Snakebite

People bitten by snakes typically live in tropical or subtropical countries where venomous species are endemic. Those most at risk include farmers or rural communities that depend on agriculture or subsistence hunting and gathering. With its highly agrarian economy, India is the region most affected by snakebite, followed by sub-Saharan Africa. The risk of death or permanent disabilities is increased in remote communities where access to care is poor, as it is in many regions with highly venomous snakes. This limited access may reflect the lack of effective, affordable antivenoms available, of health workers trained in treating snakebite, or of nearby health facilities, or ambulances that can transport patients to health facilities, so they can receive care quickly after being bitten. For these reasons, many victims turn to traditional healers, or to ineffective traditional medicines or low-quality antidotes. Young children under five have a higher risk of death, due to their lower body mass.

Different species of poisonous snakes often produce different venoms. But in general, their effects fall into three main categories:

• The first is rapid, painful swelling that can kill tissue around the bite or even the entire limb. Swelling can also affect the airway, which in severe cases may quickly lead to death.
• Second, venoms can cause bleeding and at the same time prevent blood from clotting, so that victims may bleed profusely from the bite and from other wounds. This can progress to further bleeding, shock, and convulsions.
• Third, venoms can be toxic to the central nervous system, initially causing numbness, excessive sweating, and other mild symptoms but sometimes progressing to life-threatening problems such as breathing difficulties and eventually paralysis, and complete inability to breathe.

Other common symptoms include low blood pressure, increased heart rate, upper back pain, vomiting, and diarrhea.

The first sign of a snake bite is the bite itself, often on the victim’s arms or legs, and showing two distinct puncture wounds from the snake’s fangs. It is important that the correct type of snake is identified, since this helps in choosing the appropriate antivenom. At MSF’s clinics, patients can often do this using photos of local venomous snakes. Many patients are understandably stunned immediately following a snakebite, however, and often cannot recall its shape or markings.

If the patient and medical staff are unable to identify the snake based on recall or wound appearance, they may rely on the symptomology of the patient, since the symptoms, described above, vary from snake to snake. This approach has its own difficulties, however, since the composition of snake venom can vary within species and even within generations of the same species. This variation thus potentially produces different symptoms than may be expected.

A final diagnostic approach is through laboratory analyses, which many low-resource settings lack the capacity to carry out. A patient’s blood can be tested for various clotting patterns and abnormalities, which can give clues to both the type of snake and the severity of the envenoming.

Bites from venomous snakes can kill or maim people quickly. So saving lives and reducing disability requires that snakebite victims can quickly reach a health facility that has staff trained to diagnose and manage poisonous bites and has good-quality antivenoms on hand. Serious cases may also require intravenous fluids, breathing support (including provision of oxygen), control of bleeding, and wound care. Some patients, especially those that reach care late, may have such severe tissue damage, that they require surgery or even amputation of the affected limb.

Most snakebite victims with adequate treatment will heal within two to three weeks, but a quarter of patients can take up to nine months to completely recover. Some patients, especially those who were unable to reach timely healthcare or did not have access to adequate treatment, never fully recover. Patients who survive a snakebite but lose limb function—or lose their limb altogether—need extensive rehabilitation, but this is often not available where they live. Many go on to lead lives of poverty and exclusion from their community, while families may also suffer financial ruin due to the loss of their breadwinner’s ability to work.

Necrosis, or death, of skin tissue occasionally leads to painful tightening of the skin, muscle, tendons and ligaments which requires surgical intervention (something that is unavailable to many snakebite victims). Some snakebites can cause kidney damage that can progress to chronic renal failure, and others may prompt endocrine dysfunction. The trauma of a snakebite injury has been shown to sometimes lead to depression and post-traumatic stress disorder as well.

Antivenoms are rarely available in rural and low-resource settings, where most snakebites occur. When they are available, patients are often required to pay out-of-pocket, which proves to be cost-prohibitive for many. Early access to healthcare is vital for snakebite injuries, but in rural settings where the closest health clinic may be hours away, many patients are unable to reach adequate care before it is too late.

The vast majority of antivenoms are created in a highly costly and time-consuming process that has barely changed since the 19th century, and involves immunizing animals, mainly horses, with non-fatal doses of antisera. Antibodies are then purified from the horse’s blood, creating an antivenom that can be used to treat envenomed humans. Often, however, these antivenoms are not properly created or adequately tested before being introduced to the public, calling their clinical safety and effectiveness into question. Many products don’t disclose the species of snakes used to create the antivenom, causing frequent mismatch between the antivenom and the common, local poisonous snakes. Since the cost is often prohibitive, demand for antivenoms appears to decline, further hindering the monetary incentive for pharmaceutical companies to engage in research and development. The high cost of effective antivenoms often leads individuals to pay for cheaper, less safe alternatives that contribute to snakebite morbidity and mortality.