Three new genotypes of Helicobacter bacteria have turned up in the stomach tissues of stranded pygmy sperm whales. The discovery rests on careful post-mortem work spanning more than 20 years and offers a fresh glimpse into the microbial world of deep-diving cetaceans that humans rarely see alive.
Between 1999 and 2020 a stranding response team examined 59 pygmy sperm whales along Florida's east coast. Roughly 80 percent received full post-mortem examinations. From that archive, researchers isolated samples from four individuals that stranded between 2017 and 2020. Analysis revealed three distinct Helicobacter genotypes never recorded before, named Kogia Helicobacter 1, 2 and 3.
All four whales showed gastric lesions. These included gastritis, gastric ulceration, fibrosis and infestation with gastric nematodes. One animal also had colitis. The bacteria were not listed as the cause of death, yet the lesions raise questions about whether the infection reduced the whales' fitness and contributed to stranding.
The lesions were not attributed as the cause of death but may have contributed to reduced fitness and stranding.
The work relied on preserved tissue examined through histopathology, molecular testing and DNA sequencing. Two of the genotypes sit close to Helicobacter species already known from other cetaceans, such as dolphins and porpoises, and from humans. The third falls into a more divergent lineage.
Annie Page, associate research professor and clinical veterinarian at FAU Harbor Branch, noted the broader pattern. "Helicobacter bacteria have long been associated with gastrointestinal disorders in humans and other animals, including chronic gastritis, ulcers, and even gastric cancer."
Wendy Marks, research coordinator of the marine wildlife veterinary medicine and research lab at FAU Harbor Branch, pointed to the genetic spread. "Two of the genotypes, Kogia Helicobacter 1 and 2, are genetically similar to known Helicobacter species previously found in other cetaceans – such as dolphins and porpoises – and in humans. But Kogia Helicobacter 3 belongs to a more divergent lineage, which emphasizes the possibility that there are far more undiscovered bacteria in the ocean than we realize."