Faculty of Veterinary Science
Department of Veterinary Tropical Diseases
Selected Highlights from Research Findings
Feline immunodeficiency virus (FIV) infection in lions in South Africa was first documented in 1992. Global interest in this viral infection was focused on the question whether the virus was able to infect both wild and domestic cats. During that period tests used for detection of this viral infection (a virus of the genus Lentivirus in the family Retroviridae) were based on determination of antibodies against a closely related virus of domestic cats. Our research projects that followed focused on better diagnostic tools for detection of antibodies directed at antigens derived from lentiviruses found in wild felids, and establishment of tests that will allow genetic analysis of the virus and enable studies on the molecular epidemiology of FIV infection in lions. Four publications followed during the period 2003-2011. In the first, an ELISA test employing a synthetic peptide capture antigen was described that proved to be more sensitive for the detection of antibody against a wild felid-derived virus as opposed to a related virus from domestic cats. The serological studies were followed by 3 papers describing the development of a nested polymerase chain reaction assay for detection of proviral DNA encoding the reverse transcriptase enzyme in blood samples from felids, the sensitivity and specificity of the test, and results of an epidemiological study on FIV infection in lions in the Kruger National Park.
Contact person: Prof M van Vuuren.
Canine babesiosis is a common, highly virulent disease in Southern Africa with even pups and juveniles being severely affected. This contrasts with bovine babesiosis, for example, where host, parasite and vector co-evolved and young animals develop immunity after infection without showing clinical signs. Babesia rossi, the main causative organism of canine babesiosis in sub-Saharan Africa, was first described from a side-striped jackal (Canis adustus) in Kenya. Although data are meagre, there is evidence that indigenous African canids, such as jackals and wild dogs (Lycaon pictus), can harbour the parasite without showing untoward effects. Dogs are not indigenous to Africa. The vast majority of dogs presented at veterinary facilities in South Africa represent recently introduced European, Asian or American breeds. The contention is that B. rossi is a new challenge to which these dogs have not adapted. With intensive treatment of clinical cases and a consequent high survival rate, natural selection is effectively negated and the status quo will probably be maintained indefinitely.
Contact person: Prof BL Penzhorn.
Elephant shrews are a group of small mammals endemic to Africa. In the southern African region they play an important role in the life cycles of a number of economically important ixodid tick species. Indeed, the immature stages of 22 tick species have been collected from these animals in the region. However, it had been assumed that the immature stages of only three of these species are true parasites of elephant shrews and the remainder accidental stragglers. Elephant shrews are the hosts favoured by the larvae and nymphs of the Karoo paralysis tick, Ixodes rubicundus, and of the brown paralysis tick, Rhipicephalus warburtoni, of which the adults cause paralysis in small ruminants, and also of Rhipicentor nuttalli, of which the adults cause paralysis in dogs. Sympatric rodents do not harbour the immature stages of a single one of these ticks.
A few examples. All of 132 rock elephant shrews, Elephantulus myurus examined in the south-western Free State were infested with immature ticks, and harboured a total of 4 331 larvae and nymphs of I. rubicundus and 11 601 larvae and nymphs of R. warburtoni. All of 170 rock elephant shrews in north-eastern Limpopo Province were infested and harboured 42 309 larvae and 2 754 nymphs of an undescribed tick species taxonomically and phylogenetically close to R. warburtoni. This is a new host and species record. Sixty-six Cape elephant shrews, Elephantulus edwardii in the Western Cape Province harboured 1 962 larvae and 679 nymphs of I. rubicundus, while 9 four-toed elephant shrews, Petrodromus tetradactylus in north-eastern KwaZulu-Natal harboured 2 904 larvae and 1 071 nymphs of the nyala tick, Rhipicephalus muehlensi. This is also a new host and species record. We now know that the immature stages of 24 tick species parasitize elephant shrews in southern Africa and that they are the preferred hosts of 5 of these species. Sheep and dogs may harbour the adult ticks of which the immature stages infest elephant shrews in extraordinary numbers, but in turn the elephant shrews feed the immature stages of the same ticks that will paralyse sheep and dogs.
Contact person: Prof IG Horak.
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