Faculty of Veterinary Science
Department of Paraclinical Sciences (Veterinary)
Selected Highlights from Research Findings
Between June and September 2008, the carcasses of approximately 150 Nile crocodiles, Crocodylus niloticus, were discovered in the Kruger National Park’s Olifant Gorge. However, researchers believe that a large number of carcasses might not have been detected because of the remoteness of the area and that the actual number of deaths might be as high as 500. The total population in the gorge was estimated at approximately 1 000. This means that half the population died within a short period of time. Another worrying factor is that all the dead crocodiles were large (more than three metres in length), mature animals. The loss of most of the reproductively active animals may seriously influence the ability of this population to recover in the near future. Post-mortem and histopathological investigations indicated that the crocodiles died of a condition called pansteatitis, also referred to as yellow fat disease. It can be described as a generalised inflammation of body fat and usually involves subcutaneous as well as intra-abdominal fat deposits. It is commonly found in animals that live on a diet high in polyunsaturated fatty acids. The researchers found that all the dead crocodiles from the gorge were very fat and, except for the fat lesion, no other pathology was observed. Clinical signs include a general hardening of body fat and a change in colour from white to yellow. These changes in all body fat deposits cause the crocodiles to become stiff, causing a reduction in mobility and even an inability to swim properly. Affected crocodiles become reluctant to enter the water and do not move away when approached. This leads to a slow death due to exposure, starvation and even drowning. At this stage it is not yet clear what triggered the pansteatitis outbreak in the Olifants Gorge. It is thought that the pansteatitis in the Olifants Gorge crocodiles could have been started by illegal fishermen from the Massingir Dam using their gill nets in the gorge. They most probably dumped unwanted or petrified fish or intra-abdominal organs in the water. Another possibility is that the crocodiles used the opportunity, with the gill nets in the gorge, to ‘steal’ large numbers of dead fish from the nets. Pieces of gill nets were found with some of the crocodiles. In addition, cannibalism might also have played a contributing role in sustaining the mortality by triggering the same reaction in crocodiles eating affected crocodiles. The large volume of oxidised fat in a sick crocodile is most probably enough to trigger the reaction in other crocodiles feeding on a pansteatitis case. This is the most logical explanation for the ongoing crocodile mortality in the gorge. No fish die-off was observed in the gorge before the pansteatitis outbreak started. However, post-mortems done afterwards on several fish species from the gorge clearly indicated that they were not very healthy. Blood smear and histopathological abnormalities were commonly observed. The significance of these findings in the fish from the gorge is still under investigation. A possible connection with the pansteatitis is that sick fish would be easier to catch and that crocodiles could overeat if slow-moving fish are abundant. A cyanobacterial bloom was observed before and during the early stages of the outbreak, but the relationship with the crocodile pansteatitis and the fish pathology is still unclear. Another hypothesis is that healthy crocodiles eating pansteatitis-positive crocodiles (cannibalism) are most probably taking in enough oxidised fat to trigger the same reaction, especially the intra-abdominal fat that is easy to consume in large quantities. This is the most likely explanation for the ongoing crocodile mortality in the Olifants Gorge and the Letaba and Olifants rivers
Contact person: Dr JG Myburgh.
In North West, there are small black communities living on commercial farms who have a right to live there, but who are unemployed and have no source of income. Some own cattle, sheep and goats, which are managed under an unproductive, subsistence system. On the other hand, commercial livestock farmers, especially dairy farmers in the province, often experience a shortage of feed for their animals during winter. The aim of this project was to encourage commercial farmers to establish fodder plots that can be managed by unemployed residents on the farms. The farmers will be assisted with the planning of their fodder plots. They will receive start-up funds for the establishment of such plots and will settle the labour costs incurred. Fodder plots will be planted with carob trees, prickly pears, Japanese radishes and pumpkins. Once the plots are established, the workforce will not be paid anymore, but they will be entitled to retain the produce for their own use, for consumption by their livestock, or they may sell it and retain the income. However, the farm owner will have the first option to purchase the fodder. This project will benefit previously disadvantaged communities by providing them with a source of income and by providing food for them and their animals. The commercial farmers will provide assistance to very poor, unemployed and demoralised communities living on their land, and will provide fodder for their livestock. In addition, new small-scale farmers will be trained to become proficient in sustainable, low-input agricultural production
Contact person: Prof L Prozesky.
Farmers and local veterinarians in the Vryburg area reported a new disease syndrome where cattle developed swelling in the weight-bearing joints and severe lameness. They eventually had to be slaughtered. The condition was identified as osteochondrosis, a form of defective formation of articular cartilage that is well known in several domestic animal species, but has not previously been reported on such a large scale in cattle. Preliminary investigations suggest that the cause is an imbalance of phosphorus and various trace elements in commercial mineral feed supplements. Controlled trials on a research station and a commercial farm have identified various trace minerals that might be involved. An experimental supplement is being formulated to correct the imbalance. The supplement is being tested under field conditions. If it is successful in preventing the condition, it will be made available under license to an established feed manufacturer for commercial production
Contact person: Prof L Prozesky.
Wildlife is our natural heritage in Africa. In South Africa, the wildlife industry has grown tremendously during recent years. Consequently, the number of game animal species that are immobilised for various reasons has also increased. Many of the drugs that are routinely used for the immobilisation and tranquilisation of wildlife are considered to be ‘old drugs’ and are potentially dangerous. It is therefore important that innovative drug combinations and new and improved wildlife manipulating agents are investigated. A research project to evaluate butorphanol, a mixed opioid receptor agonist/antagonist, as an adjunct to etorphine in the immobilisation of wildlife was carried out in various species, specifically the white rhinoceros, Ceratotherium simum. White rhinoceros were immobilised with a combination of etorphine and azaperone or etorphine, azaperone and butorphanol to evaluate the effect of butorphanol on blood gas parameters. The butorphanol was given at ten times or twenty times the etorphine dose. Preliminary data shows that there is a statistically significant improvement in both the oxygen saturation of red blood cells and the partial pressure of oxygen in the blood when butorphanol is given at twenty times the etorphine dose, but not at ten times the etorphine dose
Contact person: Dr LJ Venter.
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