A histologic demonstration of siliceous materials in simian lung mite infected lung tissues by microincineration.

Approximately 90% of freshly imported macaques and other Old World Monkeys are known to be infected with respiratory mites. The lung associated pigments are integral components of pulmonary acariasis in Old World Monkeys; at least three distinctive pigmental bodies are identified in association with lung mite infection. Two major components of pigments are recently identified as silica by using elemental analysis using a high voltage electron microscope and an energy-dispersive X-ray analysis technique. Since a limited number of infected monkey lung tissues and associated pigments can be examined by this tedious procedure, it was important for us to examine much greater number of specimens to verify our initial observation. Ten microincineration technique described provided a unique and practical way to identify the mineral elements in as many 27 histologic sections within a short span of time. Silica and silicates are heat resistant whereas majority of organic materials including lung mite parasites disintegrated under the extreme temperature. Mineral elements were exclusively located within the polarizable white ash. More than 90% of total pigmental bodies identified were found to be related to siliceous materials in 20 incinerated infected monkey lung tissues whereas five noninfected lungs similarly examined did not reveal any pigmental bodies. Other than a small of fine granular mucin substances which were PAS positive, the majority of lung mite associated pigments such as large granules of hemosiderin, needle-like crystals and other fine granules engulfed by macrophages were identified to be siliceous materials as they have persisted even after microincineration. Mite parasites and other organic materials were completely disintegrated. Similar pigmental bodies examined by microscope X-ray analysis were positive for silicate. This finding suggests that lung mite infection in Old Monkeys apparently predisposed silicosis. Therefore, until the link between lung mite infection and silicosis is clarified, experimental inhalation toxicologic findings in mite-infected Old World monkeys should be interpreted cautiously.