Abstract
BackgroundDogs have been implicated to serve as links for parasite exchange between livestock and humans and remain an important source of emerging and re-emerging diseases including trypanosome infections. Yet, canine African trypanosomosis (CAT), particularly in indigenous dogs (mongrel breed) remains under- reported in literature. This study evaluated the performance of loop-mediated isothermal amplification (LAMP) in detecting trypanosomes in blood from indigenous dogs of tsetse-infested Mambwe district in eastern Zambia.MethodsA cross sectional survey of CAT was conducted within 5 chiefdoms (Msoro, Kakumbi, Munkanya, Nsefu, Malama) of Mambwe district, eastern Zambia, during October 2012. Blood samples from 237 indigenous hunting dogs were collected and screened by microscopy and LAMP.ResultsOf the 237 dogs screened for CAT, 14 tested positive by microscopy (5.9%; 95% CI: 2.9 – 8.9%), all of which also tested positive by LAMP. In addition, LAMP detected 6 additional CAT cases, bringing the total cases detected by LAMP to 20 (8.4%; 95% CI: 4.9 – 12.0%). Irrespective of the detection method used, CAT was only recorded from 3 chiefdoms (Munkanya, Nsefu, Malama) out of the 5. According to LAMP, these infections were caused by Trypanosoma congolense, Trypanosoma brucei brucei and the zoonotic Trypanosoma brucei rhodesiense. Although these CAT cases generally did not manifest clinical illness, an association was observed between infection with Trypanosoma brucei subspecies and occurrence of corneal opacity.ConclusionsThis communication reports for the first time the occurrence of CAT in indigenous Zambian dogs. Our study indicates that LAMP is a potential diagnostic tool for trypanosome detection in animals. LAMP was more sensitive than microscopy and was further capable of distinguishing the closely related T. b. brucei and T. b. rhodesiense. In view of the sporadic cases of re-emerging HAT being reported within the Luangwa valley, detection of the human serum resistant associated (SRA) gene in trypanosomes from mongrels is intriguing and indicative of the risk of contracting HAT by local communities and tourists in Mambwe district. Consequently, there is a need for continuous trypanosome surveillances in animals, humans and tsetse flies using sensitive and specific tests such as LAMP.
Highlights
Dogs have been implicated to serve as links for parasite exchange between livestock and humans and remain an important source of emerging and re-emerging diseases including trypanosome infections
Detection of African trypanosomes by microscopy and loop-mediated isothermal amplification (LAMP) According to microscopy, 14 out of 237 mongrels (5.9%; 95% CI: 2.9 – 8.9%), were found to be infected with trypanosomes
According to multivariable logistic regression analysis, the risk factors that seemed to influence the prevalence of canine African trypanosomosis (CAT) in indigenous dogs included location/chiefdom, (Odds ratio (OR) 6; 95% CI: 2.0 – 16.4; p = 0.002), vision, age and illegal hunting
Summary
Dogs have been implicated to serve as links for parasite exchange between livestock and humans and remain an important source of emerging and re-emerging diseases including trypanosome infections. Dogs have served as a link for parasite exchange among livestock, wildlife and humans, and remain an important source of emerging and re-emerging infectious diseases [4,5]. According to Abenga et al [6], indigenous dog breeds in tsetse-infested regions of sub-Saharan Africa seem to be trypanotolerant. Such dogs get infected with trypanosomes, they either exhibit subclinical signs or may not exhibit any overt clinical signs of the disease at all. Such dogs may act as sources of infection to other domesticated animals and, more importantly, those with the humaninfective T. brucei rhodesiense and T. brucei gambiense may serve as a source of infection for humans [5,8,11,12,13]
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