Scientists Uncover Mysterious Bacteria Inside the Ocean’s Most Elusive Whale

Much of the knowledge surrounding pygmy sperm whales stems from those that have washed ashore. Strandings are particularly prevalent along the southeastern United States, where this species is more commonly found than many other large marine mammals.

Understanding Whale Strandings: Hidden Health Issues Uncovered

Examinations of stranded pygmy sperm whales have unveiled several recurring health concerns, notably stomach ulcers. These ulcers may be linked to Helicobacter, a group of bacteria capable of inhabiting the stomachs and intestines of various species, including humans and whales.

In reviewing over 20 years of stranding data and archived tissue samples, researchers from Florida Atlantic University’s Harbor Branch Marine Research Institute, along with partner institutions, identified three previously undocumented Helicobacter genotypes.

This groundbreaking research, published in the Wildlife Disease Journal, marks the first confirmed identification of these genotypes in pygmy sperm whales, designated as Kogia Helicobacter 1, 2, and 3. This discovery not only enhances our understanding of this elusive whale species but also raises important questions regarding the impact of bacterial infections on marine wildlife and overall ocean health.

“Helicobacter bacteria have long been associated with gastrointestinal disorders in both humans and animals, leading to issues like chronic gastritis, ulcers, and potentially gastric cancer,” stated senior author Annie Page, DVM, associate research professor and clinical veterinarian at FAU Harbor Branch. “Discovering new species of these bacteria in deep-diving whales is an exciting development.”

First-time Discovery of Three Bacterial Genotypes

From 1999 to 2020, the FAU Harbor Branch responded to 59 stranding cases involving pygmy sperm whales, with post-mortem examinations completed on 80% of the individuals.

In four cases, scientists identified spiral-shaped “spiral” bacteria within the stomach tissues. Further investigation of archived samples involved histopathology, molecular testing, and DNA sequencing, which revealed several unknown Helicobacter genotypes.

“Two of the newly identified genotypes, Kogia Helicobacter 1 and 2, bear genetic similarities to Helicobacter species found in other cetaceans, such as dolphins and porpoises, as well as in humans,” explained corresponding author Wendy Marks, research coordinator with FAU Harbor Branch’s Marine Wildlife Veterinary Medicine and Laboratory. “In contrast, Kogia Helicobacter 3 is part of a more diverse lineage, indicating that there could be numerous undiscovered bacteria lurking in our oceans.”

Both Kogia Helicobacter 1 and 3 were found in the forestomach tissue of one whale.

Infection and Gastric Damage in Whales

All four tested whales exhibited noticeable signs of gastrointestinal issues.

“The four whales that tested positive for Helicobacter displayed visible gastric lesions,” Page noted. “We observed signs of gastritis, gastric ulcers, tissue scarring, and nematode infestations. In one instance, we even detected colitis, suggesting that the infection may extend beyond the stomach. While Helicobacter was not listed as the direct cause of death for any of these whales, these lesions spark inquiries into the potential role of Helicobacter in gastrointestinal diseases.”

While no direct causation between Helicobacter and the whales’ mortality was established, the frequent presence of inflammation, ulcers, and other digestive complications implies that these bacteria may contribute to chronic health problems.

Helicobacter was first documented in marine mammals in 2000. Since then, related bacteria have been identified in several cetacean species globally. In certain cases, such infections correlate with symptoms such as low energy, diminished appetite, reflux, and stomach ulcers, mirroring issues seen in human infections.

Risks to At-Risk Whale Populations

“Much like humans, whales seem to be susceptible to certain microbial infections, but our understanding of these issues is still in its infancy,” Marks emphasized. “If chronic Helicobacter infections do have health implications for these animals, they could affect not only the well-being of individual whales but also the health of entire populations, particularly those that are already at risk.”

Studying pygmy sperm whales in their ocean environment poses significant challenges, leaving researchers uncertain about the distribution of these newly identified bacteria and their long-term effects on the species. Future testing will be crucial for determining whether these infections are linked to disease, strandings, or broader health issues at a population level.

This project involved collaboration among researchers from FAU Harbor Branch, the University of Florida College of Veterinary Medicine, Colorado State University, and the Marine Mammal Pathology Service.

Long-Term Stranding Research Yields Significant Insights

“This study underscores the importance of long-term marine mammal stranding programs,” Page concluded. “Without decades of research on these stranded animals, we would not have made these groundbreaking discoveries. Every whale has a story, and sometimes those stories guide us into entirely new scientific territories.”

Co-authors of this study include Dr. Jessy Castellanos-Gell, Dr. Stephen Tillis, James FX Wellehan, DVM, Ph.D., DACZM, April Childress from the University of Florida College of Veterinary Medicine, Nicole Pegg of FAU Harbor Branch, David Rotstein, DVM of the Marine Mammal Pathology Service, Sushan Han, DVM, Ph.D. from the Colorado State University Diagnostic Medicine Center, and Steve Burton, Stranding and Population Assessment Director at FAU Harbor Branch.

This important research was supported by the Florida Specialty License Plate Program through a grant administered by the Harbor Branch Marine Laboratory Foundation for “Florida Whale Conservation.”