Spider Bites

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Introduction

The most frequently asked question related to spiders is “is it poisonous?” The answer is that I do not know. One has to eat a spider and if this results in one becoming sick or dying then the spider can be said to be poisonous. The question should be “is it harmful or dangerous and of medical importance?” Ménez writes that in 1781 Italian researcher Felix Fontana proved that viper venom was harmless when swallowed but highly toxic when injected into rabbits. Venom is the term used for toxic substances, composed of complex proteins and enzymes, that have to be injected into animal tissue with an injecting apparatus such as the sting of a scorpion or insect or the fangs of a spider or snake.

It must be noted that deaths from spider envenomation are rare and appear to be grossly exaggerated in all parts of the world. Deaths normally are the result of complications, such as infections or a weakened condition, and improper medical care.

Death or severe skin injuries are often reported in newspapers or via the internet but these are normally hoax claims which are circulated in ignorance. It has been estimated that of all the cytotoxic spider bites reported by doctors, 70-80% are proven not to be spider related at all. Further it must be noted that some people show reactions to relatively harmless spider bites. Despite all the anxiety over being bitten by spiders, there have been no known deaths from spiders bites in South Africa in the past 60 years.

To confirm a positive spider bite the spider has to be caught in the act of biting or the resulting signs and symptoms have to follow a specific course. A spider found randomly in the vicinity does not imply that it is the culprit and it is important that an expert identifies the collected specimen. Medical practitioners are not spider or spider bite experts and often make an incorrect diagnosis. Treatment must always be directed at treating the signs and symptoms that present and not the bite. Scorpions and venomous snakes can administer a full sting or bite without injecting venom and spiders can similarly bite without injecting venom. This is referred to as a dry bite.

Not everyone will be affected in the same way by a spider bite. The severity depends on the amount of venom injected, the health of the patient, allergies, age (small children and the elderly are more adversely affected) and the site of the bite. Some patients display symptoms of stress/trauma, incorrectly called “shock” that can be misleading, leading one to fear the worst of a harmless spider bite. Others will present with mild reactions.

Types of bites

Currently there are over 42751 described species of spiders in 110 families. Of these, about 2000 species and 70 families are known from South Africa. All these families, bar the Uloboridae, possess venom glands and are thus venomous but only three families  are known to contain spiders that are of medical importance and can therefore be said to be harmful to humans. There are probably other spiders that can inflict serious bites but only those that come into regular contact with humans are recorded as medically important. The medically important spiders can be summarised as follows (follow the links for more details):

Neurotoxic bites

Neurotoxic venom affects the neuromuscular junctions and has a general effect on the physiology of the person bitten with symptoms including sharp burning pain at the bite site, tender lymph nodes, severe muscle pain and cramps, chest tightness and pain, tremors, excessive salivation and watery eyes, facial swelling, droopy eyelids, anxiety, slight fever, slurred speech, nausea, vomiting and headaches,excessive sweating, heart palpitations, pins and needles, and breathing difficulties

 
 

Button spider (Latrodectus) bites

Button spiders fall in the genus Latrodectus (family Theridiidae) with six species occurring in southern Africa. Of these, Latrodectus indistinctus (Black button spider) is the most important species medically.

 

Cytotoxic bites

Cytotoxic venom causes death of tissue at the site of the bite, resulting often in a large ulcerating wound.

 

 

 

Sac spider (Cheiracanthium) bites

The Long-legged sac spider, Cheiracanthium furculatum is often found in houses and in South Africa has been implicated in 70-75% of spider bites that cause death of tissue at the site of the bite (necrotic envenomations).

 

Violin spider (Loxosceles) bites

The cytotoxic effects are more extreme with violin spider bites than with those of sac spiders. Bites normally occur at night and are not felt as the tiny fangs only just penetrate the skin. A swelling develops eventually resulting in a blister after 2-3 days. This collapses at 10 days leaving a necrotic crater-like lesion 20-100mm in diameter.

 

Sicarius bites

These spiders live in arid regions and hence are rarely associated with people. There are very few documented bites of humans by these spiders. Experimental animals bitten by Sicarius presented with massive tissue destruction and  death (77%), a postmortem revealing destruction of the internal organs. These spiders must be regarded as potentially lethal.

Minor Spider Bites

In 1939 Finlayson reported that the bite of Harpactirella lightfooti Purcell, 1902, Lightfoot’s lesser baboon spider, from Jutton Island and the Paarl area, to be of medical importance as test animals died. There appears to be no proof that these lesser baboon spiders are any more venomous than other local species of Harpactira (common baboon spider). Harpactirella are usually rather aggressive spiders but probably present with a similar reaction as some species of Harpactira namely, extreme local pain lasting from 1-20 hours. No further signs or symptoms were noticed.

Early experiments were done by Steyn (1959), where Palystes superciliosus (= Palystes natalius) were forced to bite guinea pigs on the nose with the subsequent death of the animals. Newlands and Martindale (1981) repeated the experiment and it was found that the guinea pigs died of stress/trauma. Anaesthetised guinea pigs did not die. There have been cases where humans bitten have presented with psychosomatic symptoms that are no more than an irritating reaction to Palystes bites.

There have been reports of bites by species of Pararabeus and Araneus (Araneidae), which resulted in a mild envenomation similar to button spider bites. Bites by spiders of the families Salticidae (jumping spiders) and Lycosidae (wolf spiders) may result in mild cytotoxic envenomation that is usually no more than a slight irritation. No treatment was required besides cleaning the bitten area.

