NE vaccine trials in Europe
Two clinical field trials conducted
in Europe demonstrated that
vaccination of hens with Netvax, a
Clostridium perfringens type A toxoid
vaccine, prevented development of NE
in broiler progeny, reported Dr. Luciano
Gobbi, Intervet/Schering-Plough
Animal Health’s technical manager
for poultry, Italy.
Netvax, which contains a toxoid of
C. perfringens type A toxin, was administered
to hens to convey immunity against
NE to their progeny via passive transfer of
maternal antibodies.
Investigators conducted trials on
commercial farms in Italy and Germany
as part of the application process for
licensure of Netvax in the EU.
They used mortality, evidence of
C. perfringens type A-associated gut
lesions, weight gain and feed-conversion
ratio to evaluate vaccine performance.
The investigators also monitored antibody
levels in vaccinated breeder hens, their
eggs and in hatched, 7-day-old progeny.
Vaccinating breeders with Netvax
induced a significant antibody response
against C. perfringens alpha-toxin,
Gobbi said. This response was found not
only in breeders but also in their eggs
and in serum from progeny chicks. The
high antibody titers were reflected in
the level of NE infection. None of the
progeny of vaccinated breeders had
C. perfringens-associated gut lesions,
but control birds did.
Weight gain and feed-conversion ratios were satisfactory and within the standards of the two poultry companies hosting the trials. And with one exception caused by a yolk-sac infection rather than NE, mortality figures in the trials favored the vaccinated birds' progeny, compared to controls.
Investigators also measured clinical safety
and reported no animal health or welfare
issues due to the vaccination of breeders.
Birds received intramuscular vaccination
in the breast, although the toxoid vaccine
can also be given subcutaneously.
Gobbi noted that although clinical
NE can cause significant mortality, the
underlying costs of subclinical disease —
estimated at US $0.05 per bird — should
not be discounted. In addition, 95% of
NE that occurs is subclinical.
Protection of broilers against the alphatoxin
through maternal antibodies lasted
for about 3 weeks, Gobbi explained in an
interview with Intestinal Health. By the
time antibody titers dropped, the birds’
gut development was sufficiently advanced
to establish their own immunity.
Gobbi, who was lead investigator for the trial in Italy, said that poultry companies involved in the trials are interested in using the vaccine, once registration is completed, probably in 2009.
Back to European Edition (#2)
