In search of the vector(s) of Babesia rossi in Nigeria: molecular detection of B. rossi DNA in Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) ticks collected from dogs, circumstantial evidence worth exploring.

The brown dog tick Rhipicephalus sanguineus (sensu lato) (Acari: Ixodidae) has a cosmopolitan distribution, is a proven vector of a host of pathogens with emerging evidence incriminating it in the transmission of some others. Specifically it is reputed as the main vector of Babesia vogeli whereas the southern African yellow dog tick Haemaphysalis elliptica, long considered to be H. leachi, is apparently the only proven vector of B. rossi, since the resurrection of the separate species H. elliptica as a member of the leachi-group by Apanaskevich et al. However, recent epidemiological surveys conducted in Nigeria show higher prevalence of B. rossi than B. vogeli infection in dogs most of whom were infested with R. sanguineus and rarely with ticks of the H. leachi group. The discrepancy between tick distribution and Babesia spp. prevalent in dogs stimulated us to investigate the possible role of R. sanguineus (s.l.) in the natural transmission of B. rossi. Out of a total of 66 tick samples identified morphologically and molecularly as R. sanguineus collected from dogs manifesting clinical signs of tick-borne diseases, eight (12%) were positive in nested PCR for Babesia sp. DNA. Sequencing results for these amplified products showed that all of the 18S rDNA sequences (693 bp) were identical to each other, and bore 99.3-99.9% identities with those from other B. rossi isolates accessible in GenBank. None of the ticks harbored the DNA of B. vogeli or B. canis. The possible implications for the detection of B. rossi DNA in R. sanguineus (s.l.) ticks collected from dogs in the epidemiology of B. rossi infection of dogs in Nigeria is highlighted.

First detection and molecular characterization of Ehrlichia canis from dogs in Nigeria.

The present study aimed to detect the presence of Ehrlichia canis in naturally infected dogs in Nigeria, using a combination of PCR and sequence analysis of the 16S rRNA gene and two genes encoding the tandem repeat-containing proteins (TRPs), TRP19 and TRP36. Out of a total of 100 blood samples collected from domestic dogs presented to veterinary hospitals in Jos, the capital city of Plateau State of Nigeria, 11 were positive in nested PCR for E. canis. Sequencing results for these amplicons showed that all of the 16S rDNA sequences (1623 bp) or the TRP19 coding sequences (414 bp) were identical to each other and had very high similarities (99.3-100%) with those from other E. canis strains accessible in GenBank. The TRP36 gene sequences derived from the 11 Nigerian isolates were identical to each other except for the number of the 27-bp repeat unit in a tandem repeat region, which was found to be 8, 12 or 18. Without considering the number of tandem repeats, these sequences had 100% identity to that of the reported Cameroon 71 isolate, but distinctly differed from those obtained from other geographically distant E. canis strains previously published. A phylogenetic tree of E. canis based on the TRP36 amino acid sequences showed that the Nigerian isolates and the Cameroon 71 isolate fell into a separate clade, indicating that they may share a common ancestor. Overall, this study not only provides the first molecular evidence of E. canis infections in dogs from Nigeria but also highlights the value of the TRP36 gene as a tool to classify E. canis isolates and to elucidate their phylogeographic relationships.