Pullorum Disease (Salmonella pullorum)
Etiology, vertical egg transmission, pathognomonic lesions, and eradication protocols.
Scientific Overview
Pullorum Disease is a severe, highly contagious septicemic bacterial disease of young chicks and turkey poults caused by Salmonella enterica serovar Gallinarum biovar Pullorum. Characterized by high mortality during the first 3 weeks of life, chalky-white diarrhea, and characteristic necrotic foci in internal organs.
1. Etiology & Vertical Transmission
Salmonella pullorum is a non-motile Gram-negative bacterium uniquely adapted to avian hosts. Unlike paratyphoid salmonellae, S. pullorum is primarily transmitted vertically from carrier hens through infected egg yolks to developing embryos. In hatcheries, down feathers, dust, and chick-to-chick contact rapidly spread infection across incubators.
2. Clinical Symptoms & Necropsy Pathology
Chicks exhibit acute huddling near brooders, shivering, depressed appetite, and a characteristic chalky-white diarrhea that pastes vent feathers. Upon necropsy, classic lesions include unabsorbed yolk sacs, grayish-white necrotic nodules in lungs, liver, gizzard wall, and heart muscle, alongside cheesy cecal cores.
3. Prevention & NPIP Eradication
Erased from commercial flocks in developed nations through the National Poultry Improvement Plan (NPIP), Pullorum is managed by blood-testing breeder stock using the whole-blood plate agglutination test. Positive reactors are immediately culled. Antibiotic treatment is discouraged as it creates chronic asymptomatic carriers.