Spiking Mortality and Rickets Reported by VLA28 September 2009
UK - According to VLA Monthly Scanning Surveillance Report for August 2009, spiking mortality syndrome caused an increase in mortality among young broilers, and a deficiency of vitamin D or calcium was blamed for the deaths of 20 per cent of a small flock of young turkeys.
Commercial Layers and Layer Breeders
A problem of poor eggshell pigmentation affecting 25 per cent of the egg production in a flock of 46-week-old free-range layers was thought to be related to predator attacks. There had been recent losses to foxes and buzzards. Examination of recent deaths revealed injuries consistent with predation. In the absence of disease, stress is one of the most important factors affecting the intensity of brown shell coloration (The release of adrenaline in stress situations may cause a delay in oviposition and an arrest of cuticular pigment deposition resulting in an increased proportion of poorly pigmented and whitish eggshells). It was reported later on that the birds had started to produce normal brown-coloured eggs once the problem with predatory attacks was resolved.
Sutton Bonington investigated an outbreak of ocular discharge and coughing affecting 132 Orpington chickens. A single carcass was presented at Sutton Bonington for necropsy which revealed significant thickening of the air sacs together with purulent fluid and white plaques. The lungs were dark red with white foci present along the dorsal midline aspect together with a pericardial effusion. The lesions were suggestive of mycoplasmosis. Subsequent DDGE testing of lung tissue demonstrated the presence of Mycoplasma iners an organism of uncertain pathogenicity which has been previously isolated from the respiratory tract of chickens, turkeys, pheasants and partridges.
Broilers and Broiler Breeders
Spiking Mortality Syndrome
A case of spiking mortality syndrome (probable hypoglycaemia) was suspected to be the cause of a sharp and transient increase in mortality in a flock of 19-day-old broilers. Post-mortem examination findings included congested subcutaneous fat and livers, pale spleens with blood splashes and absence of food in the upper digestive tract. Histological examination of fat stained sections (Oil red O) revealed numerous lipid droplets in renal tubular epithelium and myocardial cells, supporting the possibility of a metabolic problem, e.g. hypoglycaemia, leading to the mobilisation of fat stores as an alternative energy source. However a definitive diagnosis for this condition depends on the demonstration of blood glucose levels below 150mg/dl.
Hepatic 'target' lesions typical of Blackhead were seen in necropsy specimens from a small flock of 300, 10-week-old poults with a history of increased mortality. Post-mortem examination revealed multiple random 'target' lesions on the liver surface and throughout its substance. The mucosa of the caeca had discreet raised rounded nodules. Histological examination confirmed histomoniasis.
Listlessness and reluctance to stand in a group of six-week-old turkey poults was investigated by Bury. There had been 70 deaths in a group of 325. Birds were fed a home-mixed organic feed including barley, wheat, peas and maize. Three submitted birds showed enlargement of the ends of the long bones, in particular the upper tibia and upper metatarsi. Bones were also easily fractured. Histology showed abnormalities of the growth plate suggestive of a calcium/vitamin D deficiency rickets.
There were numerous reports of mite infestations causing losses in backyard flocks. Shrewsbury investigated a case in which 10 out of a group of 16 free-range backyard hens were reported to have died following a period of intermittent malaise and lethargy. The birds were approximately 15 months old and one live affected hen was submitted. It was thin, weak and reluctant to move, with a yellow discolouration to the skin. Many mites were visible on the skin. The mites were identified as Northern Fowl Mite and further discussion with the owner suggested red mites were also likely to be present as many mites were visible in the house and bedding. The owner also had subsequently found mites on himself which were causing pruritus. He was advised to seek medical attention.
Ducks and Geese
Increased mortality (10/2000) in a group of six-week-old ducks being reared for meat was investigated by Preston. Clinical signs observed prior to death included dyspnoea (panting/mouth breathing) and recumbency. Necropsy of two birds revealed airsacculitis associated with Aspergillus fumigatus in one bird (the birds were bedded on chopped straw, which may have been a source of spores). In the second bird, there was evidence of caseous airsacculitis, fibrinous pericarditis and pneumonia. Organisms recovered from this bird were identified as Riemerella anatipestifer, a frequent cause of septicaemia pericarditis, perihepatitis and airsacculitis in ducks.
Deterioration of body condition and ill-thrift in a flock of 3500, eight-week-old birds was attributed to a combination of failure to find food and chronic infection with Spironucleus (Hexamita) sp. Post-mortem examination revealed dehydration and loss of condition and motile protozoa consistent with Spironucleus sp. were seen in wet smears. Histological examination revealed no significant coccidial infection and confirmed protozoa in the intestinal crypts of the mid-gut and ileum consistent with Spironucleus sp.
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