Bites and Infestations

Question 1

Dangerious spiders?

Answer 1

• black widows
• brown recluse or fiddlebacked
• funnel web

- broad range of rxns:
local rxns (necrotic lesions), syst rxns, and allergic rxns 

tarantulas: non-aggressive and rarely bite, body hairs are venomous and can induce anaphylactic rxns

Question 2

Criteria that must be met to attribute a rxn to spider bite?

Answer 2

• spider must be seen during biting
• spider must be recovered, collected and sent for ID
• other conditions that could explain rxn must be ruled out
• most suspected spider bites were found to have a diff cause that actual spider

Question 3

minor local rxn due to arachnid?

Answer 3

• majority of time a spider bite will only cause minor local rxn
• fang markings: 1 or 2 sep ports of entry
• local erythema w/ bright red tender nodule appearing w/in min w/ subsequent induration
• no blister
• lasts about 7-10 days

Question 4

Necrotizing local rxn due to arachnid?

Answer 4

• brown recluse (black widow bites don’t generally cause necrotic lesion)
• initial erythema that expands to 5-15 cm followed by blister w/in 15-36 hours
• blister opens and oozes w/in 24 hrs
• subsequent ulcer w/ crater
• lesion can take several months to heal and leave permanent scarring

Question 5

Systemic and allergica rxn from arachnids?

Answer 5

• systemic:
  sxs may include fever, myalgias, fatigue, lymphadenopathy, rarely hemolysis and coagulopathy
• allergic:
  may be limited to localized urticaria or may be systemic: anaphylaxis

Question 6

Characteristics of black widows?

Answer 6

• found predominantly in warmer climates
• live in piles of firewoord, old lumber, rock biles, hay
• not aggressive, timid biting only when bothered or protecting egg sac
• hundreds of bites from brown recluse spiders are reported for each black widow bite
• may have immediate sharp pain w/ bite, may also be painless and go unnoticed
• two fang marks visible in approx 80% of cases
• live in Western half of US

Question 7

Phases of black widow bites?

Answer 7

• mild rxns resolve w/in 12 hrs
• systemic rxn known as latrodectism has 3 phases:
  1) exacerbation phase: up to 24 hrs following bite - muscle spasms near bite but can occur anywhere in body esp abdomen, and lower extremities, autonomic stim may include sweating, nausea, vomiting, tachycardia, tachypnea, restlessness, HTN and HA
• coma and death can ensue but is rare and is usually in a child
  2) dissipation phase (1-3 days following bite): sxs decline in most cases w/o specific tx
  3) residual phase (wks to months following bite): muscle spasms, tingling, nervousness, weakness may occur
• antivenom is available for pts experiencing severe systemic rxns

Question 8

Characteristics of brown recluse spiders and bites?

Answer 8

• live in human dwellings
• distributed in midwest and south central region of US: below interstate 80 (missouri)
• bites are trivial in more than 95% of cases
• occasionally cause severe local necrotic rxn
• systemic rxn known as loxoscelism can result in syndrome assoc w/ hemolysis (may result in death but very rare)

Question 9

Where do funnel web spiders live?

Answer 9

• like houses

- some species in NW but bite doesn’t cause serious rxns in humans

Question 10

Tx of local nonnecrotic simple rxns to spider bites?

Answer 10

• cleaning w/ soap and water
• ice packs
• observing for 24 hrs to see if systemic involvement
• tetanus prophylaxis recommended

Question 11

Tx of necrotic lesions?

Answer 11

• initially tx as simple rxns
• if center less than 2 cm large - conservative tx
• if larger than 2 cm - systemic corticosteroids for 5-7 days
• aluminum acetate soaking, clean dressings, debridement once ulceration develops
• abx if signs of secondary bacterial infection
• on rare occasions will reqr surgical revision (including skin grafting)

Question 12

Tx of systemic rxns?

