Prevention of Escherichia coli infection in broiler chickens with a bacteriophage aerosol spray

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Abstract
Bacteriophage to an Escherichia coli isolate that is pathogenic in poultry were isolated from municipal sewer treatment facilities or poultry processing plants. Three studies were conducted to determine the efficacy of aerosol administration of bacteriophage to prevent an E. coli respiratory infection in broiler chickens. In all three studies the experimental design consisted of nine treatments with three replicate pens of 10 birds. Three treatments were not challenged with E. coli and consisted of unsprayed birds, birds sprayed with a diluent control, and birds sprayed with a combination of two bacteriophages. Six treatments were challenged with E. coli by injecting 10(4) cfu into the thoracic air sac when birds were 7, 8, or 10 d of age after being sprayed at 7 d of age with either a diluent control or a combination of two bacteriophages. In Studies 1 and 2, BW at 2 wk of age of all the birds challenged with E. coli, regardless of spray treatment, were decreased significantly from the unchallenged controls, except in Study 2 for the birds sprayed with bacteriophage and challenged at 10 d of age. There was a significant decrease in mortality in Studies 1 and 2 when the birds were challenged with E. coli immediately after bacteriophage administration and in Study 2 in birds challenged at 10 d of age. In Study 3 a suspected pre-existing E. coli infection resulted in mortality in the unchallenged, unsprayed controls, and in the diluent sprayed controls of 20 and 27%, respectively. The mortality in the unchallenged bacteriophage sprayed birds was 3%, representing a significant decrease. Mortality in Study 3 was significantly decreased in the bacteriophage-sprayed birds challenged with E. coli immediately or 1 d later but not 3 d after bacteriophage administration. The decrease in BW at 2 wk of age in challenged birds indicates that bacteriophage treatment did not provide complete protection; however, in all three studies mortality was significantly decreased, indicating that aerosol spray of bacteriophage may be practical for administration of bacteriophage and may provide an alternative to the use of antibiotics in poultry production.