Part 1: Prevention & Treatment - Summary

• Travelers face a higher risk of snakebites in Asia, especially in dense vegetation, near water
  sources, and during warm, rainy seasons; high-risk activities include hiking and camping,
  especially at night when snakes are most active.
• Travelers engaging in high-risk activities should follow snakebite prevention advice, such as
  avoiding contact with snakes, wearing protective clothing, steering clear of tall grass, using a
  flashlight at night, and teaching children to avoid snakes.
• Correctly identifying whether a snake is venomous is difficult, even for experts. When in
  doubt, assume the bite may be venomous and seek medical assistance as soon as possible
  (a picture of the snake taken at a distance might help guide therapy).
• If bitten, move away from the snake, remain calm, gently bandage the wound, immobilize the
  affected limb, avoid walking/exertion when possible, and seek immediate medical care from trained professionals, which may require travel to the nearest medical facility.
• Commercial snakebite kits are generally ineffective and may cause harm, with the exception
  of carefully applied compression bandages for specific life-threatening elapid bites.

Where and when are travelers most likely to be bitten by a snake?

Observational studies related to traveler-specific risk for snakebites are limited. However, based on the literature, several factors may be extrapolated to the traveler situation. Asia appears to be a high-risk location based on a recent study published from the GeoSentinel Network. During 2007-18, nineteen snakebites were recorded among 6,470 travelers; almost half (n = 9) occurred in Nepal and 17 of the 19 occurred in Asia/Southeast Asia (1 snakebite reported in Africa). Specific environments of travel where there is dense vegetation, proximity to water sources, and specific climatic conditions (such as warm weather and rainy seasons) increase risk. With respect to high-risk itineraries, studies have shown that activities such as hiking and camping, as well as behaviors such as handling or attempting to capture snakes puts a person at risk. Lastly, snakebites occur more frequently during the night and in warm weather because snakes are more active during these times.

How can travelers prevent snakebites?

For travelers whose itineraries place them at increased risk of snakebite exposures, including adventure travelers, campers, and hikers (see question above), pretravel counseling should focus on the following key snakebite prevention measures:

• A snake that has been surprised or cornered is likely to bite.
• Never threaten a snake or attempt to pick one up.
• If a snake is seen, stop, back off, and wait for it to move away.
• When hiking/trekking in a high-risk country, wear boots and long trousers/pants.
• Avoid walking through tall grass whenever possible. In dense vegetation move slowly, beating the vegetation with a long stick to scare off any snakes. Tread carefully in sand.
• Do not put hands down holes in the ground or cracks between rocks.
• When camping, sleep under a bed net.
• When walking after dark, use a torch/flashlight.
• When performing activities in at risk areas with children, keep them close and teach them not to touch or approach snakes.

How can travelers tell if a snake is venomous?

Although experts in herpetology can usually identify snakes (venomous and non-venomous), health care providers and patients alike overestimate their ability to identify snakes and determine whether they might be venomous, either based on verbal descriptions, or even when photos (or actual specimens) are available. In a 2020 review of 150 publications, 9 studies that evaluated photographs of the biting snake reviewed by snake experts found that the snake was correctly identified to the species/genus level in only 18,065 of 33,827 (53%) snakebite cases. Interestingly, 70% of victims/bystanders spotted the snake responsible for the bite and 38% captured/killed it and brought it to the health care facility. However, a significant number of bites have been attributed to attempts to either capture the offending snake or from taking a picture at a close distance. Once the patient is safely away from the snake, if a picture can be taken without getting too close, it may be helpful in identification and may support targeted management. In the US, venomous snakes often have a triangular head, elliptical (slitted) pupils, and pits between their eyes and nostrils compared to non-venomous snakes that typically have rounded heads and pupils; however, this is not true for all snakes and is even less reliable elsewhere in the world. Puncture wounds from fangs are indicative of having been bitten by a venomous snake but are not universally present. Rather than waiting for swelling and/or other symptoms of envenomation to begin before seeking assistance, early transport to an emergency facility for evaluation and observation is prudent. Artificial intelligence (AI) in the identification of snakes is now being employed in several situations, and overall, the AI-based methods seem to accurately determine snake species and classify venomous and non-venomous snakes when high quality photos are available. However, the ability to evaluate the site of a bite for characteristics consistent with a venom exposure is not accurate at this time.

