Faculty of Veterinary Science
Department of Veterinary Tropical Diseases
Selected Highlights from Research Findings
Trypanosomosis or Nagana which is transmitted by tsetse flies, remains a major constraint to livestock production in sub-Saharan Africa. The disease causes increased mortality rates and reproduction is also severely reduced. In an attempt to develop sustainable trypanosomosis control strategies, researchers in the Department collaborated with the Institute of Tropical Medicine, Antwerp, Belgium, and the ARC-Onderstepoort Veterinary Institute. The research has resulted in a number of interesting findings.
Studies on the virulence and transmissibility of Trypanosoma congolense isolated in eastern Zambia revealed a high level of genetic diversity in the trypanosome population. This variability was reflected in different levels of pathogenicity and transmissibility by tsetse flies.
Studies on factors determining the susceptibility of tsetse flies to trypanosome infection showed that starvation significantly increased the flies’ susceptibility. On the other hand, subsequent studies revealed that feeding tsetse flies a single blood meal containing a trypanocidal drug (isometamidium chloride) made treated flies resistant to infection with trypanosomes.
Field studies in KwaZulu-Natal showed the high prevalence of trypanosomal infection in cattle kept at the edge of Hluhluwe-iMfolozi Park. Field experiments determined the effectiveness of various control methods under the conditions prevailing in the province
Contact person: Prof P van den Bossche.
Research into ticks continued being productive. Researchers in the Department established that the bont-legged tick, previously known as Hyalomma marginatum turanicum in South Africa, was in fact Hyalomma glabrum. This is the only bont-legged tick that occurs exclusively in the southern hemisphere.
The geographic distributions of the six tick species that infest tortoises and other reptiles in South Africa were all mapped from collection data. The known distributions and ecological preferences of blue ticks of the subgenus Boophilus in Africa and Latin America were established.
It was established that, contrary to popular belief, not one of five burning regimens that were applied in the south of the Kruger National Park had an effect on the numbers of free-living ticks on the vegetation
Contact person: Prof IG Horak.
The objective of this study was to compare the presence on goats and cattle of adult ticks that usually infest cattle. To this end ticks collected from sets of five goats were compared with those collected from sets of five cattle at 72 communal dip-tanks in the eastern region of the Eastern Cape Province.
The bont tick Amblyomma hebraeum was present on goats at 25 and on cattle at 39 dip-tanks, and a total of 61 goats and 138 cattle were infested. Adult blue ticks, Rhipicephalus (Boophilus) microplus were present on goats at 48 and on cattle at 69 dip-tanks, and a total of 113 goats and 242 cattle were infested.
Adult brown ear ticks, Rhipicephalus appendiculatus were present on goats at 70 and on cattle at 67 dip-tanks, and a total of 296 goats and 271 cattle were infested. Adult red-legged ticks, Rhipicephalus evertsi evertsi were present on goats and cattle at all 72 sampling localities, and a total of 334 goats and 316 cattle were infested.
These results underscore the necessity of including goats in any tick control programme designed for cattle at the same locality
Contact person: Prof IG Horak.
The objective of this study was to assess the host status of African buffaloes, Syncerus caffer, for the blue tick Rhipicephalus (Boophilus) decoloratus. This tick is a vector of babesiosis (redwater) in cattle. To this end the blue tick burdens of ten buffaloes examined in three north-eastern KwaZulu-Natal Province (KZN) nature reserves were compared with those of medium-sized to large antelope species in these reserves and in the southern Kruger National Park (KNP) in Mpumalanga Province.
The blue tick burdens of the buffaloes were considerably smaller than those of the antelopes in the KNP, but not those in the KZN reserves. The life-stage structure of the blue tick populations on the buffaloes, in which larvae predominated, was closer to that of this tick on blue wildebeest, Connochaetes taurinus, a tick-resistant animal, than to that on other antelopes.
A single buffalo examined in the KNP was not infested with blue ticks, whereas a giraffe, Giraffa camelopardalis, examined at the same locality and time, harboured a small number of ticks.
In a nature reserve in Mpumalanga Province adjacent to the KNP, two immobilized buffaloes, from which only adult ticks were collected, were not infested with blue ticks, whereas greater kudus, Tragelaphus strepsiceros, examined during the same time of year in the KNP harboured large numbers of adult ticks of this species.
African buffaloes would thus appear to be resistant to infestation with blue ticks, and this resistance is expressed as the prevention of the majority of tick larvae from developing to nymphs
Contact person: Prof IG Horak.
|
