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

Abstract

<i>Toxoplasma gondii</i> has been found to infect almost all warm-blooded animals; however, some hosts lack direct evidence of <i>T. gondii</i> infection. The red panda (<i>Ailurus fulgens</i>) is an endangered species that mainly lives in temperate forests of South Asia. Here, <i>T. gondii</i> infection in red pandas from zoos in China were reported. Antibodies to <i>T. gondii</i> 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 <i>T. gondii</i> 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. <i>T. gondii</i> 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 <i>T. gondii</i> base on morphological characteristics. To our knowledge, this study is the first to report on the isolation of <i>T. gondii</i> from red panda. Additionally, this report provides direct evidence of red panda as an intermediate host of <i>T. gondii</i> and <i>Sarcocystis</i> species.