Prevalence and genetic diversity of Theileria and Anaplasma species infecting cattle in Paraguay

Abstract

Bovine theileriosis and anaplasmosis are major tick-borne diseases affecting cattle health and productivity worldwide. Although cattle farming significantly contributes to Paraguay's economy, limited epidemiological data on the causative agents hinder the formulation of disease control measures. To address this challenge, the present study investigated the prevalence, risk factors, and genetic diversity of Theileria annulata, Theileria orientalis, and Anaplasma marginale among cattle populations in Paraguay. Blood DNA samples from 326 cattle in nine departments of Paraguay were screened with the pathogen-specific PCR assays. All three pathogens were detected with A. marginale (18.0 %) being the most prevalent, followed by T. orientalis (2.4 %) and T. annulata (1.5 %). In addition, further screening of A. marginale-negative samples using two PCR assays targeting the 16S rRNA and groEL genes of Anaplasma spp., followed by sequencing, detected an infection with Candidatus Anaplasma cinensis. We observed significantly higher A. marginale-positive rates in the Eastern region, males, and extensively managed cattle, as compared to those in the Western region, females, and semi-intensively managed cattle, respectively. Phylogenetic analyses revealed that T. annulata tams1 gene sequences were diverse and occurred in multiple clades, while T. orientalis mpsp gene sequences clustered into the genotypes 1, 2, and 3. In contrast, A. marginale msp5 gene sequences occurred within a single clade, suggesting a low genetic diversity. In conclusion, the detection of T. annulata, T. orientalis genotype 2, and A. marginale indicates that cattle populations in Paraguay are at risk of clinical theileriosis and anaplasmosis, highlighting the need to develop disease management strategies. © 2025 Elsevier B.V