Commercial Layers and Layer Breeders

Red mite infestation

A sudden rise in mortality in a flock of 8000, 31-week-old free-range layers was attributed to red mite infestation and acute anaemia. Post mortem examination revealed birds in good bodily condition and fully in lay with marked pallor of the carcasses and internal organs.

Broilers and Broiler Breeders

Gizzard impaction

Impaction of the gizzard and upper small intestine was seen in a flock of 12-day-old free-range broilers submitted for examination due to poor performance. Birds with an average body weight of 80g had large bundles of long grass/hay fibres distending the gizzard and duodenum. The provision of insoluble grit of the correct size for the age and size of bird to help the gizzard in its grinding function was discussed.

Enterococcus hirae

Increased mortality associated with neurological signs (toticollis) in five-day-old chicks was attributed to Enterococcus hirae septicaemia. Post-mortem findings included slightly enlarged, often pale spleens. Histopathological examination of brains revealed lesions of encephalomalacia in the cerebrum and midbrain but not in the cerebellum, consistent with E. hirae-associated encephalomalacia. Routine bacteriological cultures of spleens yielded heavy pure growths of Enterococcus species with biochemical features consistent with E. hirae.

Staphylococcal tenosynovitis

Lameness and swelling of tendons and feet ('bumblefoot') was investigated in a flock of approximately 4,000, 26-week-old broiler breeders. Post-mortem examination revealed marked swelling of plantar and digital pads and swelling of the Achilles tendon with oedema and small amounts of caseous exudate within the tendon sheaths. Routine cultures from lesions produced pure growths of Staphylococcus aureus.

Backyard Flocks

Lead exposure in a backyard laying flock

Blood samples were submitted to Starcross from a backyard flock of 25 free-range laying hens following the death of a goose with access to the same range area. Post-mortem examination on farm identified a large amount of lead shot in the gizzard and concern was then raised over exposure of the chickens. Egg sales at the farm gate and home consumption were immediately halted. Of the 10 blood samples submitted only five were suitable for examination. One of samples showed significant lead exposure with a blood lead level of 8.36µmol/l. Two other samples were close to the food safety trigger level of 0.48µmol/l and as a result the case was reported to the Food Standards Agency. A local game shoot uses fields close to the range area of the birds and this was thought to be the source of the lead shot. The farmer was advised to move the birds to a non-contaminated area and increase the level of insoluble and soluble calcium in the diet to reduce absorption of the lead. The remaining birds were placed under a 16-week restriction period, during which time no eggs will be consumed or sold. Exposed birds will then be re-tested to reassess their lead exposure to determine if egg consumption can resume.

European QX strain of infectious bronchitis (IB)

Bury diagnosed IB as the cause of death of three chickens following the development of respiratory signs and malaise. The birds were from a small flock of 11 birds of mixed ages varying from one year to seven years old. Following necropsy, infectious bronchitis virus (IBV) was detected by PCR on kidney tissue and an oropharyngeal swab. On S1 genotyping these products showed 98.6 per cent and 97.9 per cent similarity to the European QX strain of IBV. In another case, a tracheal and a kidney swab from 10-week-old layer pullets were examined by PCR examination and showed the presence of an IB virus with a 97.1 per cent similarity to the European QX strain of IB.

Ducks and Geese

Duck virus enteritis (DVE)

Sutton Bonington diagnosed DVE in pet ducks from a small holding using an ornamental pond which was accessible to wild birds including mallards. Four ducks out of 15 showed clinical signs, which included drooping neck, lethargy, unwillingness to walk and green diarrhoea. The post-mortem examinations revealed longitudinal folds ranging from raised plaques to diphteritic elevated areas in the oesophagus, enlarged and irregular shaped livers and ecchymotic hemorrhages in the proventriculus and epicardium. In two females, there was also a secondary fibrinous peritonitis and airsacculitis and haemorrhagic follicles in the ovaries.

Gamebirds

Listeriosis in partridge

RVC investigated an atypical outbreak of Listeriosis in red-legged partridges. A game bird rearer had been losing approximately 30 partridge chicks, out of a group of 25,000 imported birds, daily for the previous eight days. The affected 16-day-old partridges were observed to hold their head to one side and to be slightly incoordinated (Figure 1) and unable to use the nipple drinkers. Following antibiotic treatment there had been only a very slight initial improvement. Four affected live partridges were submitted for euthanasia and post mortem examination. Because of the CNS signs exhibited the case was reported as a suspect notifiable disease to AHVLA. which was subsequently negated. On bacteriological culture of a brain swab of one of the partridges, Listeria monocytogenes was isolated and lesions consistent with listeriosis were detected in the brains of all four birds on histopathology. Investigations continue in order to try to identify how the partridges might have been infected.

Figure 1. Listeriosis affecting a partridge chick

Omphalitis in pheasants

An incident involving the deaths of 50 of 1,000, three-day-old pheasant chicks which had been imported from Europe was investigated by Penrith. Yolk sac infections and omphalitis caused by E. coli were diagnosed in three of four birds submitted for necropsy, in the fourth the predominant isolate was Enterococcus casseliflavus, a probable opportunistic pathogen. Luddington also diagnosed the condition in imported birds. Yolk sac infections caused the loss of 250 six-day-old pheasant chicks in a group of 1,200 chicks imported as day-olds. E. coli was the predominant organism isolated.

Further Reading

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Further Reading

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