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ARTHROPOD BITES AND STINGS. Chrisnel Jean, D.O March 9, 2006 EM Lecture Session. Hymenoptera: Most important venomous insect known to humans More fatalities result from stings by these insects. Three major subgroups: Apidae  includes honeybee and bumblebee

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arthropod bites and stings


Chrisnel Jean, D.O

March 9, 2006

EM Lecture Session

hymenoptera wasps bees and ants

Most important venomous insect known to humans

More fatalities result from stings by these insects.

Three major subgroups:

Apidae includes honeybee and bumblebee

Vespidae includes yellow jackets, hornets and wasps

Formicidae  ants

Most of all allergic reaction reported yearly occur from vespid stings.

Apids are usually docile, stinging only when provoked.

Female bee is capable of stinging only once. (Male bees have no stinger).

Vespidhave ability to perform multiple stings.

Hymenoptera (WASPS, BEES, AND ANTS)
africanized honeybees
Africanized honeybees
  • Known as killer bees
  • Now found in Texas, Arizona, California, and most of the temperate southeastern and southwestern states.
  • Attack from these bees  massive stinging resulting in multisystem damage and death from severe venom toxicity.
hymenoptera venom
Hymenoptera Venom
  • Contain several components.
  • Histamine is only a minor component within the venom.
  • 50% of the venom consist of Melittin.
  • Melittin is a known membrane-active polpeptide that can cause degranulation of basophils and mast cells.
  • Yellow jackets venom is perhaps the most potent sensitizer.
hymenoptera venom local reaction toxic reaction
Urticarial lesion contiguous with the sting site.

Severe local reaction may involve one or more neighboring joints.

If the sting involve the mouth or throat, it can produce airway obstruction.

Multiple stings (Africanized bees) can lead to systemic toxic reaction.

Symptoms may resemble anaphylaxis, but these pts can also develop N/V/D.

They may also have HA, fever, drowsiness, involuntary muscle spasms, edema without urticaria, and convulsions.

Complication Renal / Hepatic failure, DIC, and Death

Hymenoptera Venom: Local Reaction Toxic Reaction
hymenoptera venom anaphylactic reaction
Hymenoptera Venom: Anaphylactic Reaction
  • Can occur from a single sting or multiple stings.
  • May range from mild to fatal and death within minutes.
  • There is no correlation between the systemic reaction and the number of stings.
hymenoptera venom delayed reaction
Hymenoptera Venom: Delayed Reaction
  • Delayed reaction appearing 5 – 14 days after the sting consists of serum sickness-like signs and symptoms.
      • Pts can develop fever, malaise, HA, urticaria, lymphadenopathy, and polyarthritis.
  • This reaction is believed to be immune complex-mediated.
hymenoptera venom treatment
Immediate removal of the bee stinger from the wound, is the important principle rather than the method of removal.

Wash the sting site with soap and water to decrease risk of infection.

Intermittently apply ice to the site to limit local reaction and delay absorption of venom.

Oral antihistamines and analgesic may limit discomfort, pruritis, and decrease local reaction.

If pts develop symptoms of anaphylaxis then most important agent to give is Epinepherine.

Epinepherine 0.3 to 0.5mg (0.3 to 0.5 mL of 1:1000 conc.) in adults and 0.01 mg/kg in children (never more than 0.3 mg) given IM

Hymenoptera Venom: Treatment
hymenoptera venom treatment9
Hymenoptera Venom: Treatment
  • Other treatment should include:
    • Diphenhydramine 25 to 50 mg IV, IM or PO
    • H2-receptor antagonists (ranitidine 50 mg IV)
    • Methylprednisolone 125 mg
    • Use Beta agonist nebulization if pt has evidence of bronchospasm
    • IVF, oxygen, cardiac monitor, pulse ox.
    • Persistent hypotension after multiple IVF bolus may require Dopamine or Epinepherine drip
hymenoptera venom disposition
Hymenoptera Venom: Disposition
  • Pts who develop severe systemic reactions should be admitted monitored for potential cardiac, bleeding, renal or neurologic complications.
  • Skin tests and RASTs (radioallergosorbent test) are not reliable in determining which patients are at risk in developing future systemic reactions.
hymenoptera venom disposition11
Hymenoptera Venom: Disposition
  • Every patient who has had a systemic reaction should be provided with an insect sting kit containing premeasured epinepherine and be carefully instructed in its use. The physician should stress that the patient must inject the epinepherine at the first sign of a systemic reaction.
ants formicidae
Ants (Formicidae)
  • 5 known species of fire ants (Solenopsis)
    • (S. aurea, S. geminata, S. xyloni, S. invicta, and S. richteri)
    • Fire ants swarm when provoked and they may attack in numbers.
    • Fire ants sting simultaneously in response to an alarm pheromone released

