Palestras e Artigos Científicos - Embrapa Suínos e Aves

XIII Congresso Brasileiro de Veterinários Especialistas em Suínos – ABRAVES
16 a 19 de outubro de 2007 - Florianópolis, SC
Aujeszky’s Disease Virus (ADV) affects the respiratory and reproductive systems.
Eradication needed to be on a regional basis in order to prevent the risk of rapid reinfection
from the environment.
At an early stage, the percentage of gE-positives declined very quickly on one
infected farm, which amply demonstrated the effects of vaccination. Sows became
predominantly gE-free after 24 months, by replacing 40% of the sows per year and
introducing only gE–ve gilts (Figure 2).
In an ADV positive herd the transmission rate of AD field virus in a vaccinated herd
with only previously infected pigs was well below 1, which led to the infection dying out.
Vaccination was demonstrated not to prevent infection, but to raise the threshold at which
animals became infected, and to lower the volume and duration of virus excretion following
infection, resulting in less transmission.
To demonstrate that a region could also be cleared of the disease, a large field trial
was arranged around the village of Diessen in an intensive pig-farming area in the
southern Netherlands. Breeding stock were vaccinated on all farms three times a year,
and finishers at around 10 and 14 weeks of age. Gilts were vaccinated three times before
being introduced into the herd. Blood and colostrum were sampled from all sows postfarrowing,
and gE+ve sows were culled after weaning.
This trial clearly showed that even in a region with several hundred farms, it was
possible to create gE-ve farms (3,5,10). It was then logical to extend the programme
nationwide which was completed by the early part of this century. Farms continued with
intensive vaccination and culled their gE+ve sows.
A well-designed vaccination regime with gold-standard vaccines, strict biosecurity
and carefully controlled introductions to the herd (mainly replacement gilts), all made the
eradication of AD possible, and the advent of marker vaccines had a further, very
significant, effect (Figure 3).
This eradication strategy has also been successful in other parts of The
Netherlands, and in parts of Germany, Belgium and France. Spain, Portugal, Greece and
Italy are presently undergoing similar AD eradication campaigns.
Foot and Mouth Disease (FMD)
Foot and Mouth Disease is an increasingly important problem for international trade
in livestock products. Trade in both animals and their products has increased, leading to
more international contacts and the enhanced spread of disease, including Foot-and-
Mouth Disease. New strains continue to emerge and existing strains appear in countries
which had previously been free.
Vaccination already plays an important part in controlling the disease in Asia, the
Middle East, Africa and South America. But the development of a more rapid, more
international, approach to diagnosis and vaccine production is essential.
The European Union has applied a non-vaccination policy since 1995. Beforehand,
the yearly vaccination of cattle created a barrier to the FMD-virus. In the EU, we are now
dealing with a naive FMD-susceptible cattle population. Northwest Europe has already
faced several outbreaks this century, and the disease proved difficult to control in the UK
in 2001.
Dijkhuizen and Meeuwissen calculated the economic consequences of FMD
outbreaks for The Netherlands (8). In the 2001 outbreaks, the damage was far higher than
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