VLA: Game Birds May be Reservoir for Salmonella

UK - Salmonella pullorum caused losses of two-week-old pheasant poults, according to the Veterinary Laboratories Agency (VLA) report for July 2010, indicating that game birds may act as a potential reservoir of this salmonella species that may also affect commercial poultry.
calendar icon 14 September 2010
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Commercial Layers and Layer Breeders


Coccidiosis due to Eimeria acervulina and Eimeria necatrix were seen in two flocks of 26- and 42-day-old birds and a flock of 96-day old birds, respectively.

In the younger flocks, post mortem examination revealed sparse intestinal contents, either empty or containing small amounts of clear watery fluid in some cases whitish catarrh. Occasional focal congestion of the mucosal surface in the mid to lower intestine with red stippling was also a feature. Histological examination of intestinal mucosa revealed clusters of intraepithelial coccidial forms consistent in size and location with those of E. acervulina.

The older flock's post mortem examination revealed a marked 'ballooning' of the intestine with pale mottling visible from the serosal surface. In this case' wet smear examinations of mucosal scrapings revealed structures consistent with coccidial schizonts. Histology confirmed the presence of clusters of large coccidial schizonts, sometimes associated with areas of haemorrhage and consistent in size and location with those of E. necatrix.


Histomoniasis lacking the classical blackhead hepatic 'target' lesions was diagnosed in a flock of 60-week-old free-range layers. Post mortem examination revealed multiple random mottling lesions on the liver surface and enlargement of spleen and kidneys. Liver histology confirmed lesions consistent with histomoniasis.

Broilers and Broiler Breeders

E.coli septic arthritis

E. coli septic arthritis was diagnosed in two submissions of six-day-old chicks with a history of lameness. Post mortem examination revealed a creamy off-white exudate affecting mostly the hock joints and occasionally the knee joints, from which light to moderate growths of E. coli were cultured. In most carcasses, a small remnant of infected yolk sac was also present.

Spiking mortality syndrome

Hypoglycaemia – spiking mortality syndrome was the tentative diagnosis in one submission of 20-day-old broilers presented with a history of sharp and transient increased mortality. Findings at post-mortem examination included marked congestion of subcutaneous fat, myocardial pallor, mixed areas of pallor and congestion in the kidneys and congested livers. Histological examination of heart and kidney tissues, which is used to support this diagnosis is still ongoing.

Backyard Flocks

Infectious Laryngotracheitis (ILT)

ILT was diagnosed in a backyard flock of show chickens. Birds were seen to be gasping for breath and died 12 hours later. At post-mortem examination, typical necrotic diphtheritic lesions in the upper respiratory tract were seen and histopathology confirmed chronic fibrino-granulocytic tracheitis and laryngitis with characteristic intranuclear inclusion bodies.

Red mite

Two cases of red mite infestation were diagnosed by Truro, both presenting as severe anaemia and death in infected birds. In the first case, an 18-month-old cockerel was submitted after six of 12 birds had died in a backyard flock. In the second case, a one-year-old Dutch bantam hen was one of two birds in a backyard flock of 12 to die. In both cases, there were large numbers of red mites (Dermanyssus gallinae) present on the feathers, skin and skeletal muscles and viscera were generally pale.

Langford diagnosed the disease affecting three cockerels and Winchester attributed a sharp increase in mortality in 39-week-old layers to the infestation. The cumulative mortality in the worst affected part of the house was 400 birds out of 5,000 placed. The housing had been sprayed against red mite approximately two weeks previously but the treatment appeared to have been ineffective.


Failure to thrive in pheasants

Winchester received a number of pheasant poult submissions during the month, commonly around eight to 11-weeks of age. Similar clinical signs were described on most units, namely weight loss and failure to thrive with mild dehydration and copious yellow coloured liquid to soft caecal content. A variety of aetiological agents were identified including Spironucleus (Hexamita), Syngamus trachea (gapes) but often at relatively low levels. It is speculated that many of these losses are cumulative as a result of progressive parasite damage to gut leading to malabsorption and weakness.

Salmonella pullorum

Luddington investigated an outbreak of Salmonella pullorum infection which resulted in the death of 70 of 500 two-week-old pheasants reported over a 24-hour period with 80 per cent affected group mortality over five days.

Salmonella pullorum is host-adapted and vertical transmission has an important role in the perpetuation of infection. In this incident, all the eggs have been sourced from a single population of 700 laying hens on site. However, it was probable that the source of infection arose from persistent sub-clinical infection in the general pheasant population which may include infected itinerant game or wild pheasants gathered at the beginning of the breeding season.

Further Reading

- Find out more information on the diseases mentioned in this article by clicking here.
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