Venomous animals, including insects, spiders, and snakes, can cause injury and death through injection of toxic venom. Bees and wasps are the most common cause of fatal insect envenomation, while black widow spider bites, though rarely lethal for adults, pose more risk for children. Snake venom contains various toxins that can induce local tissue damage as well as systemic effects like coagulopathy, shock, and multi-organ failure. Proper first aid like immobilization, compression, and antivenom administration are crucial for managing snake bites. Symptoms of envenomation depend on the type, amount, and potency of venom injected.
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Venomous animals
1. VENOMOUS ANIMALS
INTRODUCTION
Fatalities: insects 50%, snakes 30%, spiders 13%
Bees are the MCC of fatal venomous animal injuries
Black widow is the MCC of spider related death
Poisonous animal = animal contains toxin, may become toxic by eating
Venomous animal = animal has a specific gland for producing the toxic venom which is connected
to an apparatus for delivering the venom to another animal
Toxicity is highly variable even with the same kind of snake: depends on degree of envenomation
Many snake bites DO NOT result in envenomation (30-50%)
Toxicity: local pain, burning -------------> DIC, shock, ARDS, MSOF, death
Anaphylactoid reaction can also occur
SNAKES
INTRODUCTION
Five families of venomous snakes
Crotalidae (pit vipers): rattlesnakes, water moccasins, copper heads
Colubridae: bird snake, boomslang
Hydrophidae: sea snakes
Elapidae: cobras, coral snakes, etc
Viperidae (true vipers): Russell’s viper, puff adder, etc
Identifiication
Only experts should handle snakes; dead snakes can still envenomate
Pit Vipers: pit between eye and nostril on both sides of head which is a heat-
sensitive organ to locate warm-blooded prey; presence of the pit is 100% accurate;
other features include elliptic pupil, triangular shaped head, and presence of fangs
but these are less uniform
Toxins
Toxins have variable toxicity
Hosts have variable responses to the same toxin
Venoms are neurotoxic and hematotoxic
Can be classified s protein and non-protein components
Protein components: enzymes and polypeptides
Enzymes: coagulation, anticoagulation, cell lysis, hemorrhage, hemolysis,
destruction of nucleic acids
Polypeptides: neurotoxins, cardiotoxins, etc
Phospholipase A: enzyme that inhibits the electron transport chain at cytochrome
C, inhibits neurve axons,, leads to destruction of Ach at nerve terminals, causes
hemolysis: this enzyme has been identified in the venom of all venomous snakes
Venom Delivery
Two venom glands, hollow or grooved fangs, ducts connecting the fangs to the
venom gland which are evolved from salivary glands
Venom glands have nerve supply to allow the control of the gland
The snake can control the amount of venom that is injected
2. RATTLESNAKE BITES
LOCAL TOXICITY
Immediate burning, pain, erythema, edema
Petechiae, ecchymosis, hemorrhagic bullae, necrosis
Severity of local symptoms/signs related to amount of venom injected
Compartment syndromes from massive edema has occurred
Local infections are a later concern
Tetanus, osteomyelitis, cellulitis, gangrene can occur
SYSTEMIC TOXICITY
Systemic symptoms: weakness, nausea, fever, vomiting, sweating, metallic taste in mouth,
fasiculations, hypotension, SOB, chest pain
Death results form disruption of coagulation system and increased capillary lead
ARDS, shock, DIC, ARF, hepatic failure, MSOF
PREHOSPITAL CARE
Remove patient from environment
Calm the patient and immobilize the limb: movement increases the spread of venom
Place a constricting band above the bite: tight enough to stop venous flow only
Immobilization and Compression technique: wrap the bitten extremity in an elastic
bandage or place in an air splint ----> technique used in Australia
Monash method: thick pad and bandage over the bite wound and extremity ---->
another technique used in Australia
Suction the wound if the bite occurred < 15 minutes ago
Apply ice bag wrapped in a towel: decreases pain but does not decrease spread of venom (do NOT
immerse in ice water or pack the extremity in ice b/c of increased tissue destruction)
Identify the snake and bring to hospital if possible
NPO, NO etoh
Cardiac monitor, establish iv access
ED ASSESSMENT
Important historical features
Time since bite
Circumstances around bite
First aid provided
Location of bite(s)
Local and systemic symptoms
PMHx, tetanus, meds
ALLERGY: ? horses, ? previous serum injections, hay fever, urticaria (all increase
the risk of reaction to antivenin
Important physical exam features