What should travelers do if a snakebite occurs far from medical help?

Several organizations provide guidelines and/or protocols for the management of snakebites, several of which highlight best practices in prehospital care. Principles that are accepted by most authoritative sources include:

• Stay calm and rest (away from the snake or its territory).
• Identify/photograph the snake only if it is safe and will not delay transport to definitive care; do not handle the snake or snake parts.
• Remove jewelry or footwear or tight clothing from the affected extremity.
• Do not manipulate the wound except to permit gentle bandaging.
• Apply pressure immobilization or a pressure pad if indicated (see below).
• Immobilize the injured part of the body in a functional position using a rigid object as a splint, avoiding direct pressure injury. Limited evidence exists and expert recommendations vary regarding the recommended height of the bite wound relative to the level of the heart.
• Transport to the nearest medical facility as quickly as possible.
• If possible, do not walk because exertion (and with bite wounds on the lower extremity, local muscle contraction) may increase snake-venom absorption.
• Withhold alcohol and any drugs (aspirin, nonsteroidal anti-inflammatory medications, etc.).

Snakebites from species with venoms that cause little to no local tissue damage (e.g., Australian elapids, kraits, neurotoxic cobras, coral snakes, or South American rattlesnakes) should receive pressure immobilization rather than immobilization alone. Use in species whose venom is associated with significant local tissue necrosis (e.g., many cobras, adders, pit vipers, and rattlesnakes) may worsen tissue damage and raise compartment pressures. To apply a pressure bandage do not remove clothing; avoid excessive movement of the affected limb; keep the affected area below the heart; wrap the extremity with an elastic bandage, pantyhose, or other clothing torn into wide strips, with the same tightness used for wrapping a sprained ankle; and then splint with a rigid object.

Do snakebite kits work?

Snakebite kits may contain tourniquets, splints, scalpels, vacuum or suction extractors, and loose and compression bandages with or without pads. The general idea of snakebite kits is to lessen both the volume of venom after a bite and the speed at which it enters circulation. Unfortunately, evidence has not demonstrated that kit components accomplish this. The best demonstration of reducing the volume of venom by extraction was in a group of people that had volunteered to be injected with radioactive tracer to simulate envenomation followed by 15 minutes of suction at the wound—the envenomation load only decreased by 0.04% in the circulation and 2% in the wound. Earlier studies had suggested wound injury from the other suction processes. Cutting the wound risks infection and healing challenges. Whether patients experienced a crotalid (pit viper; predominantly necrotic acting venom) or elapid (e.g., asp or Coral snake; predominantly neurotoxin acting venom) has been considered in some practice guidelines. However, increasingly, snakes are recognized to have a mix of cytotoxic, inflammatory, and neurotoxic venom components. Tourniquet studies where vascular flow was impeded have demonstrated worse tissue healing following snakebite, as has splinting in some instances, mostly from direct pressure injury at joining sites. The story of compression bandages (targeting lymphatic only and not vascular flow) is more complicated—results range from ineffective (in particular, North American crotalid bites) to potentially useful by delaying neurologic effects (elapid bites, such as a cobra or Coral snake). Consistent application of these tools in the field has also been problematic when carefully assessed. Snakebite kits may change in the future, and perhaps incorporate updated practices and revised tools, such as topical chemicals that inhibit lymphatic flow or mitigating pharmacologic therapies. For now, snakebite kits and their common components are unlikely to improve patient outcomes and may cause harm, with the possible exception of carefully applied compression bandages when a known, life-threatening elapid exposure has occurred. Professional groups recommend against these measures. The most important course of action for a traveler after a snakebite is to immediately report the bite and their location and to obtain rapid medical care by trained professionals familiar with the local diaspora of snakes and available proven remedies.

Part 2: Antivenom - Summary

• Antivenom is not always required: It is indicated when envenomation symptoms are severe or worsening, including progressive local tissue injury, systemic toxicity, or abnormal laboratory results. Minor envenomation may not require treatment.
• Antivenom carries risks: It can cause acute (e.g., anaphylaxis) and delayed hypersensitivity reactions (e.g., serum sickness). The likelihood of these side effects depends on the formulation, dose, and source animal (e.g., horse or sheep).
• Finding antivenom: Regional poison centers, the WHO database, and local health care facilities can help locate antivenom when traveling in areas with venomous snakes.
• Immediate treatment is preferred: Receiving antivenom in a low-resource setting is generally better than delaying treatment for medical evacuation because early administration improves outcomes and prevents complications.

