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Faculty of Veterinary Science
Department of Veterinary Tropical Diseases

Selected Highlights from Research Findings

The genera Ostertagia and Teladorsagia consist of nematodes that parasitize the abomasum of a variety of ruminants. The worms cause profound pathologic changes in the mucosa of the abomasum which interferes with secretion of hydrochloric acid and pepsinogen, the precursor of pepsin, an important enzyme in the digestive process. Hydrochloric acid provides the acid environment necessary for the conversion of pepsinogen to pepsin. In 1932, Mönnig described Ostertagia hamata from the abomasum of a springbok, Antidorcas marsupialis. Based on the structure of the bursal rays, this nematode was transferred to the genus Teladorsagia. During a survey of the parasites of bontebok, Damaliscus pygargus dorcas, and grey rhebuck, Pelea capreolus, in the Bontebok National Park, a number Ostertagia species were collected from the abomasa of 21 out of 25 grey rhebuck examined but none out of any of the bontebok. Because these worms resembled T. hamata they were first identified as such but re-examination proved them to belong to the genus Ostertagia. Subsequently they were described as Ostertagia triquetra. The major differences between these two nematode genera lie in the configuration of the dorsal rays (2-1-2 in Ostertagia and 2-2-1 in Teladorsagia) and the interno-dorsal branch of the spicules. The branches of O. triquetra are bent and have convex tips while those of T. hamata are straight and have concave tips. In view of the fact that new nematodes have been recovered only from grey rhebuck and not from bontebok, with whom they shared pastures, it is concluded that the parasites are host specific.
Die genera Ostertagia en Teladorsagia bevat wurms wat die abomasum van ‘n verskeidenheid herkouers parasiteer. Die wurm veroorsaak uitgesproke letsels in die wand van die abomasum en dit beïnvloed die afskeiding van soutsuur en pepsinogeen, die voorloper van pepsien, wat ‘n belangrike spysverteringsensiem is. Soutsuur veskaf die suur omgewing wat noodsaaklik is vir die omskakeling van pepsinogeen na pepsien. In 1932 het Mönnig Ostertagia hamata uit die abomasum van ‘n springbok, Antidorcas marsupialis, beskryf. Na aanleiding van die struktuur van die dorsale beursstrale is die nematode na die genus Teladorsagia verskuif. Gedurende ‘n opname van die parasiete van bontebokke, Damaliscus pygargus dorcas, en grys reebokke, Pelea capreolus, in die Nasionale Bontebokpark, is ‘n aantal Ostertagia species uit die abomasum van 21 uit 25 reebokke versamel, terwyl geen in die bontebokke gevind is nie. Omdat die wurms aan T. hamata herinner het, is hulle aanvanklik as sulks geïdentifiseer, maar nadere ondersoek het getoon dat hulle in werklikheid ‘n species van Ostertagia is. Die wurms is as Ostertagia triquetra beskryf. Die hoof verskille tussen die twee genera van nematodes lê in die konfigurasie van die bursale strale (2-1-2 in Ostertagia en 2-2-1 in Teladorsagia) en die interno-dorsale tak van die spikula. Die takke van O. triquetra is gebuig en die punte is konveks, terwyl die van T. hamata reguit is met konkawe punte. In die lig daarvan dat die wurms slegs in reebokke gevind is, en nie in bontebokke met wie hulle die weiveld deel nie, word dit afgelei dat hierdie parasiete gasheerspesifiek is.
Contact person: Prof JDF Boomker.

Salmonellosis is an infectious bacterial disease of mammals and birds that can result in enterocolitis, septicemia and death. Salmonella serovars naturally inhabit the intestinal tract of many species and are common in their environment. Infection with Salmonella does not always include clinical signs and asymptomatic carriers may shed organisms in faeces and infect other animals. Malnutrition could also immunosuppress Salmonellacarriers, leading to overt infection. Prolonged low cheetah (Acinonyx jubatus) birth rates were observed in a captive breeding facility in which Salmonella, possibly arising from contaminated beef, was isolated from still-born lion (Panthera leo) cubs. Therefore the possible role of Salmonellain the perinatal mortalities of cheetah was investigated. Although it is difficult to identify a food item as the only vector in an outbreak of salmonellosis, faecal specimens from both cheetah and lion and meat fed to them were cultured for Salmonella. Genetic methodology was employed to determine if the Salmonellathat was isolated from faeces could have originated from contaminated meat. From the bacterial serotyping, two Salmonellaserovars, S. typhimurium and S. muenchen dominated in both the raw meat fed to the carnivores and the faeces of cheetahs. Low numbers of other serovars were isolated but these were not analyzed molecularly because they did not occur both in meat and faecal samples. Salmonella typhimurium is normally the most frequently isolated serovar. The fact that S. typhimurium and S. muenchen predominated in the meat and in the faeces suggested that the meat was the source of the bacteria in the faeces. Detectable imbalances or shortages in the cheetah’s diets at the facility were also corrected, and strict hygiene measures were instituted at the feedlots where the meat was processed, including installation of freezers, transport under frozen conditions, and disinfection of rooms and apparatus used in the processing of the meat. Neonatal mortality diminished drastically.
Contact person: Prof EH Venter.

Black rhinos are critically endangered - any factors impacting negatively on this species are therefore of grave concern to conservationists. A team from the Faculty of Veterinary Science and Utrecht University recently described two new blood protozoa from this species: Babesia bicornis and Theileria bicornis. The descriptions were based on molecular characterisation of the DNA of the parasites. It was found that many healthy rhinos harbour these parasites. Although a stable situation seems to exist, the situation changes once an animal is stressed: then clinical symptoms resembling those of so-called redwater in domestic cattle become evident. Babesia bicornis is incriminated in this clinical syndrome, whilst Theileria bicornis has not been proven harmful. Conservators and wildlife managers should be aware of the potential problem, and should take appropriate preventative measures when black rhinos are immobilised, translocated or kept in bomas.
Swartrenosters word deur uitwissing bedreig - enige faktor met ’n negatiewe uitwerking op hierdie diersoort is dus van groot belang vir natuurbewaarders. ’n Span van die Fakulteit Veeartsenykunde en die Universiteit van Utrecht het onlangs twee nuwe bloedparasiete, Babesia bicornis en Theileria bicornis, uit hierdie spesie beskryf. Die beskrywings is gegrond op molekulêre karakterisering van die parasiete se DNS. Daar is bevind dat talle gesonde renosters die parasiete huisves. Die toestand blyk stabiel te wees, maar verander egter sodra die dier onder spanning geplaas word: dan tree kliniese simptome wat met sogenaamde rooiwater in beeste ooreenstem, te voorskyn. Babesia bicornis word met hierdie sindroom verbind, maar die skadelikheid van Theileria bicornis is nog nie aangetoon nie. Natuurbewaarders en wildplaasbestuurders moet kennis neem van die sluimerende probleem, en moet toepaslike voorsorgmaatreëls tref wanneer swartrenosters geïmmobiliseer, vervoer of in bomas aangehou word.
Contact person: Prof BL Penzhorn.


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