Molecular detection of tick-borne haemoparasites in cattle and buffalo samples from Mashonaland West and Masvingo Provinces, Zimbabwe

Abstract

Tick-borne haemoparasite diseases caused by Babesia, Theileria, Anaplasma and Ehrlichia species are a major constraint to the beef and dairy cattle industry, causing the most economic losses of cattle in sub-Saharan Africa. The cattle industry in Zimbabwe is continuously threatened by the spread of tick-borne diseases, which significantly affect the economy not only through morbidity and mortality but also through the costs involved in the control of diseases and treatment of sick animals. However, there is a lack of current data on the distribution of tick-borne diseases in Hurungwe district, Mashonaland West Province. The current study used molecular tools to investigate the occurrence of haemoparasites in cattle from Hurungwe district in Mashonaland West Province and buffalo from Gonarezhou National Park in Zimbabwe. DNA was extracted from 87 whole blood samples including 80 cattle and seven buffalo. The DNA samples were subjected to the Reverse-line blot hybridization (RLB) and quantitative real-time polymerase chain reaction (qPCR) analyses. Haemoparasite infections were detected in 58 samples (67 %) by RLB, and 55 % of these only hybridized to the genus-specific probes. Tick-borne haemoparasites detected by RLB included three Theileria species (T. mutans, T. velifera, and Theileria sp. sable), detected in single and mixed-parasite infections. Anaplasma centrale (3 %) and Babesia bigemina (1 %) were also detected by the RLB assay. The most commonly occurring tick-borne pathogens in cattle detected by qPCR assays were A. marginale (28 %) and B. bigemina (9 %); followed by A. centrale (8 %) and B. bovis (3 %). While in buffalo A. marginale (86 %), followed by A. centrale (14 %) were mostly detected. The results of the current study indicated that the species-specific qPCR assays used were more sensitive in detecting haemoparasites than the RLB assay. Anaplasma marginale and Babesia bovis were only detected by the species-specific qPCR assays and not by the RLB assay, which suggests that these haemoparasite infections were present at low levels thus could not be detected by RLB assay. The RLB assay suffers lower sensitivity when a sample is infected with more than one haemoparasite, especially when the levels of infection vary; the high infection will be preferentially detected over low infections of the same genus due to primer competition. Notably, T. parva or E. ruminantium was not detected from the investigated samples. The amplification and sequencing of the 16S and 18S rRNA genes from samples that hybridized exclusively to the RLB genus-specific probes yielded nine and one good quality sequences, for the 16S and 18S rRNA genes respectively. However, BLASTn analysis did not reveal hits to any haemoparasites expected to occur in cattle and buffalo. Our results did not follow the common trend for the prevalence of tick-borne diseases of cattle in Zimbabwe. Bovine theileriosis has recently been reported to be responsible for most cattle mortalities in Zimbabwe, followed by babesiosis, heartwater, and then anaplasmosis. Our results therefore suggest that the trend of occurrence of tick-borne diseases depends on the vector-parasite-host-environment dynamics for each province, thus may vary between provinces. Finally, this study confirms that buffalo in the sampled area are carriers of tick-borne diseases that pose risk to the cattle population.