BACKGROUND

Snakebite, recently declared a neglected tropical disease and global health priority by the World Health Organization (WHO), results in an estimated 2.5 million envenomations, 138,000 deaths and over 500,000 cases of permanent disability worldwide every year.1–10 Snake, spider, and scorpion envenomations are a common environmental and occupational hazard for military forces worldwide.11–46 The consequences of an envenomation range from mild local effects to permanent disability or death, and the outcome is largely determined by the time to antivenom treatment and the level of training of the medical providers involved. Clinical outcomes and survival of the snakebite patient require administering antivenom quickly and immediate care by trained medics or medical professionals. Antivenom and appropriate early care are critical to saving lives and preventing long-term complications like amputations, blindness, or loss of limb function.

Venomous snakebites can induce a range of clinical syndromes, largely categorized by the primary type of toxin in the venom. Cytotoxic venoms, found in snakes like spitting cobras, copperheads, and puff adders cause severe localized tissue damage. This manifests as painful progressive swelling that starts at the bite site and can spread rapidly, leading to complications such as blistering, tissue death (necrosis), and compartment syndrome, a condition where swelling cuts off blood circulation. Hemotoxic venoms, on the other hand, disrupt the body's ability to clot blood, leading to bleeding from various sites, including the gums, nose, and the bite wound itself. Snakes such as Russell's vipers, saw-scaled vipers, and boomslangs possess hemotoxic venom, which can cause coagulopathy, a condition of abnormal blood clotting, and in severe instances, disseminated intravascular coagulation (DIC).

Neurotoxic venoms primarily affect the nervous system, causing progressive weakness and paralysis. Symptoms of neurotoxic envenomation include drooping eyelids (ptosis), blurred vision, difficulty breathing, and can advance to paralysis of the respiratory muscles, which can be fatal. Cobras, kraits, and mambas are well-known for their neurotoxic venom. Systemic instability is a broader category of effects that can result from various types of snake venoms and their systemic impacts. This can include a mix of syndromes (eg HEMO + CYTO), such as painful progressive swelling combined with bleeding, as seen in bites from many vipers including rattlesnakes, gaboon vipers, the Fer-de-lance, and others. It can also manifest as life-threatening systemic complications like dangerously low blood pressure (hypotension), shock, acute kidney injury, and acute respiratory distress syndrome (ARDS), which can be triggered by fluid loss from cytotoxic effects, widespread bleeding from hemotoxic effects, or direct shock-inducing venom components.

Once a snakebite occurs, it is a race against time to prevent severe local tissue damage and deadly systemic symptoms. Some types of necrosis caused by cytotoxic venoms cannot be reversed but can be prevented by early antivenom administration (or arrested before further damage can occur in cases of late antivenom treatment).1,7,47-49 Hemotoxic venoms can induce bleeding and clotting abnormalities within minutes, which progresses over hours or days into widespread external and internal bleeding. Neurotoxic venoms can act rapidly and be fatal. When a neurotoxic snake bite occurs, rapid antivenom administration prior to the onset of respiratory failure can arrest the progression of descending paralysis before serious systemic manifestations develop.1,50,51 In many cases paralysis will reverse rapidly. When paralysis cannot be reversed before mechanical ventilation is needed (e.g. late-presenting krait envenomations), antivenom still plays a key role: clearance of unbound circulating venom, which permits recovery of damaged nerve terminals and reduces time to extubation to an average of 2 – 5 days versus weeks of ventilation in untreated patients. Every hour wasted between bite and antivenom administration is strongly associated with sharp increases in mortality and the development of chronic or permanent sequelae including amputation, disfigurement, PTSD, blindness, kidney injury, infections, and partial or complete loss of function of the bitten limb.4,7,8,52–58

This CPG provides comprehensive guidance on how to manage snakebites in all geographic CCMDs, with clear steps for providers of all levels to follow in the field and the clinic.