Spreading of Human Babesiosis in China: Current Epidemiological Status and Future Challenges

Abstract

Human babesiosis is an infection caused by intraerythrocytic protozoa of the genus Babesia and is a worldwide emerging tick-borne disease (1). Babesia is mainly parasitized in erythrocytes of human or other vertebrates and transmitted by the bite of ticks, blood transfusion, or organ transplantation (1). Humans are generally susceptible to Babesia, especially those who are immunocompromised with conditions such as splenectomy or splenic dysfunction, as well as those of old age, with infirmity, or with other severe diseases. The life cycle of Babesia includes a definitive host and an intermediate host, and its definitive host (vector) is Ixodes (2). The main species Ixodes that can transmit Babesia include Dermacentor nuttalli, D. silvarum, D. niveus, D. sinicus, Rhipicephalus haemaphysaloides, Haemaphysalis longicornis, Ixodes persulcatus, and I. ricinus. Babesia species have a wide range of intermediate hosts including humans, rodents (such as Niviventer niviventer, Rattus norvegicus, Rattus flavipectus, and Apodemus agrarius), and other animals (e.g., cattle, deer, dogs, raccoons, and birds). Since Babesia bigemina was first discovered in red blood cells of infected cattle in 1888 by Babes (3), more than 100 species of Babesia have been identified and reported. However, only B. microti, B. diversens, B. duncani, B. venatorum, and other species can infect humans (2).