Many lesions of Newcastle disease occur because the virus infects and damages which tissues?

• A. Lymphoid tissues and neurons
• B. Neurons only
• C. Red blood cells and platelets
• D. Gastrointestinal epithelial cells

Answer: (A)

Newcastle disease virus shows a clear preference for two tissue types, and that pattern explains why many lesions are seen there: the immune system organs and the nervous system. The virus replicates in lymphoid tissues such as the bursa of Fabricius, thymus, and spleen, causing lymphoid depletion and necrosis. This targets the bird’s immune response, leading to immunosuppression and widespread tissue damage as the infection spreads.

Some strains are neurotropic and invade the nervous system, producing neuronal damage and encephalitis. When neurons are affected, you get characteristic nervous signs and corresponding brain and spinal cord pathology, including neuronal necrosis and inflammatory changes around blood vessels.

Because these two tissue groups—lymphoid tissues and neurons—are the primary sites of virus damage, lesions commonly reflect infection and injury in those areas. Other tissues can be involved, but they aren’t the main source of the hallmark lesions.