Page 117 - VHSA - Onderstepoort 100 Years - Part 3

ONDERSTEPOORT 100
R. Meiswinkel, expert entomologist, identifying species of Culicoides midges caught in a light trap on Kaalplaas, the Institute’s adjacent farm
vaccinated sheep were extreme- ly well protected. Unfortunate- ly, however, many farmers were not prepared to handle their sheep three times per year and all possible variables came into practice, the most common of which was to combine bottles A and B and to discard C (which contained Type 2, the most prevalent BT virus for several decades).
In 1975 Erasmus was invited by the Australian Veterinary authorities (together with six other scientists) to advise them on measures to keep Australia free from BT and, in the event of its introduction, how to recognise, diagnose and control the condition. After tours to various ecologically different parts of Australia, the scientists convened in Adelaide to present various papers on BT at the annual meeting of the Australian Vete- rinary Association (see the Australian Vete-
rinary Journal, 51, (4) 165-232 for details).
A generally accepted recommendation was
to start careful monitoring for virus in
wild-caught Culicoides midges as well as
for clinical signs and antibodies to BT in
sentinel Merino sheep and cattle to be
strategically placed in the Northern Territory.
The outcome of this was the isolation of the
first BT strain in Australia (confirmed as BT
by group specific test reagents previously
supplied by Onderstepoort and serotyped as
BT 20 at Onderstepoort). This was followed
by two more hirtherto unknown serotypes
(Types 21 and 23) as well as several known
serotypes of BT virus in subsequent years.
for virus isolation or for serotyping were received from many countries such as Greece (Type 4), Brazil, Argentina, Canada, India and Indonesia (Types 1, 6, 9, 12, 14 and 23).
During the 1990s Barnard and members of his team collaborated with G.J. (Gert) Venter and R. (Rudi) Meiswinkel from the Entomology Section in a study to determine the ability of various Culicoides species to act as vectors, i.e. to transmit the orbiviruses. At a later stage this work formed
part of a large EU-funded project involving
an international consortium. The role of different vectors became a crucial issue 207 during the first decade of the 21st century
when BT gradually spread northwards in
Europe as a result of global warming and
its effect on the distribution of these insects
(see also Part 3: Parasitology).
• Foot and mouth disease / African swine fever
Foot and mouth disease (FMD) is peculiar in that, although it is widely recognized as an important animal disease, the reasons are understood by few people, even within the veterinary fraternity. Furthermore, because of its potential trade implications, events associated with the disease often have a political dimension. An early illustration of this occurred in 1931 when FMD suddenly re-appeared in southern Africa (on Nuanetsi
Ranch in what is now Zimbabwe) after an apparent absence of more than 30 years. This event resulted in much speculation as to the origin of the infection. One popular theory was bio- terrorism!
Since the first isolation of BT in California
in 1952 many more isolates were made
in the USA. These seemed to fall into
four distinct groups but, despite the fact
that all prototype BT viruses were supplied
by Onderstepoort to the Plum Island
laboratory, the American workers struggled to serotype these isolates. Eventually in 1975, some representative isolates were submitted to Onderstepoort and, apart from types 11 and 13, a new serotype 17 was found. In ensuing years samples
“Only many years later was it realized that the Great Rinderpest Pandemic, which swept through eastern and southern Africa during the last decade of the 19th Century decimating cattle and wildlife populations, had reduced buffalo populations as well as cattle to levels below that where buffalo-cattle contact rates were adequate to result in transmission of FMD to domestic livestock.”
Virology
1908-2008
Years