A Solenopsis xyloni major

worker surrounded by minor workers

ants formicidae13
Fire ants sting result in a papule that becomes a sterile pustule in 6 to 24 hrs.

Pustule can lead to localized necrosis  scarring  secondary infection.

Systemic reaction (urticaria / angioedema) can also occur.

Treatment includes:

local wound care.

Usual treatment for anaphylaxis should be initiated if there is evidence of systemic reaction.

Ants (Formicidae)
spiders araneae
Spiders (Araneae)
  • More than 34000 species of spiders worldwide
  • Only few dozen produce medically significant envenomations in humans
  • Refer to Table 194 – 3 for medically important spiders by geographic location.
necrotic arachnidism loxosceles
Three species:

L. reclusa(true brown recluse)

L. laeta (corner spider)

L. arizonica(Arizona brown spider) – produce majority of Loxosceles bites in the US.

Prefers warm and dry areas (abandon buildings / woodpiles, and cellars)

L. reclusa (true brown recluse)

One of the most common species found in the US.

Definitively diagnosing a brown recluse bite is difficult.

The necrotic wound that develop can resemble other unrelated arthropod species and medical disorder (i.e. Necrotizing Fascitis).

Necrotic Arachnidism (Loxosceles)
l reclusa true brown recluse
L. reclusa (true brown recluse)
  • Brown recluse has a dark brown violin shape on the cephalothorax (the portion of the body to which the legs attach).  The neck of the violin points backward toward the abdomen.  However, what you should look at instead is the eye pattern of 6 eyes in pairs with a space separating the pairs.  Most spiders have 8 eyes in 2 rows of 4.
l reclusa brown recluse
Venom includes multiple enzymes such as


Alkaline phosphate

5’ –ribonucleotide phosphohydrolase

Sphingomyelinase D (major enzyme responsible for necrosis.)

Necrotic wounds occur by way of neutrophil activation, platelet aggregation, and intravascular thrombosis.

Clinical Features:

Initially pts develop mild to severe pain several hrs after the bite 

Erythema and blister formation 

Bluish discoloration within the first 24 hrs 

Lesion may become necrotic with eschar formation in 3 to 4 days.

L. Reclusa (brown recluse)
l reclusa brown recluse systemic reaction
L. Reclusa (brown recluse): Systemic reaction
  • Are rare in adults, however more common in children
  • Occur in 24 – 72 hrs after the bite.
  • Can lead to N/V, Fever/chills, arthralgias, hemolysis, thrombocytopenia, hemoglobinuria, and renal failure.
  • DIC and Death are rare
l reclusa brown recluse19
If a brown recluse bite is suspected, the following labs test should be perform:


Basic Chemistry tests

BUN / Creatinine

Coagulation Profile


Supportive measure should be the initial goal (Analgesic / clean wound site).

Consider using antibiotics if any s/sx of infection develop.

Must have close follow – up with physician for serial evaluations of the wound.

L. Reclusa (brown recluse)
hobo spider tegenaria agrestis
Found in the Pacific northwest of the US

They are aggressive because it bite with minor provocation.

Live in moist dark areas (woodpiles/basements).

