Saturday, 2 June 2012

Loxosceles reclusa, playing with poisonous violins

It has been quite a while since my last post on Poisons and Antidotes, but again, an email from my mother made me think of how important it is to help keep people updated on poisons and ways of fighting them. It is Springtime now, Summer is coming here in less than a month (at least in Europe) and we definitely need to be aware of insects and other sorts of animals that represent a danger for our sensitive organisms. An email my mum got from a friend containing pictures of a wounded man and his escalating injury, due to sting/bite from a Loxosceles reclusa, the brown recluse spider, triggered this informative post. The pictures are impressive, what makes the awareness ever more important. I am summarising in this post valuable information for you to build your knowledge and avoid being caught unprepared to fight back the necrosis caused by the venom of this common spider. The spider responded with legitimacy as a defense mechanism because it may have felt threatened, so don't go out there killing life forms, on the contrary, pretty much every poisonous organism represent a future medicine... so learn how to deal with it and protect yourself.


"Recluse spiders avoid areas where there is human activity, and prefer closets, guest rooms, basements, and attics. Outside, they like piles of rocks and leaves." [1].

Preferential biting:

"Most people are bitten on the hands or feet when they are handling infested items." [1]


"The spiders are tan to dark brown and nearly 1/4 (dime) to 1/2 inch (quarter) in body size. The immature spiderlings resemble adults in structure but have somewhat lighter coloration." [1].

The spider and the progression of its bite:

"The brown recluse spider is nicknamed the fiddleback or violin spider because of the distinctive dark violin-shaped marking on top of the cephlothoraxfront body section." [1] (see image below, right slide on the bottom).

"The bite of the brown recluse spider is usually painless. However, localized burning sensation often develops within the first hour and during the next 6-12 hours, a small pimple or blister forms. The surrounding tissue begins to darken and take a raised appearance. The venom of this spider can cause extensive tissue damage (necrotic reaction) and over the next 10-14 days, a sunken, open, ulcerated sore up to several centimeters in diameter. It normally takes 6-8 weeks for a brown recluse spider bite to heal. A large sunken scar may persist that requires surgery to repair. Not every brown recluse bite results in ulcer formation." [1]


"Brown recluse venom, like many of the other brown spider venoms, is cytotoxic and hemolytic. It contains at least 8 components, including enzymes such as hyaluronidase, deoxyribonuclease, ribonuclease, alkaline phosphatase, and lipase. Sphingomyelinase D is thought to be the protein component responsible for most of the tissue destruction and hemolysis caused by brown recluse spider envenomation." [2]


"Symptoms of systemic loxoscelism are not related to the extent of local tissue reaction and include the following:
  • Morbilliform rash
  • Fever
  • Chills
  • Nausea
  • Vomiting
  • Joint pain
  • Hemolysis
  • Disseminated intravascular coagulation (DIC)
  • Renal failure
  • Seizures
  • Coma" [2]

Treatment and Antidotes

"Treatment of brown recluse envenomation is directed by the severity of the injury. General wound management consists of local debridement, elevation, and loose immobilization of the affected area. Because the activity of sphingomyelinase D is temperature dependent, application of local cool compresses is helpful and should be continued until progression of the necrotic process appears to have stopped." [2]

Dapsone, an antibacterial inhibitor of the dihydrofolic acid, is not very recommended for the treatment due to the  strong secondary effects, for example hemolysis.

"No antivenom is currently approved for use in the United States, several groups in other countries are developing a Loxosceles antivenom. [2]

Current and Future Research 

"Experimental anti-North American Loxosceles antivenoms protected mice of the systemic toxicity and were able to prevent necrosis in rabbit skin after the injection of the venom." [3]

[1] Enthomology and Plant Pathology (University of Oklahoma), [], last accessed on the 02nd of June 2012, last update unknown.

[2] Medscape reference, Brown recluse spider envenomation, [], last access on the 02nd of June 2012, last updated on the 21st of May 2010.

[3] de Roodt, A. R., Estevez-Ramírez J., Litwin, S., Magaña P., Olvera, A., Alagón, A.. (2007). "Toxicity of two North American Loxosceles (brown recluse spiders) venoms and their neutralization by antivenoms". Clin Toxicol. 45(6), pp. 678-87.

1st image from [2].

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