Page 76 - VHSA - Onderstepoort 100 Years - Part 3

ONDERSTEPOORT 100
De Waal became head of the Protozoology Section when Potgieter was promoted to Deputy Director of the Institute in 1988. It was in that year that separate vaccines for B. bigemina and B. bovis were introduced (see above). Although the presence of Babesia trautmanni of pigs in South Africa (and many other parts of Africa) has been known for some time, the tick vector was unknown. However, in 1992 and 1994, respectively, de Waal and some of his colleagues in the Section discovered that the ticks Rhipicephalus simus and Rhipicephalus turanicus could transmit the parasite.
De Vos had obtained an M.Med.Vet. (Parasit.) degree in 1982 from the Faculty of Veterinary Science, University of Pretoria, before he left for Australia. The dissertation that he submitted was entitled: The identity of bovine Theileria spp. in South Africa. This study on local Theileria spp. generated new information which promoted further efforts by W.H. (Hein) Stoltsz, who was appointed in 1984, to study the possible transformation of T. parva lawrencei during tick passage of the infection through a series of cattle. Rhipicephalus zambezien- sis was the vector used to investigate transformation of the parasite causing the typical Corridor disease-type of infection to that of the East Coast fever-type. Although transforma- tion did not occur, even after seven tick passages in cattle, a noteworthy finding was that Corridor
disease is not necessarily self-limiting in
cattle, as appears to be the case from field
observations. It was shown that recovered
cattle could become carriers of buffalo-
derived T. parva lawrencei infections.
The tick R. zambeziensis was found by Blouin and Stoltsz in 1989 to be a more efficient vector of Corridor disease than R.
166 appendiculatus. This was done by analysing the level of infection with sporozoites in their salivary glands with the light microscope. It was found that the infection rate was higher in the former species, which warranted the above conclusion.
Another important result obtained was
the successful in vitro culture of lympho-
blastoid cell lines infected with both the East Coast fever- and Corridor disease-causing parasites and their preservation in the deep frozen form as stabilates. The non-pathogenic theilerial parasite infecting sheep in South Africa, referred to as Theileria ovis, has now been identified as Theileria separata. Both Rhipicephalus evertsi evertsi and Rhipicephalus evertsi mimeticus ticks have been confirmed as vectors.
A fatal theilerial disease, originally described by Neitz as cytauxzoonosis, has been diagnosed in a wide variety of antelope species in South Africa such as duiker, kudus, tsessebes, sable antelopes, roan antelopes and giraffes. The opportunity to investigate the relationship of this theilerial parasite to those of livestock presented itself in a sable antelope calf that developed a fatal form of the disease following natural infection. Both small piroplasms and schizonts could
be demonstrated in blood and organ smears respectively. Schizont-infected spleen cells were established in culture and maintained as continuous lymphoblastoid cell lines. How- ever, attempts to infect a sheep, a goat and a calf with culture material all failed. There are indications that this parasite is distinct from any of the theilerias known to infect livestock.
Transformation (1992-2008)
The Veterinary Research Institute, Onder- stepoort was transferred to the newly established Agricultural Research Council in 1992 and changed its name to the Onderstepoort Veterinary Institute (OVI). It also changed its organizational structure quite drastically to a matrix system. Section- based research was replaced by multi- disciplinary programmes and heads of sec- tions became managers. De Waal became Manager: Ticks and Tick-borne Diseases and Blood Vaccines, and much of the research on protozoal diseases was conducted under his direction. However, there was al-
so a programme for Haemoparasitic Diseases, headed by Allsopp, which conducted molecular biological research on diseases such as babesiosis, anaplasmosis (recognised as a rickettsial disease for some time on the basis of its ultrastructure), theileriosis and heartwater.
A very promising competition inhibition ELISA test was developed in collaboration with Washington State University using a cloned Anaplasma marginale antigen for the sero- logical studies on inter alia the epidemiology of anaplas- mosis. The results obtained compare well with the very reliable card agglutination test, a serological test originally developed in the USA.
Significant progress has been made with the in vitro cul- tivation of parasitic protozoa and rickettsias since E. Zwey- garth joined the Section in 1993. With the excellent technical
“A fatal theilerial disease, originally described by Neitz as cytauxzoonosis, has been diagnosed in a wide variety of antelope species in South Africa such as duiker, kudus, tsessebes, sable antelopes, roan antelopes and giraffes.”
PART 3
History of Individual Disciplines
1908-2008
Years