Veterinary Services

The acute form of Marek’s disease was diagnosed in two layers from a small flock. The birds had lost weight and postmortem examination revealed tumours of the liver and kidney. Histopathological examination confirmed the diagnosis of Marek’s disease. A cockerel from another small flock lost weight, had poor proprioception, and became unable to balance. No significant gross lesions were found on postmortem examination, but a severe non-suppurative encephalitis consistent with the transient paralysis form of Marek’s disease ("floppy broiler syndrome") was found on histopathology. Twisting of the neck, weight loss and recumbency was described in an adult layer from another small flock. On this occasion a vegetative endocarditis was found, from which an Enterococcus species was isolated. Histopathological examination of the brain revealed fibrin thrombi in blood vessels with an associated cellular reaction, and it was concluded that septic thrombo-emboli from the vegetative endocarditis had lead to thrombosis within the brain, resulting in the head twist described. Evidence of septic thrombo-emboli was also found in the spleen and kidney. The Enterococcus species was not further identified but was most likely Enterococcus hirae, a recognised cause of vegetative endocarditis in poultry.

Ducklings

Three ducklings aged four weeks were submitted from a non-commercial free-range flock in which 10 ducklings had died in the past week. The ducklings were in good body condition, and post mortem examination showed consolidation of the lungs with yellow fibrinous pleurisy, increased pericardial fluid and splenic enlargement. E. coli was isolated in pure or mixed culture from the lungs, spleens and intestines. Histopathology of the lungs revealed diffuse obliteration of the air capillary space due to a massive increase in cellularity, associated with large numbers of intracellular spherical basophilic bodies that stained Gram and MZN negative and PAS and Giemsa positive. These organisms were also visible within endothelial cells in the kidney, liver and spleen, and within cardiac myocytes. Similar gross and histological findings have been described previously in Muscovy and domestic ducks, but the identity of the intra-cellular organisms remains unclear. Chickens, turkeys and pigs on the farm were unaffected.

Game birds

Protozoal infections (Spironucleus [Hexamita] species, Trichomonas species, coccidia) were commonly found in pheasants and red-legged partridges in July. In some incidents there was an associated increase in mortality but on other occasions birds were submitted at an early stage of the disease process, when the birds were looking dull and depressed but before mortality was significantly increased. In older birds the protozoal infections were sometimes complicated by concurrent burdens of the gapeworm Syngamus trachea.

Salmonellosis due to S. Typhimurium DT2 was confirmed in a batch of pheasant chicks aged one week, in which losses had exceeded 10%. The same organism was recovered in profusion from red-legged partridges aged six weeks, in which mortality had escalated in the past week. All showed thickened caeca with white necrotic cores. This phage type is more commonly associated with pigeons.

Liver abnormalities were described in game birds from three locations. One incident occurred in pheasants aged six weeks, when a high percentage of the batch of 1,500 birds showed signs of depression. Two of the birds had enlarged mottled livers with pale miliary foci, and histopathological examination demonstrated fatty degeneration of hepatocytes progressing to single cell necrosis. There was marked biliary hyperplasia, localised haemorrhage and multifocal small lymphoid infiltrations, but no viral inclusions were found in the hepatocytes. There were also marked histopathological changes in the pancreas of these birds. In one bird there were multifocal areas of degenerating acinar cells, with mixed inflammatory cell infiltration, and hyperplasia of the pancreatic ducts. In two birds there was very little recognisable pancreatic tissue remaining, with marked interstitial and capsular fibroplasia. There was evidence of some pale eosinophilic intranuclear inclusion bodies in the pancreatic cells of one bird, suggesting a possible viral aetiology.

The second incident involved red-legged partridges from the age of seven weeks, in which there was a problem of ongoing low-grade mortality that persisted till the birds were 16 weeks of age. Liver pathology was noted in birds from seven to 16 weeks, including slight to marked hepatomegaly, liver haemorrhages, mottling of the liver, and in some birds multiple pale hepatic foci. Similar to the pheasants described in the first incident, histopathology consistently demonstrated multifocal areas of hepatocyte fatty degeneration leading to single cell necrosis, and in some birds multifocal lymphoid infiltration and biliary hyperplasia. In a small number of birds multiple granuloma formation was superimposed on the degenerative changes, associated with large numbers of Gram-positive filamentous bacteria. Similar granulomata were present in the spleen of a few birds. No significant bacteria were isolated from birds from this site, and although a reovirus-like virus was isolated from the intestine of two birds, the significance remains uncertain. Unlike the first incident, no pancreatic lesions were detected.

The third incident of hepatic pathology occurred in red-legged partridges aged 13 weeks, in which a slight increase in mortality had occurred. Indistinct foci of necrosis were seen in the liver of two birds, one bird also had ulceration of the duodenum and the other bird had ulcerative lesions in the caeca. Histopathology of the liver showed acute necrosis and fibrinous exudation with numerous bacilli, and fibrinous necrosis with extensive bacterial infiltration in the duodenum. The lesions were considered to be consistent with "ulcerative enteritis", caused by Clostridium colinum. On this occasion Clostridium colinum was not isolated but Clostridium sordellii was recovered from the livers and a combination of Clostridium sordellii and Clostridium perfringens was isolated from the intestines. No evidence of histomoniasis (blackhead) was found.

Racing pigeons

Pigeon paramyxovirus 1 (PPMV-1) infection was diagnosed in five lofts in the west/south-west of Scotland in July. All the birds submitted for examination were current-year birds aged approximately two to four months, but adult birds were also affected on some sites. The presenting signs were typically of green watery diarrhoea (polyuria) and weight loss, resulting in death or culling. Some birds exhibited neurological signs such as circling and opisthotonus. Most affected birds had not been vaccinated against PPMV-1 but in one loft the birds had been vaccinated around seven days prior to the onset of clinical disease. Diagnosis was based on high titres to PPMV-1 in unvaccinated birds or on virus isolation and identification. In some lofts there was evidence of concurrent circovirus infection. PPMV-1 infection is a notifiable disease, and the Divisional Veterinary Managers of the appropriate Animal Health Offices were informed.