Molecular Detection and Phylogenetic Analysis of Tick-Borne Pathogens Isolated from Cattle and Questing Ticks in Gairo and Monduli Districts, Tanzania

Ticks and tick-borne diseases pose serious constraints to the improvement of livestock production in tropical and subtropical regions of the world, including Tanzania. Despite their wide distribution, the information on the tick, pathogen, and host relationship particularly that obtained using molecular techniques is scarce in Tanzania. This cross-sectional study aimed to detect and genetically characterize Babesia bigemina, Babesia bovis, Theileria parva, and Anaplasma marginale from pools of questing ticks in Gairo and Monduli districts of Tanzania. In addition, DNA samples from cattle blood which were positive for B. bigemina, B. bovis, T. parva and A. marginale previously collected from the same districts, were also included for DNA sequencing. Partial gene sequence analysis was done based on the data published in the GenBank using standard nucleotide BLAST. The most common tick species that were identified were Rhipicephalus pulchellus (n = 243, 23.8%), Amblyomma variegatum (n = 176, 17.3%), Rhipicephalus appendiculatus (n = 149, 14.6%), Rhipicephalus decoloratus (n = 121, 11.9%), Rhipicephalus microplus (n = 107, 10.5%), Rhipicephalus evertsi evertsi (n = 97, 10 %), Hyalomma truncatum (n = 74, 7%) and Amblyomma gemma (n = 53, 5%).In total, 155 tick pools were tested for tick-borne pathogens (TBPs) by PCR. Of these, 17, 4, 3, and 2 pools were positive for A. marginale, T. parva, B. bigemina, and B. bovis resulting in an overall minimum infection rate (MIR) of 2.2%, 0.5%, 0.4%, and 0.3%, respectively. Anaplasma marginale was the most prevalent pathogen, detected in six (R. microplus, R. decoloratus, R. pulchellus, R. appendiculatus, A. variegatum, and R. evertsi evertsi) out of the eight identified tick species. The MIR of A. marginale was highest in A. variegatum (8.0%), followed by R. decoloratus (6.2%) tick pools.Babesia bovis and B. bigemina were detected only in R. microplus and B. decoloratus tick pools, respectively. Theileria parva was detected only in R. appendiculatus and R. pulchellus tick pools.All the tick pools of A. gemma and H. truncatum collected in this study were negative for all the pathogens tested. Sequence analysis revealed that B. bigemina RAP1a, B. bovis SBP-4, and T. parva p104 genes were conserved among pathogens in Gairo and Monduli districts. The present study further confirms the presence of diverse tick species that were infected by various tick-borne pathogens in the study area. This information adds to the knowledge of TBPs epidemiology and will contribute to the scientific basis for planning future control strategies.