Key result
CEO and TCO vaccines yield low neutralization titers while drinking-water delivery maximizes ILT virus protection.
Why the study?
Does vaccination with CEO or TCO vaccines via different routes improve VN titers and survival against ILT challenge in broiler chickens?
Does vaccination with CEO or TCO vaccines via different routes improve VN titers and survival against ILT challenge in broiler chickens?
In broiler chickens, CEO vaccines and drinking-water administration provide better immunity and protection against ILT than TCO vaccines and spray administration.
Drinking-water CEO vaccination may enhance ILT protection in broilers despite low titers; leaves open optimal strategies pending field confirmation.
Broiler chickens were vaccinated at 18 days of age against infectious laryngotracheitis (ILT) using chicken-embryo-origin (CEO) and tissue-culture-origin (TCO) vaccines, each vaccine given either by drinking water, spray, or eyedrop. Controls were not vaccinated. The broilers were challenged 3 weeks later with virulent ILT virus (USDA challenge strain). Serum samples taken before challenge were analyzed by a virus neutralization (VN) test to determine titers due to vaccination. Both vaccines, regardless of route of administration, produced low VN titers, geometric mean titer (GMT) being less than 4.0 in all vaccinated groups. When administered by the same route, the CEO vaccine produced higher titers than the TCO vaccine. Titers following drinking-water or eyedrop administration of vaccines were higher than titers following spray vaccination. There was an inverse relationship between pre-challenge VN titers of groups of birds and the percentage of birds in the groups dying from ILT virus challenge. The drinking-water route of vaccination provided the most protection, while the spray provided the least.
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Andreasen et al. (1989) studied Infectious laryngotracheitis (ILT). Chicken-embryo-origin (CEO) and tissue-culture-origin (TCO) vaccines vs. Unvaccinated controls was evaluated on Virus neutralization (VN) titers and mortality from ILT virus challenge. Vaccination with CEO and TCO vaccines produced low virus neutralization titers (GMT < 4.0), with the drinking-water route providing the most protection against ILT virus challenge.
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