Poisonous Spiders: Bites, Symptoms, and Treatment; an Educational Review

Abstract

More than 40,000 species of spiders have been identified in the world. Spider bites is a common problem among people, however few of them are harmful but delay in treatment can cause death. Since the spider bites are risk full to human, they should be taken seriously, especially in endemic areas. Our objective in this review was to study about poisonous spiders and find out treatments of them. Therefore we collected related articles from PubMed database and Google Scholar. Three important syndromes caused by spider bites are loxoscelism, latrodectism and funnel web spider syndrome. Many treatments are used but much more studies should have done to decrease the mortality. In this review, we describes different venomous spiders according to their ap- pearance, symptoms after their bites and available treatments.

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Emergency (2014); 2 (2): 54-58
EDUCATIONAL REVEIW
Poisonous Spiders: Bites, Symptoms, and Treatment; an Educational Review
Farzad Rahmani1*, Seyed Mahdi Banan Khojasteh2, Hanieh Ebrahimi Bakhtavar3, Farnaz Rahmani4,
Kavous Shahsavari Nia5, Gholamreza Faridaalaee6
1. Department of Emergency medicine, Tabriz University of Medical Sciences, Tabriz, Iran
2. Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
3. Department of Emergency Medicine, Ardabil University of Medical Sciences, Ardabil, Iran
4. Department of Psychiatric Nursing, School of Nursing and Midwifery, Tabriz University of Medical Sciences, Tabriz, Iran
5. Road Traffic Injury Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
6. Department of Emergency Medicine, Urmia University of Medical Sciences, Urmia, Iran
Abstract
More than 40,000 species of spiders have been identified in the world. Spider bites is a common problem among
people, however few of them are harmful but delay in treatment can cause death. Since the spider bites are risk
full to human, they should be taken seriously, especially in endemic areas. Our objective in this review was to
study about poisonous spiders and find out treatments of them. Therefore we collected related articles from
PubMed database and Google Scholar. Three important syndromes caused by spider bites are loxoscelism,
latrodectism and funnel web spider syndrome. Many treatments are used but much more studies should have
done to decrease the mortality. In this review, we describes different venomous spiders according to their ap-
pearance, symptoms after their bites and available treatments.
Key words: Spiders, spider bites, spider venoms, black widow spider, emergency treatment
Cite This Article as: Rahmani F, Banan Khojasteh M, Ebrahimi Bakhtavar H, Rahmani F, Shahsavari Nia K, Faridaalaee GH.
Poisonous Spiders: Bites, Symptoms, and Treatment; an Educational Review. Emergency. 2014;2(2):54-8
Introduction:
1
piders belong to a branch of invertebrate animals
called arthropods. Arthropods have the largest
number of species. Along with ticks, mites and
scorpions, spiders fall into the subphylum chelicerata
and class of arachnids (1, 2). The arachnid class has
very diverse members in a way that more than 80,000
species belonging to that class have been identified to
date. Spiders are a large group of arachnids belonging
to the araneae order (1). More than 40,000 species of
spider have been identified to date but the real number
is estimated at 4 times more than that number (3). Ex-
cept for two small groups in the arachnid family, all spi-
ders have poison glands and release their secretions
into their venom sacs near their chelicerae. However,
the majority of spiders do not bite humans and except
for a few cases, they are not harmful to the human being
or other mammals (2).Spider bites are common but the
majority of species create little clinical presentations
(3). There is only one aggressive spider named funnel-
web in Australia which attacks the human being with-
out provocation. The majority of venomous spiders are
found in Latin America. These large spiders are quite
*Corresponding Author: Farzad Rahmani, MD; Emergency Medicine Depart-
ment, Imam Reza Hospital, Tabriz University of Medical Sciences, Golgasht
Avenue, Tabriz, Iran. Postal code: 5166614756.
Phon/Fax: 00984113352078. Email: Farzadrhn88@gmail.com
Received: 7March 2014; Accepted: 27 Ma rch 2014
aggressive and their venom is pharmacologically highly
toxic. Their bite results in severe pain, neurotoxic ef-
fects, diaphoresis, severe allergic reaction and priapism
(1). Other spiders normally exhibit aggressive behavior
after being trapped, injured or provoked. The severity
of reactions to spider venom depends on factors such as
its amount, site of biting and its duration and also age
and health condition. Mortality due to spider bite is rare
(2). Spider venom includes different peptides and sub-
stances affecting sodium, calcium and potassium chan-
nels in neurons and also glutamate and acetylcholine
receptors (4).Spider bite victims develop symptoms
such as pain and swelling in the site of biting, necrosis,
pyrexia, pulmonary edema, respiratory distress, hyper-
tension, kidney dysfunction and death. Treatment pro-
tocol in the case of critically ill patients includes sup-
portive measures and antivenom injection. Respiratory
support and monitoring the hemodynamic status of
these patients are of fundamental importance (5). High-
ly venomous spiders, funnel-web in Australia and ar-
madeiras (armed spiders) in South America require
antivenom and intensive therapeutic interventions (6).
Three important syndromes are caused by spider bites:
latrodectism, loxoscelism, and funnel-web spider syn-
drome (7). Here, we discuss about poisonous spiders
and find out treatments of them.
S

