Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/1999
Publication Date: N/A
Interpretive Summary: The recent isolation of phage type 4 Salmonella enteritidis (SE) strains from poultry and humans in the United States has generated considerable concern, as this phage type is predominant in both animals and humans in many other nations. Understanding whether the presence of these strains in poultry flocks poses an elevated threat to public health is a critical issue for developing effective disease control programs. The present study determined how often SE strains of three different phage types found in poultry in the United States (4, 8, and 13a) would be transmitted horizontally from a few experimentally infected "seeder" chicks to their uninoculated penmates. Phage type 4 strains were not transmitted at an elevated frequency in comparison to strains of other phage types, although they tended to be highly invasive in reaching internal organs. Assessing horizontal transmission does not appear to be useful for predicting the probable public health significance of SE phage types.
Technical Abstract: The present study evaluated whether Salmonella enteritidis (SE) strains of various phage types found in poultry in the United States (4, 8, and 13a) differed in their potential for horizontal transmission from experimentally infected chicks to uninoculated chicks housed in the same isolator units. After 2 seeder chicks in each group of 12 were inoculated with oral doses of approximately 1000 SE cells at 8 days of age, ceca and livers were sampled 5 days later from seeder chicks and from their contact-exposed penmates. Based on the detection of SE in cecal samples, phage type 4 strains were transmitted horizontally at a significantly lower frequency than were strains of other phage types. Nevertheless, 2 of 3 phage type 4 strains evaluated were very highly invasive. Assessing differences in the potential for horizontal transmission by the challenge model used in the present study does not appear to be an effective method for predicting the probable public health significance of SE phage types.