Clinical crenosomosis in a black bear (Ursus americanus)

An orphaned black bear (Ursus americanus) cub, estimated to be 9 months-of-age was presented to a wildlife rehabilitation facility in December of 2016. The cub was afebrile, under-weight (6.8 kg) and had a cough condition. Centrifugal sugar fecal flotation examination failed to detect any gastrointestinal helminth or protozoan parasites, but revealed the presence of first-stage nematode larvae (L₁). Large numbers of L₁ (>8000 L₁/g) identified as Crenosoma sp. based on morphology were recovered using the Baermann technique. Three species (Crenosoma petrowi, Crenosoma potos, Crenosoma vulpis) have been reported from black bears. Based on larval length measurements (range = 253-277 μm; mean = 263 μm; n = 8), the L₁ were tentatively identified as C. petrowi. Further molecular characterization using Polymerase Chain Reaction (PCR) and DNA sequencing of the small subunit (SSU) RNA gene and two regions of the large subunit (LSU) rRNA gene did not match any submissions in GenBank, but were most similar to Crenosoma mephiditis. There is a paucity of molecular data for members of the genus Crenosoma, with only information for Crenosoma vulpis (red fox), C. mephitidis (skunks), Crenosoma striatum (hedgehog) and Crenosoma sp. (red panda) in GenBank. Molecular analysis eliminates C. vulpis as a possibility in this case but due to the lack of submissions in GenBank, the identification of the L₁ as C. petrowi based on length measurements could not be confirmed. Receiving in total, three separate courses of treatment with fenbendazole (50 mg/kg, oral, once a day for 3 days), fecal larval shedding ceased and clinical signs resolved. The black bear cub was released into the wild in June 2017. This is the first report of clinical chronic respiratory disease due to Crenosoma sp. infection in a black bear.