Faculty of Veterinary Science
Department of Paraclinical Sciences (Veterinary)
Selected Highlights from Research Findings
Crocodiles are surviving representatives of the dinosaurs. In structure, and probably also in habits, crocodiles have changed little since the dinosaur era that ended some 70 million years ago. Crocodiles, as top predators in the aquatic ecosystem, are considered to be valuable bioindicators of aquatic pollution. Scientists studying the effects that aquatic pollutants have on crocodiles must rely solely on blood samples to monitor these effects. However, we discovered that an additional biological sample, urine, can easily be collected from live crocodiles. Collection of urine from the cloaca is a simple and atraumatic procedure. An ordinary dog urinary catheter is used to collect “clean” urine from the urodeum in the cloaca. Separation of urine from faeces in the cloaca of the crocodile is very similar to that in the ostrich. The faeces are stored in the rectum (coprodeum) and held back by a powerful sphincter (coprodeal sphincter) separating the coprodeum from the urodeum. The urinary catheter is inserted via the cloacal opening and is gently pushed in a cranial direction. The urodeum is not far from the cloacal opening. This collection technique could easily be used by any scientist with no previous clinical experience. Seeing that urine is routinely used in human and other animal patients to diagnose endocrine problems, it could be a valuable sample for crocodiles. However, not much work has been done on crocodile urine! Urine steroid profiling in humans can be indicative of numerous endocrine dysfunctions, including enzyme deficiencies or excesses, and reproductive, adrenal and thyroid disorders. Establishment of reference values for steroid metabolites in crocodilians could enable us to use steroid profiling as an indicative tool of endocrine disruptive pollution.
Contact person: Dr JG Myburgh.
Poisoning of livestock by cardiac glycoside-containing plants has the greatest economic impact of all plant-associated poisonings in the Republic of South Africa. Collectively they are held responsible for 33 % of all mortalities from plant poisonings of cattle and 10 % of those in small stock. A practical way to control these plant poisonings could be by immunization of the animal. However, most phytotoxins are not immunogenic due to their small molecular size and, in order to induce immunity following parenteral administration to an animal, must first be coupled to carrier proteins. A prophylactic "krimpsiekte" vaccine was synthesized by conjugation of one of the poisonous principles (cotyledoside) to bovine serum albumin. The efficacy of the cotyledoside-conjugate in inducing an immunological response was ascertained in rabbits and sheep by determining cotyledoside antibody titres with a self developed ELISA using cotyledoside-hen ovalbumin as antigen. The formation of anticotyledoside antibodies was detected in both rabbits and sheep following immunization with the cotyledoside-protein conjugate. Protection provided by the vaccine was demonstrated by challenging sheep with repeated, daily doses of cotyledoside administered intravenously at known toxic concentrations. This preliminary trial verified that the cotyledoside-protein conjugate does indeed induce protective anticotyledoside antibody titres in rabbits and sheep. In addition, the prophylactic potential of this “monovalent vaccine” was demonstrated in the limited challenge study in the sheep. Thus, vaccination as a means of preventing “krimpsiekte” seems to be quite feasible and deserves further investigation. This concept will now be extended to other cardiac glycoside-containing plants, such as tulp, to explore if naïve cattle can be protected against poisoning. If a prophylactic vaccine can be produced the incidence of and mortalities caused by this economically important plant poisoning could be curtailed.
Contact person: Prof CJ Botha.
|
