livescience.com– Wed Jun 24,
3:35 pm ET<!-- end .byline -->
Cancer accounts for about
10 percent of all human deaths. If you think that sets us apart,
scientists have news for you: Wild animals die of cancer at
about the same rate, and it threatens some species with
extinction.
"Cancer is one of the leading health concerns for humans," Dr.
Denise McAloose, a pathologist for the Wildlife Conservation
Society, said in a statement. "But we now understand that cancer
can kill wild animals at similar rates."
McAloose and her colleagues compiled information on cancer in
wildlife and concluded that cancer poses a conservation threat to
certain species. The team called for greater protection of animals
and people through increased health monitoring. They published
their research in the July edition of the journal Nature Reviews
Cancer.
Cancer threatens the survival of entire species, McAloose said. For
instance, the Tasmanian devil, the world's largest carnivorous
marsupial, faces extinction from a cancer known as devil facial
tumor disease. This contagious cancer spreads among devils usually
through fighting and biting. To save the species, conservationists
are relocating cancer-free Tasmanian devils to geographically
isolated areas or zoos.
The study suggests links between wildlife cancers and human
pollutants, as well. For example, beluga whales in the St. Lawrence
River system have an extraordinarily high rate of intestinal cancer
- it is their second leading cause of death. One kind of pollutant
in the waters, called polycyclic aromatic hydrocarbons, is known to
cause cancer in humans. The compounds are suspected carcinogens for
beluga whales as well. Fish in other polluted waterways, including
brown bullhead catfish and English sole, also exhibit high levels
of cancer.
Viruses are another culprit. In some animals, viruses can induce
cancers that interfere with reproduction. Genital tumors in
California sea lions occur at much higher rates than previously
documented, the paper shows. Dolphins, such as the dusky dolphin
and Burmeister's porpoise, found off South American coasts, are
also showing higher rates of genital tumors.
Other virus-induced cancers can affect an animal's eyesight or its
ability to feed. Green sea turtles suffer from fibropapillomatosis,
a disease that causes tumors to grow on the skin and internal
organs. A virus is suspected to cause these tumors.
Monitoring the health of wildlife can illuminate the causes of
cancer in animal populations and better safeguard us and them
against diseases, McAloose said.