Abstract
An unpredicted outbreak of African animal trypanosomosis or nagana in 1990 in north-eastern KwaZulu-Natal necessitated an emergency control programme, utilising the extensive cattle-dipping system in the area, as well as a reassessment of the tsetse and trypanosomosis problem in the province. Since 1990, sporadic blood sampling of cattle at the dip tanks in the nagana-infested areas were undertaken to identify trypanosome species involved and to determine the infection prevalence in cattle. The distribution and species composition of the tsetse populations in the area were also investigated. From November 2005 to November 2007 selected dip tanks were surveyed for trypanosome infection prevalence. During April 2005 to August 2009 the distribution and abundance of tsetse populations were assessed with odour-baited H traps. The tsetse and trypanosome distribution maps were updated and potential correlations between tsetse apparent densities (ADs) and the prevalence of trypanosomosis were assessed. Glossina brevipalpis Newstead and Glossina austeni Newstead were recorded in locations where they have not previously been collected. No significant correlation between tsetse relative abundance and nagana prevalence was found, which indicated complex interactions between tsetse fly presence and disease prevalence. This was epitomised by data that indicated that despite large differences in the ADs of G. austeni and G. brevipalpis, trypanosome infection prevalence was similar in all three districts in the area. This study clearly indicated that both tsetse species play significant roles in trypanosome transmission and that it will be essential that any control strategy, which aims at sustainable management of the disease, should target both species.
Highlights
The discovery that Trypanosoma brucei Plimmer & Bradford was the cause of African animal trypanosomosis (AAT), known as nagana, can be dated back to the 1880s when it was recorded for the first time in north-eastern KwaZulu-Natal, South Africa (Bagnall 1993; Bruce 1895; Steverding 2008)
A total of 77 H traps were deployed at 18 sites located in four magisterial districts, that is, Ingwavuma, Ubombo, Hlabisa and Enseleni (Table 1; Figure 1a, b). These traps collected a total of 216 449 G. brevipalpis (AD = 2.64 flies/trap/day) and 17 097 G. austeni (AD = 0.21 flies/trap/day) between 01 April 2005 and 31 August 2009 (Table 1; Figure 1a, b)
Comparison of the apparent densities (ADs) in the three northerly districts indicated that the AD of G. brevipalpis was significantly higher than that of G. austeni in the Ingwavuma (p = 0.008) and Hlabisa (p < 0.001) districts (Table 1; Figure 1a, b)
Summary
The discovery that Trypanosoma brucei Plimmer & Bradford was the cause of African animal trypanosomosis (AAT), known as nagana, can be dated back to the 1880s when it was recorded for the first time in north-eastern KwaZulu-Natal (formerly known as Zululand), South Africa (Bagnall 1993; Bruce 1895; Steverding 2008). The other three species of tsetse, that is, G. pallidipes, G. brevipalpis and G. austeni, remained present in the former Zululand in the north-eastern part of KwaZulu-Natal Province (Fuller 1923). Glossina pallidipes was the predominant species in north-eastern KwaZulu-Natal, and based on its abundance it was considered the most important vector of AAT at that time. The sheer abundance of G. pallidipes was illustrated by large numbers of flies being trapped on certain occasions, that is, in 1932, 2 million flies were collected within a http://www.ojvr.org
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