Scientists studying stranded pygmy sperm whales have uncovered three previously unknown genotypes of Helicobacter bacteria living in the animals’ stomach tissues.
Pygmy sperm whales (Kogia breviceps) rank among the ocean’s most mysterious marine mammals. These animals are seldom observed and remain poorly studied because they spend most of their lives far from shore. They typically travel in small groups and dive deep to hunt squid and fish. Their quiet behavior and preference for offshore habitats make them difficult for scientists to observe directly in the wild.
Researchers rarely encounter pygmy sperm whales while they are swimming freely. For that reason, much of what scientists know about the species has come from stranded animals. This is especially true along the southeastern coast of the United States, where pygmy sperm whales strand more often than nearly any other large marine mammal.
Examinations of stranded whales have revealed several recurring health problems, including stomach ulcers. Many of these ulcers are linked to Helicobacter bacteria, a group of microorganisms that inhabit the stomach and intestines of many animals, including whales and humans.
Using more than twenty years of records from stranded pygmy sperm whales, scientists at Florida Atlantic University’s Harbor Branch Oceanographic Institute and their collaborators have identified three previously unknown genetic types of Helicobacter living in these elusive whales.
Discovery of Previously Unknown Bacterial Genotypes
The findings, published in the Journal of Wildlife Diseases, mark the first confirmed record of these unique Helicobacter genotypes in pygmy sperm whales. The newly identified forms have been named Kogia Helicobacter 1, 2, and 3. According to the researchers, the discovery broadens scientific understanding of this little-studied whale species and highlights the potential influence of microbial pathogens in marine ecosystems.
“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.”
Between 1999 and 2020, the FAU Harbor Branch stranding response team investigated 59 pygmy sperm whale strandings. Researchers performed postmortem examinations on about 80 percent of those animals. In four cases, scientists found spiral-shaped bacteria described as “spirilliform” embedded within stomach tissue.
The team revisited these samples using several laboratory methods, including histopathology, molecular diagnostic testing, and DNA sequencing. This detailed analysis revealed three previously unknown Helicobacter genotypes that had not been documented before.
Genetic Analysis Reveals Distinct Lineages
“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.”
In one stranded whale, scientists detected both Kogia Helicobacter 1 and Kogia Helicobacter 3 within the forestomach tissue.
“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.”
Implications for Whale Health and Ocean Ecosystems
Since scientists first reported Helicobacter in marine mammals in 2000, the bacteria have been detected in several cetacean species worldwide. In some instances, infections have been associated with symptoms such as lethargy, reduced appetite, regurgitation, stomach ulcers, and inflammation of the stomach lining. These symptoms closely resemble those seen in humans infected with certain Helicobacter species.
“Whales, like humans, appear to be susceptible to certain microbial infections that we’re only beginning to understand,” said Marks. “If chronic Helicobacter infections are causing health issues in these animals, it could have implications not only for individual whale health, but for entire populations – especially for species that are already vulnerable.”
“This research underscores the value of long-term marine mammal stranding response programs,” said Page. “Without the ability to study these stranded animals over decades, we never would have discovered these bacteria. Every whale tells a story, and sometimes that story leads us into entirely new scientific territory.”
Reference: “Novel Gastric Helicobacter Species in Stranded Pygmy Sperm Whales (Kogia breviceps) on the East Coast of Florida, USA” by Wendy Marks, Jessy Castellanos-Gell, Steven B. Tillis, Nicole Pegg, David Rotstein, Sushan Han, James F. X. Wellehan, April Childress, Steve Burton and Annie Page, 16 February 2026, Journal of Wildlife Diseases.
DOI: https://doi.org/10.7589/JWD-D-24-00204
The work was made possible through funding from the Florida State Specialty License Plate Program under the “Protect Florida Whales” grant, administered by the Harbor Branch Oceanographic Institute Foundation.
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