Epidemiological Investigation, Cleanup, and Eradication of Pullorum Disease in Adult Chickens and Ducks in Two Small-Farm Flocks

Abstract

Pullorum disease causing acute septicemia and mortality in adult brown chickens was diagnosed in a small-farm chicken flock in Iowa. Also, Salmonella Pullorum was isolated from the intestine of one of four rats trapped on this index farm. Tracing movements of spent hens from the index farm resulted in identification of a second infected flock on a contact farm. Poultry on the contact farm were tested with the stained-antigen, rapid whole-blood test, and two ducks and one chicken gave positive reactions. Reactors were necropsied and cultures of appropriate tissues resulted in isolation of Salmonella Pullorum from one duck and the chicken. Pulsed-field gel electrophoresis banding patterns of Salmonella Pullorum isolates from chickens on the index and contact farms, the duck, and the rat demonstrated that all isolates were genetically very similar. Both flocks were quarantined and depopulated and a detailed flock cleanup plan was created for both farms. After extensive cleaning and disinfection procedures were completed on the index farm, environmental monitoring and bioassays of trapped mice were conducted. Negative cultures of environmental swabs and trapped mice and negative blood tests of all birds conducted 4 mo after placement of a new flock on the index farm demonstrated that cleaning and disinfection methods used in this outbreak had successfully eliminated Salmonella Pullorum organisms from this farm.