Occurrence of tick-borne haemoparasites in South African rodent species evidence of Babesia microti-like sequence variants in two Rhabdomys species

Abstract

In recent years, vector-borne viral, bacterial and parasitic diseases have emerged or re-emerged in many geographic regions, causing health and economic problems. Wildlife can act as reservoirs for many human and livestock diseases and that arthropods are often involved in the transmission of these pathogens. Little is known about the zoonotic pathogens that naturally occur in wild rodent and insectivorous shrew species in South Africa. The aims of the study were to: 1) record the tick-borne haemoparasite diversity associated with rodents and shrews at several localities in South Africa, and 2) characterise Babesia microti that occur in rodents using Sanger sequencing of the parasite 18S ribosomal RNA (rRNA) gene and internal transcribed spacer region 1 (ITS1). Nine wild rodent genera (species: n = 412) and two insectivorous shrew genera (species: n = 11) were simultaneously screened for the presence of Theileria, Babesia, Ehrlichia and Anaplasma species using the Reverse Line Blot (RLB) hybridization assay. The RLB PCR amplicons obtained from Mastomys spp., Micaelamys namaquensis, Mus musculus, Rhabdomys dilectus and R. pumilio hybridized with the following RLB species-specific probes: Babesia microti (11.3%), Anaplasma bovis (3.5%), Anaplasma phagocytophilum (1.8%) and Ehrlichia ruminantium (3.5%). The near full-length 18S rRNA gene and partial ITS1 spacer region of 12 of the specimens were cloned and the recombinants sequenced. Babesia microti-like 18S rDNA and ITS1 sequence variants were recorded in two rodent species (Rhabdomys dilectus and Rhabdomys pumilio). The B. microti-like 18S rDNA sequence variants, obtained in this study, clustered phylogenetically within the established B. microti-like clade (Clade I). Nevertheless, they formed a distinct South African group that seems to differ significantly from B. microti sensu stricto and could potentially represent a fifth distinct lineage within the B. microti-like clade.The study highlights the potential of small mammals acting as important reservoirs for vector-borne haemoparasites in South Africa.

HIGHLIGHTS • Most extensive study on haemoparasites associated with small mammals in Southern Africa to date. • 63.3% rodent samples positive for Theileria/Babesia/Ehrlichia/Anaplasma DNA. • Regional-specific Babesia microti-like sequence variants recorded in two commensal and wide-spread rodent species.