A case of pulmonary cestodiasis in a simian immunodeficiency virus-infected pigtailed macaque (Macaca nemestrina) in which virus-infected leukocytes are present within the lesion.

The larvae of Mesocestoides are rarely encountered in nonhuman primates, with most cases reported in baboons. Infection of macaques has been occasionally diagnosed, but Mesocestoides in the lung parenchyma is extremely rare. We have previously demonstrated that in macaques with terminal AIDS, simian immunodeficiency virus (SIV)-infected leukocytes are rarely found in cellular infiltrates associated with opportunistic infections or preexisting disease. Here we describe larvae (tetrathyridia) of the cestode Mesocestoides in the lung of an adult, pigtailed macaque (Macaca nemestrina) during acute SIV infection in which virus-positive cells are present within the cellular infiltrates. These results describe a rare parasitic disease in pigtailed macaques and demonstrate that lentivirus-infected leukocytes can be associated with inflammatory sites during acute infection.