African animal trypanosomosis (nagana) in northern KwaZulu-Natal, South Africa: Strategic treatment of cattle on a farm in endemic area.

African animal trypanosomosis (AAT) is caused by several species of the genus Trypanosoma, a parasitic protozoan infecting domestic and wild animals. One of the major effects of infection with pathogenic trypanosome is anaemia. Currently, the control policies for tsetse and trypanosomosis are less effective in South Africa. The only response was to block treat all infected herds and change the dip chemical to one which controls tsetse flies during severe outbreaks. This policy proved to be less effective as demonstrated by the current high level of trypanosome infections in cattle. Our objective was to study the impacts of AAT (nagana) on animal productivity by monitoring the health of cattle herds kept in tsetse and trypanosomosis endemic areas before and after an intervention that reduces the incidence of the disease. The study was conducted on a farm in northern KwaZulu-Natal which kept a commercial cattle herd. There was no history of any cattle treatment for trypanosome. All cattle were generally in poor health condition at the start of the study though the herd received regular anthelminthic treatment. A treatment strategy using two drugs, homidium bromide (ethidium) and homidium chloride (novidium), was implemented. Cattle were monitored regularly for 13 months for herd trypanosomosis prevalence (HP), herd average packed cell volume (H-PCV) and the percentage of the herd that was anaemic (HA). A total of six odour-baited H-traps were deployed where cattle grazed from January 2006 to August 2007 to monitor the tsetse population. Glossina brevipalpis Newstead and Glossina austeni Newstead were collected continuously for the entire study period. High trypanosomes HP (44%), low average H-PCV (29.5) and HA (24%) were rerecorded in the baseline survey. All cattle in the herd received their first treatment with ethidium bromide. Regular monthly sampling of cattle for the next 142 days showed a decline in HP of 2.2% - 2.8%. However, an HP of 20% was recorded by day 220 and the herd received the second treatment using novidium chloride. The HP dropped to 0.0% and HA to 0.0% by day 116 after the second treatment. The cow group was treated again by day 160 when the HP and HA were 27.3% and 11%, respectively. The same strategy was applied to the other two groups of weaners and the calves at the time when their HP reached 20%. Ethidium and novidium treatment protected cattle, that were under continuous tsetse and trypanosomosis challenge, for up to 6 months. Two to three treatments per year may be sufficient for extended protection. However, this strategy would need to be included into an integrated pest management approach combining vector control for it to be sustainable.

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.

Bovine trypanosomosis prevalence at the edge of Hluhluwe-iMfolozi Park, KwaZulu-Natal, South Africa.

The northern KwaZulu-Natal (NKZN) region of South Africa is the southern limit of the African tsetse belt. Entomological information on Glossina brevipalpis and Glossina austeni was generated following the outbreak of trypanosomosis in cattle in 1990. However, these data have not been supported by parallel studies on epidemiology of the disease and therefore there has been no control policy in place. This study presented the first intensive investigations to address the epidemiology of trypanosomosis in NKZN. Tsetse abundance, trypanosome herd average prevalence (HAP), herd average anaemia (HAA) and herd average packed cell volume (HA-PCV) were investigated at three communal diptanks located at the edge of Hluhluwe-iMfolozi Park by monthly sampling from June 2006 - November 2007. Seasonal trypanosome surveys were conducted at seven other communal diptanks. Glossina brevipalpis prevalence was high at two of the diptanks, Mvutshini and Ekuphindisweni, but low at Ocilwane, whilst G. austeni was only collected from Mvutshini. This high and low tsetse challenge presented different disease scenarios. Cattle at Mvutshini and Ekuphindisweni had the highest HAP of 12.3% and 8.9% respectively, both significantly different (p = 0.001) from the HAP obtained from cattle at Ocilwane (2.9%). These two cattle herds also had the highest HAA, 27.7% and 33.4% respectively, whilst cattle at Ocilwane had the lowest, 11.1% (p = 0.001). Conversely, cattle at Ocilwane had the highest HA-PCV, ranging between 29.0% and 32.0%, whilst cattle at Mvutshini and Ekuphindisweni had the lowest HA-PCV (24.0% - 29.0%). By combining the data from the three diptanks (1318 observations), 62.0% of the infected cattle were found anaemic, compared to 20.0% in the uninfected group. Trypanosome seasonal surveys showed that cattle at all the seven diptanks were infected with trypanosomes; mean HAP, HAA and HA-PCV of 10.2%, 46.6% and 23.7%, respectively. This study generated information on the epidemiological factors related to the wide spread of trypanosome-infected cattle and tsetse flies. Trypanosomosis is a disease of economic importance impacting the livelihood of resource-poor farmers in NKZN.