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ARS Home » Plains Area » Kerrville, Texas » Knipling-Bushland U.S. Livestock Insects Research Laboratory » Cattle Fever Tick Research Unit » Research » Research Project #437038

Research Project: Year 2 CFT Eradication Program Funding - Are Nilgai Antelope and Axis Deer Susceptible to Infection with a Virulent Strain of Babesia bovis?

Location: Cattle Fever Tick Research Unit

Project Number: 3094-32000-042-034-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jul 15, 2019
End Date: Apr 30, 2022

Nilgai antelope and axis deer can serve as alternative vertebrate hosts for cattle fever ticks, as they have been found infested with R. microplus both within the TEQA and in the Free Area. There have been no studies conducted to evaluate the role that nilgai antelope and axis deer may play in the bovine babesiosis disease transmission cycle. 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. The objective of this study will be to evaluate susceptibility of nilgai and axis hosts to infection with a virulent strain of Babesia bovis, and to asses their propensity to serve as sources of infections to tick vectors.

Nilgai calves and axis fawns will be acquired from a licensed/registered vendor/breeder in the Fall and Spring, respectively, and they will be hand-reared to optimize human handling and minimize impact of stress on their biological response. These exotic ungulate species (N = 4 per species, ~4 - 6 mos old) will be challenged with an inoculum of the merozoite stage of B. bovis, which is found in parasitized cattle red blood cells and is known to be virulent to cattle. In parallel, a bovine host (N = 1) will be inoculated as a positive control for infection during each challenge. To determine the infection status all individuals will be monitored for clinical signs of babesiosis including changes in body temperature and packed cell volume. Blood samples and serum will be collected daily from 0 to 15 days post inoculation and then weekly for up to 3 months post challenge. Infection status will be confirmed by performing molecular and serological assays including PCR assays targeting 18s and rap1 genes and immunoblotting.