Look for signs of envenomation: edema, petechiae, ecchymosis, bullae
Check distal neurovasc supply
Check for signs of compartment syndrome
General exam
3. ED MANAGEMENT
General
First aid maneuvers if not done in field and still applicable
ECG monitoring, iv access
Labs: cbc, lytes, creat, coags, liver enzymes, fibrinogen, crossmatch for 2 units, CK
and urine for myogloin
Tetanus, Ancef prophylaxis, Fasciotomies prn
Grading of Envenomation
Grade 0
- No evidence of envenomation
- Fang wound may be present
- Minimal pain
- Minimal edema (< 2cm)
- Minimal erythema
- No systemic symptoms within 12hrs
- No antivenom neccessary
Grade I
- No envenomation
- Fang wounds preent
- Moderate pain or throbbing
- Edema/erythema 1-10 cm around bite
- No systemic symptoms w/i 12hrs
- No lab changes
- No antivenom necessary
Grade II
- Moderate envenomation
- More severe pain
- Edema, erythema spreading toward the trunk
- Petechieae and ecchymosis limited to the area of bite
- Systemic symptoms of N/V and mild temp
- 5 vials of antivenom
Grade III
- Severe envenomation
- May initially look to be grade I or II but progresses rapidly within
the first 12 hours
- Edema spreads to the trunk
- Generarlized petechieae and echhymosis
- Tachycardia, hypotension, hypothermia
- 10 vials of antivenom
Grade IV
- Very severe envenomation
- Sudden, severe pain with rapid progression of swelling,
ecchymoses, bleb formation, and necrosis
- Systemic symptoms within 15 min of bite: weakness, N/V, vertigo,
numbness of face, fasiculations, cramping, pallor, sweating,
tachycardia, hypotension, seizures, decreasing LOC
- 15 vials of antivenom
4. Skin Testing
Must be done regardless of history
Negative skin test decreases chance of reaction but they are still possible
Skin test may ppt bad reaction
0.02 ml o 1:1000 solution
Positive reactions occur within 5-30min: edema around the wheal
Dosing and precautions
ANTIVENOM is the only proven therapy
Be ready for anaphylaxis
Children’s dose is relatively more than adults
Pregnancy is not a contraindication
Do not administer near the bite
Repeat doses q1-2 hours prn
5-15 vials iv, 1:10 dilution
Gravol and steroids for serum sickness
Crofab
Fewer allergic reactions
Developed from sheep
Disposition
Sick: admit to ICU
Asymptomatic: observe 4-6hrs
Local symptoms: observe 12 hours for progression, d/c if no progression
VENOMOUS ARTHROPODS
INTRODUCTION
Arthropods = animals with segmented bodies and jointed appendages
Two classes of interest: Insecta and Arachnida
More deaths than snakes
Most deaths from allergic response to venom rather than venom itself
Three mechanisms: stinging, bitting, secreting venom through pores or hairs
HYMENOPTERA
Bees, ants, wasps, hornets, yellow jackets, ants
Most sting but some bite and sting
Bee: ovipositors protrude from adbomen with barbed stinging apparatus; bee dies with sting
Wasp: unbarbed stinger, stings without hurting the wasp
Phospholipase A and hyaluronidase are the most common enzymes
Many antigens exist that account for the induction of allergy and anaphylaxis
Sting to the lip, mouth, or tongue has high risk of airway obstruction
Honeybee venom causes much more histamine release than other hymenoptera venom
There is little antigenic overlap b/w species thus variability in reaction to stings
Local effects: immediate pain, swelling, redness, ithcing
Allergic symptoms: SOB, urticaria, wheezing, throat swelling, cough, resp arrrest
Killer Bees
Aggressive bee from Africa and Brazil
Attach humans or cattle in clouds of bees
5. Fire Ants
Small, light - reddish born to dark brown ant
Venom is unique in that it is 90% alkaloid
Toxic venoum
Sting produced by a bite
Sterile pustule develops at site of bite
Local symptoms common
Allergic reaction in 10%
Managment
Ice bag to sting to relieve pain
Anaphylaxis: iv fluids, benadryl, epi, steroids, ventolin, atrovent, nebulized epi,
ranitidine
NO specific antivenom for hymenoptera stings
Benadryl q6hr X 24hrs
Uritcarial rash only: subQ epi + gravol + ranitidine and observe to r/o progression
Allergic reactions: prescribe EPIPEN and refer to allergist for testing and/or
desensitization
BLACK WIDOW SPIDERS (Latrodectus mactans)
General
Found throughout southern Canada
Female is twice the size of the male
Only the female is venomous
Glossy black, bright - red marking on abdomen (“black and red widow”)
Red marking may look like an hour glass or only two dots
Spider is about 3cm long
Found in protected spaces: under rocks, woodpiles, etc
Female can be aggressive when guarding eggs
Adults: symptomatic for days, usually not lethal
Children: higher risk of death!
