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A giant cane toad, plague of Australia. See more pictures of amphibians.

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Do toads cause warts?

­Australia has a big problem. Back in 19­35, the government imported 101­ giant cane toads (Bofo marinus) from Hawaii to Queensland to combat an infestation of cane beetles. Cane toads, which can weigh up to two pounds (0.9 kilograms), are indigenous to Central and South America [source: Florida Gardener]. Like most other non-native species introduced into an ecosystem (manatees in Florida rivers and kudzu vines in the Southeastern United States are two examples), the cane toads soon began to wreak havoc, all the while shirking their original task -- eradicating cane beetles.

By 2008, the descendents of the original 101 cane toads brought to Australia numbered in the billions. What's more, they were on the move, leaving Queensland and encroaching upon cities in the Northern Territory, like Perth and eventually Sydney [source: Reuters, Peatling]. Billions of toads slowly moving toward civilization is unsettling enough; the bigger problem is the fact that cane toads are poisonous to many animals, including crocodiles, dingoes, some marsupials and myriad smaller animals.

­Because they're relatively new to Australia, cane toads don't have any natural predators as they do back in Hawaii. What's more, since they've only been on the continent for a relatively short time, other animals looking for a large, amphibious meal have yet to figure out that cane toads will kill them. It's the toxic cocktail of 14 chemicals that the toads secrete from their glands that poses such a danger. When the toad is threatened, these glands spring into action; the toxins are transferred from toad to the predator's mouth when it attempts to eat the toad. The chemicals work quickly and can cause nausea, paralysis and death.

Biologists and geneticists in Australia are studying the cane toad's life cycle in an effort to remove the development of a gene that allows them to reproduce [source: National Geographic]. Eventually the billions of toads will die out and the cane toad will become a bad memory in Australia. Despite the threat the can­e toad poses to Australia's environment, the Aussies can rest easy that they won't also cause an outbreak of warts.

That's because the cane toad (or any toad, for that matter) isn't capable of producing warts.

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Culture of cervical cancer cells under microscope.

Loren Rodgers/iStockphoto

Toads and HPV

­It's likely that the idea that toads can cause warts stems from the wart-like bumps that toads bear on their backs. These are actually glands that produce and secrete toxins that serve to defend toads from predators. All toads have them; some are more toxic than others. Although they resemble warts in appearance, these glands aren't warts. This is the first problem with the idea that toads can caus­e warts: If toads actually did have warts, they conceivably could be capable of producing warts in humans when handled, since warts can be transferred from person to person.

Toads would have to secrete a virus called the human papillomavirus (HPV) in order to cause warts. That's because warts are the result of an HPV infection, not toad secretions.

HPV may have a familiar ring to it. Beginning in 2006, a battle over mandatory HPV vaccinations took place in the U.S. One particularly virulent sexually-transmitted strain of the virus has been shown to cause cervical cancer in women and many groups (led largely by Women in Government, or WIG) wanted states to mandate the addition of HPV vaccines to the roster of inoculations required for children to attend school.

The state-by-state campaign by WIG lost some steam in 2007, after it was revealed that the group (which is composed of elected female officials around the U.S.) was partly funded by Merck, the pharmaceutical company that produced Gardasil, the only FDA-approved vaccine for HPV [source: AP]. The potential benefits for reducing the prevalence of cervical cancer (which affects around 10,000 women in the U.S. annually) appeared to outweigh any controversy, however [source: Rein and Wiggins]. By the end of 2008, 41 states had introduced legislation to create mandatory HPV inoculation programs and 19 states had already enacted them [source: NCSL].

An estimated 20 million people in the U.S. are infected with a form of the HPV virus; there are about 100 types of the virus [source: Rein and Wiggins, Mayo Clinic]. Most of them are fairly harmless to humans, producing benign maladies like warts, for example.

