Lesson Overview
Learning Objectives
- Assess and manage animal bite wounds with proper wound care priorities
- Recognize and manage venomous snakebites including pit viper and coral snake envenomation
- Treat hymenoptera stings, spider bites, and identify neurotoxic vs. cytotoxic presentations
- Properly remove ticks and recognize tick-borne illness presentations
- Manage marine envenomation including jellyfish, stingray, and sea urchin injuries
Why This Lesson Matters
Most bites are minor. The ones that aren't—a rattlesnake, an unnoticed bat bite—punish guesswork. This lesson is about knowing which is which.
Envenomation in the Wilderness
North America's list of animals that can genuinely hurt you is short. Don't handle them, and most of this lesson stays theoretical. Envenomation occurs when venom is injected into tissue, and the effects vary dramatically based on the species. Hemotoxic venoms (pit vipers) cause local tissue destruction and coagulation abnormalities, while neurotoxic venoms (coral snakes, some spiders) affect the nervous system. Your ability to identify the offending species and recognize the type of venom effect will guide your treatment decisions.
Animal Bite Assessment & Management
Wound Assessment Priorities
When evaluating an animal bite, gather information systematically:
- Depth: Does the bite penetrate the dermis? Are deeper structures (tendon, bone, vessel) involved?
- Mechanism: Was it a crush injury, puncture, tear, or laceration? This affects infection and healing risk.
- Contamination: All animal bites are contaminated. Note the animal species and whether it was provoked or unprovoked.
- Neurovascular Status: Check distal pulses, capillary refill, sensation, and motor function. Serious bites may require urgent vascular assessment.
- Time Elapsed: How long since the bite occurred? This affects infection risk and wound closure decisions.
Wound Care Principles
Aggressive irrigation is the most important intervention for animal bite wounds. Use clean water or saline and irrigate copiously—aim for at least 1-2 liters for a significant bite. Irrigation removes bacteria and debris that would otherwise establish infection. Do NOT close bite wounds with sutures or adhesive strips in the wilderness setting. Bite wounds should be left open to drain and should heal by secondary intention. Closure increases infection risk by sealing bacteria inside the wound.
Dogs & Cats
Most common bite sources. Cat bites are HIGH infection risk: their needle-like teeth drive bacteria deep into tissue, and infection develops in roughly one in three cat bites—they warrant early medical evaluation even when the wound looks small. Dog bites carry lower infection risk but still need thorough irrigation. Current pet vaccination status is important for rabies assessment.
Wild Mammals (Bear, Mountain Lion)
Crush and laceration injuries with severe tissue damage. Often result in major hemorrhage and deep tissue trauma. Treat as major trauma until proven otherwise.
Rodents & Rabbits
Small puncture wounds with low rabies risk. Clean with irrigation. Infection risk is low to moderate. Rabies from rodents and rabbits is close to unheard of—low risk, not zero.
Human Bites
High infection risk due to oral flora. More contaminated than many animal bites. Treat aggressively with irrigation and evacuation. Always irrigate thoroughly and do NOT close the wound.
Rabies Assessment & Management
Once clinical symptoms appear, rabies is virtually always fatal. However, post-exposure prophylaxis (PEP) is highly effective if given before symptoms develop.
First step in the field: Immediately wash any bite or scratch from a potentially rabid animal thoroughly with soap and water for several minutes. Vigorous wound washing significantly reduces the risk of rabies transmission and is a specific, proven risk-reduction step—do it before anything else.
| Risk Category | Animal Examples |
|---|---|
| HIGH RISK | Bats, raccoons, foxes, skunks, coyotes, unvaccinated dogs and cats |
| LOW RISK | Rodents (squirrels, rats, mice), lagomorphs (rabbits, hares) |
Post-Exposure Prophylaxis (PEP)
PEP consists of a series of rabies vaccines (modern versions use 4 doses over 14 days) and, for high-risk exposures, rabies immunoglobulin. PEP must be started as soon as possible after exposure—ideally within days. Importantly, there is NO deadline after which PEP stops being indicated: a person who presents late, even weeks after exposure, should still receive PEP as long as they have not developed symptoms. If the patient is bitten in the wilderness, they must be evacuated urgently for medical evaluation and PEP initiation. There is no field alternative to hospital-based PEP.
