Dolphins could be ideal model to study human cervical cancer, veterinarians say

"We discovered that dolphins get multiple infections of apillomaviruses, which are known to be linked with cervical cancer in women," said Hendrik Nollens, a marine mammal biologist and clinical assistant professor at UF's College of Veterinary Medicine Feb. 18 at the annual meeting of the American Academy for the Advancement of Science. "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-type infections of up to eight HPV types have been reported in humans, he said.

"Even more surprisingly, some virus groups have shown the ability to cross the marine-terrestrial ecosystem boundary -- from sea to land," Nollens said. "We have demonstrated at least one case of genetic recombination between viruses of human and marine mammals. So 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."

The presence of coinfections is believed to be one of the biggest risk factors for the development of cervical cancer in humans, Nollens said, although he added that 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 said.

Of all creatures that inhabit the ocean, dolphins and other marine mammals are the closest relatives of humans, but scientific knowledge of infectious diseases, particularly viral diseases, affecting these animals is limited, researchers say. No animals are harmed during collection of cell and tissue samples, although some are obtained from animals that have died of natural causes in the wild.

In hopes of shedding more light on the nature, prevalence and potential of such diseases to be passed to humans, Nollens and his colleagues at UF's Marine Animal Disease Laboratory have embarked on a large-scale collaborative research project to catalogue previously unrecognized and emerging viruses of marine mammals, both in collections and in the wild.

Over a four-year period, some 1,500 blood, tissue and fecal samples from taken from dolphins have been analyzed at different laboratories across the United States, Nollens said.

"Some 90 percent of what we do in the laboratory is molecular analyses," Nollens said. "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."

All viruses found in the laboratory and suspected of having pathogenic potential are further evaluated to assess the impact each virus could have on the health of individual dolphins, he added. The potential impact on collection animals as well as free-ranging dolphin populations is assessed, with information then used to generate guidelines for disease outbreak management and prevention strategies.

"This process helps us understand disease and disease prevention," Nollens said, 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 said. "It wouldn't be the first time we've come up with useful information from looking at marine animals."