How Warts Spread and What to Do About Them

In addition to cervical cancer, HPV can also cause genital warts, another sexually transmitted disease. However, most people affected by a strain of the virus develop only regular old warts, however. Most of the time these warts appear on the hands or fingers of the sufferer and, aside from aesthetics, pose no threat to humans. Warts aren't cancerous, which is odd because they're the result of rapid growth of epidermal cells, and cancer is uncontrolled cellular growth. Warts will eventually stop growing, although they can easily spread. The HPV strain that causes common warts is hearty and can be transferred from person to person by shared objects.

To make matters worse, warts can sometimes be difficult to get rid of quickly without medicine. When a wart dies, it sloughs off skin cells that still carry HPV. These skin cells spread across previously unaffected areas of the skin and effectively produces a cycle of infection [source: Mayo Clinic]. Warts should eventually go away on their own, once the antibodies required to end the infection ward off the HPV.

There are options to get rid of warts for people too self-conscious to wait (and many people are). Freezing the warts off (cryotherapy) is a popular method. At the doctor's office, liquid nitrogen is used and some over-the-counter home remedies have salicyclic acid as the active ingredient. Both remedies create a blister around the site of a wart, which will be shed once the blister falls off. A similar goal is achieved using the extract from a blister beetle, which lives up to its name when it contacts the skin. In severe cases, laser surgery or prescription treatments used to combat genital warts may be prescribed.

Regardless of what course of treatment is taken to remove them, any common warts a person may have were certainly not contracted from handling a toad. The concept is as unfounded as one of the cures for warts, burying a cat at midnight [source: Chicago Sun-Times]. It's still a good idea to think twice before picking up a toad as it hops past. Those defensive toxins they secrete can affect humans by acting as a skin irritant. In addition, toads have the unfortunate habit of urinating when a human picks them up. That won't cause warts, sure, but it's still fairly gross.

Lots More Information

Related HowStuffWorks ArticlesMore Great LinksSources
  • Associated Press. "Drug maker wants law to require STD shot." January 30, 2007. http://www.msnbc.msn.com/id/16891832/
  • Chicago Sun-Times. "Dreaded warts are quite common." October 24, 1993. http://www.encyclopedia.com/doc/1P2-4196438.html
  • Florida Gardener. "Bofo marius: giant toad, cane toad, marine toad." Accessed February 19, 2009. http://floridagardener.com/critters/BufoMarinus.htm
  • Gibbons, Whit. "Can toads give you warts?" University of Georgia. December 4, 2005.http://www.uga.edu/srel/ecoviews/ecoview051204.htm
  • Gibbs, James P. "The amphibians and reptiles of New York State." Oxford University Press. 2007. http://books.google.com/books?id=ZazMa1YzV44C&pg=PA118&lpg=PA118&dq=do+toads+cause+warts&source=web&ots=00cSiNOG3S&sig=c_9cydCBduuY-IUq03P8BySlnEU&hl=en&ei=tAqbSfXzLIrmyAW3j42YCg&sa=X&oi=book_result&resnum=9&ct=result#PPA118,M1
  • Krautwurst, Terry. "Nature myths, debunked." Mother Earth News. April/May 2006. http://www.motherearthnews.com/Nature-Community/2006-04-01/Nature-Myths.aspx
  • Mayo Clinic. "Common warts." Accessed February 17, 2009. http://www.mayoclinic.com/health/common-warts/DS00370/DSECTION=causes
  • National Conference of State Legislatures. "HPV vaccine." November 18, 2008. http://www.ncsl.org/programs/health/HPVvaccine.htm
  • Peatling, Stephanie. "Poison toads leap across Australia." National Geographic. November 29, 2004. http://news.nationalgeographic.com/news/2004/11/1129_041129_cane_toads.html
  • Rein, Lisa and Wiggins, Oveta. "Many in senate back mandatory HPV vaccination." Washington Post. January 19, 2007. http://www.washingtonpost.com/wp-dyn/content/article/2007/01/18/AR2007011801772.html
  • Reuters. "Bad back may stop cane toad." December 2, 2008. http://www.reuters.com/article/scienceNews/idUSTRE4B11UT20081202