Answer 12

• supportive therapy directed at involved organ systems
• loxoscelism w/ extensive hemolysis tx as other hemolytic states
• careful hydration
• analgesics
• calcium gluconate for relief of muscular pain w/ lactrodectism was found not to be effective
• benzos and opioids generally used for spasms and pain w/ lactrodectism
• prompt antivenom considered for black widow bite IF pt having typical muscle spasms and bite was noticed or fang markings ID

Question 13

Caution w/ black widow antivenom?

Answer 13

• don’t give indiscriminately

- severe SEs occur in up to 9% of pts: may include serum sickness (horse serum) and anaphylaxis

Question 14

Tx od allergic rxns?

Answer 14

• H1 and H2 blockers for local urticarial rxns
• epi is appropriate for anaphylaxis
• topical steroids for large localized lesions

Question 15

Scorpions found in US?

Answer 15

• most dangerous ones found outside US
• w/in US - one scorpion that is considered to be dangerous - bark scorpion
• found mostly in Arizona, NM, SE california, texas and Mexico
• use venom only for defense and rarely sting their prey

Question 16

Presentation of scorpion bite?

Answer 16

• neurotoxin can cause prolonged and excessive depolarization
• systemic sxs not common but can be severe esp in kids:
  pain and paresthesias in stung extremity - may become generalized
• abnormal EOMs, blurred vision, pharyngeal muscle incoordination and drooling
• excessive motor activity may appear seizure like
• may have N/V, tachycardia, severe agiitation
• w/o antivenom sxs can last 24-48 hrs
• deaths are rare

Question 17

Tx of scorpion bite?

Answer 17

• initially supportive w/ analgesics
• antivenom only available in AZ and production has been stopped - shold be reserved for cases of severe systemic toxicity

Question 18

Stings from what group result in more fatalities than any other arthropod?

Answer 18

• hymenopterans

- bees, wasps, ants

Question 19

Bee stings?

Answer 19

• honeybees and bumblebees docile, sting only when provoked
• males don’t have stingers
• africanized honeybees (killer bees) very aggressive:
  no more toxic than nonaggressive bees
• worry about venom toxicity w/ africanized bees - still greatest worry is an anaphylactic rxn

Question 20

Wasp stings?

Answer 20

• most of allergic rxns for hymenoptera occur from wasps and relatives (hornets and yellowjackets)
• much less docile than normal honeybees and may be disturbed by work taking place around the nest
• only females have stingers and unlike bees can withdraw stingers which allows them to sting mult times

Question 21

Hymenopteran venom?

Answer 21

• melittin big player - can cause degranulation of basophils and mast cells
• venom of all hymenopterans share many of the same components and therefore cross sensitization may occur

Question 22

Presentation of hymenopteran sting?

Answer 22

• local rxn
• anaphlactic
• toxic
• delayed

Question 23

Local reaction to hymenopteran sting?

Answer 23

• urticarial lesion contiguous w/ sting site
• can involve 1 or more neighboring jts w/ severe local rxn
• local rxn of mouth or throat can produce airway obstruction
• if local rxns become increasingly severe - can increase likelihood of systemic rxn down the road
• tx:
  remove stinger, wash site w/ soap and water, ice packs, antihistamines, and analgesics

Question 24

Anaphylactic rxn of hymenopteran sting?

Answer 24

• systemic rxn which may range from mild to fatal, death can occur in min.
• majority of rxns occur w/in 1st 15 min and nearly all w/in 6 hrs
• initial sxs: itchy eyes, facial flushing, generalized urticaria, dry cough
• sxs may then intensify rapidly w/ chest or throat constriction, wheezing, dyspnea, cyanosis, abdominal cramps, diarrhea, N/V, vertigo, chills, fever, laryngeal stridor, shock, syncope, involuntary bowel or bladder action, and bloody frothy sputum

Question 25

Tx priorities for hymenopterans - anaphylaxis?

Answer 25

- ABCs then depending on severity:
O2 by NC or FM
epi 0.3-0.5ml 1:1000 SQ
IV access, 1 or 2 large bore IVs of NS
diphenhydramine 50 mg PO/IV
famotidine 40 mg PO or 20 mg IV
methylprednisolone 125 mg IV

Question 26

Toxic rxn of hymenopteran sting?

