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 preparedblood DNA samples from 13 cattle with clinical babesiosis from the Badulla (n 8),Jaffna (n 3), and Kilinochchi (n 2) districts in Sri Lanka. These DNA samplestested positive in PCR assays specific for Babesia bovis (n 9), Babesia bigemina(n 9), and Babesia ovata (n 1). Twelve cattle were positive for B. bovis and/or B.bigemina. One cow was negative for the tested Babesia species but was positive forBabesia on microscopic examination; the phylogenetic positions of 18S rRNA and cytochrome oxidase subunit III gene sequences suggested that the cow was infectedwith Babesia sp. Mymensingh, which was recently reported from a healthy cow inBangladesh. We then developed a novel Babesia sp. Mymensingh-specific PCR assayand obtained positive results for one other sample. Analysis of gene sequences fromthe cow with positive B. ovata-specific PCR results demonstrated that the animalwas infected not with B. ovata but with Babesia sp. Hue-1, which was recently reported from asymptomatic cattle in Vietnam. The virulence of Babesia sp. Hue-1 isunclear, as the cow was coinfected with B. bovis and B. bigemina. However, Babesiasp. Mymensingh probably causes severe clinical babesiosis, as it was the sole Babesiaspecies detected in a clinical case. The present study revealed the presence of twobovine Babesia species not previously reported in Sri Lanka, plus the first case of severe bovine babesiosis caused by a Babesia species other than B. bovis, B. bigemina,and Babesia divergens.