Why dolphins get the virus, not the cancer
U. FLORIDA (US)—Aquatic animal health experts say they have found the ideal model for the study of cervical cancer in people: dolphins.
“We discovered that dolphins get multiple infections of papillomaviruses, which are known to be linked with cervical cancer in women,” says Hendrik Nollens, a marine mammal biologist and clinical assistant professor at the University of Florida’s College of Veterinary Medicine.
“Dolphins are the only species besides humans that we know of that can harbor coinfections, or infections of multiple papillomavirus types, in the genital mucosa.”
There are approximately 100 types of human papillomaviruses, and multiple infections of up to eight HPV types have been reported in humans.
“Even more surprisingly, some virus groups have shown the ability to cross the marine-terrestrial ecosystem boundary—from sea to land,” Nollens says.
“We have demonstrated at least one case of genetic recombination between viruses of human and marine mammals.
“While it’s exciting that dolphins can provide a unique window into the role of coinfection in human cervical cancer, we can’t rule out that the next high-risk virus, such as SARS, or West Nile, might actually come from the marine environment.”
Coinfections are believed to be one of the biggest risk factors for the development of cervical cancer in humans, Nollens explains. There is no evidence that dolphins develop the disease.
“Why do people develop the disease, but dolphins don’t? If we can figure out why, the human medical community might be very interested in how that information might be applied to human strategies for preventing the disease,” he says.
Of all the creatures that live in the ocean, dolphins and other marine mammals are the closest relatives of humans, but researchers say scientific knowledge of infectious diseases, particularly viral diseases, affecting these animals is limited.
For four years, Nollens has collected about 1,500 blood, tissue and fecal samples taken from dolphins have been analyzed at different laboratories across the United States.
No animals were harmed during collection of cell and tissue samples, although some were obtained from animals that have died of natural causes in the wild.
“Some 90 percent of what we do in the laboratory is molecular analyses,” Nollens explains. “Because of advances in molecular medicine since January 2006, we’ve found more than 40 new viruses in dolphins alone. When the last textbook came out in 2003, only 19 were noted.”
The researchers further evaluate all viruses found in the laboratory and suspected of having pathogenic potential to assess the impact each could have on the health of individual dolphins.
The information is then used to generate guidelines for disease outbreak management and prevention strategies.
“This process helps us understand disease and disease prevention,” Nollens says, adding that for more than a decade, scientists have been looking for cures to human diseases, including cancer, among marine invertebrates.
“Maybe there will be a similar story with dolphin papilloma viruses and prevention of cervical cancer in humans,” he says. “It wouldn’t be the first time we’ve come up with useful information from looking at marine animals.”
The discovery of new infectious diseases and viruses in marine mammals is important for conservation as well as for a better scientific understanding of the connections between oceans and people, says Teri Rowles, director of the National Oceanic and Atmospheric Administration’s Marine Mammal Health and Stranding Response Program.
“This work highlights the importance of partnerships in this type of interdisciplinary ‘One Health’ science to allow us to be better stewards of healthy oceans and coasts, healthy marine mammal populations, and healthy people,” Rowles says.
The work was funded by the Office of Naval Research, UF Aquatic Animal Health Program, U.S. Navy Marine Mammal Program, and Hubbs-SeaWorld Research Institute.
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