C. Infectious Bronchitis (IB)

One hundred and fourteen groups were tested by HI, mainly in 1993, and 614 by Elisa, mainly in 1994. As in the case of ND, HI titres suggestive of challenge are common at slaughter (Figure 3.18). The Elisa results show a clear trend to increasing titre with increasing age (Figure 3.19). As in the parents the 793B variant seems to be involved in a proportion of the broiler flocks (Figure 3.20).