Pullorum disease (bacillary white diarrhea)
This disease is caused by poultry-adapted strain of Salmonella genus- Salmonella Pullorum and considered an important hatchery infection. It mainly affects young chicks (below 3 weeks) and also causing high mortality in turkey poults. The organism can persist outside the body for many months. Infected hens pass the infection vertically to the eggs.
Symptoms and lesions: The common symptoms seen are loss of appetite, depression, drooping wings, respiratory distress, increased water consumption and whitish diarrhea with pasty vent. Death may occur suddenly in 95% of the total hatch in severe outbreaks. In less acute cases, nervous symptoms including staggering and in-coordination of the limbs, swollen hock joints and poor growth rate may be seen. The initial indications may be reduced hatchability, a large number of dead-in-shell chicks or chicks dying shortly after hatching. Surviving chicks may appear weak and drowsy at 4-5 days of age, with white pasty diarrhea around the vent. Respiratory signs may occur and at 2-3 weeks of age, higher losses are recorded. Surviving birds may not show clinical signs, but may become carriers.
The gross lesions are congestion of spleen and yellow colored liver with hemorrhagic streaks, chicks that die in 1-2 weeks may show necrotic foci in liver. Pale areas in the myocardium and gizzard muscles are also seen. In chronic cases, the ovary of adult hens show pedunculate and misshapened ova which get detached into the peritoneal cavity. Serofibrinous perciarditis and peritonitis may also be present. The liver is congested with multiple small areas of necrosis. Kidney and spleen may be enlarged.
Diagnosis: The clinical picture and lesions are indicative but confirmation is done by isolation and identification of the salmonellae from visceral organs or heart blood. Enrichment and selective media may be used for isolation. S. Pullorum grows slowly and sometimes incubation for 48-72 h may be required. Detection of antibodies in the suspected flock is made by whole blood agglutination test.
Prevention and control: Prevention is based on flock testing (whole blood, tube agglutination or rapid plate agglutination) to establish disease free breeder and parent flocks. Reacting birds are culled and regular testing is done to find out any new reactor. Thorough cleaning and fumigation of incubators between hatches may eliminate carryover of S. Pullorum or other pathogenic bacteria and frequent sampling can be used to monitor the bacterial presence.