Special Consideration: Bat Exposure
Bats have very small teeth and can inflict bites that go unnoticed. If a bat is found in the room with a person who was sleeping, and the person cannot rule out direct contact, standard public health guidance recommends assuming potential exposure and proceeding with rabies PEP evaluation. Do not dismiss bat exposures as insignificant.
Reporting Requirements
All significant animal bites must be reported to local public health authorities. This applies especially to bites from wild animals or unvaccinated domestic animals. Public health officials will assess rabies risk and coordinate testing of the animal if possible.
Bear and Mountain Lion Attacks
These are severe trauma situations. Your first priority is to extricate the victim safely—ensure the animal is no longer a threat. Then treat as major trauma with emphasis on hemorrhage control and shock management. These bites often involve crush injuries, lacerations to multiple body areas, and potential vascular injuries. Transport urgently.
Venomous Snakebite Management
North American Venomous Snakes
| Species | Characteristics | Venom Type & Effects |
|---|---|---|
| Pit Vipers: Rattlesnakes, Copperheads, Cottonmouths | Heat-sensing pits between eyes and nostrils; triangular head; rattles (rattlesnakes) | Hemotoxic: Local tissue destruction, progressive swelling, coagulation abnormalities, bleeding |
| Coral Snake | Colorful bands (red, yellow, black); small mouth; no rattles; docile | Neurotoxic: Delayed neurologic symptoms; may have minimal local signs initially |
Coral Snake Identification
This rhyme identifies the coral snake: the red and yellow bands touch each other. Non-venomous mimics (like the kingsnake) have red and black bands touching.
Signs of Envenomation
Local Signs (Pit Viper)
- Fang marks (may be 1-4 marks depending on strike angle)
- Immediate pain at bite site
- Progressive swelling within minutes to hours
- Mark swelling boundary with a pen and note the time every 15 minutes to objectively assess progression
Systemic Signs (Pit Viper)
- Nausea and vomiting
- Weakness and fatigue
- Numbness and paresthesias (often perioral)
- Bleeding or bruising distant from bite (coagulopathy)
- Hypotension, tachycardia, shock
Systemic Signs (Coral Snake)
- Delayed onset (may be hours)
- Ptosis (drooping eyelids)
- Diplopia (double vision)
- Respiratory paralysis (most dangerous)
- Can occur with minimal local symptoms initially
Dry Bite
Approximately 20% of venomous snakebites result in minimal or no venom injection ("dry bite"). However, you cannot determine this in the field. Every snakebite evacuates now. The 8–12-hour observation happens at (or on the way to) medical care—a dry bite is a diagnosis made in hindsight, not at the trailhead. Document serial marking of swelling to support this assessment.
Correct Field Management for Pit Viper Bites
- Calm the patient and minimize movement: Movement increases venom spread. Keep the patient at rest.
- Remove jewelry and tight clothing: Swelling is inevitable. Remove constrictive items before swelling makes removal difficult.
- Immobilize the extremity at heart level: Splint or sling to prevent movement. Position at same level as heart (not elevated, as gravity may increase local swelling).
- Mark swelling with pen and time every 15 minutes: Objective documentation of progression guides treatment decisions.
- Urgent evacuation: Antivenom is the only definitive treatment and must be administered in a hospital. Evacuate immediately.
- Nothing by mouth: Nil per os status in case surgical intervention is needed.
- Monitor vital signs: Reassess XABCDE every 5 minutes for systemic signs.
- Cut an X over fang marks and suck—ineffective and causes additional tissue damage and infection
- Use commercial suction or venom-extractor devices (e.g., Sawyer Extractor)—they do not remove venom and can worsen tissue damage
- Apply a tourniquet—can cause more tissue damage than the venom itself
- Apply ice—causes frostbite and worsens tissue damage
- Use electric shock—no evidence of benefit, and causes burns
- Apply constriction bands or compression wraps to any snakebite—they can increase local tissue damage and compartment syndrome risk
Coral Snake Bites: Same Field Management
At this course's level, treat EVERY suspected snakebite—pit viper or coral snake—the same way: remove jewelry and tight clothing, splint and immobilize the bitten limb at heart level, keep the patient calm and at rest, and evacuate urgently. Do NOT apply constriction bands or compression wraps of any kind. Note that a "constriction band" is not the same thing as pressure immobilization bandaging.
