Black-backed jackals (Canis mesomelas) are natural hosts of Babesia rossi, the virulent causative agent of canine babesiosis in sub-Saharan Africa

摘要

BACKGROUND : Babesia rossi, which is transmitted by Haemaphysalis spp. and is highly virulent to domestic dogs, occursonly in sub-Saharan Africa. Since dogs are not native to the region, it has been postulated that the natural host of B.rossi is an indigenous African canid. Although various attempts at artificial infection indicated that black-backed jackals(Canis mesomelas) could become subclinically infected with B. rossi, data on occurrence of B. rossi in free-ranging jackalswas lacking. A long-term behaviour study in which free-ranging black-backed jackals were radio-collared offered theopportunity of collecting blood specimens from a large number of free-ranging jackals.METHODS : Genomic DNA was extracted from the EDTA blood samples (n = 107). PCR products were subjected toReverse Line Blot hybridization using Theileria and Babesia genera-specific as well as 28 species-specific oligonucleotideprobes, including Babesia canis, Babesia rossi, Babesia vogeli and Babesia gibsoni. The near full-length parasite 18S rRNAgene was amplified from two selected samples (free-ranging jackals), cloned and a total of six recombinants weresequenced.RESULTS : Of 91 free-ranging jackals, 77 (84.6%) reacted with the Babesia genus-specific probe; 27 (29.7%) also reactedwith the B. rossi probe. Of 16 captive jackals, 6 (37.5%) reacted with the B. rossi probe, while one further sample reactedwith the Babesia genus-specific probe only. After cloning, 6 recombinants yielded identical sequences identical to thatof B. rossi (L19079) and differing by 2 base pairs from B. rossi (DQ111760) in GenBank. The observed sequencesimilarities were confirmed by phylogenetic analyses using neighbour joining and maximum parsimony.CONCLUSIONS : Black-backed jackals are natural hosts of B. rossi.