Page 116 - VHSA - Onderstepoort 100 Years - Part 3

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ERSTEPOORT 100
During the outbreak of Bluetongue (BT) in Cyprus in 1943 (the first confirmed BT outbreak outside Africa), blood samples were submitted to Onderstepoort from which virus was isolated and confirmed as BT virus which was subsequently identified as
Type 3. (The Cyprus strain happened to be one of the most pathogenic BT virus strains ever identified.) The Cyprus isolate was attenuated in embryonated eggs at Onderstepoort and the resultant vaccine which was used in Cyprus in 1946 and 1947 successfully curtailed the outbreak. In 1952 Onderstepoort confirmed the presence of BT in Israel and as a consequence Leah Goldsmit (co- developer of the Komarov Newcastle disease vaccine) visited Onderstepoort for 1 year to study BT techniques which she later fruitfully applied in Israel.
Also in 1952 a condition termed ‘sore muzzle’ was described in California and, although its aetiology could not be established, its similarity to BT was noticed. In 1953 Alexander was invited to the USA to give expert advice on BT. During his visit there were no sick animals but from preserved material he could confirm the diagnosis and from the presence of several breaks in the hooves of some sheep (resulting from severe coronitis) even predicted the existence of two or three different serotypes. He took preserved blood and organ material back to Onderstepoort where he isolated the causal virus and indentified it as BT (later serotyped as Type 10). In 1956 BT outbreaks occurred in Portugal and Spain (and eventually in Morocco). The virus was isolated at Onderstepoort and later identified as Type 10 thus confirming the first outbreak of BT in Europe.
In 1963 Onderstepoort was appointed World Reference Centre for BT with Howell as responsible officer. In 1960 he identified BT type 16 in Pakistan, in 1966 BT types 1, 4 and 12 in samples from the United Arab Republic, and in 1970 BT types 1 and 16 from India. In 1973 Howell joined the Veterinary Faculty and Baltus Erasmus became responsible for BT research and was also responsible for the OIE World Reference Centre for BT until 1995.
Since 1999 there have been outbreaks of bluetongue in Greece, Italy, Corsica, the Balearic Islands and various Balkan countries, involving serotypes 2, 4, 9 and 16. From 2002, BT 4 was reported in Spain and Portugal. The live attenuated BT vaccine from OBP was used in different countries: BT 2, 4, 9 and 16 in Italy, BT 2 and 4 in Corsica, and BT 2 and 4 in Spain and Portugal. Since 2006 BT 8 has emerged in Northern Europe, presumably due to global warming, and also infecting cattle in the Netherlands, Belgium, Germany, Luxemburg and France. From the summer of 2007, BT 8 spread to the UK, Switzerland, Denmark, Spain, Poland and Italy. For safety reasons an inactivated BT8 vaccine is being used in affected European countries rather than the live Onderstepoort vaccine.
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irrespective of the number of live attenuated strains contained in a BT vaccine, sheep will on average respond to three strains only (not necessarily the same three strains!). The logical option was to issue three pentavalent vaccines. Five trivalent vaccines would give superior results, but five annual vacci- nations were totally unacceptable to sheep farmers. Following the success that was achieved with strain 19 it was decided by Erasmus (and Weiss, who after his retirement as Director in June 1980 rejoined the Virology section from 1982 to October 1983 in a temporary capacity) to apply this approach to all the BT vaccine strains. The lowest egg passage levels available
were used, and at least ten plaques of each selected and then screened and processed as was done with Type 19.
To encourage correct use, the three pentavalent BT vaccines were packed and sold as a unit and the order in which the vaccines were to be administered was clearly indicated (Bottle A contained Serotypes 1, 4, 6, 12 and 14; Bottle B 3, 8, 9, 10 and 11, and Bottle C contained 2, 5, 7, 13 and 19). When used correctly this vaccine, after a single series of vaccinations, resulted in demonstrable antibody levels in sheep to about nine serotypes on average. Subsequent boosters broadened the scope of immunity to the extent that properly
PART 3
History of Individual Disciplines
1908-2008
Years