Histoplasmosis is a worldwide distributed disease but is more frequent in tropical and subtropical climates.3 In Europe, it has been described in wild badgers (Meles meles).6 The dimorphic fungus Histoplasma capsulatum var. capsulatum has a virulent yeast-phase that is found in the tissues of infected mammals. Infection is acquired from the environment usually by inhalation of infective mycelial-phase.3 This study describes an outbreak of histoplasmosis in maras at Africam Safari (Puebla, México) and an isolated case in a wallaby at Aqualeón (Tarragona, Spain).
A young adult captive-born male mara was presented for necropsy with a history of weight loss. Eight months before its death, another mara died with disseminated histoplasmosis (Rosas-Rosas et al. 2004).3 At necropsy of the second mara, there was marked thickening of the colonic and cecal mucosa with watery intestinal contents. A 3-yr-old, captive-born male wallaby (Macropus rufogriseus) housed at a zoo in northeastern Spain had at necropsy whitish areas throughout the liver with increased consistency.
In both cases, foci of granulomatous inflammation involved mainly the intestine, liver, lymph nodes, and adrenals. Abundant 2–4 µm in diameter, PAS- and GMS-positive yeast-like organisms were observed in the cytoplasm of macrophages and adrenocortical cells. These organisms stained positive for Histoplasma capsulatum antigen by immunohistochemistry. H. capsulatum var. capsulatum was isolated from the mara and by PCR was determined to be closely related to an isolate obtained from a mara dying previously of histoplasmosis at the same colony. PCR was also positive for H. capsulatum in the wallaby. Mice inoculated with homogenates of soil samples from the mara facility seroconverted to H. capsulatum. Intradermal histoplasmin and candidin testing was negative for all maras in the colony.
Histoplasmosis is uncommon in any species and can occur in immunocompromised and immunocompetent humans5; however, it has been described in a variety of domestic and wild mammals3. There is also one report of an epizootic in a zoo in the USA4, and it was also diagnosed in a colony of wallabies infected with a retrovirus1. The immunologic status of the affected maras and wallaby is unknown, but there is evidence of stress-induced immunosuppression in the mara colony, and there was an ongoing outbreak of a variety of infectious diseases at the wallaby colony.2
Although most pathologic findings are characteristic of histoplasmosis in other species,3 there were no pulmonary inflammation in any case.
1. Kapustin N, Ch Kanitz, T Muench. 1999. Identification of a retrovirus in Bennett’s (Macropus rufogriseus frutica) and Dama (Tammar) (Macropus eugenii) wallabies. Proc. Am. Assoc. Zoo. Vet. Pp. 261–262.
2. Rosas-Rosas AG, C Juan-Sallés, MM Garner. 2006. Pathological findings in a captive colony of maras (Dolichotis patagonum). Vet. Rec. In press.
3. Rosas-Rosas A, C Juan-Sallés, G Rodríguez-Arellanes, ML Taylor, MM Garner. 2004. Disseminated Histoplasma capsulatum var. capsulatum infection in a captive mara (Dolichotis patagonum). Vet. Rec. 155:426–428.
4. Tocidlowski ME 2003. Histoplasmosis outbreak at the Houston Zoo. Proc. Am. Assoc. Zoo Vet. Pp. 141–142.
5. Valdez H, RA Salata. 1999. Bat-associated histoplasmosis in returning travelers: case presentation and description of a cluster. J. Travel. Med. 6: 258–260.
6. Wohlsein P, B Bauder, ES Kuttin, L Kaufman, F Seeliger, M von Keyserlingk. 2001. Histoplasmosis in two badgers (Meles meles) in northern Germany. Dtsch. Tierarztl. Wochenschr. 108: 273–276.