Abstract:
This study was conducted to determine the composition of ticks and tick-borne pathogens, circulating in livestock in Tchicala-Tcholoanga Municipality, Huambo Province, Angola. Samples were collected from cattle, goats, sheep and dogs during January 2016. Using stereomicroscopic observation, ticks were identified to species level. A total of 2,963 ticks, including nymphs and adults, belonging to 5 genera and 17 tick species were recorded; i.e. Amblyomma pomposum, Haemaphysalis leachi, H. paraleachi, Hyalomma truncatum, Ixodes cavipalpus, Rhipicephalus decoloratus, R. microplus, R. compositus, R. evertsi evertsi, R. evertsi mimeticus, R. kochi, R. lunulatus, R. punctatus, R. simus, R. sulcatus, R. turanicus and R. tricuspis. Moreover, using the reverse line blot (RLB) hybridization assay, 340 DNA samples from different animal species (cattle, goats, sheep and dogs) were analysed, targeting the parasite 16S rRNA gene for Ehrlichia/Anaplasma and 18S rRNA gene for Theileria/Babesia. Fifteen tick-borne pathogens were detected: Anaplasma centrale, A. marginale, A. bovis, A. platys, Anaplasma sp. Omatjenne, Babesia bigemina, B. bovis, B. rossi, B. vogeli, Ehrlichia canis, Theileria sp. (sable), T. mutans, T. velifera, T. bicornis and T. ovis. The RLB assay detected low numbers (3.4 %) of B. bigemina positive cases and no E. ruminantium DNA was detected. Thus, other tools, such as real-time qPCR for B. bigemina and B. bovis targeting the 18S rRNA gene, as well as E. ruminantium, targeting pCS20 gene were used to screen blood samples and A. pomposum ticks. Fifty-three samples, corresponding to 66.3% of the cattle blood samples analyzed, were positive for the presence of B. bigemina DNA, while no B. bovis DNA could be detected. In addition, E. ruminantium was detected in 4.3% blood samples and 7% from A. pomposum ticks. The parasite 16S rRNA gene of A. platys RLB selected positive cattle and sheep samples were subsequently amplified, cloned and sequenced. Six recombinant sequences were obtained from cattle and five from sheep samples; of these only three near full-length sequences (1249 bp) could be obtained (7f, 26g, 47b). BLASTn homology searches showed that sequence 7f was identical to Ehrlichia sp. Bom Pastor (AF318023). As such, sequences 26g and 47b had 99% identity to various A. platys sequences available on GenBank (including the type strain sequence M82801), as well as 99% identity to Ehrlichia (Anaplasma) sp. Bom Pastor (AF318023) and Anaplasma sp. Omatjenne (U54806). As for the partial sequences obtained, sequence 255a (337 bp) obtained from a sheep sample showed 99% identity to A. ovis (KX579073), whereas two sequences obtained from cattle, 82b (323 bp) and 64c (287 bp), showed 100% identity to A. marginale (KT264188).
This study constituted pioneer work in Angola and showed the diversity of ticks and tick-borne pathogens among domestic ruminants and dogs in the Tchicala-Tcholoanga region.
