results, the high percentage of stray cats were infected with T. gondii in this area. The oocyst of THLO were found in fecal samples of a few cats that the most of them were seronegative. The IFN-γ concentration of seropositive cats was higher than the seronegative cats.

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