Experimental infection of Toxoplasma gondii in specific pathogen-free and commercial broiler chicks

Toxoplasma gondii is an intracellular protozoan parasite that infects most warm-blooded animals, including humans, and causes toxoplasmosis. In this study, the pathogenicity of RH strain of T. gondii in broiler chicks was investigated and the susceptible tissues of chicks were clarified. Fourteen-day-old broiler chicks were injected intraperitoneally with 1 × 10⁷, 1 × 10⁶, and 1 × 10⁵ tachyzoites of T. gondii, respectively. The results showed that the spleen and lungs were frequently positive for T. gondii DNA. Moreover, in chicks, infection with only 1 × 10⁷ tachyzoites resulted in clinical symptoms, with lower weight gain, higher body temperature, anorexia and apathy, indicating that chicks are insusceptible to T. gondii infection. Then, this study investigated the relationship between T. gondii survival and chick body temperature. In the experiment, the invasion and proliferation of T. gondii were evaluated at 37 °C and 41 °C, respectively, and the survival of the parasites was significantly inhibited at 41 °C. In conclusion, broiler chicks are insusceptible to T. gondii infection, and the higher body temperature compared to other susceptible animals is a key factor in the reduction of T. gondii pathogenicity.