Killer funnel-web spiders invade Sydney!

January 22, 2010, 1:37 am

The Independent (U.K.) reported today that the potentially deadly funnel-web spider (Atrax robustus) has had a banner year in the area around Sydney, Australia, where a combination of unusual moisture and cool temperatures have created ideal conditions for the creatures to breed.  Funnel-webs have not only long (4-5  mm) and extremely sharp fangs, but also a neurotoxin that can be fatal if not counteracted with antivenom.  This neurotoxin causes wholesale relase of neurotransmitters, especially acetylcholine.  The puncture wound is intensely painful. After an initial period of hypertension caused by α-adrenergic components, victims present with the typical muscarinic manifestations of cholinergic syndrome (mnemonic: SLUGBAM): Salivation, Lacrimation, Urination, Gastronintestinal emptying (Diarrhea), Bronchorrhea and Bronchospasm, Abdominal distress, and Miosis.  Nicotinic manifestations — fasciculations, muscle spasms — also occur.  Death can happen early from the “Killer Bs” — bronchorrhea and bronchospasm — or later from pulmonary edema and cardiovascular collapse.  Fortunately, the Indepedent‘s headline — “Killer funnel-web spiders” — was somewhat hyperactive.  Although the bite of Atrax robustus can be and has been fatal, there have been no reported deaths since the introduction of the antivenom in 1981.  This may be because all Sydney funnel-webs live within commuting distance of the Opera House, a relatively small area dense with well-supplied hospitals.

The initial treatment of funnel-web spider bites involves the so-called pressure immobilization technique.  The affected limb is wrapped entirely in an elastic compressive bandage (to decrease lymphatic spread of the toxin) and splinted.  The patient is then transported to the nearest hospital where antivenom can be administered if indicated.  As in cases involving other cholinergic toxins such as organophosphate insecticides or nerve agents, atropine can be used to diminish airway secretions.

This clip from World’s Deadliest Animals: Urban Jungle gives another look at this fascinating spider:

Finally, as always when I read about Australia’s many poisonous creatures, I’m drawn back to Bill Bryson’s brilliant travel book In a Sunburned Country:

“As you can imagine, I was particularly attracted to all those things that might hurt me, which in an Australian context is practically everything.  It really is the most extraordinarily lethal country.  Naturally they play down the fact that every time you set your feet on the floor something is likely to jump out and seize an ankle. . . .

“Sydney has no box jellyfish, I was pleased to learn.  The famous local danger is the funnel web spider, the most poisonous insect in the world with a venom that is ‘highly toxic and fast-acting’ A single nip, if not promptly treated, will leave you bouncing around in the grip of seizures of an incomparable liveliness; then you turn blue; then you die. Thirteen deaths are on record, though none since 1981, when an antidote was devised.”

5 Comments:

  1. cjpharm Says:

    It’s probably worth noting that Sydney Funnel Webs have been known to turn tourist and pack themselves in peoples suitcases – they like any warm dark space. My brother was actually bitten in Victoria (on a Navy Base) and the fact that the Base Hospital had antivenom in stock indicates it wasn’t unheard of there.

    Also, there are many other Funnel Web tarantulas in Australia (e.g. the Northern Tree Dwelling Funnel Web) which can be even more toxic than their Sydney cousin. They haven’t, however, caused as many deaths, mainly due to the low population in their natural habitats.

    The MJA published a very good review of reported cases of Australian Funnel Web bites in 2005 (MJA 2005; 182 (8): 407-411).

    Christine

  2. Leon Says:

    Christine:

    Thanks for the comments. It is my understanding — correct me if I’m wrong — that although other funnel-webs are found in other areas of Australia, and may be chemically more toxic than the Sydney, Atrax Robustus is the only species that has been associated with human fatalities.

    I did look at the MJA review form 2005 while compiling this post.
    For the record, the authors of that study analyzed 138 cases of funnel-web bites in which the spider was definitely identified by experts; 77 cases were classified as severe, and antivenom was used in 29. Some of their findings:

    – Although definite funnel-web bites occurred in all eastern states and territories of Australia, severe envenomation occurred only in New South Wales and southern Queensland.

    – There were 13 deaths (7 in children) all before 1981.

    -There were 3 adverse effects in 75 patients who received antivenom.

    – There was complete response to antivenom in 97% of expertly identified cases (some of which involved, not. A. robustus, but Hadronyche species).

  3. Nick Says:

    watching the video by chance or design,well it is obviously by chance it is so deadly to primates,but very strange how it doesn’t effect other mammals

  4. Leon Says:

    It is an interesting and mystifying quirk of nature, Nick. I think most scientists consider the unique sensitivity of the nervous systems of humans and other primates to Sydney funnel-web spider venom (atratoxin) to be just bad luck. it is true that mice, rabbits, and other non-primate mammals are relatively immune to the effects of the venom, requiring many times the dose that will affect humans. However, atratoxin is also quite effective in killing insects, which is certainly why it evolved.

  5. Nick Says:

    @Leon I also find it fascinating how it doesn’t effect other mammals only primates the way it does,one gene here or there and this is what you get

    But v annoying if it wasn’t for this i wouldn’t fear oz quite so much!