Pullorum Diagnosis

Information about how the disease is diagnosed.

Lesions may be highly suggestive, but diagnosis should be confirmed by isolation and identification of S pullorum. In its acute form, pullorum disease is almost exclusively a disease of young chickens, and the agent can be recovered from almost all organs, tissues and feces.

Samples may be obtained from live birds, fresh or freshly frozen carcasses, egg materials, fresh feces., or any contaminated materials from housing, incubators or transport boxes.

Swabs may be taken from the cloaca of live birds. Samples from visibly abnormal tissues are preferable to fecal and environmental samples.

When floor litter or fecal material is sampled, it should be remembered that S. Pullorum is more difficult to isolate from fecal and environmental samples than other salmonellae. Samples should include floor feces, moist and dry litter and swabs from open drinkers. These samples should be cultured by direct inoculation of a selective enrichment broth such as selenite cysteine, followed by plating on selective media such as brilliant green agar.

In older birds that have become carriers, S. Pullorum is most commonly recovered from the ova, and only exceptionally from other organs and tissues, including the alimentary tract. Infections in mature birds can be identified by serological tests, followed by necropsy and culturing for confirmation.

Serological tests are best applied as a flock test, because results for individual birds will vary according to the stage of infection. It is therefore necessary to take sufficient individual samples to determine infection in the flock. If the test is to be used for detecting individual infected birds for culling, it should be repeated at least twice and preferably until the whole flock has given at least two negative tests.

The tests that are most readily applied include rapid whole blood agglutination, rapid serum agglutination (RST), tube agglutination and micro-agglutination. Other invasive Salmonella such as S. Enteritidis and S. Typhimurium may give false-positive results in serological tests for S. Pullorum.