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Rahmani et al
Figure 1: Flowchart of study
Introduction of venomous spiders
This section describes different venomous spiders ac-
cording to their appearance, symptoms after their bites
and available treatments. Therefore we collected relat-
ed articles from PubMed and Google scholar (Figure 1).
a) The brown recluse spider
The brown recluse spider is recognized by the violin-
shaped marking on its back (Figure 2). This spider takes
rest during the day and is not aggressive but it will at-
tack in the case of provocation. Patients are usually bit-
ten by wearing clothes and shoes with spiders in them
(2).
Loxoscelism syndrome is the symptoms caused by the
bite of the brown recluse spider. This spider's bite is
usually painless but it later becomes an inflammatory,
hemorrhagic and painful lesion (8). Necrosis spreads a
few days following the bite and loxoscelism syndrome
results in dermatitis necrosis in the site of biting,
around which becomes red, white and blue, respective-
ly (9). The venom of this spider contains hyaluronidase
and sphingomyelinase D enzymes and results in necro-
sis. Moreover, neutrophil activity and platelet aggrega-
tion and thrombosis exacerbate necrosis (8). Local
manifestations of the bite of this spider include edema,
inflammation, hemorrhage, damage to the vessel wall,
thrombosis, and necrosis (10) but systematic symptoms
including acute renal failure, rhabdomyolysis and intra-
vascular hemolysis have also been reported (11). In
some cases, severe coagulopathy can result in stroke
(7).Considering extensive differential diagnosis for skin
necrosis, the standard criteria for the diagnosis of lox-
oscelism syndrome is capturing the spider during biting
or capturing it in the place where biting occurred and
its confirmation by a reliable arachnologist(12).
Dapsone, antihistamines, colchicine, corticosteroids and
hyperbaric oxygen have been used for treatment.
Treatment with dapsone can alleviate bite marks and
symptoms (8, 13). Antivenom reduces the size of the
necrotic area. The faster the antivenom is administered,
the less the manifestations. It has been proven useful
during the first 4 hours after the bite but according to
an investigation, it was useful even after 12 hours (14).
The bite-induced necrosis spreads in a few days and is
completed in a few weeks. Treatments include initial
debridement and in later stages, after improvement of
the inflammation, graft is used in case of severity (9).
b) Hobo spider
Hobo spider is a brown-colored spider with gray marks
along its body (Figure 3). The reason for its name is its
aggressive behavior following slight provocation. Symp-
toms induced by its bite are similar to those of the
brown recluse spider but necrosis is rare and perma-
nent scar is probable on the site of biting (12). The
cause of necrosis is the hemolytic property of the ven-
om or transmission of pathogenic bacteria inside the
site of biting (15). The systemic symptoms of biting are
reportedly cephalalgia and in some rare cases anaphy-
laxis and death. The treatment is similar to that of the
brown recluse spider. Moreover, resection should not
be conducted before the completion of the necrosis
process (8).
c) Black widow spider
Black widow spiders have a black hairless body. Males
are smaller than females. Its major characteristic is a
red marking on its abdomen similar to an hourglass
(Figure 4). It is not aggressive under normal circum-
stances but attacks if disturbed, especially while pro-
tecting its egg sacs. Moreover, it is the most important
venomous spider in North America and Australia (2, 3).
Its venom is alpha-latrotoxin (neurotoxic venom) which
results in the exocytosis of synaptic vesicles from para-
sympathetic terminals due to the stimulation of calci-
um-dependent mechanisms, releasing catecholamines
and acetylcholine (8).
The symptoms induced by the bite of this spider are
called latrodectism. The pain from its bite is similar to
that of a pinprick. A lesion similar to the target lesion
can be observed in the site of biting (16).Latrodectism
starts in a few minutes with the development of pain th-
Studies include in qualitative synthesis
N=25
Observational 10
Review 7
Book 2
Case report 2
Randomized clinical trial 1
Case series 1
Photo quiz 1
Guideline 1
Excluded by published in other
language (except English or Persian)
and/or full text review: 21 records
Excluded by abstract and/or full text
review: 211 records
Duplicate records: 6 records
Studies that we couldn’t access
abstract or full text of them: 9 records
Total search result:
272 records
Additional records identified in
Google Scholar: 2 records
Primary Search result:
270 records

