Evidence of red panda as an intermediate host of Toxoplasma gondii and Sarcocystis species

Toxoplasma gondii has been found to infect almost all warm-blooded animals; however, some hosts lack direct evidence of T. gondii infection. The red panda (Ailurus fulgens) is an endangered species that mainly lives in temperate forests of South Asia. Here, T. gondii infection in red pandas from zoos in China were reported. Antibodies to T. gondii were found in 14.3% (2/14) of red pandas via the modified agglutination test (MAT) with a cut-off titer of 1:25. One viable T. gondii strain was isolated from tissues of red panda and designated as TgRedpandaCHn1. DNA from tachyzoites obtained from cell culture was characterized by PCR-RFLP with 10 markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) and virulence genes of ROP5 and ROP18. The results indicate that this isolate belonged to ToxoDB genotype #20. The ROP18/ROP5 genotype combination predicated that this strain is non-lethal to mice, which is supported by the infection in mice. T. gondii tissue cysts were readily formed and mice survived. Tissue cysts observed in the histopathological sections of the tongue and diaphragm of one red panda were speculated as sarcocysts, but not T. gondii base on morphological characteristics. To our knowledge, this study is the first to report on the isolation of T. gondii from red panda. Additionally, this report provides direct evidence of red panda as an intermediate host of T. gondii and Sarcocystis species.