Salmonellosis (Pullorum, Bacillary white diarrhoea)

Occurrence: Worldwide.
Species affected: All.
Age affected: All.
Causes: Non-motile gram negative bacterium Salmonella pullorum.
Effects: Young birds have a pasted vent. White diarrhoea, huddling, lameness, somnolence (sleepiness), laboured breathing and blindness can occur. Mortality peaks at 7-10 days with up to 100% mortality and/or morbidity. Adults usually have subclinical disease, or a drop in egg production, fertility, or hatchability may occur. Occasionally see depression, anorexia, diarrhoea and dehydration.

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Causes

All species of bird of all ages are susceptible to this acute to chronic disease (acute in young birds and chronic in older flocks). The agent involved in the aetiology of the disease is Salmonella pullorum, which is a non-motile, non-spore or capsule forming gram-negative rod-shaped bacteria.

Mode of transmission

Vertically spread through egg (transovarian) or on egg (by faecal contamination) or by feed and water contamination, contaminated incubators, exploding eggs, and bird to bird (horizontal) transmission. It is species specific (occurs in birds only).

Clinical signs

Young birds have a pasted vent. White diarrhoea, huddling, lameness, somnolence (sleepy), laboured breathing and blindness can occur. Mortality peaks at 7-10 days with up to 100% mortality and/or morbidity. Adults are usually subclinical and a drop in egg production, fertility or hatchability may occur. Depression, anorexia (won’t eat), diarrhoea and dehydration are occasionally seen.

Postmortem lesions

Young birds have a red-streaked liver, enlarged spleen and grey nodules in the peritoneum. White caecal plug, misshapen yolk and omphalitis (swollen navel) can occur. White areas on gizzard, liver, heart, lungs, swollen joints and swollen urate filled kidneys may be seen.

Salmonellosis

Prevention

Some countries still vaccinate using modified live vaccines. Control rodents and reduce poultry by products in the feed.

Special note

It is a notifiable disease. It has been eradicated from most commercial flocks around the world (by testing and slaughter of positive breeder flocks, but is still common in backyard flocks and commercial flocks in third world countries. A few isolated outbreaks of pullorum occasionally occur in broiler breeder and broiler flocks from more developed countries.