Page 121 - VHSA - Onderstepoort 100 Years - Part 3

membranes (CAM) of embryonated eggs. In 1959 van Rooyen, Kümm, Weiss and Alexander eventually succeeded in adapting the Neethling strain of LSD virus to 5-day-old embryonated eggs incubated at 33.5 - 35°C.
Weiss used a combination of host systems to attenuate the virus and eventually obtained best results after 60 passages in lamb kidney cells and 20 passages on the CAM of 8 day-old embryonated eggs. This vaccine has been available commercially since 1962. Despite the development of extensive local swellings in some cattle (particularly Jerseys), which disappear after 3-6 weeks, this vaccine was remarkably effective. It was used extensively in South Africa between 1962 and 1966 and during the 1970s LSD virtually disappeared from South Africa. It is debatable whether the outbreaks in the 1980s were a resurgence of smouldering infections or a reintroduction as in 1944. The discovery
of the aetiological agent as well as the
subsequent development of an efficacious
vaccine are undoubtedly major milestones.
• Bovine ephemeral fever
Bovine ephemeral fever (BEF) has probably been present in tropical Africa for many centuries. The first case recorded by Theiler was at Pretoria in February 1907. Theiler (1908) also succeeded in transmitting the disease by the subinoculation of defibrinated blood. Apart from Africa, BEF also occurs in Asia (as far east as Japan), Indonesia, Malaysia, Australia and many other tropical and subtropical countries. A great deal of research work was conducted in various countries to establish the aetiology. Several workers at Onderstepoort attempted virus isolation in laboratory animals (including mice), embryonated eggs and primary cell cultures to no avail.
ONDERSTEPOORT 100
disease upon intravenous and subcutaneous inoculation into cattle. The cattle even failed to develop antibodies against the inoculated virus.
Fortunately van der Westhuizen was not discouraged by these unexpected set-backs. He next administered infective mouse brain suspensions mixed with incomplete Freund’s adjuvant and attempted to induce immunity in cattle by administration of three successive inoculations. Control animals received normal mouse brain suspensions with the same adjuvant. Most of the vaccinated animals developed high levels of neutralizing antibodies against the mouse isolate and resisted challenge with known virulent BEF challenge virus. The control animals remained sero-negative and developed severe reactions following challenge. Even though Koch’s postulates could not be met, this experiment proved that the virus which
B. van der Westhuizen was tasked to
conduct research on BEF. In 1964 he discovered a blood sample that had been collected in 1958 and then stored under dry ice refrigeration for the intervening 6 years. Intravenous inoculation of 3.0 ml of this blood into a 2 year-old steer resulted in the reproduction of BEF. A large volume of blood was collected at the height of the febrile reaction and the leukocyte-platelet fraction was stored at -76°C. Some of this material was inoculated intracerebrally into newborn mice. From the 10th day onwards a few of the mice showed signs of lethargy and paralysis.
Subinoculation of brain suspensions into further families of newborn mice resulted in an increased mortality reaching 100 percent by the third passage. Similarly the mean survival time was reduced and by the eighth passage stabilized at about 3 days. One disturbing fact was that this virus isolate (third to ninth serial mouse brain passage) did not produce any clinical
then be homogenised with the oil phase is rather strange. It is obviously not a very user-friendly product but when used correctly it is highly effective.
• Rift Valley fever
In the autumn of 1951 an apparently new disease char- acterized by abortions in ewes and cows and mortality of particularly young lambs and calves appeared in the Orange Free State. Several veterinarians and assistants who conducted autopsies on dead animals also contracted a severe influenza-like illness. The disease was highly remi- niscent of Rift Valley fever (RVF), a disease described in Kenya in 1931. Virus isolations conducted at Onderste- poort and at the Poliomyelitis Research Institute Laboratory confirmed that the new disease was indeed RVF.
The mouse-brain adapted Smithburn strain of RVF virus
“Bovine ephemeral fever (BEF) has probably been present in tropical Africa for many centuries. The first case recorded by Theiler was at Pretoria in February 1907. Theiler (1908) also succeeded in transmitting the disease by the subinoculation of defibrinated blood. Apart from Africa, BEF also occurs in Asia (as far east as Japan), Indonesia, Malaysia, Australia and many other tropical and subtropical countries.”
was serially passaged in the mouse brains was indeed BEF virus but that it had lost its pathogenicity for cattle as well as most of its immunogenicity.
Using the same procedure van der Westhuizen made four more isolations of BEF virus which allowed workers in Australia, Japan and elsewhere to successfully isolate local strains of the virus. The first cultivation of BEF virus in the world, achieved at Onderstepoort, will be remembered as a major breakthrough that was the result of persistence and ingenious research work.
Between 1969 and 1973 Theodoridis
built on the solid foundation that was laid
by van der Westhuizen. He made further
isolates and compared various adjuvants
in an attempt to develop a useful vaccine. 211 Freund’s incomplete mineral oil adjuvant
proved to be the best adjuvant and a commercial vaccine has been in use since
1973. The fact that a lyophilized live virus
should be mixed immediately before use
with the water phase of the adjuvant and
Virology
1908-2008
Years