They are brown with grey markings, have 7 – 14mm body length and 27 – 45mm leg span

Hobo Spider (Tegenaria agrestis)
hobo spider tegenaria agrestis clinical features
Hobo Spider (Tegenaria agrestis)Clinical Features:
  • Present similar to that of brown recluse spider.
  • Initial bite is painless  delay presentation
  • Induration may occur with surrounding erythema, followed by blistering, rupture, and necrosis.
  • HA is the most common systemic symptom, but N/V and fatigue can occur.
  • Aplastic anemia and death are rare complications.
hobo spider tegenaria agrestis treatment
Hobo Spider (Tegenaria agrestis)Treatment:
  • No diagnostic test for hobo spider envenomation.
  • No proven treatment for local or systemic complications.
  • Surgical resection with skin grafting may be necessary after the necrotizing process is completed.
widow spiders latrodectus
Widow Spiders (Latrodectus)
  • Has a worldwide distribution
  • In the US, the black widow is the most well known of the 5 Latrodectus species
  • L. mactans, L. various, and L. hesperus are black
  • L. geometricus are brown and L. bishopi are red.
  • Found most often in woodpiles, basements, garages, and sheds.
widow spiders latrodectus26
Female spiders

Large in size

Body size = 1.5 cm

Leg spans 4 -5 cm

Bites can penetrate human skin.

Become aggressive when protecting her web and eggs.

Male spiders

Smaller in size

1/3 the size of female

Liter in color

Bites cannot penetrate human skin.

Widow Spiders (Latrodectus)
widow spiders latrodectus27
Widow Spiders (Latrodectus)
  • Most bites occur between April and October and are usually seen on the hands and forearm.
  • Inject a highly potent venom – most active component is latrotoxin.
  • Through a calcium – mediated mechanism, latrotoxin cause the release of acetylcholine and norepinephrine from nerve terminals.
widow spiders latrodectus clinical features
Widow Spiders (Latrodectus)Clinical Features:
  • Most bite site, initially feels like a pinprick then quickly cause increasing local pain that then involve the entire extremity.
  • In 1/3 of cases the initial erythema evolves into a larger “target lesion”.
      • The presence of the target lesion, severe pain and muscle spasm is pathognomonic for widow spider bites.
  • Pts most commonly c/o muscle cramp like spasms in large muscle groups.
widow spiders latrodectus clinical features29
Widow Spiders (Latrodectus)Clinical Features:
  • Other s/sx:
    • HA, nausea, diarrhea, diaphoresis, photophobia and dyspnea.
    • May experience intermittent severe pain for 24+ hours
  • Laboratory test to confirm Latrodectus bite is not available.
widow spiders latrodectus treatment
Widow Spiders (Latrodectus)Treatment:
  • Initial Tx: Support ABC.
  • Clean the bite site.
  • Use Opioids and benzodiazepines to control pain and muscle spasms.
  • The most effective tx for severe envenomation are parental opioids and Latrodectus antivenom.
widow spiders latrodectus treatment31
Widow Spiders (Latrodectus)Treatment:
  • Latrodectus antivenom:
    • Cause rapid resolution of symptoms and significantly shorten the course of illness.
    • When given properly, pt can often be d/c form ED after a short period of observation
  • Produced in three countries:
    • Anti Latrodectus antivenom available in Argentina
    • Red-backed spider antivenom available in Australia
    • Antivenin ( Latrodectus mactans ) available in U.S.A. (1-800-396-6250)
  • Indications, amount, and route of administration vary according to product.
  • Large hairy spiders
  • Popular as pets
  • Family Theraphosidae
  • Hairs found on the abdomen and legs are use defensively
When threaten, they may flick some of their hair.

The hair cannot penetrate human skin however can cause conjunctiva and cornea injury.

Pts who are handling tarantula and present with red eye must be evaluated via Slit-Lamp to identify hairs

Hairs that are identify must be surgically removed.

Initiate topical steroid tx to help control inflammation.

Initial bite are painful  local erythema edema  Local joint stiffness following nearby bites. (systemic sx are rare).

scorpions scorpionidae
World-wide distribution

Highly toxic species are found in Middle East, India, North Africa, South America, Mexico, and Trinidad.

In the US, only the Centruroides exilicauda (bark scorpion) possesses venom potent enough to cause systemic toxicity.

