Lymphoid leucosis

A healthy chicken at a show

Lymphoid leucosis is a neoplastic disease in chickens caused by the avian leukosis virus (ALV), which is a member of the Retroviridae family. This disease primarily affects the lymphoid tissue and is characterized by the formation of tumors in various organs, particularly the bursa of Fabricius, liver, and spleen.

Etiology

Lymphoid leucosis is caused by the avian leukosis virus, which is an oncogenic virus. The virus is transmitted vertically from hen to egg and horizontally among chickens. The disease is most commonly seen in chickens over 14 weeks of age.

Pathogenesis

The virus infects the B cells in the bursa of Fabricius, leading to the transformation of these cells into neoplastic cells. The neoplastic cells proliferate and form tumors in various organs. The disease progresses slowly, and clinical signs may not be apparent until the tumors are well developed.

Clinical Signs

Chickens affected by lymphoid leucosis may exhibit a range of clinical signs, including:

• Weight loss
• Weakness
• Decreased egg production
• Enlargement of the abdomen due to tumor growth
• Pale comb and wattles

Diagnosis

Diagnosis of lymphoid leucosis is based on clinical signs, post-mortem examination, and laboratory tests. The presence of tumors in the bursa of Fabricius, liver, and spleen is indicative of the disease. Laboratory tests such as polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) can be used to detect the presence of the virus.

Control and Prevention

Control of lymphoid leucosis involves good management practices to prevent the spread of the virus. This includes:

• Maintaining a closed flock to prevent introduction of the virus
• Regular testing of breeding stock
• Culling of infected birds
• Vaccination is not commonly used due to the complexity of the virus and the availability of other control measures.

Related Pages

• Avian leukosis virus
• Retroviridae
• Bursa of Fabricius
• Neoplastic disease