By César Barrio Amorós1 y Santiago Ayerbe2
1Herpetólogist, CRWild (Costa Rica).
2 Toxinologist CEVAP/UNESP (Brasil), Pediatra Unicauca Popayán (Colombia), Intensivista Hospital Militar Central, Bogotá D.C. (Colombia).
Summary
We present a straightforward identification scale (ranging from 0 to 10) designed to quickly assess the potential impact of a snakebite based on the species involved. This scale allows for a simplified understanding of the medical significance of different snakebites. For instance, a bite from a medium-sized aglyphous snake (Mastigodryas) causing only a superficial wound with no medical importance would rate as a 2 on the scale. In contrast, a bite from a large viper (Lachesis) delivering a significant amount of venom, posing a life-threatening risk without immediate treatment, would rank as a 10.
Snakes are commonly categorized as venomous or non-venomous, but the reality is far more complex. Among venomous snakes, there are at least three distinct methods of venom delivery, and many species exhibit mechanisms that are not yet fully understood.
Snake dentition is typically classified into four main types:
Aglyphous:These snakes lack specialized venom-injecting fangs and possess only regular teeth. Examples include boas, pythons, and many common non-venomous snakes, as well as blind snakes.
Opisthoglyphous:These snakes have enlarged, grooved fangs located towards the middle or rear of the upper jaw, which help guide venom into prey. Some species, like those in the subfamily Xenodontinae, have particularly prominent rear fangs. This dentition is common among many members of the Colubridae and Dipsadidae families, including genera like Oxybelis, Leptodeira, Phylodryas, Clelia, and Sibon. These snakes are often known as racers, snail-eaters, false corals, and false vipers.
Proteroglyphous:These snakes have short, fixed fangs located at the front of the upper jaw. The fangs have a semi-enclosed venom duct for efficient venom delivery. This dentition is characteristic of the Elapidae family, which includes cobras, coral snakes, sea snakes, taipans, and mambas.
Solenoglyphous:Solenoglyphous snakes possess long, hollow, hypodermic needle-like fangs located at the front of the upper jaw. These fangs are mobile, allowing them to fold against the roof of the mouth when not in use, and are replaceable. This fang type is found exclusively in the Viperidae family, which is divided into two subfamilies:
Viperinae (Old World vipers): Includes genera like Vipera, Cerastes, Bitis, and Daboia.
Crotalinae (pit vipers from the Americas and parts of Asia): Includes rattlesnakes (Crotalus), fer-de-lances (Bothrops), bushmasters (Lachesis), and others like Bothriechis, Bothrocophias, Atropoides, Agkistrodon, and Porthidium.
It is crucial to understand that when a bite is caused by proteroglyphous or solenoglyphous snakes, the only way to ensure survival is to seek immediate medical attention at the nearest hospital. Prompt administration of the appropriate antivenom is essential:
Polyvalent Bothropic-Crotalic-Lachesic Antivenom for bites from Viperidae (e.g., pit vipers, bushmasters, rattlesnakes).
Polyvalent Anticoral Antivenom (Antielapid or Antimicruric) for bites from Elapidae (e.g., coral snakes).
In contrast, bites from aglyphous snakes (such as boas and pythons) are generally non-venomous, and the severity of the injury depends on the size of the snake and the extent of the bite. In many cases, the bite may be as harmless as a superficial scratch (similar to a kitten’s scratch). However, bites from larger constrictors like boas, anacondas, or pythons can result in deep lacerations that may require medical care, including debridement and sutures.
Opisthoglyphous snakes present a unique challenge. Many species in this group possess venom that is poorly studied or entirely undocumented, leading to uncertainty about the potential effects on humans. Reactions can range from mild to severe, depending on the species and individual response.
Factors Affecting Snakebite Severity
It’s important to note that not all venomous snakebites have the same impact. Several factors influence the severity of a bite:
Species and Venom Potency: Some species have more toxic venom than others.
Snake Size and Venom Volume: Juvenile snakes may inject less venom, while adults can deliver larger doses. In many cases (up to 50% of viper and coral snake bites), no venom is injected—a phenomenon known as a dry bite. This can occur if the snake has recently fed or if its venom glands are depleted or overfilled.
Human Factors: The victim’s age, size, immune response, and pre-existing medical conditions play significant roles. A child or a person with allergies or chronic illnesses may suffer more severe effects than a healthy adult. Previous snakebites can also influence an individual's sensitivity.
For instance, a bite from a Bothrops asper (commonly known as the fer-de-lance) can produce vastly different outcomes depending on whether the snake is a juvenile or adult, how much venom is injected, and the physical condition of the person bitten.
A Scale for Assessing Snakebite Severity
To help classify and assess the severity of snakebites, we have developed a scale based on scientific literature, as well as our empirical and medical experience. This scale applies to snake species from Costa Rica and Colombia, and can be extended to other regions within the Neotropics.
The scale ranges from 0 to 10:
0 – 1: No effect or negligible symptoms.
10: The most severe cases, with certain death without immediate medical intervention.
This classification provides a practical guide for evaluating snakebite risks and underscores the importance of tailored medical responses based on the specific circumstances of each bite.
Snakebite Severity Scale (0–10)
From least to most medically significant bites.
0 – No Medical Importance
Snakes that rarely, if ever, bite humans, and if they do, there are no adverse effects.
Examples: Imantodes, Sibon, Dipsas, Ninia, Tantilla, Urotheca, Rhadinaea, Amastridium, Oxyrhopus, etc.
