2. ORDER ARANEA
All spiders, with the exception of two small
groups, are venomous. There are over
100,000 species of spiders. However, only
about 20 species cause serious envenoming
in humans, while about 150 to 180 can cause
significant toxicity. The common Indian
species that cause serious envenomation
include brown recluse, black widow, wolf
spider, and tarantula. Funnel web spider
which can cause significant envenomation is
found only in the Australian continent.
3.
4. GENERAL ANATOMY
■ Anatomically, a spider has a cephalothorax
and an abdomen with 4 pairs of legs fanning
out from the thorax. Two claw-like fangs called
celicera protrude from the head and are
connected to venom glands which are under
voluntary control.
■ Although the venom is quite potent in many
species, serious envenomation is rare because
of inadequate injection mechanism, and small
quantity injected with each bite.
■ During its normal life span of 1 to 2 years, a
spider moults several times, as a result of
which there may be periodic changes in colour
and markings
5. ■ Spiders are extremely shortsighted,
and depend mainly on sense of touch
and vibration. The eyes are on the
front part of the cephalothorax. Most
spiders have 8 eyes. Their size and
position varies by spider type.
■ Some large spiders (e.g. Huntsman
spider, wolf spider, orb weaving
spider), possess large spines on their
legs. The spines are raised from a
prostrate to a vertical position when
the spider is irritated.
6. If the spider is grabbed,
picked up, or brushed
off, injuries
(severe pain, erythema,
pruritus) from the
spines may occur.
These injuries often
occur in conjunction
with a bite by the same
spider, and splinters are
usually found at bite
sites.
7.
8. BROWN RECLUSE
OTHER COMMON NAMES
Fiddle back, violin, or brown
spider.
SPECIES
Loxosceles reclusa,
L. Laeta,
L. Deserta,
L. Unicolor,
L. Arizonica,
L. Rufescens.
9. PHYSICAL APPEARANCE
■ It is a small (6 to 20 mm long), orange or
reddish brown or grey spider, with a brown
violin shaped mark on its back. It infests
dark areas such as basements, under rocks,
and amid woodpiles. The female is more
aggressive than the male and bites when
provoked.
■ Loxosceles spiders can be differentiated
from most other “garden” brown spiders, of
which there are many, by its set of six eyes
(three pairs), rather than eight. Their webs
are distinguished by a bluish hue.
11. VENOM
■ The venom is cytotoxic and consists of
several toxic components including
hyaluronidase, ribonuclease,
deoxyribonuclease, alkaline phosphatase,
lipase, and sphingomyelinase D. The last
mentioned is the main constituent which is
responsible for tissue destruction. It reacts
with sphingomyelin in the RBC membrane
causing the release of choline and n-
acylsphingosine phosphate. This causes
severe intravascular occlusion of micro-
circulation leading to necrosis.
12. ■ Venom toxins may act as proteases upon
molecular constituents of plasma
extracellular matrix (fibronectin and
fibrinogen), and basement membrane
constituents (entactin and heparin sulfate
proteoglycan). All of these degrading
activities may be responsible for producing
hemorrhage, delayed wound healing, and
renal failure, as well as the spreading of
other noxious toxins (e.g. Dermonecrotic
protein). By disrupting the sub endothelial
basement membrane, blood vessel wall
instability and increased permeability can
occur.
13. CLINICAL FEATURES
1. LOCAL
A. The bite itself is usually painless, but later begins
to bleed and ulcerate in 2 to 8 hours. The initial
reaction often consists of erythema and pain or
pruritus. A small vesicle may form at the bite area,
and the lesion may take on a “bulls eye” or “halo”
appearance, having a central vesicle surrounded by
an erythematous and ecchymotic area.
B. Ulcerated lesions if untreated, usually enlarge
until about a week when eschar formation takes
place. Granulation and healing takes up to 2 months
to be completed.
C. In severe cases, cutaneous necrosis may occur
and may extend to involve subcutaneous fat and
muscle.
14.
15. 2. SYSTEMIC
A. Systemic features (“loxoscelism”)
include fever, chills, nausea, skin rash,
myalgia, arthralgia, headache, vomiting,
haemolysis, DIC, shock, renal failure,
jaundice, convulsions and coma.
B. Acute tubular necrosis with resulting
oliguria or anuria may develop in
patients with severe haemolysis.
C. Fever is common in patients with
systemic effects and may develop more
often in children. Fever may be
associated with chills and night sweats.
16.
17. DIAGNOSIS
1. Leucocytosis (20,000 to 30,000 per
cubic mm).
2. Evidence of haemolysis and dic:
decreased levels of fibrinogen, clotting
factors, and platelets; increased levels
of fibrin degradation products;
prolonged PT and PTT; spherocytosis,
positive d-dimer assay, and coomb
positive haemolytic anaemia.
3. Abnormal renal and liver function
tests.
18. TREATMENT
1. LOCAL
A. Wound cleansing.
B. Immobilization of bitten
extremity.
C. Tetanus prophylaxis.
D. Analgesics: persistent pain may
necessitate lumbar sympathetic blocks.
Application of cold compresses may help.
