Molecular and pathological investigations of Marek’s disease outbreaks in vaccinated poultry farms in Plateau State, North Central-Nigeria

Abstract

Marek’s disease (MD) is a devastating neoplastic disease of poultry caused by MD virus (MDV). MD is one of the several diseases limiting the thriving Nigerian poultry industry. MD is mostly diagnosed in Nigeria based on history and gross lesions without laboratory investigations leading to underreporting of the disease. This study investigated MD outbreaks in poultry farms using polymerase chain reaction (PCR) and histopathology. Tumourous visceral organs were collected from dead chickens presented to veterinary clinics from 110 farms in Plateau State, North Central Nigeria from April 2013 to August 2014. Clinical signs observed in affected chickens were paralysis, stunting and uneven growth. Whilst the gross lesions observed were hepatomegaly, splenomegaly with lymphoma, prominent peripheral nerves and cachexia. The meq gene of MDV‑1 was detected by PCR in 55.0% (n = 11/20) of broilers and 71.1% (n = 64/90) of vaccinated layer chicken samples collected. Microscopy revealed severe diffuse lymphocytic infiltrations in the heart, spleen and liver of chickens with tumourous gross lesions. Based on history, gross lesions, detection of meq gene of MDV‑1 by PCR and histopathology results, MD was confirmed in the affected farms. Despite vaccination, outbreaks of MD still occurs in poultry farms in Nigeria. This study represents the first confirmatory diagnosis of MD in vaccinated poultry in Nigeria.

Keywords

• Histopathology
• Nigeria
• Marek’s disease
• PCR
• Vaccinated