In Mnisi, a rural community in South Africa, Rhipicephalus sanguineus is one of the most prevalent ticks found on dogs. The community lies at the wildlife/livestock/human interface where humans are at risk of tick-borne diseases. The aim of this study was to investigate the diversity of the bacterial microbiome in R. sanguineus that may impact human health. Over a 12-month period, R. sanguineus (n=1,788), Rhipicephalus simus (n=61), Rhipicephalus turanicus (n=73), Amblyomma hebraeum (n=68), Haemaphysalis leachi (n=219) and Hyalomma truncatum (n=1) ticks were collected from 64 dogs. Genomic DNA was extracted from salivary gland and midgut tissues of 62 R. sanguineus tick pools (1 pool = 10 ticks); identifications were confirmed using Cytochrome c oxidase I barcoding. The 16S rRNA gene was amplified using barcoded primers and sent for Pacific Bioscience’s circular consensus sequencing. Characterisation of the bacterial microbiome of midgut and salivary gland pools revealed a total of 260,312 sequences with Proteobacteria (85.44%) being the most prevalent phylum found; with Anaplasma (21.69%), Coxiella (12.12%) and Ehrlichia (19.94%) species dominating the microbiome. Further classification of Ehrlichia revealed 95.46% Ehrlichia canis and 4.54% Ehrlichia species Anaplasma consisted of 15.36% Anaplasma centrale, 75.82% Anaplasma platys and 8.82% Anaplasma species Phylogenetic analysis indicated that the A. centrale and A. platys clustered with various other published A. centrale and A. platys sequences, respectively. It also confirmed that all Ehrlichia species sequences detected in this study are E. canis sequences (94.46%). Furthermore, we determined that the Coxiella sequences detected in the study belong to the R. sanguineus Coxiella-like endosymbionts group. Assessment of risk factors for R. sanguineus infestation indicates that higher average monthly temperatures have a significant association with an increased risk of R. sanguineus tick infestations on dogs. Additionally, rearing chickens at the household was significantly associated with a decreased risk of R. sanguineus tick infestations on dogs. Our study indicated that R. sanguineus could be a potential reservoir for important bacterial pathogens of zoonotic importance.
Dissertation (MSc (Veterinary Science))--University of Pretoria, 2019.