Detection and characterization of Histoplasma capsulatum in a German badger (Meles meles) by ITS sequencing and multilocus sequencing analysis

Abstract

A wild badger (Meles meles) with a severe nodular dermatitis was presented for post mortem examination. Numerous cutaneous granulomas with superficial ulceration were present especially on head, dorsum, and forearms were found at necropsy. Histopathological examination of the skin revealed a severe granulomatous dermatitis with abundant intralesional round to spherical yeast-like cells, 2-5 μm in diameter, altogether consistent with the clinical appearance of histoplasmosis farciminosi. The structures stained positively with Grocott's methenamine silver and Periodic acid-Schiff stains, but attempts to isolate the etiologic agent at 25 and 37°C failed. DNA was directly extracted from tissue samples and the ribosomal genes ITS1-5.8S-ITS2 were partially sequenced. This revealed 99% identity to sequences from Ajellomyces capsulatus, the teleomorph of Histoplasma capsulatum, which was derived from a human case in Japan, as well as from horses from Egypt and Poland. Phylogenetic multi-locus sequence analysis demonstrated that the fungus in our case belonged to the Eurasian clade which contains members of former varieties H. capsulatum var. capsulatum, H. capsulatum var. farciminosum. This is the first study of molecular and phylogenetic aspects of H. capsulatum, as well as evidence for histoplasmosis farciminosi in a badger, further illuminating the role of this rare pathogen in Central Europe.