Western
Meeting of Poultry
Clinicians and Pathologists
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Clinicians and Pathologists
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Transient Paralysis Keith McMillian Lilydale Coop.
The earliest report of peripheral nerve infiltration with mononuclear cells was reported by Marek in 1907 and thus the name Marek’s disease. Since that time tumorous lesions involving many body organs besides nervous tissue have been reported. The development and use of vaccines in the late ‘60’s and early ‘70’s have dramatically reduced mortality and consequently the economic losses to this disease. However, there appears to have been an increase in the incidence of Marek’s cases in Western Canada in the last year and a half to two years. Some cases typify what has been described as Transient Paralysis, on of which will be described here. Broiler type chickens were reported to be showing leg weakness, with variable degrees of paralysis of one or more of their extremities. A number of birds appeared to fall forward with neck extended similar to the limber-neck appearance of a bird suffering from botulism. A number of these birds would recover if removed from the flock and placed with easy access to feed. On necropsy, only one of several birds showed any gross enlargement of peripheral nerves. Histologically, peripheral nerves had variable degrees of mononuclear infiltration. The majority of birds had prominent brain lesions, which consisted of perivascular cuffing with dark staining lymphocytes. It was concluded that the Marek’s lesions being more prominent in brain than peripheral nerve accounted for the appearance of signs similar to botulism in the flock. Although the flock appeared to pass through a temporary recovery, a high percentage of birds (19-20%) were condemned at slaughter for skin and visceral tumor lesions. This case is presented as a reminder that Marek’s disease is still an item of concern and that we need to continue vaccination and diligent sanitation practices.
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