Seroprevalence and associated risk factors of Toxoplasma gondii infection in yaks (Bos grunniens) on the Qinghai–Tibetan Plateau of China oleh Sun Tao, Rahman Sajid Ur, Cai Jinzhong, Zeng Jiangyong, Mi Rongsheng, Zhang Yehua, Gong Haiyan, Ma Hongcai, Huang Yan, Han Xiangan, Zhao Quan, Chen Zhaoguo