FIRST DETECTION OF BABESIA MICROTI IN PEOPLE LIVING IN THE PLURINATIONAL STATE OF BOLIVIA

INTRODUCTION: Tick-transmitted hemoparasites of the genus Babesia (phylum Apicomplexa) show a worldwide distribution and have a wide spectrum of vertebrate hosts that includes, occasionally, humans (Gray et al, Ticks Tick Borne Dis, 2010, 1:3–10). Indeed, the cattle species B. divergens (and B. venatorum) in Europe and the rodent species B. microti (and B. duncani) in North America have been shown as responsible for most human infections. Babesiosis is a malaria-like illness that ranges from asymptomatic infection to an even fatal disease, associated to hemolytic anemia and severe systemic complications (Vannier et al., N Engl J Med, 2012, 366:2397–407). B. microti infection is generally mild, self-limiting or asymptomatic, but a fatal outcome may be occasionally observed. Deer, heavily infested by vector ticks that -at larval stage- feed on rodents, are important in the epidemiology of the infection (Telford et al., J Med Entomol, 1993, 30:223-7). In Bolivia, only B bovis and B. bigemina have been investigated in cattle and seem to be stably endemic in the Eastern part of the country (Carrique et al., Veterinary J, 2000, 160:162–4). No data are available about the presence of B. microti. MATERIALS AND METHODS: Research aims to investigate on human babesiosis in two rural communities of Southeastern Bolivia (Ivamirapinta and Bartolo), as part of a screening on hematic parasites carried out in 2013. In the study area, economy is based on agriculture and animal farming, and people live in close contact with pets and wild animals (deer included). Blood samples were taken from 273 healthy subjects (1-83 years-old) and used to arrange thick and thin smears, to extract DNAs, and to obtain sera. Smears were Giemsa stained and examined by microscopy. DNAs were amplified by PCR using a pair of generic apicomplexan 18S rRNA-specific primers. Positive amplicons were confirmed by sequencing. Several sera (from infected people and from older components of some families) were submitted to an IFI test available to detect B. microti infection in humans (B. microti-IFA IgG Antibody kit, Fuller Laboratories, Fullerton, CA). RESULTS: A total of 10 (3.7%) thin smears were positive to B. microti. Morphological diagnosis was confirmed by sequencing. As expected, preliminary serological results evidenced reactivity to B. microti antigens not only in all positive subjects (at >1:128 dilutions) but also in further 4/43 subjects negative to microscopy and PCR (at dilutions 1:64 or 1:128). CONCLUSIONS: This is the first record of human babesiosis in the Plurinational State of Bolivia, in areas where people is exposed to many other parasites that can induce severe anemia. More extensive studies are needed to improve knowledge about all zoonotic babesial species, and people should be alerted about sanitary risks originated by ticks. Finally, physicians should be aware of the presence of B. microti, and well trained on clinical features of babesiosis in order to intervene, when needed, with appropriate treatment.