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Emergency (2014); 2 (2): 54-58
56
Figure 2: Brown Recluse Spider. Photograph by Richard
S.Vetter.Reproduced with permission
from:australianmuseum.net.au
Figure 3: Eratigena-Agrestis (Hobo) Spider. Reproduced
with permission from:www.spiders.us
Figure 4: Black Widow Spider (Photograph by Eric R.
Eaton. Reproduced with permission from
bugeric.blogspot.com
Figure 5: Phoneutria, commonly known as Brazilian wan-
dering spider or armed spider. Image
source:wikipedia.org
rough the whole body and symptoms such as emesis,
respiratory failure, delirium, partial paralysis of limbs,
abdominal muscle cramps, hypertension, pyrexia, fas-
ciculation and muscle spasm are developed within a
few hours (17). Symptoms may be mistaken with acute
abdomen. Mortality following biting is less than 1 %
and the risk of death following biting is high in two age
spectrums. Bites usually occur during warm months
(7). The chelicerae of this spider rarely leave a mark.
Following the bite, erythema, diaphoresis and piloerec-
tion are observed around the site of bite in 25 % of the
cases (3). Diagnosis is based on the patient's history.
While it can be difficult in children, hypertension, dis-
tress, diaphoresis and irritability can suggest diagnosis
in these cases (18).
The treatment of these patients consists of using muscle
relaxants, narcotics, analgesics, intravenous calcium
and antivenom. Narcotics and benzodiazepines relieve
muscle spasms. Antivenom treatment is recommended
for children, pregnant women the elderly and also pa-
tients with severe local symptoms, severe pains neces-
sitating repeated administration of narcotics and sys-
tematic symptoms (3). In the case of IV administration,
the antivenom should be diluted and injected slowly
(17). However, some centers have recommended IM
administration in order to reduce its complications. In
the case of IM administration, the effect is delayed and
symptoms take longer to improve (3) (within 1-5 days).
Some may suffer from chronic pains even after proper
antivenom treatment (18).
d) Armadeiras (armed spiders)
Armed spiders have long arms. Since they often hide in
banana boxes, they are known as banana bunch spiders
by locals (Figure 5).The symptom of its bite is severe

