There are more than 34,000 different species of spiders
worldwide. However, there are only a few dozen spiders that
cause fairly pronounced envenomations in human beings. All
spiders are poisonous. However, all cannot pierce the skin,
and all do not have significant amounts of venom that cause
skin lesions or systemic illness in humans. Spiders have long
been a major cause of fears and phobias. The media has not
done the spider population any favors, and have always portrayed
them as evil creatures, dating back to the early days of film.
It is somewhat surprising that something so small can cause
such great fear. However, when one looks at an arthropod with
eight eyes and eight legs that can also run very fast, one
can easily understand how fears and phobias can develop.
Many spiders are capable of wind-blown disbursal. This is
called ballooning. It gives us some understand how spiders
have been found on even isolated islands.
The anatomy of an arthropod is segmented into two body parts,
the cephalothorax, which is the head and the upper torso,
and the abdomen. They have eight legs and the pedipalp, frequently
mistaken for fangs, is actually used to hold prey. Fangs are
usually tucked in, and therefore difficult to see.
Spider bite appearance/assessment
Spider bites can only be diagnosed if an individual brings
in the spider itself, or even crushed parts of the spider.
Beyond that, a diagnosis is based on clinical assumptions
and a good history. A spider bite is often confused among
healthcare providers with a variety of other illnesses including
bacterial infection, viral infection such as herpes, Lyme
disease, and bites of other insects. Treatment by the patient
prior to coming in can mask the appearance. Many individuals
will use Neosporin, and individuals who have an allergic response
to the Neomycin in the Neosporin can have a very red and inflamed
area, which on the surface makes the bite look much worse
then it actually is. A thorough history is very important.
Where have they been in the last week? Have they been indoors
or outdoors? When did the patient first notice the bite? Does
it itch? Does it burn? Have they recently traveled to another
area of the country? All of these questions are important,
when trying to diagnose a spider bite. Multiple bites are
rarely caused by spiders, as generally spiders usually only
bite once. A typical spider usually has a vesicle, and within
24-48 hours, it may or may not necrose, meaning the skin tissue
in the center may start to become friable and die. It is also
not uncommon to see satellite vesicles, which are small blisters
away from the main bite site. These can be anywhere from a
few inches to a foot away from the main bite site. Necrotic
arachnidism is a term given specifically to the bite of a
brown recluse spider. This refers to the ulcerative type lesion
that usually accompanies the spider bite, which has gotten
an enormous amount of press in the last few years. The venom
of a brown recluse is primarily comprised of proteins and
enzymes that actually cause some platelet disruption and tissue
damage. Rarely do these bites cause death. However there have
been reports in young children and the elderly. If there is
going to be systemic effects, which are generalized effects,
they will usually occur within the first 3 days of the bite,
and individuals will experience nausea, fever, chills, and
generalized muscle aches.
Spider Bite Treatment
Treatment is mostly supportive. If the healthcare provider
feels there is a secondary infection, then antibiotics should
be given. Those that cover staph and strep are highly advised.
Surgical debridement of the wound can be very helpful, cutting
back to clear clean margins and wet to dry dressings have
been very effective. Treatment such as localized electrical
shock, i.e. stun guns, hypobaric oxygen chambers, have all
been found to be useless, and can create more damage, despite
what you may see on other websites. There is no brown recluse
anti-venom that is commercially available at this time.
It is important to note that in May, 2002,
American College of Emergency Physicians contained an article
about new methods for detecting brown recluse spider venom.
This is important because accurately diagnosing a brown recluse
bite definitely impacts treatment. As per the article, one
of the most famous misdiagnoses occurred in New York with
a 7-month old who contacted cutaneous anthrax, but who was
initially diagnosed with a brown recluse spider bite. In a
study at the University if Michigan by a team of emergency
medicine investigators found early evidence that invasive
biopsies are not necessary and, in fact, the Loxosceles ELISA
assay was able to find brown recluse venom in hair samples.
However, testing must occur at least 7 days after the initial
envenomation. Since the vast majority of spider bite diagnoses,
specifically brown recluse spider bites, are difficult to
diagnose since the spider is not brought in, this would be
a beneficial test, to ascertain the etiology of the skin lesion.1
1American College of Emergency Physicians,
New Methods for Detecting Brown Recluse Spider Venom, May,
1. Emergency Medicine,
A Comprehensive Study, Tintinalli, Judith, Kelen, Gabor, Stapczynski,
2. Wilderness Medicine, Auerbach.