Faculty of Veterinary Science
Department of Paraclinical Sciences (Veterinary)
Selected Highlights from Research Findings
Veterinary use of the nonsteroidal anti-inflammatory (INSAID) drug diclofenac in South Asia has resulted in the collapse of populations of three vulture species of the genus Gyps to the most severe category of global extinction risk. Vultures are exposed to diclofenac when scavenging on livestock treated with the drug shortly before death.
Diclofenac causes kidney damage, increased serum uric acid concentrations, visceral gout and death. Concern about this issue led the Indian Government to announce its intention to ban the veterinary use of diclofenac by September 2005. Implementation of a ban is still in progress late in 2005 and to facilitate this, researchers at Onderstepoort’s Paraclinical Sciences sought potential alternative NSAIDS by obtaining information from captive bird collections worldwide.
Researchers form the Royal Society for Protection of Birds in the United Kingdom found that the NSAID meloxicam had been administered to 35 captive Gyps vultures with no apparent ill effects. The researchers then undertook a phased programme of safety testing of meloxicam on the African white-backed vulture Gyps africanus, which they had previously establed to be as susceptible to diclofenac poisoning as the endangered Asian Gyps vultures.
In addition, they estimated the likely maximum level of exposure (MLE) of wild vultures and dosed birds by gavage (oral administration) with increasing quantities of the drug until the likely MLE was exceeded in a sample of forty Gyps africanus.
Subsequently, six Gyps africanus were fed tissue from cattle which had been treated with a higher than standard veterinary course of meloxicam prior to death.
In the final phase, ten Asian vultures of two of the endangered species (Gyps bengalenis and Gyps indicus) were dosed with meloxicam by gavage; five of them at more than the likely MLE dosage. All meloxicamn-treated birds survived all treatments and none suffered any obvious clinical effects. Serum uric acid concentrations remained within the normal limits throughout, and were significantly lower than those from birds treated with diclofenac in other suties.
The researchers concluded that meloxicam is of low toxicity to Gyps vultures and that its use in place of diclofenac would reduce vulture mortality substantially in the Indian subcontinent. Meloxicam is already available for veterinary use in India.
Swan was awarded the 2005 Sasol Vulture Conservation Award in recognition of his leadership role in this research project. He received the award in 2006
Contact person: Prof GE Swan.
Theileriosis is the single most important fatal disease of Roan and Sable antelope, contributing to decreasing population numbers throughout South Africa. High mortalities are especially encountered among calves. Theileriosis is a tick-transmitted bloodborne protozoal disease.
Conventional methods of control failed to prevent the disease on game ranches throughout the country. Research into vaccination as a method of control has been conducted since 2002 on a game ranch in Malelane.
An in-depth article about this research project appeared in the 2004 Research Report. Since then, the following progress has been made:
The tick vectors involved were identified. The main vector involved is the "red legged tick" (Rhipicephalus evertsi evertsi) with the "brown ear tick" (R.appendiculatus) playing a suspected secondary amplification role during theileriosis outbreaks;
A tick derived stabilate was prepared by laboratory infection of ticks (R. e. evertsi) and processing to obtain an injectable infective material. This will be used as a live vaccine during the vaccination procedure, resulting in life long immunity.
Successful inoculation, treatment and post vaccination challenge with infected ticks
proving immunity; and
Vaccination trials, under various management systems (intensive vs. semi-extensive
conditions) showed that the stabilate can be used effectively in practise.
The researchers are currently testing the production of a similar vaccine for Sable antelope under field conditions
Contact person: Dr JCA Steyl.
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