More to lizard bite than a nasty nip

MELBOURNE - More lizard families than previously believed are venomous, including several species that are popular pets.

Until now, pain and swelling from lizard bites assumed to be non-venomous were attributed to the bacteria that thrive on bits of meat left between the reptiles' teeth from their scavenging diet.

But the symptoms are actually from the venom, a finding that could have implications for medical research, says Dr Bryan Fry, of the University of Melbourne, lead author of the research published online by Nature.

"The venom is the perfect knock-out punch by monitor lizards to their prey like small mammals and lizards."

It stopped blood clotting, rapidly dropped blood pressure and heightened the feeling of bite pain, said Fry.

His team of international scientists isolated crotamine - the classic venom of rattlesnakes, whose bite can be fatal to humans - in the eastern bearded dragon, a popular pet. The dragon's delivery system is primitive and it is present in such small amounts that it would not harm a human.

Fry said Indonesia's komodo dragon - the world's largest lizard, weighing up to 160kg - was also venomous.

"There are so many more reptiles with venom now than we previously thought. That fact itself has massive implications for a vast array of areas, whether it be evolution, drug design and development or ecology."

Snake toxins are widely used in medicines to treat epilepsy, haemophilia and thrombosis. The new lizard venom toxins and their molecules present a huge untapped resource for drug design.

Fry said lizard owners should not be unduly concerned.

"If you're dinner then the venom plays a role, but if you're human it's most likely just to make your hand throb. We don't want people to suddenly be afraid of their pets. Nor do we want any silly laws being passed against the keeping of these lizards."

Toting toxins

* The number of potentially venomous reptile species has risen to 4600 from 2300.

* Previously it was thought that only two families of reptiles were venomous: advanced snakes and helodermatid lizards.

* There are venom toxins in two more lizard families: monitor lizards (such as komodo dragon) and iguania (bearded dragon, green iguana).

Their toxin secreting glands are smaller than those of snakes.

- REUTERS