PCR Based Approach for Detection of Bovine Babesiosis in Suspected Carrier Cattle and Vector Ticks in Sri Lanka

Purpose: Cattle recovered from clinical babesiosis become carriers for a certain period posing a threat of transmitting the disease to the entire herd. Diagnosis of carrier cattle is important for preventing outbreaks of babesiosis. The objective of the present study therefore, was to establish a sensitive rapid detection method for bovine babesiosis in suspected carrier cattle using nested PCR (nPCR). Research Method: Accordingly, 30 blood samples and ticks were collected from suspected carrier cattle representing two bio-climatic zones of Sri Lanka. Blood samples were analysed by both microscopically and nested nPCR methods for detection of bovine babesiosis. Further ticks were analysed for morphological idenfication using micrscopy and for babesiosis with nPCR. Findings: 47% (14/30) among the investigated samples became positive for the babesia infection with light microscopy, while nPCR analysis diagnosed 90% (27/30) as positive. This indicates that, 43% (13/30) of the animals which appeared to be healthy through routine light microscopical diagnosis were in fact carriers posing a major threat to the  healthy herd. Further, according to the results of nPCR, 22% (6/27) of the blood samples were positive only for Babesia bovis infection, 11% (3/27) only for Babesia bigemina infection and 67% (18/27) for mixed infection with both parasites. The dominant tick vector isolated from both zones was Rhiphicephalus microplus. Out of the examined ticks, 21% (5/24) were positive for Babesia bigemina infection. Research limitations: Since the  sample size from all sites of both climatic zones were uneven and small, data could not be analysed for statistical significance. Originality/Value: However, the results from this study indicate that nPCR provides a sensitive screening method to detect bovine babesiosis compared to the conventional microscopic analysis.