Merck Manual

Please confirm that you are a health care professional

honeypot link

Alligator, Crocodile, Iguana, and Venomous Lizard Bites

By

Robert A. Barish

, MD, MBA, University of Illinois at Chicago;


Thomas Arnold

, MD, Department of Emergency Medicine, LSU Health Sciences Center Shreveport

Last full review/revision Apr 2020| Content last modified Apr 2020
Click here for Patient Education

Venomous lizards

Venomous lizards include the following:

  • Gila monster (Heloderma suspectum), present in the southwestern US and Mexico

  • Beaded lizard (H. horridum) of Mexico

The complex venom of these lizards contains serotonin, arginine esterase, hyaluronidase, phospholipase A2, and ≥ 1 salivary kallikreins but lacks neurotoxic components or coagulopathic enzymes. Bites are rarely fatal. Varanids (eg, Komodo dragon [Varanus komodoensis], crocodile monitor lizard [Varanus salvadorii]) are also venomous and pose little risk to humans. When venomous lizards bite, they clamp on firmly and chew the venom into the person.

Symptoms and signs include intense pain, swelling, ecchymosis, lymphangitis, and lymphadenopathy. Systemic manifestations, including weakness, sweating, thirst, headache, and tinnitus, may develop in moderate or severe cases. Cardiovascular collapse occurs rarely. The clinical course is similar to that of a minimal to moderate envenomation by a larger species of rattlesnake (see Symptoms and Signs Symptoms and Signs Of about 3000 snake species throughout the world, only about 15% worldwide and 20% in the US are dangerous to humans because of venom or toxic salivary secretions (see table Significant Venomous... read more Symptoms and Signs ).

Treatment in the field involves removing the lizard’s jaws by using pliers, applying a flame to the lizard’s chin, or immersing the animal entirely underwater. In a hospital, treatment is supportive and similar to that for pit viper envenomation Treatment Of about 3000 snake species throughout the world, only about 15% worldwide and 20% in the US are dangerous to humans because of venom or toxic salivary secretions (see table Significant Venomous... read more Treatment ; no antivenom is available. The wound should be probed with a small needle for broken or shed teeth and then cleaned. If the wound is deep, an x-ray can be done to rule out a retained foreign body or bone fracture. Prophylactic antibiotics are usually not recommended.

Iguanas

Bites and claw injuries from iguanas are becoming more frequent as more iguanas are kept as pets. Wounds are superficial, and treatment is local. Soft-tissue infection is uncommon, but when infection occurs, Salmonella is a common cause; infection can be treated with a fluoroquinolone. A secondary but growing concern is infection with Serratia marcescens, which is usually sensitive to trimethoprim/sulfamethoxazole.

Alligators and crocodiles

Alligator and crocodile bites usually result from handling; however, rarely, native encounters occur. Bites are not venomous, are notable for a high frequency of soft-tissue infections by Aeromonas species (usually Aeromonas hydrophila), and are generally treated as major trauma.

Wounds should be irrigated and debrided; then delayed primary closure can be done or the wounds allowed to heal by secondary intention. Optimal antibiotic coverage may include trimethoprim/sulfamethoxazole, a fluoroquinolone, a 3rd-generation cephalosporin, an aminoglycoside, or a combination. Additionally, patients can be treated preventively with clindamycin and trimethoprim/sulfamethoxazole (first choice) or tetracycline.

Drugs Mentioned In This Article

Drug Name Select Trade
No US brand name
ACHROMYCIN V
CLEOCIN
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Test your knowledge

Snakebites
More than 60,000 bites and stings are reported to poison centers in the US each year, about 45,000 of which are snakebites (of which 7,000 to 8,000 are venomous and cause about 5 deaths). Which of the following types of snakes accounts for the majority of these bites and almost all deaths? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP