Venomous lizards, alligators and crocodiles, and iguanas can cause clinically significant bites. Tetanus prophylaxis should be given (see table ).
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 of venomous lizard bites 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 of Snakebites 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 ). At least one... read more ).
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 ). At least one... read more ; 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.
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.
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