A 20-year-old female Japanese macaque, weighing 8.7 kg, developed severe pu
lmonary acariasis. Numerous whitish nodules, 2-4 mm, were scattered through
out the lungs. Histologically multifocal granulomatous lesions consisting o
f a large number of eosinophils, epithelioid cells, foreign body type giant
cells, and collagen fibers were aggregated around the malt bodies. Numerou
s mast cells were also detected in the lesions by toluidine blue staining,
and tested positive for tryptase by immunohistochemistry. This may be the f
irst reported case of severe pulmonary acariasis in a Japanese macaque.