Genetic Analysis of Babesia Isolates from Cattle with Clinical Babesiosis in Sri Lanka

Abstract

Bovine babesiosis is a serious threat to the cattle industry. We prepared blood DNA samples from 13 cattle with clinical babesiosis from the Badulla (<i>n</i> = 8), Jaffna (<i>n</i> = 3), and Kilinochchi (<i>n</i> = 2) districts in Sri Lanka. These DNA samples tested positive in PCR assays specific for <i>Babesia</i><i>bovis</i> (<i>n</i> = 9), <i>Babesia bigemina</i> (<i>n</i> = 9), and <i>Babesia</i><i>ovata</i> (<i>n</i> = 1). Twelve cattle were positive for <i>B. bovis</i> and/or <i>B. bigemina</i> One cow was negative for the tested <i>Babesia</i> species but was positive for <i>Babesia</i> on microscopic examination; the phylogenetic positions of 18S rRNA and cytochrome oxidase subunit III gene sequences suggested that the cow was infected with <i>Babesia</i> sp. Mymensingh, which was recently reported from a healthy cow in Bangladesh. We then developed a novel <i>Babesia</i> sp. Mymensingh-specific PCR assay and obtained positive results for one other sample. Analysis of gene sequences from the cow with positive <i>B. ovata</i>-specific PCR results demonstrated that the animal was infected not with <i>B. ovata</i> but with <i>Babesia</i> sp. Hue-1, which was recently reported from asymptomatic cattle in Vietnam. The virulence of <i>Babesia</i> sp. Hue-1 is unclear, as the cow was coinfected with <i>B. bovis</i> and <i>B. bigemina</i> However, <i>Babesia</i> sp. Mymensingh probably causes severe clinical babesiosis, as it was the sole <i>Babesia</i> species detected in a clinical case. The present study revealed the presence of two bovine <i>Babesia</i> species not previously reported in Sri Lanka, plus the first case of severe bovine babesiosis caused by a <i>Babesia</i> species other than <i>B. bovis</i>, <i>B. bigemina</i>, and <i>Babesia</i><i>divergens</i>.