Answer 26

• mult stings and therefore person has systemic response

- can mimic anaphylaxis but there is generally greater frequency of N/V, and diarrhea

Question 27

Delayed rxn of hymenopteran sting?

Answer 27

• immune complex mediated rxn
• appears 5-14 days after sting
• sxs: fever, malaise, HA, urticaria, lymphadenopathy, polyarthritis (serum like sickness) - not anaphylactic rxn
• delay from sting to sxs makes this hard to dx

Question 28

Ant bites?

Answer 28

• pontential x-reactivity w/ other hymenoptera
• individual stings may produce systemic toxicity in sensitized individuals
• tendency to attack in great numbers when provoked (fire ants have simultaneous stinging mechanism)
• local lesions: papule that may become sterile pustule in 6-24 hrs
• tx: localized wound care

Question 29

3 major groups of venomous snakes?

Answer 29

• vipers: crotalinae subfamily - rattlesnakes
• elapidae: coral snakes
• hydrophiidae

Question 30

Rattlesnake bites?

Answer 30

• mostly found in southwest US, some in Eastern US
• some in MT - 4-5 bites reported/year
• rattlesnakes don’t always rattle b/f striking
• venom can cause local tissue injury, systemic vascular damage, hemolysis, fibrinolysis, and neuromuscular dysfxn
• 25% are dry bites where venom effects don’t develop

Question 31

Presentation of rattlesnake bite?

Answer 31

• cardinal manifestations include presence of one or more fang marks, localized pain, and progressive edema extending from bite site
• other early sxs and signs include: N/V, weakness, oral numbness, tachycardia, dizziness, muscle fasciculation
• ecchymoses may appear as venom can consume fibrinogen and platelets

Question 32

Tx for rattlesnake bites?

Answer 32

• txs such as suction and incision are dangerous and shouldnt be done
• ice tx also shouldnt be done (ice water immersion worsens venom injury)
• tourniquets shouldn’t be used (may obstruct arterial flow and cause ischemia)
• constriction band may be of some use, key is to ensure there are distal pulses and capillary filling
• nothing should delay the person from seeking immediate definitive medical care of the admin of antivenin

Question 33

Initial emergency management for rattlesnake bite?

Answer 33

• immobilize limb, est IV access, admin O2, tx w/ advanced life support as necessary
• ED management:
• antivenin is mainstay (polyvalent Crotalidae immune fab) for any bites that show evidence of progressive signs and sxs
• aggressive supportive care w/ isotonic fluids and vasopressor agents are needed for hypotension
• blood component replacement may be necessary if active bleeding

Question 34

Coral snake bites?

Answer 34

• primarily found in SE US: Texas and AZ
• account for 20-25 bites in US/year
• venom primarily composed of neurotoxic components that don’t cause marked local injury
• sxs primarily neurologic and include: tremors, salivation, dysarthria, dipolopia, fixed and contracted pupils, dysphagia, dyspnea, and seizures
• death can result from paralysis of resp muscles
• signs and sxs may be delayed up to 12 hrs

Question 35

coral snakes rhyme?

Answer 35

• red and yellow kill a fellow = coral snake

- red and black venom lack = milk snake

Question 36

Management of coral snake bite?

Answer 36

• pt should be admitted for observation
• baseline and serial pulmonary fxn measures
• antivenin for pts who have definitely been bitten
• it may not be possible to prevent further effects or reverse effects that have already developed
• ventilatory support as reqd

Question 37

When does transmission usually occur by tick? 2 main tick diseases in US?

Answer 37

• disease transmission usually occurs near end of blood meal as tick becomes engorged
• 2 diseases: lyme disease (Borrelia burgdorferi) spread by deer ticks, and RMS (rickettsia ricketsii) - dog ticks

Question 38

What diseases do ticks carry?

