13 Bites and Stings Flashcards
More fatalities result from stings by these insects than by stings or bites of any other insects
Hymenoptera stings
(wasps, bees, and ants)
In the US, anaphlactic reactions to Hymenoptera stings account for the most fatal arthropod envenomations
although exposures to all athropodsª can result in potential emergencies
ªthe phylum Arthropoda is the largest division of the animal kingdom
What are the 3 major subgroups or “superfamiles” nder the order Hymenoptera?
Apidae (honeybee and bumblebee)
Vespidae (yellow jackets, hornets, and wasps)
Formicidae (ants)
Most of the allergic reactions reported each year due Hymenoptera occur from
wasp, hornet, and yellow jacket stings (Vespids)
These arthropods typically nest in the
- ground (yellowjackets)
- trees and shrubs (hornets)
- wall (wasps)
Although vespids also possess barbed stingers, they can withdraw their stingers from victim, which permits multiple stings (unlike bees)
components of hymenoptera venom
Histamin
Mellitin (>50% of dryweight of vee venom)
Phospholipase
Hyaluronidase
Remarks from reactions from hymenoptera stings
Most reactions develop within the first 15 minutes, and nearly all occur within 6 hours
In genereal, the shorter the interval between the sting and the onset of symptoms, the more severe is the reaction.
Fatalities that occur within the first hour after the sting usually result from airway obstruction or hypotension
In general, definitive insect identification is unnecessary, because signs and symptoms of envenomation are similar for all species of Hymenoptera
Treatment of hymenoptera stings
- Immediate removal (method of removal is irrelevant)
- Wash with soap and water
- Cold compress
- Oral analgesics (NSAIDs)
- Antihistamine
- Elevation and Rest
Epinephrine dosing for anaphylaxis
Adults:
0.3 to 0.5 mg IM
(0.3 to 0.5 mL of 1:1000 concentration)
Children:
0.01 mg/kg
up to 0.3 mg
Spiders causing necrotic arachnidism
Loxosceles
The brown recluse spider
The brown recluse spider is most accurately identified by their
Eye pattern: 6 paired eyes (1 anterior pair, 2 lateral pair) that give the appearnce of three black dots
A pigmented violin-shaped pattern on the cephalothorax is often present, however unreliable and often misinterpreted
venom of brown recluse contains
hyaluronidase
sphingomyelinase D (major enzyme responsible for necrosis)
“*Although both local and systemic complications of Loxosceles envenomation have been well described, the perceived threat of the brown recluse far exceeds its actual danger.”
Characteristics of the bites of brown recluse spiders
- Initially painless (prohibits possible identification of the spider)
- occasional hemorrhagic blister by 24 hours
- by day 3 or 4, “red white, and blue” sign (erythema, blanching, and ecchymosis)
- the ecchymotic area may become necrotic, with eschar formation by day 7
Surgical debridement in brown recluse wounds
Surgical debridement should be delayed until clear margins are established, often 2 to 3 weeks after the bite
Black widow is aka
Latrodectus spiders
charaterizes black widow spiders
Orange-red hourglass shaped markings
Most active component of black widow’s venom
a-latrotoxin
- leads to massive release of neurotransmitters (predominantly acetylcholine and norepinephrine) leading to neuromuscular and cardiovascular manifestations respectively
Clinical features of black widow bites
- Painful bide, sometimes leading to target lesion
- Latrodectism: progressive cramping in large muscle groups, with systemic symptoms
Treatment of black widow bites
Opioids
Benzodiazepines
Antivenomª (successful treatment even with administration 90 hours after envenomation has been reported)
ªThe recent questions of antivenom efficacy and potential for fatal reactions, particularly with the curren US product, should be considered, particularly since envenomation from a Latrodectus bite is rarely life threatening itself
Deadliest spiders in the world
Funnel-web spiders (Atrax / Hadronyche)
Venom of funnel-web spiders
Their venom contains atracotoxin, which like scorpion venom, binds to sodium channels and causes release of neurotramitters leading to both autonomic and neuromotor effects
Clinical features of funnel-web spiderbites
Wheal formation and symptoms of cholinergic excess
Remarks on tarantulas
Patients who manifest a red eye and pain after handling a tarantula should be examined to determine if offending barbed hairs are present in the cornea or conjunctiva.
Toxins of scorpion stings
Scorpion toxins with the most serious medical effects can open neuronal sodium channels and cause prolonged and excessive depolarization
Somatic and autonomic (parasympathetic and sympathetic) systems are affected
The most dangerous clinical manifestation of scorpion envenomation worldwide is
acute heart failure and pulmonary edema
It remains unclear whether an initial massive catecholamine release and myocardial stunning is universally responsible for this
Treatment for scorpion stings include
Opioids (pain control)
Benzodiazepines (sedation)
Antivenom (restricted to severe systemic symptoms)
Atropine (for cholinergic effects)
Prazosin (to counteract initial adrenergic response)
Dobutamine (may be appropriate to support cardiac dysfunction)
Flea bites
Frequently found in zigzag lines, especially on the legs and in the waist area
The lesions most often have a hemorrhagic-appearing center surrounded by erythematous and urticarial patches.
Refers to the adverse effects resulting from contact with butterflies, moths, or their caterpillars
Lepidopterism
These account for most of the serious [Lepidoptera] envenomations in the US
The puss caterpillar (Megalopyge opercularis)
After initial contact, intense local burning pain, rather than pruritus, is typical
A grid-like pattern of hemorrhagic papules may be seen within 2 to 3 hours of exposure
Blister beetles
The most well-known blister beetle is the “Spanish fly” (Cantharis vesicatoria)
They contain a highly potent vesicant (either canthardin or pederin) that can be exuded or released if the beetle is brushed against, pressed, or crushed on the skin.
For this reason, a blister beetle should be removed from the skin by blowing or flicking.
Pederin vs cathardin
Pederin-containing dermal exposures result in a more delayed (up to 36 to 72 hours) but more painful and symptomatic eruption than thsoe from canthardin-containing beetles