Scorpions (Scorpionidae)
scorpions centruroides exilicauda clinical features
Scorpions - Centruroides exilicauda Clinical features:
  • Venom can open neuronal sodium channels and cause prolonged and excessive depolarization.
  • Immediate onset of pain and parathesias in the stung extremity is noted and may become generalized.
scorpions centruroides exilicauda clinical features36
Scorpions - Centruroides exilicauda Clinical features:
  • Severe Systemic cases after bite can lead to:
    • Abnormal roving eye movements, blurred vision, pharyngeal muscle incoordination and drooling.
  • Other s/sx:
      • Restlessness, seizure – like activity, N/V, tachycardia, and severe agitation.
  • Symptoms can last 24 – 48hrs without anitvenom treatment.
  • Cardiac dysfunction, pulmonary edema, pancreatitis, bleeding d/o, skin necrosis, and occasionally death can be seen with stings from Asian and African scorpions.
scorpions centruroides exilicauda treatment
Scorpions - Centruroides exilicauda Treatment:
  • Initial treatment is supportive / analgesics.
  • Centruroides-specific antivenom is only available in Arizona and is produce from goat serum.(production has been stop, only used in severe systemic toxicity cases).
  • Scorpion antivenom directed against different species is now used and available in 10 other countries.
reptile bites
Reptile Bites
  • Approx 3 million bites and 150,000 deaths occur each year from venomous snakes in the world.
  • Most bites occur in the warm summer months (snakes and victims are most active).
  • In the US, mortality has improve from 25% to only <0.5% (5 – 10 deaths /year).
  • Major venomous snakes can be divided into 3 groups:
    • Viperidae (vipers)
    • Elapidae
    • Hydrophiinae (sea snakes)
crotalinae pit viper bites
Referred to as pit vipers because of bilateral depressions or pits located midway between and below the level of the eye and the nostril

With in the pit vipers, the rattle distinguishes the rattlesnake from other crotaline snakes.

Pit is a heat sensor that guides strikes at warm-blooded prey or predators.

Crotalinae (Pit Viper) Bites:
crotalinae pit viper bites venom
Crotalinae (Pit Viper) Bites:Venom

Causes the following:

  • Local tissue injury, systemic vascular damage, hemolysis, fibrinolysis, and neuromuscular dysfunction (CN weakness / resp. failure / MS∆.
  • Quickly alters blood vessels permeability leading to loss of plasma and blood into the surrounding tissue  hypovolemia.
  • Activates and consumes fibrinogen and platelets, causing a coagulopathy
crotalinae pit viper bites clinical features
Crotalinae (Pit Viper) Bites:Clinical features
  • The severity of poisoning following a crotaline bite depend on these factor:
    • The species and size of the snake
    • The age and size of the victim
    • The time elapsed since the bite
    • Characteristics of the bite (location, depth, and number, the amount of venom injected
    • 25% of crotaline snakebites are termed dry :venom effects do not develop.
crotalinae pit viper bites clinical features42
Crotalinae (Pit Viper) Bites: Clinical features
  • S/Sx of a bite:
    • One or more fang mark on the body
    • Localized pain with progressive edema.
    • N/V, weakness, oral numbness, tachycardia, dizziness, and muscle fasciculation.
    • Systemic reaction will lead to tachypnea, tachycardia, hypotension, and MS∆
crotalinae pit viper bites clinical features43
Crotalinae (Pit Viper) Bites: Clinical features

Diagnosis is

determined on the presence of fang marks and a history consistent with exposure to a snake

crotalinae pit viper bites clinical features44
Crotalinae (Pit Viper) Bites: Clinical features
  • Snake bite injury maybe manifested in three ways:
    • Local injury (swelling, pain, ecchymosis)
    • Coagulopathy (Thrombocytopenia, elevated PT, hypofibrinogenemia)
    • Systemic effects (oral swelling / parathesias, metallic or rubbery taste in the mouth, hypotension, tachycardia)
crotalinae pit viper bites treatment do s and don t
Crotalinae (Pit Viper) Bites: Treatment – Do’s and Don’t
  • First aid treatment such as suction and incision are dangerous and should not be used.
  • Tourniquets are contraindicated because they obstruct arterial flow and cause ischemia
  • Constriction bands** may be of some use especially when immediate medical care is not available.

