Initial vaccination:
weanlings at approximately 6 months
of age
Secondary vaccination:
yearlings at approximately 12 months
of age
Annual booster:
All horses in high-risk areas should be
vaccinated in late winter or spring
(Sept-Nov).
DAFF have recently restricted the AHS vaccination period in the AHS
Controlled Area following evidence that the Porterville AHS outbreak in 2014
was caused by recombination of serotypes 1 and 4 from the modified live
vaccine and subsequent transmission. A summary of the restricted period is
given below:
Although there are no registered products currently commercially available,
inactivated or recombinant vaccines would prove to be valuable alternatives to
the current modified live virus vaccines. Foals of immune dams acquire a
passive colostral immunity that may protect them against infection for between
3 to 6 months. Vaccination is still the mainstay in terms of preventative
measures. Despite the rigorous use of vaccination to control AHS in RSA,
cases of AHS occur annually in certain high-risk areas (including
Onderstepoort). It has also been shown that vaccinated horses can become
infected with AHSV without developing clinical signs of infection. Such
animals may provide a source of virus for midges and as such may well play a
role in the spread of the disease if such animals are relocated during the
infectious period.
The introduction of equids incubating AHS is the most important means of
introducing the disease into an area or country free of the disease. Zebra and
African donkeys that do not develop clinical signs of AHS are particularly
dangerous. Equids imported from infected countries should be quarantined in
15-‐18
February
2016
East
London
Convention
Centre,
East
London,
South
Africa
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