Wildlife Faces Cancer Threat

June 24, 2009

A paper by WCS-Global Health scientists suggests that cancer is a growing threat to wildlife populations, and that environmental pollutants are a major cause.

New studies show that cancer has become a major threat to wild animals. A paper by Wildlife Conservation Society (WCS) scientists published in the July edition of Nature Reviews Cancer suggests that the disease is spreading in wildlife populations, and threatens the survival of certain species. The authors highlight the critical need to protect both animals and people through increased health monitoring.

“Cancer is one of the leading health concerns for humans, accounting for more than ten percent of human deaths,” said Dr. Denise McAloose, lead author and chief pathologist for WCS-Global Health. “But we now understand that cancer kills some wild animals at similar rates.”

One species facing a risk of extinction due to the disease is the Tasmanian devil, the world’s largest carnivorous marsupial. An infectious form of cancer known as devil facial tumor disease spreads between individual animals through direct contact (primarily fighting and biting). To save the species from this fatal disease, conservationists are relocating cancer-free Tasmanian devils to geographically isolated areas or zoos.

Many species living within polluted aquatic environments suffer high rates of cancerous tumors, and studies strongly suggest that human pollutants can trigger the disease. For example, beluga whales in the St. Lawrence River are extraordinarily prone to intestinal cancer, the second leading cause of their death. One type of pollutant in these waters suspected as a carcinogen for belugas is polycyclic aromatic hydrocarbons (PAHs)—a well-known cause of cancer for humans. Bottom-dwelling fish in other industrialized waterways, including brown bullhead catfish and English sole, also exhibit high levels of cancer.

Virus-induced cancers can affect the ability of some wildlife populations to reproduce. California sea lions on the West Coast are increasingly afflicted with genital tumors. Oceanic dolphins such as the dusky dolphin and Burmeister’s porpoise, both found in the coastal waters of South America, are also showing higher rates of genital carcinomas.

Other cancers can affect the feeding ability or eyesight of wildlife. Green sea turtles—a migratory species in oceans across the globe—suffer from fibropapillomatosis, a disease that causes skin and internal organ tumors. While these cancers are induced by viruses, environmental factors such as human-manufactured carcinogens might exacerbate their severity or prevalence.

The paper concludes that more resources are needed to support wildlife health monitoring, which can illuminate the causes of cancer and help to safeguard animals and humans against possible disease. Evaluating cancer threats in wildlife populations requires the collaborative efforts of biologists, veterinarians, and pathologists, as well as the earnest engagement of governments and international agencies.

“Examining the impact of cancer in wildlife, in particular those instances when human activities are identified as the cause, can contribute to more effective conservation and fits within WCS’s One World-One Health approach of reducing threats to both human and animal health,” said Dr. William Karesh, Vice President and Director of WCS- Global Health.

Read the press release: WCS Says Wildlife Faces Cancer Threat

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