Fetal membrane and tissue culture suspensions of the coccobacilliform bodies are infective for normal fowl. Intranasal injection is commonly followed by a coryza which is serially transmissible and communicable by direct contact. The specific bodies are generally demonstrable in the nasal exudate of birds infected either by injection or contact.
Compared with the original strain of the coryza of slow onset the reaction produced by these suspensions is often less vigorous; the incidence of apparent cases, characterized by a nasal discharge, being 97 per cent and 53 per cent, respectively. The apparent cases are similarly characterized by a long incubation period and a tendency towards chronicity.