Coccidioidomycosis in an Indoor-housed Rhesus Macaque (Macaca mulatta)

Coccidioides spp. are saprophytic, dimorphic fungi that are endemic to arid climates, are capable of infecting many species, and result in diverse clinical presentations. An indoor-housed laboratory rhesus macaque presented with weight loss and decreased activity and appetite. During the diagnostic evaluation, a bronchiolar-alveolar pattern in the cranial lung lobes, consistent with bronchopneumonia, was noted on radiographs. Given the poor prognosis, the macaque was euthanized. Confirming the radiographic assessment, gross necropsy findings included multifocal to coalescing areas of consolidation in the right and left cranial lung lobes. Microscopically, the consolidated regions were consistent with a pyogranulomatous bronchopneumonia and contained round, nonbudding, fungal yeast structures considered to be morphologically consistent with Coccidioides immitis. Culture and colony morphology results were confirmed through additional diagnostic testing. Sequencing of the D1-D2 domain of the 28S large ribosomal subunit positively matched with a known sequence specific to C. immitis. Serology for Coccidioides spp. by both latex agglutination (IgM) and immunodiffusion (IgG) was positive. In this rhesus macaque, the concordant results from histology, culture, DNA sequencing, and serology were collectively used to confirm the diagnosis of coccidioidomycosis. This animal likely acquired a latent pulmonary infection with Coccidioides months prior to arrival, when housed outdoors in a Coccidioides-endemic area. The nonspecific clinical presentation in this macaque, coupled with the recent history of indoor housing and lag between clinical presentation and outdoor housing, can make similar diagnostic cases challenging and highlights the need for awareness regarding animal source when making an accurate diagnosis in an institutional laboratory setting.