Page 33 - VHSA - Onderstepoort 100 Years - Part 3

In this chapter Parasitology includes the disciplines of Entomology (the study of insects), which includes Acarology (the study of ticks and mites) and Helmintho- logy (the study of worms). Because the chronology of professional appointments at Onderstepoort in these fields and incidents in the lives of the persons
who practised them overlap, the sequence of events in the two disciplines have for the sake of clarity been separated. Whenever a single person has contributed to both fields, mention is also made of his or her contribution to the other field. Extensive use has been made of two earlier reviews by G. Theiler (1975) and Penzhorn and Krecek (1997).
Entomology
One of the reputed reasons for deciding on
Onderstepoort as the site for the Veterinary
Research Institute was that it was notorious
for the occurrence of African horsesickness.
This implied that it was also an ideal habitat
for the Culicoides midges that transmit the
virus causing this disease. Thus a minute
insect played an important role in determining where the Institute would be located. Arnold Theiler, the first Director of the Institute, personally devoted a considerable portion of his time to parasitic diseases and their vectors.
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Parasitology I.G. HORAK
ONDERSTEPOORT 100
organism by demonstrating it in the tissues of infected animals and in vector ticks.
G.A.H. Bedford was appointed as a full-time entomologist at the Institute in 1912 and in the same year already had an article published on the spinose ear tick, Otobius megnini, a tick
that at that time was new to South Africa as it had reputedly been introduced with horses from South America. According to Gertrud Theiler, Bedford was a taxonomist ‘par excellence’. He described many arthropod species that were new to science infesting both domestic and wild animals. He listed and described the species of Gasterophilus (horse botflies) that occur in South Africa and also produced extensive parasite and host lists as well as host and parasite lists of the ectoparasites that infested domestic animals and wildlife in South Africa.
He experimented with various com- pounds as dipping agents against ticks, and even dosed tick infested cattle with aloes, a remedy that farmers, then and now, believe has an effect on these parasites. His results and those of modern day efficacy tests indicate that aloes do not have an
effect on ticks. Sheep scab, caused by the mite Psoroptes ovis, was as much a problem in those days as it is now, and Bedford determined the minimum effective concentration of
He was instrumental in recognizing the red- legged tick, Rhipicephalus evertsi evertsi as a vector of Babesia equi (now Piroplasma equi), the cause of biliary fever in horses, and the blue tick Boophilus decoloratus as a vector of Anaplasma marginale, the cause of gallsickness in cattle. According to one of his daughters, Gertrud, Arnold Theiler was also adept at breeding ticks and at establishing tick colonies in his search for the vectors of tick-borne diseases.
“One of the reputed reasons for deciding on Onderstepoort as the site for the Veterinary Research Institute was that it was notorious for the occurrence of African horsesickness. Thus a minute insect played an important role in determining where the Institute would be located.”
lime-sulphur that had to be present in a dip if the mite was to be eradicated. He also studied the off-host survival of the mite. The latter work indicated that structures in which mite-infested sheep had been held or transported could be used again after 17 days without fear of reinfestation. These findings have helped formulate the present quarantine regulations governing the control of outbreaks of sheep scab in South Africa.
One of the first South African-born parasitologists to be appointed at the Institute was H.O. (Hermann) Mönnig in 1922. Originally trained as a zoologist, in which discipline he held a PhD degree, he was persuaded by Arnold Theiler to study veterinary science and was a member of
Because it was essential to identify these
tick vectors correctly, Theiler had all his tick
identifications confirmed by the renowned
taxonomist L.G. Neumann of Toulouse.
Theiler also encouraged visits to the Institute
by eminent overseas researchers, and E.V.
Cowdry, a visitor from the Rockefeller Institute for Medical Research in New York, confirmed Theiler’s suspicions that the disease known as heartwater was caused by a rickettsial
the third class of veterinary students to graduate at the recently established Faculty of Veterinary Science in 1926. His pioneering book Veterinary Parasitology, lavishly illustrated
Parasitology
1908-2008
Years