DNA detection of Babesia bovis in sheep, ticks and cattle during an outbreak of sheep ixodidiosis by Rhipicephalus microplus

Abstract

This study describes, for the first time, the molecular and phylogenetic detection of Babesia bovis in sheep, with concurrent detection in cattle and R. microplus ticks during a severe tick infestation outbreak in northeastern Brazil. The affected herd, located in São Pedro, Rio Grande do Norte State, comprised sheep and cattle raised under a semi-intensive system. Blood, fecal, and tick samples were collected from 20 sheep and three cattle. Blood samples were subjected to complete blood count analysis and, together with tick samples, to DNA extraction and molecular detection of Anaplasma marginale , B. bovis , and Babesia bigemina . Amplified fragments were sequenced and analyzed phylogenetically. The sheep exhibited heavy tick infestations, alopecia, and skin lesions. Hematological analysis revealed anemia in 8/20 of the sheep, leukocytosis in 5/20, and thrombocytopenia in one animal. Coproparasitological examination revealed a high burden of nematode eggs of the order Strongylida in 12/20 of the evaluated sheep. Molecular analysis detected B. bovis in one sheep, one bovine, and ticks collected from sheep. Only cattle were positive for B. bigemina , whereas A. marginale was not detected in any sample. The sequence obtained from the sheep shared >97% identitity with B. bovis isolates available in GenBank and clustered with the bovine and tick isolates from the same farm, indicating a close genetic relationship and supporting the hypothesis of local circulation of the parasite. The observed anemia was likely multifactorial, associated with tick infestation, gastrointestinal parasitism, and possibly B. bovis infection. This study provides molecular and phylogenetic evidence of the occurrence of B. bovis in sheep, cattle, and R. microplus ticks during a heavy tick infestation outbreak, suggesting the circulation of a common parasite lineage and a possible epidemiological association under field conditions.