Abstract:
BACKGROUND : Babesia rossi, which is transmitted by Haemaphysalis spp. and is highly virulent to domestic dogs, occurs
only 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 jackals
was lacking. A long-term behaviour study in which free-ranging black-backed jackals were radio-collared offered the
opportunity 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 to
Reverse Line Blot hybridization using Theileria and Babesia genera-specific as well as 28 species-specific oligonucleotide
probes, including Babesia canis, Babesia rossi, Babesia vogeli and Babesia gibsoni. The near full-length parasite 18S rRNA
gene was amplified from two selected samples (free-ranging jackals), cloned and a total of six recombinants were
sequenced.
RESULTS : Of 91 free-ranging jackals, 77 (84.6%) reacted with the Babesia genus-specific probe; 27 (29.7%) also reacted
with the B. rossi probe. Of 16 captive jackals, 6 (37.5%) reacted with the B. rossi probe, while one further sample reacted
with the Babesia genus-specific probe only. After cloning, 6 recombinants yielded identical sequences identical to that
of B. rossi (L19079) and differing by 2 base pairs from B. rossi (DQ111760) in GenBank. The observed sequence
similarities were confirmed by phylogenetic analyses using neighbour joining and maximum parsimony.
CONCLUSIONS : Black-backed jackals are natural hosts of B. rossi.
