Toxoplasma gondii

Ren, Hongjie, Yang, Liulu, Zhu, Niuping, Li, Junbao, Su, Chunlei, Jiang, Yibao & Yang, Yurong, 2022, Additional evidence of tigers (Panthera tigris altaica) as intermediate hosts for Toxoplasma gondii through the isolation of viable strains, International Journal for Parasitology: Parasites and Wildlife 19, pp. 330-335 : 331

2.2. Isolation of viable T. gondii from tiger tissues using bioassay in mice

Tissue samples (50 g: namely heart, tongue, skeletal muscle, diaphragm, or brain) from the four tigers were homogenized and digested in pepsin solution, respectively (Dubey, 2010). The homogenates were injected subcutaneously into Swiss mice (n = 3–5) and IFN–γ – / – mice (n = 1). Specific pathogen–free Swiss mice were supplied by the Laboratory Animal Center at the Zhengzhou University ( China, Grant No. 41003100000236). IFN–γ – / – mice were supplied by Jackson Laboratory ( USA, product code: 002287). The remaining homogenate was saved at – 20 ◦ C for molecular analysis. After inoculation, the clinical signs of the mice were recorded every day. Impression smears of the lungs, mesenteric lymph nodes, and brain of dead mice were examined for T. gondii . The survivors were bled on day 30 post-inoculation (DPI), and 1:25 and 1:200 dilutions of mice serum samples were tested for T. gondii antibodies using a modified agglutination test (MAT). On 60–80 DPI, the mice were euthanized, and all the brains of the mice were examined for T. gondii cysts and counted as described by Dubey et al. (2012). If tissue cysts were not found in brain smears of the seropositive mice, homogenized brain and muscle were sub-passaged subcutaneously into new groups of Swiss mice. All the mice were considered successfully infected when T. gondii antibodies or parasites were detected in their serum samples or tissues.