Toxoplasma gondii in four captive kangaroos (Macropus spp.) in China: Isolation of a strain of a new genotype from an eastern grey kangaroo (Macropus giganteus)

Abstract

Marsupials are highly susceptible to <i>Toxoplasma gondii</i> infection. Here, we report <i>T. gondii</i> infection in four kangaroos from a zoo in China. Kangaroos were imported into China in 2000 and were since bred in zoo. In 2017-2018, four kangaroos died due to respiratory system disease or injury. The bodies were submitted to the laboratory to test for <i>T. gondii</i> infection. Antibodies to <i>T. gondii</i> were found in 75% (3/4) of the kangaroos via the modified agglutination test with the cut-off 1:25. Cysts were observed in the histopathological sections of tongue and diaphragm or squashes of fresh myocardium in two kangaroos. These cysts were confirmed as <i>T. gondii</i> by immunohistochemical staining and molecular biological analysis. One viable <i>T. gondii</i> strain was isolated from one kangaroo and designated as TgRooCHn1. DNA from <i>T. gondii</i> tachyzoites obtained from cell culture was characterized by 10 PCR-RFLP markers and the virulence genes ROP5 and ROP18. The genotype of this isolate did not match with any known genotypes; it was designated as ToxoDB#292. The virulence of TgRooCHn1 (10⁴ tachyzoites) was non-lethal to mice, and it formed tissue cysts. To our knowledge, the present study is the first isolation of ToxoDB#292 strain from kangaroo. Improvemets for captive settings were initiated, including greater attention being paied to birds and stray cats, fed frozen meat for carnivores.