Microscopically this case lacked the characteristic prominent yellow-brown pigment seen in the peribronchiolar areas of inflammation. This pigment is believed to be a metabolite excreted by the mite. Other lesions reported to be associated with lung mites include pneumothorax, pulmonary arteritis and pleuritis. It appears that the entire life cycle can take place in the lung. Eggs hatch in the female and larva are deposited in the airway where they mature into adults.
Transmission requires close contact such as grooming.
Lung mites are common in species of Old World monkeys. Although several species of Pneumonyssus with varying host specificity exist, Pneumonyssus simicola is the mite most commonly diagnosed in rhesus monkeys. Mites feed on host pulmonary epithelial cells, erythrocytes and lymph. The golden brown, refractile pigment produced by the mites is diagnostic, even in the absence of identifiable parasites. Tracheal washes yield primarily larva, supporting the theory that larvae migrate to the pharynx and larynx where they are transmitted to other monkeys by direct contact, or in heavy infections through coughing and sneezing.