Is antivenom always needed?

Not all venomous snake bites require antivenom. Some snakebites are “dry” and do not involve envenomation. The decision to administer antivenom depends on the presence and severity of envenomation symptoms. According to the Wilderness Medical Society, antivenom should be administered in cases of progressive local tissue injury or systemic toxicity following a pit viper bite. Antivenom may also be critical in elapid bites that result in substantial neurotoxicity, although its effectiveness in such cases may be limited.[1, 2] Patients with minor envenomation, characterized by localized swelling and pain, may be observed without antivenom unless symptoms worsen.[3]

• Progressive Local Tissue Injury: This includes worsening of local tissue injury, such as an increase in erythema by 2 cm (0.79 in) or more, significant swelling, and severe local pain. For example, bites to high-risk anatomical sites (e.g., hands, joints, or the face) may necessitate a more conservative approach, lowering the threshold for antivenom administration due to the potential for severe and long-term sequelae.[3]
• Systemic Toxicity: Systemic symptoms that warrant antivenom include hypotension, systemic bleeding, neurotoxicity, and abnormal coagulation tests with serious bleeding.[3, 4]
• Laboratory Abnormalities: Abnormal laboratory results (e.g., significantly abnormal prothrombin time, fibrinogen, and platelet count) are also indications for antivenom administration.[3, 4]
• Broad-based approaches to antivenom therapy are under development but are not yet available.[5-7]

Is antivenom dangerous?

The main risk with antivenom administration is hypersensitivity reactions.[8] Antivenom can cause both acute and delayed hypersensitivity reactions. Acute reactions, such as anaphylaxis, can occur within 1 hour of administration and may be severe, requiring immediate treatment with epinephrine, steroids, antihistamines, or emergency airway management. Delayed reactions, such as serum sickness, typically occur 5 to 14 days after administration. The Wilderness Medical Society notes that approximately 8% of patients treated with FabAV (pit viper antivenom) experience acute hypersensitivity reactions, whereas 13% develop serum sickness.[1, 3] The risk of these reactions varies depending on the source animal (e.g., horse or sheep), the type of antibody fragments used (IgG, F[ab′]2, or Fab), and the dose of antivenom provided.

Where is antivenom available?

When traveling overseas, information about the availability of antivenom can be found through several key resources:

1. Regional Poison Centers: These centers are often the most reliable source for information on the availability of specific antivenoms. They can provide guidance on where to obtain antivenom and offer expert advice on its use.
2. World Health Organization (WHO) Database: The WHO maintains a database that provides information on antivenoms available worldwide. This resource is valuable for identifying antivenoms for both indigenous and nonnative snakes.

List of Product Assessment Outcomes | WHO – Prequalification of Medical Products (IVDs, Medicines, Vaccines and Immunization Devices, Vector Control)

Snakebite Data Information Portal – Production

3. Local Health Facilities: When envenomation from an indigenous snake has occurred, local health care facilities either stock or should know how to obtain an appropriate antivenom. Consulting with local medical professionals can provide insights into the availability and sourcing of antivenoms in the region.

Lastly, academic and public health institutions often have groups focused on toxinology that may be able to provide valuable insights. Some of these groups include:

National Natural Toxins Research Center | Texas A&M University Kingsville

WCH Clinical Toxinology Resources | University of Adelaide

If antivenom is needed

It is generally better to receive antivenom immediately in a low-resource setting rather than delaying treatment for medical evacuation to a high-resource setting.[1] Early administration can reverse systemic effects (even when they have persisted for several days) and may also resolve coagulopathy that would otherwise last for weeks. Treatment should continue until clotting abnormalities resolve. Although its effectiveness in preventing local tissue damage is uncertain, administration within the first few hours may be beneficial.

Wilderness Medical Society guidelines emphasize rapid transport to the nearest emergency department for life- or limb-saving care following a venomous snakebite.[3] Delayed antivenom administration can lead to increased morbidity and mortality, whereas earlier administration is associated with improved outcomes.[4] Recent evidence from French Guiana[9] and Sri Lanka[10] further support this point, linking treatment delays with prolonged coagulopathy and other management challenges.