E. Antipruritic:
Diphenhydramine 5 mg/kg/day orally, with a
maximum dose of 25 to 50 mg four times a
day. Hydroxyzine may also be used: 25 to 50
mg every 6 to 8 hours; maximum dose 400
mg/day.
F. Antibiotics, if wound gets infected.
19. 2. SYSTEMIC
A. Admit patient to hospital and
monitor for evidence of
hemolysis, coagulopathy and
renal failure.
B. If haemoglobinuria occurs,
renal failure may be prevented by
increasing IV fluids, and
alkalinizing urine.
C. Significant hemolysis should
be treated with transfusions.
20. BLACK WIDOW
Widow (or hour-glass) spiders
belong to the latrodectus species
of phylum arthropoda.
OTHER COMMON NAMES
Hourglass
spider.
SPECIES
Latrodectus
mactans.
21. PHYSICAL APPEARANCE
■ The widow spiders are cosmopolitan
and are found all over the world, except
regions with extremes of climate (polar
regions, hot deserts, and high
mountains). They are easily identified
because they are the only spiders with a
black, globose abdomen.
■ The female is much larger than the
male with a leg span of 5 cm and body
length of 1.5 cm. It has a characteristic
red hourglass spot on the back of its
shiny black body.
22. ∙The male has more colorful white markings and
is less aggressive than the female. In fact, the
popular name “black widow” is due to the
female’s practice of killing its partner after
insemination.
■ The preferred habitats of these spiders include
outdoor toilets, stables, barns, woodpiles, and
dark crevices. They usually spin a somewhat
irregular web in various corners of undisturbed
areas of homes or the outdoors.
∙These spiders are found in open country areas,
dark places, rubbish heaps, wood heaps, stacks
of bags, or of scrap metal, under the bark of dead
trees, empty tins, unused buckets, beneath or
between stones, behind ferns, near gas or water
meters, old boxes, etc.
23. VENOM
■ The venom of black widow is
neurotoxic, with six active
components of molecular
weight ranging from 5000–
130,000 D. The main component
is alpha latrotoxin which binds
avidly to a specific presynaptic
receptor.
24. ■ The venom affects the motor
endplates of neuromuscular synaptic
membranes by the binding of
gangliosides and glycoproteins at the
synapses. This causes the channels for
sodium influx into neurons to remain
open, as a result of which there is
extensive release of acetylcholine and
noradrenaline into the synapses,
thereby inhibiting reuptake. The end
result is massive stimulation of motor
endplates as the venom travels through
the lymphatic system.
25. CLINICAL FEATURES
(LATRODECTISM )
GRADE 1
1. Sharp pain at bitesite,
which may have one or
two small puncture wounds,
1 to 2 mm apart. The immediate
area may be warm, mildly
indurated, and slightly reddened.
Swelling of the affected part may
occur after red-back spider bites.
2. No systemic features.
26. GRADE 2
1. Muscular pain in bitten
extremity.
2. Extension of pain to the
trunk.
3. Local diaphoresis of bitten
extremity.
4. Tender regional
lymphadenopathy may be
present.
5. No systemic features.
27. GRADE 3
1. Generalized muscle pain and weakness, with
difficulty in walking.
2. Generalized sweating.
3. Tachycardia and hypertension are quite
common.
4. ECG changes have been reported in a few
victims: slurring of the QRS with ST and T
segments depression, prolonged QT interval, and
changes consistent with inferolateral ischemia.
5. Leucocytosis is a common finding.
6. Nausea, vomiting, and headache are also very
common.
7. Priapism, urinary retention, pyuria, proteinuria,
microscopic haematuria, and testicular pain have
been reported in a few cases.
28. 8. During this period the victim often
displays a contorted, grimacing, sweating
facial appearance, referred to as “facies
latrodectismica”.
9. In severe cases, the following
manifestations occur: ptosis, salivation,
hyperreflexia, tremor, convulsions,
tachypnoea, and respiratory compromise.
Board-like rigidity of the abdomen,
shoulders, and back may develop. Although
uncommon, acute renal failure has been
reported following envenomation. Death is
uncommon, but is more likely in the case of
infants, old individuals, pregnant women,
and chronic invalids.
30. TREATMENT
1. Calcium gluconate IV (10 ml of 10%) has been
traditionally advocated for pain relief, but its actual
efficacy is doubtful.
2. Pain is usually better controlled with a
combination of IV morphine or pethidine and
benzodiazepines (diazepam or lorazepam). Milder
cases may be treated with aspirin, paracetamol,
and/or codeine.
3. Application of cold or warm compresses (as guided
by patient comfort) to bitten site is usually helpful.
4. Swelling responds to non-steroidal anti-
inflammatory drugs.
5. Muscle relaxants such as diazepam,
methocarbamol, or dantrolene may help relieve
muscle spasm.
6. Tetanus prophylaxis is essential.
31.
32. 7. Wound care:
A. Cleansing with antiseptics.
B. Immobilization, elevation,
and serial observation.
C. If infection sets in,
antibiotics must be
administered.
D. Surgical intervention
(excision) may be necessary if
lesion exceeds 4 cm at 12
hours post-envenomation.
