Theileria luwenshuni and Novel Babesia spp. Infections in Humans, Yunnan Province, China.

Piroplasmid parasites such as Theileria luwenshuni protozoa pose a global threat to both animal and human health. However, human theileriosis remains underexplored compared to infections caused by Plasmodium and Babesia species parasites. We investigated potential hemoparasite infections among 1,721 persons with fever, anemia, or both in Yunnan Province, China. Molecular detection identified 13 cases positive for T. luwenshuni protozoa, of which 5 patients were further confirmed by Western blot antibody analysis. We also identified 6 babesiosis cases, 3 infections with B. microti and 3 with novel Babesia spp. Subsequent vector and host investigations in the vicinity of the index cases revealed T. luwenshuni protozoa in 1 tick and 53 livestock animals. Of note, 3.3% combined vector-host samples tested positive for genetically diverse Babesia species. Our findings highlight the endemic circulation of T. luwenshuni and Babesia spp. parasites in southwest China, underscoring their importance as emerging public health concerns.