Lymphoproliferative disease virus (LPDV) was identified in the US for the first time in wild turkeys in 2009, but little was known about the ecology of the virus or the potential population impact. We determined that up to 80% of adult turkeys in NY are infected with the virus, but significant disease is rare. Our analysis of the virus genetics points to historic reintroduction programs as the mechanism of distribution, indicating it has been here undetected for decades.
Natural LPDV infection is only observed in turkeys, and most clinical disease details come from outbreaks in domestic flocks. The onset of clinical syndrome occurs between 8 to 10 weeks of age in domestic birds with a peak at 16 weeks of age. Though not documented, the incubation period has been projected to be around 7 weeks. The mortality rate in domestic flocks is 15 to 25%.
The clinical course of the disease is acute, with essentially no signs of the disease prior to death. Turkeys infected at 4 weeks of age were more likely to develop tumors, while turkeys exposed at 1 day of age were more likely to remain asymptomatic. Clinically, the most affected organ is the spleen followed by the thymus, pancreas and liver. Other organs such as the kidneys, gonads, lungs and peripheral nerves can also be affected. The characteristic lesion is a splenomegaly (large spleen) that is white to pale pink in color. The liver will often contain irregular, variable-sized pale lesions from infiltration of abnormal white blood cells.
In wild turkeys, the virus may be associated with skin nodules on the head neck and feet. In the examination of wild turkeys submitted to the NYS Wildlife Health Program, a high number of birds (more than 60% of adults) carry the virus, but actual lesions are rare. The impact on the population is unknown. There is no cure or treatment for LPDV in turkeys. Infection may be lifelong.