Expression patterns of chemokine mediators and TLR10 in natural bovine babesiosis and anaplasmosis infections

Cattle tick fever, caused by the protozoa Babesia bovis and B. bigemina and the rickettsial bacterium Anaplasma marginale, represents a significant constraint to livestock productivity worldwide. Taurine cattle are considered more susceptible to these hemoparasites than zebuine breeds. Chemokines and Toll-like Receptors (TLRs) play key roles in immune processes such as chemotaxis and inflammation, primarily through interactions with respective receptors. This study assessed the relationship between the expression of four chemokine-related genes (ccr3, cxcl12, cxcl8, and cxcr1) and one TLR (tlr10) with the infection levels of B. bovis, B. bigemina, and A. marginale in 24 naturally infected calves from two genetic groups (Angus [n = 13; 100% taurine] and Ultrablack [n = 11; 82% Angus, 18% zebuine]). Blood samples were collected every 30 days over six time points (Nov 2021-Apr 2022). DNA was used to quantify hemoparasite loads by qPCR (log DNA copy number, CNlog), while RNA was used for RT-qPCR-based gene expression analysis. A mixed model was used to assess associations between gene expression and infection levels, controlling for evaluation, sex, genetic group, and their interactions. All genes, except cxcl12, showed significant associations with at least one hemoparasite. Higher B. bovis and B. bigemina CNlog values were linked to reduced expression of most genes, whereas A. marginale infection was associated with increased gene expression. These findings highlight distinct immune modulation strategies by hemoparasites and underscore the need for species-specific interventions. Further studies are required to explore the mechanisms by which these mediators influence susceptibility or resistance in cattle.