Differential diagnosis between peripheral neuropathy and Marek's disease in laying hens: Review and suspicion of a first case in Morocco

Abstract

This study reports for the first time a suspicion of peripheral neuropathy clinically resembling Marek's disease in 3 field cases of laying hens in Morocco. Symptoms are summarized as a neurological syndrome in hens between 5 and 12 weeks of age and manifested by the position of the "wide gap" (one limb is carried forward while the other is carried backward) and a mortality rate that does not exceed 1%. Autopsy revealed thickening of the peripheral nerves and the absence of tumors on the other organs. Histological study of the nerve lesions revealed lymphoid infiltration with oedema and demyelination. Marek's disease was ruled out by real-time PCR as none of the tissues evaluated had a high load of Marek's disease virus DNA. Based on these results, peripheral neuropathy can be differentiated from Marek's disease. Indeed, the literature reports that the two diseases can be confused due to the clinical signs and lesions of thickening of the peripheral nerves. The clinical signs of peripheral neuropathy are observed as early as 5 weeks of age with type B infiltrating lesions (inflammatory) and the absence of visceral tumors, whereas those of Marek's disease only appear after 8-9 weeks of age with type A infiltrating lesions (tumors) and the presence of visceral tumors. 

Keywords: Peripheral neuropathy, Marek's disease, differential diagnosis, real-time PCR