Conclusion

It must be remembered that spiders bite as a method of defence, normally when one prods or squashes them. They are an important source of pest control thus eliminating harmful pesticides.

Publications (by date)

  • Finlayson MH, Smithers RHN. 1939. Harpactirerra lightfooti as a cause of spider-bite in the Union. South African Medical Journal 13: 808-809.
  • Steyn JJ. 1959. Die bekende dwaalspinnekop (Palystes Karsch) moontlik gevaarlik. Genskunde. 1: 63.
  • Dippenaar-Schoeman AS, Newland G. 1980. The Button spiders of South Africa. Pamphlet No 146, Farming in South Africa. Printed in South Africa by the Government Printer, distributed by the Director, Division Agricultural Information, Pretoria.
  • Newlands G, Martindale C, Berson SD, Rippey JJ. 1980. Cutaneous necrosis caused by the bite of Chiracanthium spiders. South African Medical Journal 57: 171-173.
  • Newlands G, Martindale CB. 1981. Wandering spider bite – much ado about nothing. South African Medical Journal 60: 142-143.
  • Martindale CB, Newlands G. 1982. The widow spiders: a complex of species. South African Journal of Science 78: 78-79.
  • Newlands G, Isaacson C, Martindale C. 1982. Loxoscelism in the Transvaal, South Africa. Transactions of the Royal Society of Tropical Medicine and Hygiene 76(5): 610-615.
  • Maretić Z. 1986. Spider venoms and their effect. In: Nentwig, W. (ed.), Ecophysiology of spiders. Springer, New York, pp. 142-159.
  • Newlands G. 1986. Necrotic arachnidism in southern Africa. Ph. D. thesis. University of Witwatersrand, Johannesburg.
  • Newlands G, Atkinson P. 1988. Review of southern African spiders of medical importance, with notes on signs and symptoms of envenomation. South African Medical Journal 73: 235-239.
  • Newlands G. 1989. Anthropods that sting and bite man – their recognition and treatment of patients. Journal of Continued Medical Education 17(7): 773-784.
  • Newlands G, Atkinson P. 1990. A key for the clinical diagnosis of araneism in Africa south of the equator. South African Medical Journal 77: 96-97.
  • Müller GJ, Koch HM, Kriegler AB, van der Walt BJ, van Jaarsveld PP. 1992. Comparison of the toxicity, neurotransmitter releasing potency and polypeptide composition of the venoms from Steotoda foravae, Latrodectus indistinctus and L. geometricus (Araneae: Theridiidae). South African Journal of Science 88:113-113.
  • Müller GJ. 1993. Black and brown widow spider bites in South Africa. A series of 45 cases. South African Medical Journal 83: 399-405.
  • Filmer MR, Newlands G. 1994. Araneism in Africa south of the equator with key to clinical diagnosis. Diseases of the Skin. 8(2): 4-10.
  • Lotz LN. 1994. Revision of the genus Latrodectus (Araneae: Theridiidae) in Africa. Navorsing van die Nasionale Museum, Bloemfontein 10(1): 1-60.
  • Croeser PC. 1996. A revision of the African huntsman spider genus Palystes L Koch, 1875 (Araneidae: Heteropodidae). Annals of the Natal Museum. 37: 1-122.
  • Lotz LN. 1996. The genus Cheiracanthium (Araneae: Clubionidae) in southern Africa. M. Sc. thesis. University of the Orange Free State, Bloemfontein, 1-96.
  • Schrire L, Müller, GJ, Pantanowitz L. 1996. The diagnosis and treatment of envenomation in South Africa. South African Institute for Medical Research, Johannesburg, pp. 51.
  • Croucamp W, Pantanowitz L. 1997. Necrotic araneism in South Africa. Diseases of the skin. 11(5): 18-25.
  • Müller GJ. 1999. Management of bites and stings: controversial aspects. Abstract of the 6th African Arachnological Colloquium. African Arachnological Society Newsletter 12.
  • Croucamp W. 2000. Spider bites – diagnosis and management. Journal of Continued Medical Education. 18(8): 670-678.
  • Haddad CR. 2002. Symptoms of the bite of an orb-web spider Araneus apricus (Araneae: Araneidae). South African Medical Journal. 92(7): 528-529.
  • Isbister GK, Gray MR. 2002. A prospective study of 750 spider bites, with expert spider identification. Queensland Journal of Medicine 95: 726–731.
  • Ménez A. 2003. The Subtle Beast. Snakes, from Myth to Medicine. Taylor & Francis, London.
  • Diaz JH. 2004. Global epidemiology, syndromic classification, management and prevention of spider bites. American Journal of Tropical Medicine and Hygiene. 71(2): 239–250.
  • Müller GJ. 2005. Management of venomous bites and stings: A mini-review. Unpublished notes.
  • Snyman C, Larsen N. 2005. Spider bite and its treatment in southern Africa. Occupational Health South Africa 11(2): 22-26.
  • Lotz LN. 2007. The genus Cheiracanthium (Araneae: Miturgidae) in the Afrotropical region. 1. Revision of known species. Navorsing van die Nasionale Museum, Bloemfontein 10(1): 1-60.
  • Vetter RS. 2008. Spiders of the genus Loxosceles (Araneae, Sicariidae): a review of biological, medical and psychological aspects regarding envenomations. Journal of Arachnology 36: 150–163.

Text by Norman Larsen ©


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