Haemophilus Infections in Chickens. III. Factors in Intraflock Transmission of Infectious Coryza and Its Chemical and Antibiotic Therapeusis

Abstract

The principal mode of transmission of infectious coryza was through drinking water. Nasal excretions from affected birds contained over 100 million H. gallinarum organisms per ml, and brief exposure of thirsty susceptible birds to water containing as few as 156 organisms per ml resulted in transfer of the disease. Infectious coryza was slowly transmitted, presumably by aerosol, to normal birds during close pen contact with infected birds in the absence of feed or water. Attempts failed to transfer the disease mechanically through the handling of infected and uninfected birds. Transmission by flies is both rare and unlikely because H. gallinarum on the legs die rapidly after exposure to water and air. Only erythromycin thiocyanate in a concentration of 0.92 mg per ml of drinking water afforded clinical relief in 4 days. This drug also demonstrated a marked capacity to limit the spread of the disease. Other drugs in similar concentration in drinking water were less effective. Intramuscular injection of 3 drugs, including erythromycin, failed to alter the course of the disease significantly.