Role of nilgai antelope in Babesia sp. transmission cycle

In the mid-1950s cattle fever ticks, Rhipicephalus microplus and R. annulatus, were considered eradicated from the US except for an area along the Texas-Mexico border, known as the Permanent Quarantine Zone (PQZ). Nilgai antelope (Boselephus tragocamelus) and white-tailed deer are two common alternative hosts for cattle fever ticks, having been found infested in Texas and Mexico. To date, there have been no studies evaluating the role that nilgai antelope may play in the bovine babesiosis disease transmission cycle. The objective of this research was to evaluate susceptibility of nilgai antelope to infection causative agents of bovine babesiosis, and to assess their propensity to serve as sources of infections to tick vectors. We hand reared nilgai antelope calves to 4-5 months of age and then challenged them with an intravenous inoculation with virulent strains of Babesia bovis or B. bigemina. Nilgai calves and control beef calves were assessed for clinical signs of infection by measuring PCV and body temperature, as well as molecularly via PCR and serology. Given the overlapping habitat of these alternative hosts with primary cattle hosts, it is imperative to understand the impacts of these exotic species, which are a new addition to the ecology and epidemiology of this disease system. If nilgai antelope are not susceptible to infection with B. bovis, as has been shown for white-tailed deer, they may act as dilution hosts by eliminating Babesia from the ticks and breaking the parasite transmission cycle, thus decreasing the likelihood of disease re-emergence and establishment.