Disease producing capability of netB positive isolates of C. perfringens recovered from normal chickens and a cow, and netB positive and negative isolates from chickens with necrotic enteritis.

Necrotic enteritis is a serious disease of chickens and turkeys caused by Clostridium perfringens. Recently, a pore forming toxin of C. perfringens, called NetB, was reported and suggested to be critical to the development of necrotic enteritis. To investigate further the importance of NetB in the development of necrotic enteritis, toxin production and disease producing ability of (1) netB positive isolates recovered from normal chickens, (2) a netB positive isolate recovered from a cow, (3) netB negative isolates recovered from chickens with necrotic enteritis and (4) netB positive isolates recovered from chickens with necrotic enteritis, were examined. None of the netB negative isolates recovered from chickens with necrotic enteritis produced disease in challenged chickens. All netB positive isolates produced necrotic enteritis in challenged chickens, although there were substantial differences in the incidence and severity of lesions. Thus, one netB isolate produced severe lesions in 80% of challenged chickens, while another produced lesions in only 20% of challenged chickens, and these were very mild. The netB positive isolate from a cow, produced lesions in 90% of challenged chickens with severe lesions in 50%. While these findings would generally support the concept that netB is very important to development of necrotic enteritis, the finding that there was a wide range of virulence among the netB positive isolates suggests that other critical factors are also involved. This study has also demonstrated for the first time that C. perfringens strains from a mammalian species and from normal chickens, can cause necrotic enteritis in chickens.