The role of vaccinations using deleted vaccines in decreasing the spread of Aujeszky's disease virus in pig farms covered within the "vaccination-eradication programme"
W. Szweda et al., The role of vaccinations using deleted vaccines in decreasing the spread of Aujeszky's disease virus in pig farms covered within the "vaccination-eradication programme", MED WETER, 56(4), 2000, pp. 229-234
Vaccinations play an important role in the control of Aujezky's disease (AD
) because they interrupt the chain of piglet morbidity and mortality as wel
l as decreasing the spread of Herpesvirus suis type 1 (SHV-1). Conventional
vaccines, however, preclude serological differentiation between vaccinated
and SHV-1 infected pigs. Such differentiation has only become possible aft
er the creation of deleted (marker) vaccines, which, together with the appr
opriate serological tests (ELISA), have enabled the realisation of a "vacci
nation - eradication programme" and presented a new perspective on AD eradi
cation in those countries where pigs are vaccinated. The purpose of this st
udy was to evaluate the influence of an intensive vaccination programme usi
ng deleted vaccine in decreasing the spread of SHV-1 in two highly infected
pig farms covered in the "vaccination - eradication programme". All pigs w
ere vaccinated with deleted, gE- and TK-negative, live attenuated Nobi - Po
rvac Aujesky Live Begonia (at present Porcilis Begonia) vaccine - Intervet
Int. Holland according to its accepted programme: reproductive pigs 4 month
s apart and fattening pigs twice at 10-12 and 14-16 week of age. Control se
rological examinations with gE-ELISA using CHEKIT-PRV-gI-EIA, dr Bommeli AG
, Switzerland were performed. In groups of sows a gradual, slow decrease of
SHV-1 infection rates from 100% before vaccination to 60% in farm R and 41
.7% in farm B after the 4(th) re-vaccination were observed. A more rapid de
crease of SHV-1 infection rates among fattening pigs - from 90% to 10% afte
r 13 months and 0% after the 19 month of herd vaccinations in farm R, and f
rom 80% to 0% as early as after 7 months of herd vaccination in farm B were
observed.
Serological examinations of all sows and boars after 2.5 years of herd vacc
ination revealed a decrease of SHV-1 infection rates from 100% to 34.9% far
m R and 28.2% in farm B respectively. This demonstrated that appropriately
prepared and consequently realised vaccination programmes of all pigs, usin
g a good quality deleted vaccine, radically decreases the spread of virulen
t SHV-1 virus in infected herds. The possibilities of serological different
iation between immunised and infected pigs combines with a natural rotation
of infected reproductive pigs and, next, with an appropriate and properly
conducted, economically viable elimination of seropositives creates a reali
stic chance of eliminating virulent SHV-1 even from highly infected swine h
erds.