Complex venom with protein and nonprotein compounds
Venom normally used to paralyze prey and liquefy tissues for digestion
NEUROTOXIN
- is the most toxic component of the venom
- more toxic than pit viper venom
- destabilizes neuronal membranes by opening ion channels, causing
depletion of Ach from presynaptic nerve terminals and increasing
the frequency of spontaneous end plate potentials at the NMJ
- MASSIVE release of Ach and norepinephrine
Clinical Features
Initial pinprick sensation followed by minimal swelling, edema, redness
Two small fang marks may be visible
The bit may not initially be felt
15-60min: dull cramping pain in the area of the bite that spreads over the body
Hypertonic Myopathic Syndrome
- Muscle cramps typically present 13-60 min after bite
- Initially muscle cramps occur at the site of the bite
6. - Progresses to the chest with UE bites and abdomen with LE bites
- Abdomen may become rigid: may mimic an acute abdomen in
rigidity but usually is not that tender
Faces Latrodectismia
- Sweating, contorted, grimaced face associated with blepharitis,
conjunctivits, rhinitis, cheilitis, trismus of the masseters
General
- N/V, headache, SOB, pruritis, sweating, weakness, restless,
difficulty speaking, ptosis, dizziness, diffuse cramping
- Hypertension
- ECG changes SIMILAR TO DIG TOXICITY
Life-Threatening Complications
- Hypertensive crisis: 30% (due to norepi release)
- Respiratory arrest secondary to respiratory muscle paralysis
- Seizures secondary to neuronal activation
Management
Ice pack to area for pain relief
Bring spider if possible!
Clean wound with soap and water
Administer tetanus booster prn
Opiods and benzodiazepines for pain control
Asymptomatic and NOT a black widow: d/c home, RTED instructions
Nitroprusside for hypertensive crisis
Symptomatic: admit to hospital
Draw cbc, lytes, coages, calcium
Calcium Gluconate
- 10 ml of 10% solution iv over 20 min
- Repeat dose prn q2-4 hrs
- Cardiac monitoring, follow Ca+ levels
- Traditionally used to decrease cramping
- Mechanism of action unknown to decrease cramping
- Some evidence that it makes things WORSE
- NOT recommended by Goldfranks
Lorazepam/Morphine
- Treatment of choice for pain control from muscle spasms
Lacrodectus Antivenom
- <12yo or > 65yo or pregnant are at highest risk of mortality and
may benefit from antivenom
- Can be used in other ages depending on systemic toxicity
- Any patient with severe envenomation should be considered
- One vial diluted n 50 ml of normal saline over 15 min
- TEST for sensitivity as per snake venom testing
- Venom is derived inn horses
7. BLACK WIDOW BOX
Found in Southern Canada
Black spider with Red abdomen
Neurotoxin: Ach and NE release
Severe muscle cramping
Resp arrest, seizures
Hypertensive crisis
Local Mx: clean wound, td
Mx: opiods and bzd for pain control
CALCIUM CONTROVERSIAL
Antivenom for young, old, pregnant, sick
BROWN-RECLUSE SPIDER
General
Several deaths have occured
Many different species
Identifying feature is the violin-shaped darker area found on the cephalothorax
No aggressive, mostly in southern US
Sphingomyelinase D is the primary component of the venom
Clinical Features
Local: pain, swelling etc w/i a few hours, bleb forms in the center of an
erythematous ring -------> resembles a BULL’S EYE
The BLEB darkens as tissue necrosis occurs and continues to spread to skin and
subcutaneous fat
Systemic
Management
Wash wound
Tetanus prophylaxis
Do NOT excise the lesion
Monitor vitals, cardiac monitor
Send labs, lytes, coags
Observe for envenomation: d/c after 6hrs if well
Dapsone
- 50-200 mg/day
- Helpful in preventing the local effects of the venom
- Risk of methemoglobinemia and hemolysis with G6PD def
Other
- HBOT to decrease tissue toxicity has been used
- Dialysis has been needed for ARF
- Antivenom not readily available
SCORPIONS
Toxicity varies greatly between species
Less dangersous produce more local symptoms
More dangerous produce more sytemic symptoms
Hemolytic enzymes and proteins in venom
Severe immediate pain at site of sting
8. Systemic symptoms: SOB, CP, sweating, muscle spasms, syncope, N/V, HTN
Cardiac arrythmias or respiratory arrest
Children are at higher risk of death
Management
Ice bag to area
Transport to ED
ANTIVENOM for all severe envenomations
Benzos for myoclonus and muscle spasms
OTHER ARTHROPODS
Ticks: wood tick and dog ticks can also have a toxin that leads to ascending paralysis = TICK
PARALYSIS
Beetles and caterpillares: irritating substances which can cause local symptoms, was area with soap
and wate, ice to area