PIB is a specialized elastic-wrap technique used by trained providers for some elapid snakebites (mainly outside North America). Its use for North American coral snakes is controversial, with limited supporting evidence. It is NOT a skill taught in this course—do not attempt it.
Antivenom
Antivenom is administered only in the hospital setting. Modern pit viper antivenom (CroFab, Anavip) is highly effective if given early. Coral snake antivenom (less commonly used) requires careful administration due to potential adverse reactions. All snakebite patients bitten by a potentially venomous species should be evacuated for hospital evaluation and possible antivenom administration, regardless of initial symptoms.
Insect Stings & Spider Bites
Hymenoptera Stings: Bees, Wasps, Yellow Jackets, Hornets, Fire Ants
Bee Stingers
Honeybee stingers are barbed and remain embedded in the skin, continuing to inject venom even after the insect has flown away. Get the stinger out fast—flick it, scrape it, pull it, whatever's quickest. Speed matters; technique doesn't. The venom sac keeps pumping while you hunt for a credit card.
Local Reaction
Pain, redness, and swelling at the sting site. Treat with ice, NSAIDs, and topical antihistamines or corticosteroid cream.
Large Local Reaction
Swelling extending far from the sting site, sometimes reaching joints (e.g., massive arm swelling from a sting on the hand). This is not anaphylaxis—it is a localized hypersensitivity reaction. Treat with oral antihistamines and seek medical evaluation for severe or spreading swelling. Monitor for anaphylaxis (see Lesson 10).
Fire Ants
Fire ant stings produce sterile pustules. Do NOT pop them, as this introduces infection. Leave pustules intact. They will typically resolve without complications if left alone.
Black Widow Spider Envenomation
Identification
Shiny black spider with a distinctive red hourglass marking on the abdomen. Body size approximately pea-sized.
Venom & Effects
Black widow venom is neurotoxic (alpha-latrotoxin), targeting presynaptic nerve terminals. This causes uncontrolled acetylcholine release, leading to characteristic symptoms.
Signs & Symptoms
- Localized bite pain (often minimal initially)
- Severe painful muscle cramps spreading from bite site within 30 minutes to hours
- Characteristic: rigid abdomen (abdominal muscles involved), but cramping can affect any muscle group
- Diaphoresis (sweating), hypertension, tachycardia
- Nausea and vomiting
- Pain in thighs and chest
- Potentially respiratory compromise if respiratory muscles are involved
Field Management
Pain management with NSAIDs and ice. Evacuation is recommended as antivenom (black widow antivenom) is available in hospitals and highly effective. Monitor for respiratory distress.
Brown Recluse Spider Envenomation
Identification
Brown spider with a distinctive violin-shaped marking on the cephalothorax. Has 6 eyes arranged in pairs (most spiders have 8).
Geography matters: Brown recluses live only in the south-central and midwestern United States. Outside that range, most suspected "recluse bites" are actually something else—commonly skin infections such as MRSA, or other conditions. Even within recluse territory, confirmed severe necrosis is uncommon.
Venom & Effects
Brown recluse venom is cytotoxic, causing tissue necrosis. This creates the characteristic "sinking lesion" or "volcano lesion" as tissue dies.
Signs & Symptoms
- Initially painless bite (may be unnoticed)
- 2-8 hours: pain appears, redness develops, blister forms
- 24-72 hours: blue-black necrotic center forms, lesion "sinks" as tissue dies
- Systemic symptoms rare but possible: fever, hemolysis (extremely rare)
- Lesion can be disfiguring
Field Management
Clean the wound, apply ice, mark the lesion boundary with a pen to track progression. Evacuate for medical evaluation. There is no antivenom available in the United States for brown recluse bite; treatment is supportive and focused on wound management and infection prevention.
Black Widow vs. Brown Recluse Comparison
| Feature | Black Widow | Brown Recluse |
|---|---|---|
| Venom Type | Neurotoxic | Cytotoxic |
| Bite Pain | Often minimal | Initially painless |
| Primary Effect | Muscle cramps, systemic symptoms | Tissue necrosis at bite site |
| Onset | Minutes to hours | Hours to days |
| Antivenom | Available | Not available in US |
Tick Removal & Tick-Borne Illness
Proper Tick Removal
Use fine-tipped tweezers to grasp the tick as close to the skin as possible. Pull steadily upward. Do NOT twist, crush, or use petroleum jelly, alcohol, or heat (burning). These methods stress the tick and may cause it to inject more pathogen into the host.
