Salmonellosis - Birds

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Also known as: Paratyphoid — Pullorum Disease — Fowl Typhoid — Arizonosis

Introduction

Salmonella species have a worldwide distribution and are the most common cause of bacterial diarrhoea in humans and animals.

Many of the species show little specificity for their host species.

The three infections in poultry causing economic losses include S. pullorum, S. gallinarum and S. arizonae. Control programs have led to a decrease in the incidence of infections.

Paratyphoid is caused by any of the non host-adapted species of Salmonella, which can infect any animal and are of public health significance via contamination and mishandling of poultry products. Common species include S. typhimurium, S. enteritidis and others.

Pullorum Disease

Infection with S. pullorum lead to a very high mortality in young chickens and turkeys. It has been eradicated from most commercial chicken flocks, but may be present in other avian species.

Transmission is through the egg, but can occur through contact with infected birds.

Clinical Signs

These include weakness, diarrhoea, anorexia and death. Survivors frequently become carriers and can produce infected progeny.

Post-mortem findings include: nodules in the liver, spleen, heart, lungs and intestine. Caecal cores may be seen. Occasionally, synovitis is present. In mature chickens, chronic infections produce lesions that are indistinguishable from those of fowl typhoid.

Diagnosis

Lesions are suggestive. Confirmation requires isolation and serotyping of the organism. Serological tests can identify infections in live adult birds.

Treatment and control

Treatment is not recommended as it might favour the carrier state. Testing and breeding to assure freedom from infection is preferable.

Fowl Typhoid

Infection with S. gallinarum produces lesions similar to S. pullorum, but can spread more readily amongst growing and mature flocks. Mortality can be high in older birds.

It is also transmitted in the egg.

Clinical Signs

These are similar to infection with S. pullorum.

Older birds may be pale, dehydrated and have diarrhoea.

Post-mortem findings in older birds include: friable swollen liver, with or without necrotic foci, enlarged spleen, anaemia, enteritis.

Diagnosis

Isolation and serotyping of S. gallinarum confirms the diagnosis.

Treatment and control

This is as for S. pullorum infection. Vaccines have been developed in some countries which show promise in protecting birds against challenge. Serology is effective in detecting S. gallinarum infection.

Arizona Infection

S. arizonae is responsible for the disease, primarily seen in turkeys, transmitted through the egg.

Reptiles, wild birds, rats and mice can be infected and serve as a reservoir of infection for poultry. Humans may contract the infection by eating contaminated food.

Clinical Signs

These are not distinctive. Mortality occurs within the first 3-4 weeks of life.

Infections tend to persist in the flock, and birds show signs such as: diarrhoea, lethargy, anorexia, blindness and neurological signs.

Post-mortem findings include: unabsorbed yolk sacs, enlarged and mottled livers, duodenal congestion and caecal cores.

Diagnosis

This is made by identifying and serotyping the organism. Eyes and brain are a good site for sampling.

Serological tests are not available.

Treatment and Control

Killed vaccines are available for infected breeder flocks to reduce egg transmission and to develop pathogen-free flocks.

Antibiotics can be given to day-old poults to minimise mortality, but the carrier state is common.

Paratyphoid

This can be caused by many species of Salmonella, including S. typhimurium, S. enteritidis and others.

Transmission occurs horizontally from infected birds, the environment or rodents. Faecal contamination of the eggshell is also common.

Clinical Signs

Mortality is limited to the first few weeks of age.

Signs include: depression, weakness, anorexia, diarrhoea and dehydration.

Post-mortem findings include: enlarged liver with focal necrosis, enteritis and caecal cores. Infection can localise in the eye and synovial structures.

Acute septicaemia can also occur, and death with no other signs is possible.

Diagnosis

Isolation, identification and serotyping of the agent involves is necessary. Serology is not reliable.

Treatment and Control

General hygiene and management control measures include: strict sanitation, fumigating the hatched eggs, pelleting of feed, cleaning and disinfection of poultry houses and rodent control.

Exclusion of wild birds, rodents and pets can help prevent entry of the organism.

Antibiotics may help prevent mortality but cannot eliminate infection.


Salmonellosis - Birds Learning Resources
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Avian Medicine Q&A 19


References

Merck and Co (2008) The Merck Veterinary Manual Merial

Pattison, M. (2008) Poultry Diseases Elsevier Health Sciences




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