THE PRODUCTION OF COLIBACILLOSIS IN TURKEYS FOLLOWING SEQUENTIAL EXPOSURE TO NEWCASTLE-DISEASE VIRUS OR BORDETELLA-AVIUM, AVIRULENT HEMORRHAGIC ENTERITIS VIRUS, AND ESCHERICHIA-COLI

Female large white turkeys were intranasally inoculated with either Ne wcastle disease virus (ND) or Bordetella avium (BA) at 4 weeks of age. This was followed by oral inoculation with an avirulent (vaccine) str ain of hemorrhagic enteritis virus (HE) at 5 weeks and intravenous ino culation with Escherichia coli (EC) at 6 weeks. Control birds received ND, BA, or HE followed by EC; EC alone; or nothing at all. Turkeys re ceiving one agent prior to EC challenge did not experience a significa nt increase in mortality or pericarditis. Those exposed to ND or BA fo llowed by HE and EC experienced a significant elevation in mortality a nd pericarditis. A highly significant positive correlation between the number of infectious agents encountered during primary exposure and t he incidence of colibacillosis after EC challenge was demonstrated.