After Removal
- Clean the bite site with soap and water
- Wash hands
- Seal the tick in a plastic bag if possible (for potential testing later)
- Do NOT crush the tick with bare hands
Disease Transmission Timeline
Lyme disease transmission usually requires the tick to be attached for 36 hours or more, and the risk rises steeply after 48 hours. Some other tick-borne diseases can transmit faster. Either way, the message is the same: prompt removal—the sooner the better—significantly reduces disease transmission risk.
Tick-Borne Diseases
| Disease | Tick Vector | Key Clinical Features |
|---|---|---|
| Lyme Disease | Deer tick (Ixodes) | Bull's-eye rash (erythema migrans), flu-like symptoms, arthritis, CNS involvement possible |
| Rocky Mountain Spotted Fever | Dog tick, wood tick | Rash starts wrists/ankles and spreads centrally, fever, headache, can be fatal if untreated |
| Ehrlichiosis | Lone Star tick | Fever, headache, myalgia, rash (sometimes), thrombocytopenia |
| Anaplasmosis | Black-legged (deer) tick | Similar to Ehrlichiosis: fever, headache, myalgia, lab abnormalities |
Marine Envenomation
Jellyfish Stings
Jellyfish nematocysts (stinging cells) fire when triggered, injecting venom. Treat by:
- Rinse with salt water (NOT fresh water, which can trigger nematocysts to fire)
- Do NOT use urine—it does not help and can trigger more nematocysts to fire
- Remove visible tentacles with tweezers (not bare hands)
- Vinegar helps deactivate box jellyfish stings, but it can WORSEN the stings of some other species—use it only when you know a box jellyfish is responsible
- When unsure of the species: rinse with seawater, remove tentacles with tweezers, then use hot water immersion (45°C / 113°F) for 20-45 minutes for pain
Stingray Injury
Stingray spines create a puncture wound and inject venom, typically into the foot or ankle. Pain is severe.
- Immerse affected limb in hot water (45°C / 113°F) for 30-90 minutes—this is more important than removing the spine initially
- Irrigate the wound
- Remove the barb if accessible without causing further injury
- Evacuate for wound management and evaluation for deep injury
Sea Urchin Spines
Sea urchin spines embed in the skin and can break off. Spines can be toxic and irritating.
- Remove accessible spines with tweezers
- Apply hot water immersion (45°C / 113°F)
- Evacuate if multiple spines are embedded or if there is risk of infection
Scenario-Based Learning
Setting: A hiker 5 miles from the trailhead reports being bitten on the ankle by what they believe was a rattlesnake. You arrive 10 minutes after the bite. The ankle is swollen and bruised, with two fang marks visible. The patient is anxious and nauseated.
Questions to Consider:
- What are your first assessment priorities?
- What field interventions will you perform?
- What are you NOT going to do?
- What is your evacuation plan?
- Primary assessment: Ensure the snake is not still present (scene safety). Perform XABCDE. Is there hemodynamic instability, respiratory distress, or signs of systemic envenomation (nausea, vomiting, hypotension)?
- Secondary assessment: Note the time of bite. Examine the bite site: two fang marks suggests pit viper (could be dry bite, but assume envenomation). Document baseline swelling with a pen and note the time.
- Field interventions: Remove patient's boot and sock carefully. Remove any jewelry (rings). Immobilize the extremity. Position the ankle at approximately heart level (not elevated). NPO status.
- What NOT to do: Do NOT cut and suck. Do NOT apply a tourniquet or constriction band. Do NOT apply ice. Do NOT attempt to kill or capture the snake.
- Evacuation: 5 miles from trailhead at 30 minutes per mile (slow pace with immobilized patient) = approximately 2.5 hours walking. Urgent evacuation is needed. If you have a satellite communicator, activate it immediately for rescue dispatch. Call for helicopter evacuation if available and weather permits. Do NOT delay evacuation.
- Monitoring: Check vital signs every 5 minutes. Re-mark swelling every 15 minutes. Watch for signs of systemic envenomation. Keep patient at rest. Reassure—anxiety increases sympathetic response which can worsen symptoms.
- Definitive care: All pit viper bites require hospital evaluation for possible antivenom, regardless of symptoms. Even dry bites warrant observation.
