Much of what researchers know about pygmy sperm whales has come from animals that wash ashore, particularly along the southeastern United States where this species appears more frequently than almost any other large marine mammal. 
Examinations of these stranded whales have uncovered recurring medical problems like stomach ulcers, which are sometimes associated with Helicobacter, a group of bacteria capable of living in the stomach and intestines of many animals, including humans and whales. 
After reviewing more than 20 years of stranding records and preserved tissue samples, researchers at Florida Atlantic University's Harbor Branch Oceanographic Institute and collaborating institutions identified three Helicobacter genotypes never before documented, marking the first confirmed discovery of these strains in pygmy sperm whales. The study, published in the Journal of Wildlife Diseases, named them Kogia Helicobacter 1, 2, and 3, offering new insight into an elusive species while raising broader questions about how bacterial infections may affect marine wildlife and ocean health. 
"Helicobacter bacteria have long been associated with gastrointestinal disorders in humans and other animals, including chronic gastritis, ulcers, and even gastric cancer," said Annie Page, D.V.M., Ph.D., senior author, an associate research professor and clinical veterinarian at FAU Harbor Branch. 
"To find novel strains of these bacteria in a deep-diving whale species is intriguing." From 1999 through 2020, FAU Harbor Branch responded to 59 pygmy sperm whale strandings, completing post-mortem examinations on 80% of those animals. In four cases, scientists found spiral-shaped, "spirilliform" bacteria within stomach tissue, and reexamining the preserved samples using histopathology, molecular testing, and DNA sequencing revealed several previously unknown Helicobacter genotypes. "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," said Wendy Marks, corresponding author and a research coordinator of the marine wildlife veterinary medicine and research lab at FAU Harbor Branch. "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." Researchers found both Kogia Helicobacter 1 and 3 in the forestomach tissue of one whale, and each of the four whales that tested positive showed clear signs of gastrointestinal disease. 
"All four whales that tested positive for Helicobacter had visible gastric pathology," said Page. "We saw signs of gastritis, gastric ulcers, fibrosis and nematode infestations. 
In one case, there was also colitis, which suggests that the infection may not be limited to the stomach. While Helicobacter wasn't listed as the cause of death in any of the whales, these lesions raise questions about its role in gastrointestinal disease." 
Although the researchers did not conclude that Helicobacter directly caused the whales' deaths, the repeated presence of inflammation, ulcers, tissue scarring, and other digestive problems suggests the bacteria could contribute to chronic illness.
Helicobacter was first reported in marine mammals in 2000, and since then, related bacteria have been detected in several cetacean species around the world, with infection in some animals connected to low energy, loss of appetite, regurgitation, stomach ulcers, and inflammation, many of which are similar to symptoms seen in infected humans.