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Toxicology – Black Widow Spider (Latrodectus) Envenomation
Source
Black widow spiders are found throughout the United States, especially in warmer southern regions. Only female spiders bite humans. They are typically identified by markings on the abdomen—most commonly a red hourglass on the underside. These spiders tend to inhabit dark, undisturbed areas such as woodpiles, garages, and sheds.
Typical Presentation
Patients often present after a painful spider bite followed by progressive muscle pain and systemic symptoms. In children, symptoms may be severe and mimic other acute conditions such as abdominal emergencies.
Clinical Features
The bite initially causes localized pain, followed by redness and sweating at the site. Systemic symptoms may include muscle cramps and fasciculations, severe abdominal pain and rigidity, nausea, vomiting, weakness, headache, dizziness, chest pain, and elevated blood pressure. In some cases, unusual findings such as priapism may occur. Symptoms tend to be more severe in children and older adults.
Mechanism of Action
The venom contains alpha-latrotoxin, a potent neurotoxin that triggers massive release of neurotransmitters by opening presynaptic calcium channels. This results in widespread neuromuscular and autonomic stimulation.
Management
Treatment is primarily supportive, focusing on pain control and symptom management. Muscle relaxants may be used for cramping. Intravenous calcium has been used in some cases, though benefits are variable. Antivenom may be considered in severe cases, particularly in high-risk patients or those with significant systemic symptoms.
Key Points
Source
Black widow spiders are found throughout the United States, especially in warmer southern regions. Only female spiders bite humans. They are typically identified by markings on the abdomen—most commonly a red hourglass on the underside. These spiders tend to inhabit dark, undisturbed areas such as woodpiles, garages, and sheds.
Typical Presentation
Patients often present after a painful spider bite followed by progressive muscle pain and systemic symptoms. In children, symptoms may be severe and mimic other acute conditions such as abdominal emergencies.
Clinical Features
The bite initially causes localized pain, followed by redness and sweating at the site. Systemic symptoms may include muscle cramps and fasciculations, severe abdominal pain and rigidity, nausea, vomiting, weakness, headache, dizziness, chest pain, and elevated blood pressure. In some cases, unusual findings such as priapism may occur. Symptoms tend to be more severe in children and older adults.
Mechanism of Action
The venom contains alpha-latrotoxin, a potent neurotoxin that triggers massive release of neurotransmitters by opening presynaptic calcium channels. This results in widespread neuromuscular and autonomic stimulation.
Management
Treatment is primarily supportive, focusing on pain control and symptom management. Muscle relaxants may be used for cramping. Intravenous calcium has been used in some cases, though benefits are variable. Antivenom may be considered in severe cases, particularly in high-risk patients or those with significant systemic symptoms.
Key Points
- Symptoms may mimic conditions such as acute abdomen or cardiac ischemia.
- Severe complications can include hypertensive crises and respiratory compromise.
- Early recognition and supportive care are essential for good outcomes.
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