Setting: You are camp staff. In the morning, a cabin of 8 campers (ages 12-15) reports that they woke up and found a bat in the cabin with them overnight. No one reports being bitten, but several were sleeping soundly. The bat has flown away.
Questions to Consider:
- Is this a rabies exposure situation?
- What do you need to do?
- YES—this IS a rabies exposure situation. Bats have very small teeth and can inflict bites that go unnoticed during sleep. Standard public health guidance states that if a bat is found in a room with a sleeping person and direct contact cannot be ruled out, assume potential exposure.
- Do NOT dismiss this situation. Do NOT assume "no visible bite means no exposure."
- Immediate actions: Call the local health department and medical director immediately. All 8 campers require evaluation for post-exposure prophylaxis (PEP).
- Notification: Notify parents/guardians of each camper immediately. Document the time the bat was discovered, which campers were in the cabin, and any symptoms noted.
- Bat handling: Do NOT attempt to catch or kill the bat (additional exposure risk). If the bat is already contained, contact public health authorities for safe handling and possible testing.
- Next steps: Arrange urgent medical evaluation for all campers. PEP must be started as soon as possible after exposure. The vaccines used today are much safer than those used historically.
Knowledge Check
10 questions. Pick an answer to get immediate feedback. Answer order is shuffled each attempt, and your best score is saved on this device.
Lesson Summary
Key Takeaways
- All animal bite wounds should be irrigated aggressively and left open to drain—do NOT close them in the wilderness.
- Rabies exposure via bats requires PEP even without a visible bite; assume exposure if a bat was in the room with a sleeping person.
- Pit viper bites: immobilize, mark swelling, do NOT use tourniquet, ice, or constriction. Evacuate for antivenom.
- Coral snake bites are neurotoxic and may have minimal local signs but can cause respiratory failure. Manage like any snakebite: immobilize at heart level, no bands or wraps, evacuate urgently.
- Get bee stingers out fast—speed matters more than method.
- Black widow venom causes muscle cramps and systemic symptoms; brown recluse causes local tissue necrosis.
- Remove ticks promptly with steady upward traction using fine tweezers; Lyme transmission usually requires 36+ hours of attachment, but some diseases transmit faster—the sooner the removal, the lower the risk.
- Marine envenomation: salt water for jellyfish, hot water immersion for stingray and sea urchin.
Glossary of Terms
- Envenomation
- The injection of venom into tissue by an animal (snake, spider, insect).
- Hemotoxin
- Venom that affects blood cells and the circulatory system, causing local tissue destruction and coagulation abnormalities. Characteristic of pit vipers.
- Neurotoxin
- Venom that affects the nervous system. Characteristic of coral snakes and some spiders; can cause paralysis.
- Antivenom
- Antibodies against a specific venom, administered intravenously to counteract envenomation. Used for pit vipers, black widows, and other serious bites.
- Rabies
- A viral infection transmitted via saliva, nearly always fatal once clinical symptoms appear. Preventable with post-exposure prophylaxis.
- Post-Exposure Prophylaxis (PEP)
- Series of vaccines and immunoglobulin given after potential rabies exposure to prevent infection.
- Dry Bite
- A venomous snakebite in which little or no venom is injected. Occurs in approximately 20% of pit viper bites. Diagnosed in hindsight, after 8–12 hours of observation at medical care.
- Black Widow Spider
- Venomous spider with distinctive red hourglass marking; venom is neurotoxic and causes muscle cramps and systemic symptoms.
- Brown Recluse Spider
- Venomous spider with violin-shaped marking; venom is cytotoxic and causes local tissue necrosis in a "sinking lesion" pattern.
- Tick-Borne Illness
- Infections transmitted by infected ticks, including Lyme disease, Rocky Mountain Spotted Fever, Ehrlichiosis, and Anaplasmosis.
- Necrotizing
- Causing tissue death; characteristic of brown recluse venom effect.
- Pressure Immobilization
- Specialized elastic-bandage technique used by trained providers for some elapid snakebites to slow lymphatic spread of venom. Controversial with limited evidence for North American coral snakes; referenced here for awareness only—not a skill taught in this course.
Wilderness Medicine: Beyond First Aid (6th ed.) - Tilton & Tilton
CDC Rabies Information: cdc.gov/rabies
UpToDate: Snakebite, Tick Removal, Marine Envenomation