Disseminated histoplasmosis in two juvenile raccoons (Procyon lotor) from a nonendemic region of the United States

Abstract

Abstract. Two 6-month-old raccoon kits, which had been rescued and fostered in preparation for return to the wild, became acutely ill and died 3 weeks before scheduled release. At necropsy, the kits had grossly enlarged livers and spleens, diffusely consolidated lungs, and generalized lymphadenopathy. Histologically, extensive infiltrates of macrophages containing yeast organisms were identified in lung, liver, kidney, spleen, lymph nodes, intestinal tissues, brain, adrenal gland, bone marrow, and thymus of both animals. Histiocytic inflammation with accompanying fibrosis was widespread, with necrotic foci evident in lungs, spleen, and intestinal sections. Fungal organisms were observed on sheep blood agar plates; however, repeated subcultures to fungal media designed to induce conidial structures for fungal identification were unsuccessful. Partial DNA sequencing of the 28S ribosomal RNA gene of the blood agar isolate identified 100% homology with Ajellomyces capsulatus (anamorphic name Histoplasma capsulatum). The kits were rescued and fostered in the San Francisco Bay area and it is likely that the exposure to H. capsulatum occurred in this area. Histoplasma sp. infection in wild mammal species is often used as an indication of spore contamination of a geographic region. Northern California is not known to be an endemic region for H. capsulatum, which is not a reportable disease in this state. The presence of severe, disseminated disease and the need for molecular identification associated with the isolate from a nonendemic region identified in the present report may indicate genetic adaptation and altered characteristics of this agent and may warrant further investigation.

Mycotic Infections Acquired outside Areas of Known Endemicity, United States

“…Histoplasmosis in other cats near Vacaville, California (G. Thompson, unpub. data), and in two 6-month-old raccoons rescued near San Francisco ( 20 ) provides further evidence that Histoplasma may be established in California.…”

Procyonidae, Viverridae, Hyenidae, Herpestidae, Eupleridae, and Prionodontidae

“…Fungal disease is rarely reported in these species. Case reports include histoplasmosis (Histoplasma capsulatum) in two raccoon kits with disseminated, systemic infection and granulomatous pneumonia, lymphadenitis, splenitis, enteritis, nephritis, encephalitis, and thymitis with intrahistiocytic yeast (Clothier et al, 2014); Trichophyton mentagrophytes alopecic dermatitis in a captive adult female spotted hyena and her two cubs (Hahn et al, 2003); and fatal meningoencephalitis due to Encephalitozoon cuniculi in captive meerkats (Ramsay, 2015).…”

Worldwide Phylogenetic Distributions and Population Dynamics of the Genus Histoplasma

“…In endemic areas of histoplasmosis throughout the Americas, bats are often infected with this fungus [ 20 , 21 ]. In addition to bats, the fungus has been detected in wild mammals such as non-human primates (e.g., baboons) [ 22 , 23 ], mustelids (e.g., badgers and northern sea otter) [ 24 – 26 ], procyonids (e.g., raccoons) [ 27 ], as well as in domesticated animals such as equines [ 28 , 29 ], felines [ 30 , 31 ] and canines [ 32 , 33 ]. This broad host range and tight association with vertebrates suggests that mammals play an important role in the speciation and dispersal mechanisms of this species complex.…”