Page 8 - VHSA - Onderstepoort 100 Years - Part 3

OND
ERSTEPOORT 100
important South African strains. Work by Cameron and Fuls
in 1980 and P. (Pamela) Hunter in 1982 also ensured that the virulence factors of E. coli, which had been discovered in the meantime, were at adequate levels in both vaccines.
Pasteurella was initially thought to contain only two species, P. haemolytica and P. multocida. This simple classification did not fit in with the various disease syndromes
shown by infected animals, nor with the
observation that some strains of Pasteurella
could also be isolated from normal animals.
Vaccines prepared in different parts of the
world from various strains also gave very
variable results. In South Africa shipping
fever in cattle, as well as pneumonic
pasteurellosis and blue udder in sheep are
usually caused by P. haemolytica and to a
lesser extent by P. multocida A and D, but
these are the types that do not produce
a good immunity. After typing sera were
prepared by Cameron during the 1960s, the
prevalence of Pasteurella serotypes in South
Africa could be determined. This formed
the basis on which vaccine strains could be
selected.
very little cross-immunity and results were variable especially as new strains were constantly being detected.
M.M. (Marijke) Henton joined the department in 1970 and began her work by researching colibacillosis in South Africa. A full set of typing antisera first had to be produced, before the incidence and importance of E. coli could be investigated
and improvements of the existing vaccine for cattle could be made. This led to the production of other sets of typing sera, such as the capsular Klebsiella sera, important in investigating venereal infections of horses. A. Garifallou was responsible for diagnostic bacteriology during the early 1970s, and when he left in 1976, Henton took over diagnostic bacteriology. She improved the service, was involved in many multidisciplinary investigations and continued the tradition of assisting the vaccine factory in vaccine improvement until she left in 2002. Other technical staff during the late 1970s were W.F. (Wilna) Botha, P.C. (Piet) Knoetze, L. (Lorraine) Pienaar and D. (Danie) du Toit.
New horizons (1981-2008)
In 1983/4 Hunter futher improved the two E.coli vaccines by adapting them from alum to oil adjuvants. The numbers and serotypes in the vaccines were constantly reviewed so that the vaccines contained strains important in South Africa at the time. As Onderstepoort was the only site in Africa where E. coli could be fully serotyped, culture collections from other African countries were regularly examined to help other researchers determine important serotypes in their countries. Jansen, who was promoted to a senior position in the Department of Agriculture in 1969, took early retirement at his own request and returned to Onderstepoort and his beloved research. He studied the aetiology and epidemiology of epididymitis in young rams on a high plane of nutrition and con- cluded that it was caused by an ascending infection by bacteria, such as Actinobacillus seminis and Histophilus ovis, which he regarded as normal flora of the intestinal tract.
An initial investigation by Cameron in 1966 showed that protective immunity and the haemagglutination titres of P. haemolytica vaccines did not correlate with each other. Further work by Cameron and G. (Gertruida) Smit in 1970 on a polyvalent vaccine intended for use in sheep confirmed that the immunity to P. multocida was far
98 better than the immunity to P. haemolytica, which also varied from strain to strain. Cameron and co-workers [M. (Marie) Engelbrecht, L (Lorraine) Pienaar, A. (Alet) Vermeulen and F. (Fay) Bester] established that cross-immunity between similar strains was poor, and that no prediction could be made on the basis of serotype as to whether a strain would be a good or poor immunogen. Immunity to single antigen vaccines were better than those prepared with more than one type, and there was interference if more than four strains of P. haemolytica were included in one vaccine.
“Three vaccines were formulated during the early 1970s by Cameron, for pneumonia and septicaemia in sheep, blue udder in sheep and shipping fever in cattle.”
Different species of animals also res-
ponded differently to different strains of Pas-
teurella, and one could therefore not trans-
pose results from one species to another.
Taking these constraints into consideration,
three vaccines were formulated during the
early 1970s by Cameron, for pneumonia and septicaemia in sheep, blue udder in sheep and shipping fever in cattle. These vaccines gave a certain amount of protection, but there was
During the mid 1980s it became apparent that leukotoxin played a major role in the pathogenesis and protective immunity of P. haemolytica infections in cattle. Hunter and Odendaal utilized this knowledge to improve the Pasteurella vaccine for cattle.
PART 3
History of Individual Disciplines
1908-2008
Years