1 – Harmless Bite (No Involvement)
Bite from a small aglyphous snake that does not break the skin. No medical care required.
Treatment: None.
Examples: Chironius, Spilotes, Drymarchon, juvenile Phrynonax.
2 – Minimal Involvement
Minor skin break (epidermis only) from a small-to-medium aglyphous snake.
Treatment: Wash the area with soap and water. No further medical care needed.
Examples: Mastigodryas, Drymobius, Lampropeltis, etc.
3 – Mild Tissue Damage
Bite from a large aglyphous snake or medium-sized boa causing deeper epidermal damage.
Treatment: Wash thoroughly with soap and water, apply disinfectant (Isodine, Povidone-iodine), and get a tetanus shot (Tetanol).
Examples: Chironius, Masticophis, Spilotes pullatus, Drymarchon, Phrynonax, Corallus, Epicrates.
4 – Moderate Laceration
Bite from a large constrictor (boa, python, anaconda) resulting in significant lacerations penetrating muscle and/or blood vessels with heavy bleeding.
Treatment: Urgent wound cleaning, disinfectant application, medical evaluation for stitches, and tetanus vaccination.
Examples: Boa, Eunectes, Python.
5 – Mild Envenomation (Aglyphous Snake)
Bite from an aglyphous snake that causes mild toxic symptoms (e.g., slight swelling or redness).
Treatment: Medical evaluation, antihistamines, analgesics, tetanus shot, and antibiotics as prescribed. Monitor for allergic reactions.
Examples: Non-opisthoglyphous Erythrolamprus (formerly Liophis), possibly Spilotes sulphureus.
6 – Mild Opisthoglyphous Envenomation
Opisthoglyphous snake bite with mild symptoms like tingling and stinging.
Treatment: Observation for allergic reactions. Medical treatment usually not required unless symptoms progress.
Examples: Leptophis, Oxybelis, Rhinobothryum.
7 – Moderate Opisthoglyphous Envenomation
Bite causing noticeable symptoms like localized swelling (edema), pain, and numbness.
Treatment: Medical evaluation, pain management, and monitoring for severe reactions.
Examples: Erythrolamprus (sensu stricto), Leptodeira, Coniophanes, Helicops.
8 – Severe Opisthoglyphous Envenomation
Severe local effects such as hemorrhage, muscle destruction (myonecrosis), and extensive edema.
Treatment: Immediate medical care with possible antivenom, wound care, and systemic treatment as needed.
Examples: Phyllodryas, Chlorosoma, Conophis, Thamnodynastes, Dryophylax.
9 – Severe Solenoglyphous and Proteroglyphous Envenomation
Bite from vipers (Viperidae) or elapids (Micrurus, sea snakes) causing significant local and systemic symptoms.
Vipers (Viperidae, Crotalinae)
Local Symptoms: Swelling, bleeding, bruising, blisters (serous or blood-filled), necrosis, intense pain, compartment syndrome.
Systemic Symptoms: Internal bleeding (gums, nose, gastrointestinal tract), organ failure, hypotension, bradycardia, myoglobinuria, hematuria, and even paralysis.
Examples: Atropoides, Bothrops, Bothrocophias, Bothriechis, Cerrophidion, Crotalus, Lachesis, Porthidium, Metlapilcoatlus.
Coral Snakes (Elapidae: Micrurus) & Sea Snakes (Hydrophis platurus)
Local Symptoms: Mild to moderate pain and tingling.
Systemic Symptoms: Neurological impairment, cranial nerve paralysis (e.g., drooping eyelids, difficulty speaking/swallowing), generalized paralysis, respiratory failure due to muscle paralysis and airway obstruction, leading to asphyxiation.
Examples: Micrurus, Hydrophis.
Treatment: Immediate hospital care, antivenom administration, intensive care for respiratory or systemic failure.
10 – Life-Threatening Envenomation
Bites leading to almost certain death without immediate medical intervention.
Coral Snakes (Micrurus): Death can occur within four hours due to respiratory paralysis.
Vipers (Bothrops, Crotalus, Lachesis): Death from multisystem organ failure within 24 hours or less.
Treatment: Immediate antivenom administration and intensive medical support.
It is important to take in count how to differentiate the terminology: when it is said that a snake is venomous, that does not mean it must be dangerous, and vice versa. A snake being dangerous is not the same as being venomous. An opistoglyph snake of scale 6, 7 and 8, even many vipers and elapids of scales 9 and 10 do not show any aggression. They do not want to bite unless they are forced, so they should not be considered dangerous, but rather "ta take care of." You have to keep an eye on them, because their venom can potentially affect a person's health or even life if they bite. And on the other hand, there are very aggressive snakes on scale 1, 2, 3 and 4 that do not have venom, so they do not present a danger of death, but they do present the possibility of minor to serious injuries (depending on the size and depth of the wounds). An emperor boa with a bad temper can cause more danger than a bushmaster. The danger always disappears when any of these calm organisms are left alone.
Literature.
Ayerbe-González, S.: Serpientes, Accidentes y Soluciones. 1a Edición, 2021, 116 p. ISBN: 978-958-49-24-87-2 www.ayerbedocserpientes.com
Ayerbe-González, S.: Accidente Ofídico, Cap. XIX, pp. 4081-4134 en: Vargas-Uricoechea et al, Eds.: Texto de Medicina Interna, 2a Edición, 2021, 4335 p. Asociación Colombiana de Endocrinología y Diabetes, Dpto. de Medicina Interna, Universidad del Cauca. ISBN: 978-958-99814-9-8. Gamar Editores, Com. Ed. E.U.
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