Pygmy sperm whales stranded along the southeastern United States carry previously undocumented bacterial strains that damage their digestive tracts, according to a study published in the Journal of Wildlife Diseases. Researchers at Florida Atlantic University’s Harbor Branch Oceanographic Institute analyzed records and tissue samples spanning more than two decades, discovering three novel Helicobacter genotypes linked to stomach ulcers, inflammation, and parasite infestations in the elusive marine mammals.
Decades of Stranding Data Reveal New Pathogens
Pygmy sperm whales (Kogia breviceps) spend most of their lives far from shore in deep water, making direct observation at sea exceedingly rare. Consequently, scientists rely heavily on animals that strand along the coastline. According to Florida Atlantic University, researchers responded to 59 pygmy sperm whale strandings between 1999 and 2020, completing post-mortem examinations on 80% of those animals.
During tissue reexaminations using histopathology, molecular testing, and DNA sequencing, scientists identified spiral-shaped spirilliform bacteria within the stomach tissue of four stranded whales. The analysis confirmed three distinct bacterial genotypes never before documented in science, named Kogia Helicobacter 1, 2, and 3 by the research team.
Genetic Lineages and Stomach Damage in Whales
The newly identified strains display varying genetic relationships to known bacteria. According to Wendy Marks, a research coordinator at the FAU Harbor Branch marine wildlife veterinary medicine lab, genotypes 1 and 2 show genetic similarity to Helicobacter species previously found in humans, dolphins, and porpoises. In contrast, Kogia Helicobacter 3 belongs to a more divergent lineage, indicating a wider diversity of undiscovered ocean bacteria.
All four whales testing positive for the bacteria exhibited visible gastrointestinal pathology. Annie Page, D.V.M., Ph.D., senior author and associate research professor at FAU Harbor Branch, noted that examinations revealed gastritis, gastric ulcers, fibrosis, and nematode infestations. One examined animal also displayed colitis, suggesting the infection extends beyond the stomach.
Implications for Vulnerable Marine Mammal Populations
While researchers did not determine that Helicobacter directly caused the deaths of the stranded whales, the recurrent presence of inflammation, scarring, and ulcers points to chronic illness. Helicobacter bacteria were first detected in marine mammals in 2000, and related strains in other cetacean species have since been connected with loss of appetite, low energy, regurgitation, and stomach ulcers.
Because pygmy sperm whales remain difficult to study in their natural offshore habitat, researchers cannot yet determine how widespread these specific bacterial strains are within living populations or how significantly they impact long-term survival. The multi-institution research effort included scientists from the University of Florida College of Veterinary Medicine, Colorado State University, and Marine Mammal Pathology Services, with funding provided by the Florida State Specialty License Plate Program through the “Protect Florida Whales” grant.