The Brown Recluse

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Source (1,2,5)

The Brown Recluse, belonging to the Loxosceles genus of arachnids, is known for its dark brown violin shape on the cephalothorax and its 6 eyes in comparison to that of most other spiders that have 8. The Brown Recluse is native to the United States and can primarily be found in the southern states, but is not confined to the regions depicted in the figure below. Brown Recluse spiders live in cool, dark areas such as under rocks or dead trees. They rarely bite unless provoked and many bites occur due to human intrusion.

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Toxicokinetics (1,5)

The Loxosceles genus of spiders contains venom that includes phospholipase, protease, esterase, collagenase, hyaluronidase, deoxyribonuclease, ribonuclease, dipeptides, dermonecrosis factors, and sphingomyelinase D. This venom is the most potent among the arachnids. Once injected, the venom can cause significant damage to blood vessels and tissues surrounding the site of envenomation. The venom will cause the patient to release cytokines and interleukins to aid in the inflammatory response, but these can have a harmful effect on the body resulting hemolysis, thrombocytopenia and end-organ damage.

The venom of the brown recluse is not known to be carcinogenic

Mechanism of Action (5)

The venom of the Brown Recluse has coagulation properties which can cause vascular endothelial damage. There are also adhesions of neutrophils to the capillary walls. Due to its synergistic effects, sphingomyelinase D is the primary enzyme responsible for the dermonecrotic factors and activates a complementary cascade causing several proteases to degrade collagen, fibronectin, fibrinogen and gelatin.

Signs and symptoms of toxicity (1)

A bite from a Brown Recluse is similar in pain to that of an ant sting and acts in various stages as seen below

  1. A burning sensation along with pruritus and an increase in erythema around the site happens within 30 to 60 minutes of the bite.
  2. At 1 to 8 hours the lesion site becomes warmer and the redness will grow in diameter and eventually start turning purple.
  3. A vesicle may form at this point and start to enlarge and is the precursor to pustule formation.
  4. Lymphadenopathy may occur as the site becomes even larger along with an increase in pain.
  5. The central pustule will eventually rupture resulting in various levels of visualized necrosis.

In more serious cases bites can often prove to be detrimental to the patient as necrosis can enter in to muscle tissue. A patient may experience symptoms such as fever, malaise, stomach cramps, nausea and vomiting, jaundice, spleen enlargement, hemolysis, hematuria, and thrombocytopenia. If the case is severe enough the patient may experience intravascular hemolysis, hemolytic anemia, thrombocytopenia, hemoglobinuria, renal failure and ultimately death.

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Treatments (3,4)

There is no antivenom for a bite produced by the Brown Recluse. Due to the very toxic nature of the venom it is important to act quickly if a bite is suspected. There are several steps t0 take after you have been bitten which are listed below.

  1. Keep affected limbs raised to help reduce swelling at the site
  2. Clean the bite with soap and water to prevent infection
  3. Apply ice to the bite to help soothe the pain and prevent inflammation
  4. Apply antibiotic cream/ointment to help relieve itching and prevent infection
  5. Take anti-inflammatory medication such as acetaminophen or ibuprofen
  6. See a doctor if symptoms worsen

Although the steps above are typical to help counteract a Brown Recluse bite, there is research that suggests a similar, but more particular regimen might be more effective. Dr. Major tested his regimen (listed below) with 20 different Brown Recluse spider bites. The treatment regimen rapidly ended toxicity and was well tolerated by each individual in the study.

  1. Tetanus booster (if not up to date)
  2. Gram positive antibiotic therapy (Cephalexin 500 bid)
  3. Aspirin (1 full strength/day) and prednisone (80-100mg/day) until surrounding erythema is reduced
  4. Gastric protection
  5. Pain relief

References

  1. Chapter 26: Toxic Effects of Plants and Animals. Toxic Effects of Plants and Animals | Casarett and Doull’s Toxicology: The Basic Science of Poisons, 8e | AccessPharmacy | McGraw Hill Medical (ohio-state.edu)
  2. How to Identify and Misidentify and a Brown Recluse Spider. UC Riverside: Spider Research. How to Identify and Misidentify a Brown Recluse Spider | Spider Research (ucr.edu)
  3. Major, T. (2017). Clinical Experience With Management of 20 Brown Recluse Spider Bites: An Effective Treatment Regimen. Clinical Experience With Management of 20 Brown Recluse Spider Bites: An Effective Treatment Regimen (nih.gov)
  4. Treatment for a Brown Recluse Bite. Treatment For A Brown Recluse Bite – HealthPrep.com
  5. Anoka, I. et al. (2020) Brown Recluse Spider Toxicity. Brown Recluse Spider Toxicity – StatPearls – NCBI Bookshelf (nih.gov)