Could Tarantula Venom Relieve Pain?

More than a few tourists in northern Chile or coastal Peru has woken up to find an unwelcome visitor on their pillows. The Peruvian green velvet tarantula, also known by its scientific name, Thrixopelma pruriens is one of three species of a genus of "colorful" tarantulas that inhabit South America. The Peruvian green velvet tarantula earns its scientific epithet "pruriens," or "itchy," by its habit of throwing its hair at potential predators, tiny daggers at the end of the hair releasing a compound that causes itching. This skill can give the spider a chance to escape getting swatted by hapless humans who encounter it on their pillows, in the bathroom, or on the breakfast table, as its victims rub their skin or eyes.

Unlike other closely related South American spiders, the Peruvian green velvet tarantula isn't especially brightly colored. Its velvety hairs do look green if you look closely enough (assuming the spider will allow you to look closely enough), but from a few feet away this spider looks a dull brown with beige stripes on its legs. This spider is much less likely to be collected by tarantula enthusiasts than the more brightly colored tarantulas from Brazil and Venezuela. What makes the Peruvian velvet tarantula stand out is the venom in its hairs, which has the unusual ability to block chronic pain.

A Different Kind of "Toxin"

Many snakes, cone snails, and spiders have toxic venoms that they can release with a bite. These venoms can make humans very sick or even kill. Peruvian green velvet tarantula venom (the kind released in a spider bite, not the kind in the spider's hairs) is also potent, but it acts as an anesthetic. Most kinds of poisonous creepy crawlies release venom that stops nerve transmissions. The venom from the Peruvian green velvet tarantula specifically stops pain transmissions.

The toxin in this species of spider is a compound called ProTx-II. This chemical, for reasons not currently known, tends to concentrate in the membrane surrounding neurons that send pain messages to the brain. It has exactly the right geometry to fit like a key in a lock in receptors that would otherwise instruct the neuron to send pain signals to the rest of the central nervous system.

READ Is Animal Research Still Necessary?

Why Would Anyone Be Interested in "Toxic" Pain Relief?

There are good reasons that researchers at the University of Queensland Institute for Bioscience, where the Peruvian green velvet tarantula's venom is being analyzed, are enthusiastic about this discovery. Many people suffer neuropathic pain. This pain is caused by injury to nerves by high blood glucose levels in uncontrolled diabetes, chemotherapy, mechanical injury, or certain kinds of viral infections (such as herpes and HIV). There are very few medications for this kind of pain that don't cause extreme drowsiness, and usually weight gain. A medication made from the this tarantula's venom might be one more weapon in modern medicine's very limited arsenal of effective medications for dealing with neuropathic pain. The toxin might also be adapted to treating chronic muscle tension in multiple sclerosis and high blood pressure.

Many Animal Toxins Have Potential For Pain Relief

The Peruvian green velvet tarantula is hardly the first animal that has been found to produce a toxin that can relieve pain. There are a variety of animal-based treatments for pain relief that have wide, if not universal, acceptance in the medical world.

• Apitherapy, or treatment by bee stings, has been used to treat the pain of arthritis (especially rheumatoid arthritis) and neuropathy for generations. Bee venom may be injected into a painful joint for pain relief. For neuropathic pain caused by multiple sclerosis or stroke, some holistic practitioners inject the venom into acupuncture points for relief of pain in other parts of the body. Exactly why this works, no one knows, but many practitioners and patients report that it indeed works. Bacteria that live in honey, scientists have also discovered, fight some of the viral infections that cause pain, such as herpes.

• An injectable form of a medication derived from the venom of a Brazilian wasp seems to be inert in healthy tissues but active in tumor tissues. The toxin tears holes in tumors that allow greater access by the immune system or chemotherapy. As such, this toxin doesn't cure cancer on its own, but enables the body's immune defenses and standard treatments to work more effectively. The preparation is known as Mitaparan.
• A marine snail that is so large that it hunts fish, Conus magnus, produces a toxin that paralyzes the fish on which it feeds. A synthetic drug called ziconotide (Prialt) that is based on the snail's toxin is one of the few medications that can be used to treat chronic, intractable pain such as spinal cord injury when Cabatrol, Lyrica, and Neurontin don't work. These snail-based medications aren't easy to use. They have to be injected intrathecally, into the spine itself, with a pump that is worn by the user. There is a very narrow range in which they are effective. Too little and there is no pain relief, too much and there are serious complications. However, for some people, they are the only effective form of pain relief other than being "knocked out."
• Erabutoxin B, found in the venom of the broad-banded blue sea snake, has the potential for treating the changes in pain sensitivity that come with nicotine withdrawal. It may also be a treatment for certain symptoms of Alzheimer's. As yet, treatments based on this naturally occurring toxin are not approved by the US Food and Drug Administration or by the regulatory bodies of the EU.

READ Safety Of Food And Recent Aflatoxin Scare In Europe

• No fewer that 240 species of spiders have been found to have venom that has the side effect of enabling pain relief. The Peruvian green velvet tarantula is currently the best studied of these spiders, but many other poisonous spiders, including the black widow and brown recluse that are common in North America, are being studied as sources of new treatments that work in relieving chronic pain that can't be treated with other drugs.