An update of the tsetse fly (Diptera: Glossinidae) distribution and African animal trypanosomosis prevalence in north-eastern KwaZulu-Natal, South Africa.

An unpredicted outbreak of African animal trypanosomosis or nagana in 1990 in north-eastern KwaZulu-Natal necessitated an emergency control programme, utilising the extensive cattledipping 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 naganainfested 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.

Survey of blackfly (Diptera: Simuliidae) annoyance levels and abundance along the Vaal and Orange Rivers, South Africa.

Blackflies (Diptera: Simuliidae) are pests in the livestock and labour-intensive farming systems along the major rivers in South Africa. Since 1995, blackflies have been controlled in the Orange River with the larvicide Bacillus thuringienses var. israelensis (Bti). During 2006-2007, the views of livestock farmers concerning blackfly annoyance were determined by means of questionnaires. The results of the questionnaires were substantiated by seasonal abundance surveys of the sub-adult stages of blackflies, conducted in 2007 at 13 sites in the Orange River and 11 sites in the Vaal River. More than half (52%) of the 39 participating farmers along the Orange River and 79% of the 52 participating farmers along the Vaal River stated that they experienced severe blackfly problems. The majority of farmers were unaware of the availability of products that could be used to protect their animals against blackfly attacks and were willing to be involved in blackfly research. High numbers of blackfly sub-adult stages found in both rivers supported the high annoyance levels reported by the respondents. Simulium chutteri, Simulium damnosum s.l., Simulium hargreavesi, Simulium adersi and Simulium alcocki were identified at Christiana and Delportshoop on the Vaal River, whilst S. chutteri, S. damnosum s.l., S. adersi, S. alcocki and Simulium gariepense were identified at Marksdrift and Ses Bridge on the Orange River. Despite the extensive control of blackflies, farmers still experience problems and this contention is supported by surveys conducted along the rivers.