UK Disease Report: Cases of Spinal Abscess, Marek's Disease04 August 2015
Cases of spinal abcess in broilers, Marek's disease in backyard pullets, and respiratory disease in pheasants all feature in this monthly Disease Surveillance Report from the UK's Animal and Plant Health Agency, which looks back at diseases reported in March 2015.
Spinal abscess: Chronic spondylitis (“spinal abscess”) was seen in a submission of 33-day-old broilers with a history of lameness.
Postmortem examination revealed large ventral swellings of the spine centred on the body of the free thoracic vertebra (“T4”), in all five birds examined.
Bacterial cultures produced good growths of Enteroccoccus–like colonies with biochemical features consistent with Enterococcus cecorum from the spinal lesions.
E. cecorum is recognised as a cause of vertebral abscesses in broilers, and infection is likely to have arisen as a result of environmental contamination with this organism.
Mortality in layers: Grumbling mortality in a flock of 4,500 19-week-old point of lay pullets prompted the submission of five birds.
Two to three birds had been found dead each day for a week, which then increased to seven. Affected birds were initially seen dull with ruffled feathers. They had moved onto the site three weeks previously.
At postmortem examination all birds were found to have fibrinous peritonitis and enlarged spleens, and three birds had fibrinous pericarditis. The ovaries were active.
The findings were suggestive of E. coli septicaemia, which was confirmed bacteriologically. It was thought the stress of coming into lay may have precipitated disease in the birds.
Erysipelas: Mortality was reported in a group of 3,500 free range 51-week-old layers in a mobile unit. Two other houses on the premises were unaffected.
Over a four day period there had been mortality of 30, 17, 16 and 16 birds. The birds had been permanently housed for the last three weeks.
Feather wear was marked and red mite (Dermanyssus gallinae) was known to be an issue. Egg production figures were not available and no clinical signs were described in the flock in general.
The predominant findings in the dead birds were enlarged spleens, small amounts of pericardial fluid and discolouration or haemorrhage of some of the ovarian follicles.
Bacterial culture produced heavy pure growths of Erysipelothrix rhusiopathiae from the liver and follicle samples confirming a diagnosis of erysipelas in the birds.
Red mite is suspected to act as a reservoir for erysipelas and may have contributed to the transmission of the disease if the organism was present in the environment.
Marek’s disease and helminth infection: Marek’s disease with concurrent Davainea proglottina and Capillaria sp. infection was diagnosed in a 26-week-old point of lay pullet from a group of 17 homebred birds, part of a backyard flock.
Four of the group had died with a further two showing clinical signs including weight loss, going off legs, abnormal head and wing position and death within ten days.
At postmortem examination intestinal smears detected very large numbers of the pathogenic poultry tapeworm Davainea proglottina in the duodenum and moderate numbers of Capillaria sp. nematode eggs.
Marek’s disease was suspected from the clinical history and the diagnosis was confirmed by histopathological examination of brachial and sciatic nerves, which exhibited a typical mild focal lymphocytic neuritis.
It is possible that the immunosuppressive effects of Marek’s disease may have contributed indirectly to the heavy tapeworm and roundworm burden, but the reverse may also have occurred and a heavy helminth burden may have contributed to the development of clinical signs of Marek’s disease in birds infected with the virus.
Under commercial conditions, vaccination would have been used to control Marek’s disease.
Respiratory disease in pheasants: An investigation was undertaken into an ongoing problem of respiratory disease in adult pheasants early in the breeding season.
Ten birds were examined, three of which showed swelling of the infra-orbital sinus adjacent to the eye, with turbid material evident within the sinuses found on postmortem examination.
No evidence was found of Mycoplasma gallisepticum involvement by serology or DGGE testing; although M. gallinaceum was detected in pooled samples, the role of this organism as a pathogen in respiratory disease in game birds is uncertain.
Pasteurella-like organisms were isolated on culture from the sinuses of two birds, and may have played an opportunistic role.
However PCR testing was positive for avian metapneumovirus type B (aMPV; formerly turkey rhinotracheitis, TRT) in two of the birds suggesting the possible involvement of this agent. AMPV is recognised as a playing a primary role in some outbreaks of respiratory disease in pheasants, and is likely have been of significance in this case.