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Are Dolphins Warning Humans About Health Risks?

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Cancer related image Photo: Getty Images

Part II in a series on the human-ocean connection and cancer.

Dolphins may well be the “canary in the coal mine” when it comes to human health and the state of our global ecosystem.

It may surprise you to learn that dolphins and humans have quite a bit in common; both are mammals and we share much of the same seafood sources. Unlike us, however, they are exposed to potential ocean health threats such as toxic algae or poor water quality 24 hours a day so scientists are looking to dolphin populations for clues about our health.

“Our ecological and physiological similarities make dolphins an important ‘sentinel species’ to not only warn of our health risks, but also provide insight into how our health can benefit from new medical discoveries,” said Carolyn Sotka with the National Oceanic and Atmospheric Administration (NOAA) Oceans and Human Health Initiative.

Sotka participated on a panel of governmental, academic and non-profit scientists who spoke at the 2010 annual meeting of the American Association for the Advancement of Science (AAAS) that focused on research suggesting that diseases found in dolphins are similar to human diseases and provide clues into how human health might be affected by exposure to contaminated coastal water or seafood.

Marine viruses and public health
Recently, the University of Florida Marine Animal Disease Lab research team has discovered at least 50 new viruses in dolphins, the majority of which have yet to be reported in any other marine mammal species. Some of these viruses could jump species and affect humans or other animals.

“We know that the ocean harbors a huge diversity of viruses; but we have very limited knowledge as to which viruses dolphins are susceptible to and how they develop the disease,” said Hendrik H. Nollens, Ph.D., research lead of the UF team. “By studying dolphin viral ecology, we learned more about how viruses infect human and land animals. This research could lead to preventing outbreaks of disease.”

One of these viruses, the human papillomavirus, was found to be common in bottlenose dolphins and likely represents the first natural model of papillomavirus outside the human species. Commonly known as HPV in humans, the virus has historically produced great health risks including cervical cancer in women, especially women with multiple types of the papillomavirus.

This new study shows that while dolphins also host multiple types of papillomaviruses they don’t appear to get cancer, only genital warts. Further research into the virus' genome in dolphins could promote greater understanding in managing and preventing cervical cancer in humans.

“Marine animal and ecosystem health are connected to public health and well-being," said Jane Lubchenco, Ph.D., under secretary of Commerce for Oceans and Atmosphere and NOAA administrator. "NOAA is committed to better understanding these connections and building the partnerships necessary to have healthy oceans, including healthy dolphins.”

Scientists have discovered 13 additional RNA-based viruses in dolphins, whales and other marine life that cause intestinal disease and encephalitis in humans. Much like West Nile, severe acute respiratory syndrome (SARS) and influenza, RNA-based viruses have the ability to quickly adapt, rapidly mutate and jump from animals to people posing potential threats to public health.

Another virus identified in the dolphin population had adapted part of a similar human virus into its DNA, making it a “very probable candidate in infect humans.

PCBs, Seafood and Cancer
NOAA researchers and its partner institutions recently discovered that bottlenose dolphins inhabiting estuaries along the Georgia coast have the highest levels of polychlorinated biphenyls (PCBs) ever reported in marine wildlife. PCBs encompass a suite of persistent contaminants that have been banned in the United States since 1979 after emaciated seabird corpses with very high PCB levels washed up on beaches. PCBs can imitate estrogen in humans and have been linked to breast, uterine and cervical cancers and liver damage.

The extraordinary high levels of PCBs measured in the dolphins, a maximum concentration of 2900 parts per million, may be suppressing their immune function, the researchers said.

PCBs have unique signatures. The compounds found in the dolphins matched contaminants consistent with a Superfund site near Brunswick, Ga. Scientists are equally concerned about the high PCB levels in dolphins sampled near a protected marine area about 30 miles from Brunswick, suggesting the contaminants are moving along the coast through the marine food web.

The NOAA team set out to investigate how these heavy chemical burdens were affecting the marine animals health, so last August they conducted a capture-release medical physical on the contaminated population and found decreased levels of thyroid hormones, elevated liver enzymes and indications of suppressed immune function. A pilot study is underway to determine if the two populations share similar adverse health symptoms and if that can be tied to eating contaminated seafood.

For more information: http://www.hml.noaa.gov/ohh/

Lynette Summerill is an award-winning writer and marine fanatic living Scottsdale, Arizona. In addition to writing about cancer-related issues, she writes a blog, Nonsmoking Nation, which follows global tobacco news and events. When not writing, she is dreaming about her next diving expedition.

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