Answer 38

ticks leading carriers (vectors) of diseases to humans in US, 2nd only to mosquitos worldwide

• lyme
• babesiosis
• erlichiosis
• RMSF
• southern tick assoc rash (STARI)
• tick borne relapsing fever
• tularemia
• anaplosmosis
• colorado tick fever
• powassan encephalitis
• Q fever

Question 39

Correct way to remove a tick?

Answer 39

• use fine tweezers to grab tick close to skin surface
• pull backwards gently and firmly, don’t jerk or twist
• don’t squeeze, crush or puncture the body of tick
• wash hands and skin thoroughly w/ soap and water
• if any mouth parts of tick left in skin - leave it alone - it will be expelled eventually, attempt of removal may result in trauma or infection

Question 40

What sxs should you monitor for lyme disease?

Answer 40

• sxs may not be obvious for days or weeks after tick bite:
  flu like sxs, fever, weakness, jt pain, swelling, SOB, erythema migrans - usually is salmon color and expands over a few days or weeks and reaches 20 cm in diameter, center of rash can then appear a lighter color giving it the bulls eye appearance
• approx 80% of people w/ lyme develop EM

Question 41

What people should receive preventative tx w/ abx?

Answer 41

only people that meet all of the following criteria:

• attached tick ID as adult or nymphal deer tick
• tick is est to have been attached for longer than 36 hrs

abx tx can begin w/in 72 hrs of tick removal

• pt can take doxycycline (not breastfeeding, preg or kid under 8)
• recommended dose: 200 mg for adult and 4 mg/kg for kid over 8

Question 42

3 distinct presentations of lice?

Answer 42

• head lice - pediculus humanus capitis
• body lice - pediculus humanus corporis
• pubic lice - pthirus pubis

Question 43

MC pop affected by lice? dx? Tx?

Answer 43

• head lice is MC form of lice infestation
• kids 3-10 MC affected
• MC transmitted via head to head contact
• dx is by demonstration of lice and nits
• OTC agents: nix lotion (permethrin 1%) rid, A200 and pronto shampoos (pyrethrin products) are usually effective (liquid over 2)
• wash and dry all bed linesn that have been in contact w/ infested person on hot cycle
• not necessary to shave person’s head

Question 44

Body lice spread? Tx?

Answer 44

• live in seams of clothing and then transfer to human host to feed
• bedbugs are related to lice (probably responsibe for most spider bites)
• tx: conservative -
  wash body thoroughly
  wash and dry all exposed linen and clothes in hot cycles, anti-lice agents usually not needed if clothing is thrown away and bed linens are washed thoroughly
• vaccuum floors and furnitur and throw vacuum bag away

Question 45

How is pubic lice transmitted? Tx?

Answer 45

• trasmitted by direct sexual contact
• intense itching of pubic area is characteristic
• tx w/ anti-lice agents and repeat in 7-10 days
• remove nits w/ fine toothed comb
• tx contacts if lice and nits are found
• wash and dry all clothes and bed linens in hot cycles

Question 46

Scabies infestation? Dx?

Answer 46

• caused by microscopic mite (sarcoptes scabiei) - incubation can be several weeks b/f sxs, earlier w/ subsequent infection
• sxs caused by mite’s tunneling below skin which causes a localized allergic rxn
• dx:
  extremely itchy rash w/ crusting, linear burrows, crusting lesions, other family members
• frequently occurs b/t fingers and toes, buttocks, creases of elbows and waist of genitals
• usually spread by skin-skin contact

Question 47

Tx of scabies?

Answer 47

• MC tx w/ 5% permethrin cream (Elimite)
• generally safe for use in kids as young as 2 months
• apply from head to bottom of feet, paying special attention to skin folds and creases
• permethrin is left on for 10-14 hrs and then washed off in shower
• itching and rash may last up to 2 wks after tx

Question 48

Tx of bed bugs?

Answer 48

• itchy red spots assoc w/ bedbug bites usually disappear on their own w/in 1 wk or 2. Might speed your recovery by using:
  skin cream containing hydrocortisone
  oral antihistamine: such as diphenydramine (benadryl)