Lymphoid leucosis in chicken - histopathology of spleen

Lymphoid leucosis has been reported in both captive and free living wild birds. It is caused by retrovirus. This disease causes severe loss due to mortality of poultry birds and depressed performance. The avian leucosis virus (ALV's) is prevalent throughout the world; new strains from one location may spread across borders, thereby undermining the disease control measures. Four commercial egg type white dead birds (33 weeks old) were received from a commercial layer poultry farm of Karachi. These birds had no previous sign of ill health. On postmortem the spleen was found diffusely enlarged and white in colour. A portion of the infected spleen tissue was preserved in 10% formalin and processed for 10 pm thick histological sections. The section of spleen showed diffused heavy infiltration of lymphoid cells. High magnification showed cells consisting of small and large lymphocytes. Cortex and medulla along with infiltration of lymphoid cells was prominent.