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Trial - Protection in the progeny of flocks vaccinated against CAV

Protection of the progeny against chicken anemia virus infection from different vaccinated flocks was estimated by challenge experiments.

Experimental design

• Day-old chickens, both SPF and commercial chickens, derived from vaccinated breeding stock, were challenged with a Japanese isolate, a Dutch isolate and an isolate from the United States
• Challenge was done by intramuscular route.
• Two weeks later blood samples were taken for determination of the haematocrit
• Also at this stage post-mortem examination of thymus and bone marrow was carried out
• Protection was assessed by the mortality due to CAV, if the haematocrit value was below 27% or if the thymus atrophy or paleness of the bone-marrow was scored as 1 or 2, according to the score table below. 

Post mortem examination

At post-mortem examination atrophy of the thymus and paleness of the bone-marrow were evaluated according to the following scoring system:

Conclusion

The progeny from breeding stock with high VN titres against CAV (in this case induced by vaccination with Nobilis CAV P4) at time of egg collection was protected against a virulent challenge with 3 different isolates of CAV