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Snake Bite

snake bite RECENT TOPIC

Snake bite is a neglected public health issue in many tropical and subtropical countries.

What are snake bites

Snakes bite either to capture prey or in self-defense. Snakes that are poisonous voluntarily emit venom when they bite. Because snakes can control the amount of venom they discharge, some bites are “dry” and only 50% – 70% of venomous snake bites result in envenoming, or poisoning.

Most snakebites are innocuous and are delivered by nonpoisonous species. North America is home to 25 species of poisonous snakes.

Worldwide, only about 15% of the more than 3000 species of snakes are considered dangerous to humans. The family Viperidae is the largest family of venomous snakes, and members can be found in Africa, Europe, Asia, and the Americas. The family Elapidae is the next largest family of venomous snakes. In North America, the venomous species are members of the families Elapidae and Viperidae, subfamily Crotalidae.

Not every snake bite is venomous but it should always be treated as a medical emergency. Even a bite from a harmless snake can be serious, leading to an allergic reaction or an infection. Venomous snake bites can produce an array of symptoms, including localized pain and swelling, convulsions, nausea, and even paralysis.

How common are snake bites

According to the World Health Organization about 5.4 million snake bites occur each year, resulting in 1.8 to 2.7 million cases of envenomings (poisoning from snake bites).There are between 81 410 and 137 880 deaths and around three times as many amputations and other permanent disabilities each year.

Most of these occur in Africa, Asia and Latin America. In Asia up to 2 million people are envenomed by snakes each year, while in Africa there are an estimated 435 000 to 580 000 snake bites annually that need treatment. Envenoming affects women, children and farmers in poor rural communities in low- and middle-income countries. The highest burden occurs in countries where health systems are weakest and medical resources sparse.

What is a venomous (poisonous) snakebite

A venomous (poisonous) snake bite is a bite or a puncture wound made by a snake that is capable of injecting, secreting, or spitting venom into the penetrated skin wound, mucus membranes or the eyes where the toxin can be absorbed.

Bites by venomous snakes can cause acute medical emergencies involving severe paralysis that may prevent breathing, cause bleeding disorders that can lead to fatal haemorrhage, cause irreversible kidney failure and severe local tissue destruction that can cause permanent disability and limb amputation. Children may suffer more severe effects, and can experience the effects more quickly than adults due to their smaller body mass.

In North America, there are about 25 species of snakes able to secrete venom. However, non-native poisonous species are present in zoos and held in private homes or other areas by snake collectors. Consequently, almost any type of venomous snake bite can be encountered in the US.

The most common venomous snakes in the US are:

  • Rattlesnakes
  • Copperheads
  • Cottonmouths/water moccasins
  • Coral snakes

The first three are pit vipers (have a pit used to detect temperature changes and two movable fangs), and the coral snake is an elapid with short fixed fangs and no pit. Brown snakes are also elapid and are very poisonous.

What is a nonvenomous (nonpoisonous) snakebite

  • A nonvenomous (nonpoisonous) snake bite is a bite or puncture wound made by a snake that is incapable of secreting venom. This should be distinguished from a dry bite.
  • A dry bite is a bite by a venomous snake that does not inject any venom.
  • Even bites that are from a nonvenomous snake or are dry need to be evaluated as they can lead to significant tissue damage or infections.

Identifying venomous snakes

If you are unfamiliar with the different types of snakes and unable to distinguish between venomous and non-venomous ones, it can be difficult to know how to respond in the event of a bite. Always treat a snake bite as if it’s venomous.

While most snakes in the U.S. are not venomous, several types do contain venom. In the U.S., all of the venomous snakes, except for the coral snake, are pit vipers. Pit vipers are distinguishable by a noticeable depression between the eye and nostril. This pit is the heat-sensing area for the snake. While all pit vipers have a triangular head, not all snakes with a triangular head are venomous.

If you or someone you are with has been bitten by a snake, you will know immediately. It’s possible, though, for the bite to happen quickly and for the snake to disappear.

To identify a snake bite, consider the following general symptoms:

  • two puncture wounds
  • swelling and redness around the wounds
  • pain at the bite site
  • difficulty breathing
  • vomiting and nausea
  • blurred vision
  • sweating and salivating
  • numbness in the face and limbs

Different species of venomous snakes carry different types of venom. In general, the major categories of venom are:

  • Cytotoxins: Cause swelling and tissue damage in the area of the bite.
  • Haemorrhagins: Cause disruption to blood vessels.
  • Anti-clotting agents: Prevent the blood from clotting.
  • Neurotoxins: Cause paralysis or other damage to the nervous system.
  • Myotoxins: Break down muscles.

First aid steps you can take after a snake bite occurs include cleaning the wound, remaining calm, and immobilizing the affected area. However, it’s essential to get to a medical facility immediately for emergency treatment. If treated in time, the outlook for recovery is good.

In contrast to many other serious health conditions, a highly effective treatment exists. Most deaths and serious consequences from snake bites are entirely preventable by making safe and effective antivenoms more widely available and accessible. High quality snake antivenoms are the only effective treatment to prevent or reverse most of the venomous effects of snake bites. They are included in the WHO List of essential medicines and should be part of any primary health care package where snake bites occur.

 

 

 

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References:

https://www.who.int/news-room/fact-sheets/detail/snakebite-envenoming

https://my.clevelandclinic.org/health/diseases/15647-snake-bites

https://emedicine.medscape.com/article/168828-overview#a4

https://www.medicinenet.com/snake_bite/article.htm#what_is_a_nonvenomous_nonpoisonous_snakebite

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