Gastric spirilliform bacteria consistent with Helicobacter spp. were identified in four pygmy sperm whales (Kogia breviceps) that stranded along the east coast of Florida, USA, during 2017-20. Six of nine (67%) stomach samples from PCR-positive cases contained spirilliform bacteria visible on histopathologic examination. Experimental PCR targeting Helicobacter-specific 16S rRNA gene sequences produced amplification in at least one gastric tissue sample (e.g., forestomach, fundus, pylorus) from all four cases. Three different novel Helicobacter sequences were identified in 13 samples from four whales. Helicobacter-positive samples could be classified into three novel sequences, Kogia Helicobacter 1, 2, and 3, represented by a common 572-base-pair region. All four whales in this study were infested with gastric nematodes and had one or more of the following histopathologic findings: gastritis, gastric ulceration, and gastric fibrosis. These lesions were not attributed as a cause of death in the whales but may have contributed to stranding via reduced fitness. This study reports three novel Helicobacter spp. bacteria identified in K. breviceps and expands the known host range of this genus. Further studies into these novel Helicobacter spp. should include additional pathologic and molecular characterization of the bacteria and any associated lesions.
Keywords: Gastric bacteria; Helicobacter; Kogia; gastritis.