Determination of the prevalence of African trypanosome species in indigenous Dogs of Mambwe District, Eastern Province of Zambia

Abstract

Throughout their long history of domestication, dogs have been sources of parasitic zoonoses, including gastrointestinal parasites and haemoparasites. As such, they have served as a link for parasite exchange, resulting in several emerging and re-emerging diseases. Among them is African trypanosomiasis, a re-emerging tsetse-transmitted disease which affects livestock and humans in sub-Saharan Africa, including Zambia. When infected with pathogenic trypanosome species such as Trypanosoma congolense and T. brucei subspecies, dogs become potential reservoirs of infection to livestock and humans, respectively. In this study, we determined the prevalence of trypanosome species in indigenous dogs of Mambwe district and investigated whether they serve as reservoirs of zoonotic T. b. rhodesiense. A cross sectional survey of canine African trypanosomiasis (CAT) was conducted within Mambwe district, situated along the Luangwa valley which supports a high density of tsetse flies and is a historical human African trypanosomiasis (HAT) focus. Snow bowling technique was used to sample dogs from 5 chiefdoms within Mambwe. Microscopy and Loop mediated isothermal amplification (LAMP) were used as diagnostic techniques to detect trypanosome species.A total of the 237 dogs were sampled and out of these, 14 (5.9%; 95% CI: 2.9 – 8.9%) were positive for CAT by microscopy. On the other hand, LAMP detected a total of 20 CAT cases (8.4%; 95% CI: 4.9 – 12.0%), including all the 14 cases detected by microscopy. According to LAMP, those infections were caused by T. congolense (4.2%; 10/237), T. b. brucei (2.5%; 6/237) and the human-infective T. b. rhodesiense (4.6%; 11/237) either as monolytic or mixed infections. CAT was detected in 3 (Munkanya, Nsefu and Malama) out of the 5 chiefdoms in Mambwe district. Detection of the Serum Resistance Associated (SRA) gene from trypanosomes isolated from dogs from the 3 chiefdoms is intriguing and suggests that the 3 chiefdoms were at risk of contracting HAT and that indigenous dogs could act as reservoirs of zoonotic T. b. rhodesiense. These findings suggest that indigenous hunting dogs, most of which exhibited trypanotolerance, may be involved in the re-emergence of HAT in Mambwe district. Future studies should investigate (i) the influence of seasonal variation on vector burden and activity, and their impact on the prevalence of trypanosomiasis by use of more sensitive and specific molecular techniques such as LAMP, (ii) possible routes of infection with CAT in the hunting dogs.