**An elastic bandage / Penrose drain, rope, or piece of clothing wrapped above the bite. It’s applied with enough tension to restrict superficial venous / lymphatic flow while maintaining distal pulses and cap. refill. It retard venom absorption, increase local tissue injury but reduce the severity of systemic effects.

crotalinae pit viper bites treatment do s and don t46
Crotalinae (Pit Viper) Bites: Treatment – Do’s and Don’t
  • The Coghlan’s Snake Bite Kit should not be used (the blade in the kit can injure digital nerves, arteries and tendons).
  • The use of the Sawyer Extractor suction pump to remove venom without incision is controversial.
  • Electric shock to the bite site should be condemned.
  • Ice water immersion worsens the venom injury
crotalinae pit viper bites treatment
Crotalinae (Pit Viper) Bites: Treatment
  • Initial treatment involves:
    • Immobilize the limb
    • IV access in the contralateral limb
    • Establish ABC, oxygen, monitor, IVF
    • Previously placed tourniquets and constriction bands should not be removed until IV access is established
    • Clean bite site and update tetanus booster.
    • Contact Poison control ASAP
crotalinae pit viper bites treatment48
Antivenom (FabAV / CroFab):

Mainstay of treatment for poisonous snakebites

Composed of heterologous antibodies derived from the serum of animal immunized with the appropriate snake venoms.

Bind and neutralize the venom molecules

Indication for antivenom tx:

All crotaline bites that show evidence of progressive signs and symptoms.

Pts with worsening of local injury (pain, ecchymosis, swelling)

Pts with lab errors (decr platelet count, incr coagulation time, decr fibrinogen)

Pts with systemic sx (unstable vitals / MS∆)

Crotalinae (Pit Viper) Bites: Treatment
crotalinae pit viper bites treatment49
Crotalinae (Pit Viper) Bites: Treatment
  • Observation for progression of edema and systemic signs of envenomation be continued during and after antivenom infusion.
  • Limb circumference serve as an index of progression as well as a guide for antivenom tx.
  • Lab results should be repeated every 4h or after every antivenom tx.
crotalinae pit viper bites other medical treatment
IVF (must be continued)

Vasopressor (maybe needed for ongoing hypot)

PRBC / FFP / Platelet may be needed if antivenom is not effective in stopping the bleeding that can occur.

Fasciotomy maybe needed if compartment syndrome occur secondary to venom spreading into the compartment.

Cultures / Antibiotics only needed if signs of infection develop.

Steroids should only be used for signs of allergic rxn or serum sickness (occur in 5% of pts after FabAV- fever / rash / arthralgias. Tx with prednisone 60mg/d for 1-2wk)

Crotalinae (Pit Viper) Bites: Other medical Treatment:
crotalinae pit viper bites disposition
Crotalinae (Pit Viper) Bites: Disposition
  • Indication for discharge:
    • Swelling begins to resolve
    • Coagulopathy is reversed
    • Pt is ambulatory.
  • Pt need close f/u for wound check
  • Pt should be observed for at least 8hrs.
  • Pts with severe sx or getting antivenom should be admitted to the ICU
cobra bite
Cobra Bite
  • Large snakes (1 – 1.5m in length)
  • Found in most of Africa and southern Asia.
  • 45% of cobra bites are dry bites.
cobra bite venom
Cobra Bite - Venom

Contain multiple toxin that produce different effect:

1. Neurotoxins in the venom bind to postsynaptic acetylcholine receptors and produce depolarizing neuromuscular blockade.

2. Some toxins from the venom poison cell membrane. Chief effect is on the heart producing arrhythmias and impaired contractility.