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57
Rahmani et al
Figure 6:Funnel Web Spider (Reproduced with permission
from australianmuseum.net.au
Figure 7:Tarantula Spider (Mexican Red Legged Tarantu-
la) Photograph byRicBolzan. Reproduced with permission
fromaustralianmuseum.net.au 
pain which is observed in 96 % of patients (18). The
bite of this spider can cause respiratory failure and
death at both ends of the age spectrum (8). Its venom is
neurotoxic thus stimulates the autonomic nervous sys-
tem (tachycardia, hypertension, diaphoresis and saliva-
tion), priapism, dizziness and visual disturbances (19).
This venom is recommended to be used for controlling
permanent pathological pains due to its different com-
pounds and also its effect on pain neurons (20).
Patients receive supportive treatment including pain
and symptom control. There is antivenom for the
treatment of these patients but it is used in few cases
(21). With regard to the probability of respiratory fail-
ure in these patients, it is contradictory to use narcotics
for pain control. Therefore, local nerve block anesthesia
is recommended (8).
e) Funnel-web spider
Funnel-web spider, the most dangerous spider in the
world, is aggressive in the absence of provocation
(Figure 6) (3). The structure of this spider’s web is fun-
nel-shaped, hence the name (8).The venom of this spi-
der is neurotoxin and contains a large amount of pep-
tides (22, 23). Delta atracotoxin, one of the peptides in
the venom, delay the activation of voltage-dependent
sodium channels resulting in repeated stimulation and
release of massive neurotransmitters in nerve endings
(24). Robustoxin is another toxin in the venom of this
spider which is a fatal peptide and can be used for im-
munization (25).
Local symptoms include pain, diaphoresis, hives and
piloerection. Systemic symptoms include stimulation of
the parasympathetic system (nausea, emesis, salivation,
sialorrhea and tearing), cardiovascular system (hyper-
tension, mostly tachycardia and in some rare cases
bradycardia and hypotension), nervous system (fas-
ciculation and perioral paresthesia), non-cardiac pul-
monary edema (more prevalent in children), agitation,
and cephalalgia(3).
Treatment includes supportive measures, elastic band-
age for blocking lymph flow, limb immobilization and
rapid transportation to the hospital. Antivenom is the
definite cure and should be administered up to 15
minutes after opening the bandage. In the case of uncer-
tainty about the bite and exhibition of the first systemic
symptoms, 2 vials of antivenom are administered and in
the case of severe symptoms 4 vials are administered.
Other therapeutic measures include hemodynamic sup-
port, ventilatory support and the administration of tet-
anus vaccine. These measures reduce the risk of neuro-
logical complications and mortality and improve the
performance of patients after being discharged (7).
f) Tarantula
Tarantula is recognized by its hairy 3-inch brown or
black colored body (Figure 7). This type of spider is
kept as pet (8). Its venom is not dangerous for the hu-
man being and merely creates lesions without any spe-
cific systemic reaction except for pyrexia. Tarantula’s
defense mechanism is the hair on its body which stands
out and moves when alarmed (2). If these hairs enter
the eye, they can result in the inflammation of all of the
layers of the eye. Eye wash and topical corticosteroids
are recommended in the case of uveitis (8).
Recommendations for future
The human being has always been frightened of spiders
but few of them are venomous and thus real threat to
human health. However, since venomous spiders are
sometimes fatal, bites are recommended to be taken
care of. Moreover, it is recommended to be adequately
familiar with necessary treatments. With regard to the
identification of venomous spiders in our country in-
cluding widow spider which exists in the majority of
provinces, healthcare personnel must be familiar with

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Emergency (2014); 2 (2): 54-58
58
the symptoms of the bites of venomous spiders and also
it is essential to prepare antivenoms in the country for
the treatment of spider bites. Finally, further domestic
investigations are necessary on the distribution of ven-
omous spiders and suspected cases of spider bite
should be reported to related centers to reduce the
damages caused by biting.
Acknowledgments:
We acknowledge Managers of www.spiders.us;www. aus-
tralianmuseum.net.au;www.bugeric.blogspot.com; and ww
w.wikipedia.orgsites for let us to use their own images.
Conflict of interest:
None
Funding support:
None
Authors’ contributions:
All authors passed four criteria for authorship contribu-
tion based on recommendations of the International
Committee of Medical Journal Editors.
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