Pathology and molecular diagnosis of histoplasmosis in a captive green monkey (Chlorocebus sabaeus) in Ibadan, Nigeria

Abstract

An adult green monkey (Chlorocebus sabaeus) donated to the zoological garden after history of attack on the owner about a year earlier was found dead a week later with history of sluggish reflexes. At necropsy, there was severe adhesive pleuritis, multifocal to coalescing broncho-interstitial granulomatous pneumonia, diffuse granulomatous splenitis, unilateral multifocal granulomatous epididymitis, and orchitis with moderately congested meningeal blood vessels and shrunken sulci. Histological examination of all tissues stained with routine Hematoxylin and Eosin, Periodic Acid Schiff, and Grocott’s methenamine silver stains showed numerous intrahistiocytic (macrophages and giant cells) and extracellular round (10–30 μm) yeast with double-contoured refractile wall. The yeasts exhibited broad-based budding in some tissues. Molecular detection of the 18S rDNA gene of the fungus was amplified from the extracted DNA using polymerase chain reaction and the gene products were partially sequenced. The gross and histologic lesions and PCR 18S rDNA gene detection were consistent with that of Histoplasma capsulatum var. duboisii as well as Blastomyces dermatitidis. However, the multiple sequence alignments of the nucleotides showed three mutations that confirmed H. capsulatum. Therefore, there is need for closer examination and monitoring of wild life for mycotic zoonoses.