Tick-borne pathogens in meat sheep from Brazil: first report of Theileria ovis in sheep in latin America.

Abstract

Tick-borne hemoparasitic diseases have a worldwide presence, impacting public health and livestock economies. In this study, 16 ewes from the same farm were evaluated, 56% (9/16) exhibited various clinical symptoms, such as conjunctivitis, nasal discharge, cough, swollen lymph nodes, fever, and tick infestation. After physical examination, ultrasound and complete blood count analysis were performed, along with molecular testing using Polymerase Chain Reaction (PCR) and Sanger sequencing. Neutrophilic leukocytosis, mild normocytic normochromic anemia, thrombocytosis, reactive lymphocytes, and intra-cytoplasmic lymphocytic inclusion bodies were all identified. Spleen and liver abnormalities were confirmed by ultrasound. In total, 44% (7/16) of ewes were infested with ticks, which were identified as Dermacentor nitens, Rhipicephalus microplus, and Amblyomma sculptum. Of the 16 sheep screened for tick-borne agents using PCR, 37% (6/16) tested positive for the Piroplasmida order. Among these, 33% (2/6) showed co-infection with Anaplasma sp. None of the samples tested positive for Ehrlichia spp. or Borrelia spp. Molecular analyses, followed by sequence comparison, revealed the pathogens to be Theileria ovis and Anaplasma sp. closely related to Candidatus Anaplasma boleense. Ewes were treated with three doses of oxytetracycline (20 mg/kg) 48 h apart. After treatment, new blood smears and whole blood samples were negative for cell inclusions, and all PCR results were negative. The study identified a tick-borne disease caused by piroplasms and Anaplasma spp. in a Brazilian sheep flock with clinical remission following treatment. Furthermore, this research marks the first documentation of T. ovis and Anaplasma sp. closely related to Candidatus A. boleense infecting sheep in Latin America, emphasizing the need for further studies and surveillance of tick-borne pathogens in Brazil.