13 Bites and Stings

Question 1

More fatalities result from stings by these insects than by stings or bites of any other insects

Answer 1

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

Question 2

What are the 3 major subgroups or “superfamiles” nder the order Hymenoptera?

Answer 2

Apidae (honeybee and bumblebee)
Vespidae (yellow jackets, hornets, and wasps)
Formicidae (ants)

Question 3

Most of the allergic reactions reported each year due Hymenoptera occur from

Answer 3

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)

Question 4

components of hymenoptera venom

Answer 4

Histamin
Mellitin (>50% of dryweight of vee venom)
Phospholipase
Hyaluronidase

Question 5

Remarks from reactions from hymenoptera stings

Answer 5

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

Question 6

Treatment of hymenoptera stings

Answer 6

1. Immediate removal (method of removal is irrelevant)
2. Wash with soap and water
3. Cold compress
4. Oral analgesics (NSAIDs)
5. Antihistamine
6. Elevation and Rest

Question 7

Epinephrine dosing for anaphylaxis

Answer 7

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

Question 8

Spiders causing necrotic arachnidism

Answer 8

Loxosceles
The brown recluse spider

Question 9

The brown recluse spider is most accurately identified by their

Answer 9

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

Question 10

venom of brown recluse contains

Answer 10

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.”

Question 11

Characteristics of the bites of brown recluse spiders

Answer 11

1. Initially painless (prohibits possible identification of the spider)
2. occasional hemorrhagic blister by 24 hours
3. by day 3 or 4, “red white, and blue” sign (erythema, blanching, and ecchymosis)
4. the ecchymotic area may become necrotic, with eschar formation by day 7

Question 12

Surgical debridement in brown recluse wounds

Answer 12

Surgical debridement should be delayed until clear margins are established, often 2 to 3 weeks after the bite

Question 13

Black widow is aka

Answer 13

Latrodectus spiders

Question 14

charaterizes black widow spiders

Answer 14

Orange-red hourglass shaped markings

Question 15

Most active component of black widow’s venom

Answer 15

a-latrotoxin
- leads to massive release of neurotransmitters (predominantly acetylcholine and norepinephrine) leading to neuromuscular and cardiovascular manifestations respectively

Question 16

Clinical features of black widow bites

Answer 16

1. Painful bide, sometimes leading to target lesion
2. Latrodectism: progressive cramping in large muscle groups, with systemic symptoms

Question 17

Treatment of black widow bites

Answer 17

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

Question 18

Deadliest spiders in the world

Answer 18

Funnel-web spiders (Atrax / Hadronyche)

Question 19

Venom of funnel-web spiders

Answer 19

Their venom contains atracotoxin, which like scorpion venom, binds to sodium channels and causes release of neurotramitters leading to both autonomic and neuromotor effects

Question 20

Clinical features of funnel-web spiderbites

Answer 20

Wheal formation and symptoms of cholinergic excess

Question 21

Remarks on tarantulas

Answer 21

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.

Question 22

Toxins of scorpion stings

Answer 22

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

Question 23

The most dangerous clinical manifestation of scorpion envenomation worldwide is

Answer 23

acute heart failure and pulmonary edema
It remains unclear whether an initial massive catecholamine release and myocardial stunning is universally responsible for this

Question 24

Treatment for scorpion stings include

Answer 24

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)

Question 25

Flea bites

Answer 25

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.

Question 26

Refers to the adverse effects resulting from contact with butterflies, moths, or their caterpillars

Answer 26

Lepidopterism

Question 27

These account for most of the serious [Lepidoptera] envenomations in the US

Answer 27

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

Question 28

Blister beetles

Answer 28

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.

Question 29

Pederin vs cathardin

Answer 29

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