Lizard Envenomation

There are 5 extant species of lizards known to be venomous, all belonging the the family ​Heloderma . The Gila monster (Heloderma suspectum with 2 subspecies)  ^[1] , and 4 beaded lizard specias: the Mexican beaded lizard (Heloderma horridum), the Rio Fuerte beaded lizard (Heloderma exasperatum) the Chiapan beaded lizard (Heloderma alvarezi), and the Guatemalan beaded lizard (Heloderma charlesbogerti). ^{[2, 3]}

There is also ongoing debate regarding possible venom production by some other lizard species such as the Komodo dragon (Varanus komodoensis), but there is no current evidence to support human envenomations by any other lizards, ^[4] and these will not be further discussed in this article. 

The Gila monster is found in the desert regions of Arizona, western New Mexico, southeastern California, ^[5] the southern tip of Nevada, extreme southwestern Utah, and northwestern Mexico. The four Bearded lizards are found in Mexico and Guatemala, south of the range of the Gila monster.

Heloderma spp lizards have heavy bodies with large heads and powerful jaws. The beaded lizards are larger than the Gila monster, reaching almost a meter in length, whereas the Gila monster's maximal size is approximately 0.5 m.

Patient education

Bitten victims should receive instructions regarding standard wound care, elevation of the bitten extremity, signs and symptoms of infection, and medications to be taken.

Patients should be educated to avoid close interactions with potentially dangerous wildlife in the future.

Signs and symptoms

Also see Presentation.

Vital signs should be assessed and closely monitored.

Local signs are as follows:

• Multiple bleeding lacerations

• Edema

• Cyanosis or ecchymosis

• Vasospasm

• Retained teeth (Closely examine wounds and probe for foreign bodies.)

• Necrosis (rare)

Systemic signs are as follows:

• Tachycardia

• Hypotension

• Respiratory distress

• Diaphoresis

• Lymphangitis and lymphadenopathy

• Airway edema

• Abdominal pain

• Vomiting

Diagnostics

A chest radiograph should be obtained if the victim is experiencing chest pain, shortness of breath, or has significant comorbidities.

Soft tissue radiographs may be obtained to look for retained teeth, although the sensitivity is low. Occasionally, gas may be seen in the soft tissues and likely represents air introduced into the wound during the biting/chewing process. ^[6]   A bedside ultrasound might also reveal retained teeth.

Obtaining an ECG is prudent. T-wave abnormalities, conduction disturbances, and 2 cases of acute myocardial infarction (one in a young patient without chest pain who had a possible history of cocaine use but no other cardiac risk factors) have been reported. ^{[7, 8]}

Also see Laboratory Studies.

Treatment

See Treatment and Medication.

Prevention

Avoid handling or otherwise disturbing venomous lizards.

Because these creatures spend approximately 99% of their lives underground, the opportunity to see one in the wild is a great privilege. The urge to pick up or capture it should be strongly suppressed. These animals are legally protected in all regions in which they occur.