Spiders & their toxins
Joe Alcock MD MS
Emergency Medicine, NM VAMC
UNM Dept Emergency Medicine
21 year old woman in Sydney
 Cleaning out swimming pool trap
 Feels a sharp pain in her right hand
 Develops nausea, paresthesias, sweats
Sydney Funnel Web Spider
Funnel Web Spider
 Australasian funnel-web
spiders
 Suborder
Mygalomorphae includes tarantulas
 Family Hexathelidae
 Sydney f.w.s Atrax
robustus
 Chelicerae (fangs)
contain venom
apparatus
 2 genera in Australia:
Atrax, Hadronyche
Range & habitat
 Eastern coast of
Australia
 Fws also found in New
Guinea & Solomon
Islands
 Spiders construct a
funnel shaped web and
wait for prey to fall in.
 Funnels constructed
near rocks, logs
 Diet consists of insects
and small vertebrates
Scope of problem
 77 severe envenomations between
1999 and 2003
 Deaths only recorded from Atrax
robustus
 No deaths since introduction of
antivenom
Toxicity




77 severe cases 1999 - 2003
Male spiders cause most bites
10-25% bites produce toxicity
Spiders measure 5 cm, fangs can penetrate
fingernails
 Delta-Atracotoxins
 Presynaptic neurotoxins - open sodium
channels - inducing action potentials
 Autonomic storm - endogenous Ach
norepinephrine & epinephrine.
Envenomation
 Painful Bite - acidic pH, large size of fangs
 Onset rapid - median 28 min, 2 cases after 2
hours (pressure dressing)
 Early symptoms: periorbital paresthesias,
facial muscle twitching, vomiting, diaphoresis,
salivation, dyspnea
 Agitation, confusion, coma, hypertension,
metabolic acidosis, mydriasis, fasciculations
 Increased ICP - death
Funnel Web Treatment





Pressure immobilization bandage
Antivenom purified rabbit IgG
Developed in 1981 in Melbourne
Fast acting and effective
Hospitalization rates have changed from
14 days to 3 days on average with no
deaths since its availability.
First Aid
 Keep victim calm and still if
possible
 Immobilize the bitten area and
keep it lower than the heart.
Remove rings.
 Pressure dressing - NOT
tourniquet
 Get patient to definitive care antivenin - Sooner the better!
Other Australian Mygalomorph
spiders
 Mouse Spider - local pain, local
paresthesias
 Trap door spider - minor effects only
60 yo m collecting yard waste
next to house
 Feels a sharp bite on forearm
 Noticed a medium sized spider with
prominent abdomen
 Red spot on underside of abdomen
 Hourglass shaped
 Should he worry?
Latrodectus
History
 Slight initial pain: pinch or pinprick
 In 1 hour, systemic symptoms begin and may
last for a few days.
 Muscle cramping - local and large muscle
groups - abdomen, back, thighs.
 Nausea and vomiting
 Headache
 Anxiety
Physical
 Abnormal vital signs, Hypertension,
Tachycardia
 Diaphoresis: local or remote from
site of envenomation
 Tiny fang marks may be visible
 Bite appearance: small circle of
redness, swelling around immediate
bite site. May have blanching with
red border
Bite after 1 hour
Physical Exam - continued
 Abdominal rigidity - acute abdomen.
 Neurotoxic effects, weakness,
fasciculations, and ptosis
 Latrodectus facies, with facial muscle
spasm of, edematous eyelids, &
lacrimation. Mimics an allergic reaction.
Grading Bites
 Grade 1 - Mild envenomation, Localized pain
at bitesite, Normal vitals
 Grade 2 - Moderate envenomation: Muscle
pain in the bitten arm or leg
Muscle pain may extend to abdomen if bitten
on leg, or to the chest with bite on arm.
Local diaphoresis of envenomation site or
involved extremity
Normal vital signs
Grade 3 Latrodectism
 Severe envenomation
Generalized muscular pain in the back,
abdomen, and chest
Diaphoresis remote from envenomation
site
Abnormal vital signs (blood pressure
>140/90 mm Hg, pulse >100)Nausea
and vomiting Headache
Antivenin
 Antivenin Latrodectus mactans - horse serum
(Merck product)
 Consider for patients with grade 2 or grade 3
envenomations in whom narcotics do not
control pain and are low risk for allergic
reactions
 Rec for certain patient groups, such as
children and elderly persons
 skin testing for possible allergic reaction to
the antivenom.
Antivenin Precautions
 Mortality from widow spider envenomation is
extremely rare, and some argue against
administration of antivenom when treatment
may be more dangerous than the injury
 some recommend routine premedication with
antihistamines (H1 and H2 blockers)
 black widow spider envenomation is
associated with abruptio placentae and fetal
demise; benefits of antivenom administration
in pregnancy must be weighed against risks
The dreaded brown recluse
 Necrotic skin ulceration
 Spiders get a bad rap - blamed for
every little skin infection, folliculitis