3. Third type of toxins contain enzyme that break down protein and connective tissue.

cobra bite clinical features
Cobra Bite – Clinical Features:
  • Develop immediate pain at the bite site
  • Reaction around the bite site may develop over 48hr (local hemorrage, bullae, and necrosis)
  • Proceed to develop local and progressive soft tissue swelling, CN dysfunction (ptosis, diplopia, dysphagia)
cobra bite clinical features55
Cobra Bite – Clinical Features:
  • Generalized muscle weakness  Flaccid paralysis
  • Parasympathetic stimulation (salivation, bronchorrhea, N/V)
  • Venom spit into the eye (spitting cobra) will produce inflammation, edema, and d/c, but no systemic s/sx.
  • Coagulopathy is rare following a cobra bite (except bites from spitting cobra bites).
cobra bite diagnosis
Cobra Bite – Diagnosis:
  • Diagnosing and distinguishing cobra bite from other snakes is difficult.
  • If possible, the snake should be caught, killed, and brought in for identification.
  • Snake venom assays have been developed to detect the type of snake from wound aspirate or urine.
cobra bite diagnosis57
Cobra Bite – Diagnosis:
  • Standard labs should be obtained:
    • CBC
    • Serum Electrolytes
    • Creatinine
    • Coagulation tests
cobra bite treatment
Cobra Bite - Treatment
  • Bite wound incisions, vacuum extractors, cooling, or ice are not beneficial
  • Proximal lymphatic and venous constricting elastic band approach used in crotalines bites is controversial.
  • One important first aid that is proven to help is to use prompt and copious irrigation of the eyes that sustained a venom exposure (spitting cobra)
cobra bite antivenom treatment
The only proven and specific tx for cobra envenomation.

Some are monovalent, specific for a single species, but most are polyvalent, containing antibodies against several important or common cobra species in that country or region.

Should be considered experimental and can have high incidence of allergic rxn.

Should be started before the constricting band is loosened.

Should be initiated in pts with s/sx of systemic toxicity.

Reduces systemic toxicity but does not reduce local tissue damage and necrosis.

Cobra Bite - Antivenom Treatment
cobra bite treatment disposition
Cobra Bite – TreatmentDisposition:
  • Pts without signs of envenomation should be admitted for at least 24 h obs
  • Death from cobra bite typically occurs within 2 – 6 h after the bite.
  • Survival is possible without antivenom in pts with good cardio-pulmonary support.
questions 1
Questions 1:
  • The edema of snakebite usually does not involve the deep compartments or cause vascular compromise. Fasciotomy should therefore be undertaken only when __.
    • findings of compartment syndrome are present
    • massive edema is present
    • the measured intracompartmental pressure is >repeat doses of antivenom and elevation have failed
    • 30-40 mmHg
    • Only a, b, d is correct
questions 2
Questions 2:
  • Much of the toxicity of coral snake venom is due to its acetylcholine receptor blocking activity. Absorption and spread of the venom is rapid. Which one of these statement is false about the treatment or sign / symptoms of coral snakes bites is incorrect?
    • Delayed: drowsiness, confusion, coma, euphoria, salivation, vomiting, seizures, paralysis and death in 8-24 hours. Progression to paralysis can occur rapidly once symptoms begin.
    • Tourniquet application, incision and suction if seen within one hour.
    • Antivenin is available for the eastern coral snake and may be lifesaving.
    • Early signs: local weakness and paresthesias may begin within 15 minutes or be delayed several hours. Mydriasis, dysphagia, ataxia, slurred speech and myalgias begin within a few hours.
    • Support respiration and treat seizures.
questions 3
Questions 3:
  • Treatment for a brown recluse spider bite does not includes:
  • cleaning the wound with soap and water and administering tetanus prophylaxis.
  • local cold compresses, elevation of the affected extremity, and loose immobilization of the affected part.
  • with severe ulceration, delayed excision and grafting may be necessary.
  • amoxicillin 125-250 mg QID may be as effective as dapsone.
questions 4
Questions 4:
  • Treatment of Hymenoptera stings includes all except:
  • epinephrine subQ (0.01 mg/kg to a 0.5 mg max) and/or IM or IV diphenhydramine (1 mg/kg) for systemic reactions. Systemic corticosteroids.
  • PO diphenhydramine, 4-5 mg/kg (75 mg max) QID, and perhaps prednisone 0.5-1.0 mg/kg/day for several days for severe local inflammation.
  • washing (to minimize infection), rest, ice, and elevation.
  • IV crystalloid and vasopressors (dopamine or epinephrine) for hypotension.
  • Nebulized albuterol or other beta-2-specific agonist for bronchospasm; intubation, cricothyroidotomy, or jet ventilation may be required for severe cases or upper airway edema.
  • All the above is true
  • 1. E
  • 2. B
  • 3. D
  • 4. F