Pathogen screening of Zambian ticks: new insights on the occurrence of tick-borne pathogens in the country

Background: Ticks are important ectoparasites for both humans and animals and can also transmit a wide range of different viral, bacterial, and parasitic pathogens, which are commonly known as “tick-borne pathogens” (TBPs). In Zambia (Southern Africa), a number of studies have been conducted on TBPs, but information on their distribution and genetic variation is still incomplete. Methods: Between 2022 and 2023, 588 ticks were collected in 3 provinces from the environment/vegetation via flagging as well as from cattle and wild host species (buffaloes and tortoises). After tick species identification and DNA/RNA extraction, the samples were tested for viral (orthonairo-, flavi- and arenaviruses) and bacterial (Rickettsia, Anaplasma, Ehrlichia, and Coxiella) pathogens using different polymerase chain reaction (PCR) assays. Subsequently, positive samples were sequenced and analyzed on the basis of different genes (rrs (16S rRNA); 23S-5S intergenic spacer region; ompB; gltA; sca4). Results: Apart from some Hyalomma and Amblyomma species, most of the ticks collected belonged to the genus Rhipicephalus, in which Rhipicephalus appendiculatus made up the largest proportions. No viral RNA was detected inside the ticks, but Rickettsia (Ri. africae, Ri. aeschlimannii, Ri. sibirica, Ri. tamurae-like agent), Anaplasma (An. bovis, An. marginale, An. platys, An. phagocytophilum-like agent), and Ehrlichia species (Eh. ruminantium, Eh. chaffeensis-like agent) were most frequently found. Conclusions: Many of the pathogens found had already been described in Zambia. Nevertheless, there were some unexpected findings. The detection of Ri. sibirica (ompB and 23S-5S spacer region; in ticks from cattle) or Eh. chaffeensis-like amplicons (rrs; in a questing Rh. appendiculatus tick) may suggest that some pathogens or closely related species might be more widespread than previously assumed. In addition to these rarely described pathogens in Africa, further studies should be carried out on the detection of TBPs of viral origin.