Abstract
BackgroundAnimal and human trypanosomiasis are constraints to both animal and human health in Sub-Saharan Africa, but there is little recent evidence as to how these parasites circulate in wild hosts in natural ecosystems. The Luangwa Valley in Zambia supports high densities of tsetse flies (Glossina species) and is recognised as an historical sleeping sickness focus. The objective of this study was to characterise the nature of the reservoir community for trypanosomiasis in the absence of influence from domesticated hosts.Methodology/Principal FindingsA cross-sectional survey of trypanosome prevalence in wildlife hosts was conducted in the Luangwa Valley from 2005 to 2007. Samples were collected from 418 animals and were examined for the presence of Trypanosoma brucei s.l., T. b. rhodesiense, Trypanosoma congolense and Trypanosoma vivax using molecular diagnostic techniques. The overall prevalence of infection in all species was 13.9% (95% confidence interval [CI]: 10.71–17.57%). Infection was significantly more likely to be detected in waterbuck (Kobus ellipsiprymnus) (Odds ratio [OR] = 10.5, 95% CI: 2.36–46.71), lion (Panthera leo) (OR = 5.3, 95% CI: 1.40–19.69), greater kudu (Tragelaphus strepsiceros) (OR = 4.7, 95% CI: 1.41–15.41) and bushbuck (Tragelaphus scriptus) (OR = 4.5, 95% CI: 1.51–13.56). Bushbucks are important hosts for T. brucei s.l. while the Bovidae appear the most important for T. congolense. The epidemiology of T. vivax was less clear, but parasites were detected most frequently in waterbuck. Human infective T. b. rhodesiense were identified for the first time in African buffalo (Syncerus caffer) and T. brucei s.l. in leopard (Panthera pardus). Variation in infection rates was demonstrated at species level rather than at family or sub-family level. A number of significant risk factors interact to influence infection rates in wildlife including taxonomy, habitat and blood meal preference.Conclusion and Significance Trypanosoma parasites circulate within a wide and diverse host community in this bio-diverse ecosystem. Consistent land use patterns over the last century have resulted in epidemiological stability, but this may be threatened by the recent influx of people and domesticated livestock into the mid-Luangwa Valley.
Highlights
Trypanosomes are true multi-host parasites capable of infecting a wide range of wildlife species that constitute a reservoir of infection for both people and domestic animals
Samples collected In total 418 samples were collected from 24 species in the survey (Table 2). The majority of these were collected from game management areas (GMAs) through the professional hunter survey in which 331 samples were collected from 22 species
With the identification of the African buffalo and the leopard as new host species for T. b. rhodesiense and T. brucei s.l. respectively, it is clear that the reservoir community is wider than previously demonstrated
Summary
Trypanosomes are true multi-host parasites capable of infecting a wide range of wildlife species that constitute a reservoir of infection for both people and domestic animals. Much knowledge about infection rates in wildlife has been generated, there have been very few attempts to conduct epidemiological analyses of data from surveys of wildlife. This is, in part due to difficulties in the collection of sufficiently large sample sizes of a representative nature from wildlife species to enable a thorough statistical analysis [19,20,21]. Some studies have examined the association between wildlife infection rates and factors that might influence them [8,17], but most have reported host species infection rates without any statistical analysis of the data. The objective of this study was to characterise the nature of the reservoir community for trypanosomiasis in the absence of influence from domesticated hosts
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