Editorial Necrotising arachnidism Does the white-tailed spider deserve its bad name?
MJA 1999; 171: 98
In 1976, Southcott brought Loxosceles to the attention of
Journal readers, reporting its occurrence in Adelaide and
Sydney.3 From the late 1970s an
increasing number of patients have been presenting to doctors
throughout Australia with bites resulting in local tissue injury,
ranging from a tiny ulcer through to very extensive areas of
full-thickness skin necrosis.2,4 Following a report of one
such case in the Journal,5 Sutherland, in an editorial
entitled "Watch out, Miss Muffet!", speculated on causative
organisms, mentioning, in particular, the white-tailed spider
(currently designated Lampona cylindrata).6
Since then Australian poisons information centres have seen a steady
increase in calls about definite or suspected spider bite, and such
calls are now the single most common reason for calling a poisons
information centre,7 with a 30% increase in calls
related to spider bite in the last two years alone. Casual
conversation with many urban general practitioners will often
reveal that they see a small but growing number of cases of suspected
spider bite resulting in local tissue injury, varying from mild to
quite severe. Currently, there is no system for national collection
of these case data to ascertain the true extent of the problem, nor to
confirm that numbers of cases are rising. In many cases the bite is
ascribed to the white-tailed spider, despite a singular lack of
evidence.
The white-tailed spider is a common native urban spider, frequently
found in homes, where it roams in search of prey.2 Published venom
research and case reports of bites have been reviewed and do not reveal
evidence that this spider commonly causes tissue injury.8,9 There are only
four published case reports of tissue injury and in none of these cases
was the spider formally identified.10-12Pincus et al add a
further 12 cases, but in only three cases was the spider formally
identified by an expert. In two this was a white-tailed spider, while
the third case involved a black house spider (Badumna
species). This adds to the still scarce case reports of necrotic bites
by identified spiders and, most importantly, provides three cases
with expert identification.
Of the two confirmed white-tailed spider bite cases reported, one
developed shallow ulcers only, the other a small ulcer that healed
within one month. Both cases are therefore at the mild end of the
necrotising arachnidism spectrum.
What is the mechanism of injury in necrotising arachnidism and how
might we treat it? Recluse spiders have been studied in detail, but the
mechanism of venom injury is still contentious.2 Worse, in North
America, where these spiders are native and frequently cause bites,
there is neither concordance on treatment nor a clearly effective
treatment.2 Experience there does
suggest that early surgical debridement may extend the lesion, that
early skin grafting usually fails, that antibiotics are unhelpful
unless there is a clearly identified and targeted secondary
infection and that no specific therapy is helpful, with the possible
exception of hyperbaric oxygen therapy.2 This treatment for
necrotising arachnidism is being tried in a number of hyperbaric
units around Australia, with mixed but encouraging
success.11 It is probably time to
formalise this by running a multicentre trial to establish the
validity and indications for this form of treatment.
In the only two cases I have seen in South Australia where a spider was
clearly caught biting and subsequently identified, it was a recluse
spider (Loxosceles), not a white-tailed spider.2 In my experience
with many cases of necrotising arachnidism over nearly 20 years, the
white-tailed spider is often suspected but never confirmed to be the
culprit. In most cases, a spider is found in the house after the bite and
an unsubstantiated link is made.
The increasing tendency of the media and the medical profession to
blame the white-tailed spider for necrotising arachnidism is
unfortunate, as it establishes a common belief that the cause is known
when in truth it is not. In Brazil, wolf spiders were long blamed for
necrotising arachnidism until a detailed study showed that recluse
spiders were the culprits.13 A concerted effort to
determine which species of spiders (or perhaps some other organism)
can cause necrotising arachnidism should become a prime focus for
research in this field. Once a cause is known, specific treatments can
be more reliably investigated and preventive measures devised.
Julian White
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- Julian White
- 1.
- Pincus GL, Winkel KD, Hawdon GM, Sutherland SK. Acute and recurrent skin ulceration after spider bite. Med J Aust 1999; 171: 99-102.
- 2.
- White J, Cardoso JL, Fan HW. Clinical toxicology of spider bites. In: Meier J, White J, editors. Handbook of clinical toxicology of animal venoms and poisons. Boca Raton: CRC Press, 1995: 259-329.
- 3.
- Southcott RV. Spiders of the genus Loxosceles in Australia. Med J Aust 1976; 1: 406-408.
- 4.
- Sutherland SK. Spider bites in Australia; there are still some mysteries [editorial]. Med J Aust 1983; 2: 597.
- 5.
- Spring W. A probable case of necrotizing arachnidism. Med J Aust 1987; 147: 605-607.
- 6.
- Sutherland SK. Watch out, Miss Muffet! [editorial]. Med J Aust 1987; 147: 531.
- 7.
- New South Wales Poisons Information Centre. 1998 Annual Report. Sydney: New Children's Hospital, 1999.
- 8.
- White J, Hirst D, Hender E. 36 cases of bites by spiders, including the white-tailed spider, Lampona cylindrata. Med J Aust 1989; 150: 401-403.
- 9.
- Atkinson RK, Wright LG. Studies of the necrotic actions of the venoms of several Australian spiders. Comp Biochem Physiol 1991; 98: 441-444.
- 10.
- Grey M. A significant illness that was produced by the white-tailed spider, Lampona cylindrata [letter]. Med J Aust 1989; 151: 114-116.
- 11.
- Skinner MW, Butler CS. Necrotising arachnidism treated with hyperbaric oxygen. Med J Aust 1995; 162: 372-373.
- 12.
- Chan SW. Recurrent necrotising arachnidism. Med J Aust 1998; 169: 642-643.
- 13.
- Ribeiro LA, Jorge MT, Piesco RV, Nishioka S deA. Wolf spider bites in Sao Paulo, Brazil; a clinical and epidemiological study of 515 cases. Toxicon 1990; 28: 715-717.