Review on Fowl Cholera

Pasteurella multocida subspecies multocida is the most common cause of fowl cholera, although pasteurellamultocida subspecies septica and gallicida may also cause fowl cholera-like disease to some extent. However, the virulence properties of the different subspecies for various hosts have not been elucidated. The seventy and incidence of pasteurellamultocida infections may vary considerably depending on several factors associated with the host (including species and age of infected birds), the environment and the bacterial strain. No single virulence factor has been associated with the observed variation in virulence among strains. Possible virulence factors include the following: the capsule, endotoxin, outer membrane proteins, and iron binding systems, heat shock proteins, neuraminidase production and antibody cleaving enzymes. Carrier birds seem to play a major role in the transmission of cholera. The site of infection for asteurella multocida is generally believed to be the respiratory tract. The outcome of infections may range from peracute/acute infections to chronic infections. In the former type of infections, few clinical signs are observed before death and the lesions will be dominated by general septicemia lesions. In chronic forms of pasteurella multocida infections, suppurative lesions may be widely distributed, often involving the respiratory tract, the conjunctiva and adjacent tissues of the head. Diagnosis is always dependent the development of safe and efficient live vaccines still poses problems.