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UMISignature was redacted for privacy.Signature was redacted for privacy.iii Pasteurella multocida causes fowl cholera in both domestic and wild birds. The high morbidity and mortality associated with this disease results in significant economic losses to the turkey industry. Transmission of the disease usually occurs following contamination of drinking water with mucous secretions firom infected birds. Experimentally, a small inoculum of virulent organisms (30-100) is capable of causing nearly 100% mortality within 48 hours. The organism is thought to enter the bird after colonizing the mucous membranes of the pharynx or upper air passages, eventually gaining access to the blood stream where it rapidly reaches very high numbers, often exceeding 10* ml "'of blood (109). However, the precise mechanisms of pathogenesis are still unclear.Serogroup A strains of P. multocida are the major cause of fowl cholera in poultry. CD44, an 85-lcDa transmembrane glycoprotein found on a wide variety of cell types, is one of several receptors capable of binding hyaluronic acid. Because CD44 is a hyaluronic acid receptor also associated with blood monocytes (23,43), it is my hypothesis that CD44 is involved in adhesion of serogroup A strains of P. multocida to turkey peripheral blood monocytes. Other reports indicate that freshly isolated human peripheral blood monocytes do not bind soluble hyaluronic acid; however, increased mucopolysaccharide binding occurs in vitro after 8 to 16hours of incubation (77) or after exposure to phorbol myristate acetate (79). Similarly, in septicemic cases of fowl cholera, minimal association occurs between peripheral blood monocytes and capsulated strai...