“Spider Bite” Lesions are Usually Diagnosed as Skin and Soft-Tissue Infections

Background: Many people seek medical attention for skin lesions and other conditions they attribute to spider bites. Prior experience suggests that many of these lesions have alternate causes, especially infections with community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). Objectives: This study determined the percentage of emergency department (ED) patients reporting a “spider bite” who received a clinical diagnosis of spider bite by their physician vs. other etiologies, and if the diagnoses correlated with demographic risk factors for developing CA-MRSA infections. Methods: ED patients who reported that their condition was caused by a “spider bite” were prospectively enrolled in an anonymous, voluntary survey regarding details of their illness and demographic information. Discharge diagnoses were also collected and categorized as: spider bite, bite from other animal (including unknown arthropod), infection, or other diagnosis. Results: There were 182 patients enrolled over 23 months. Seven patients (3.8%) were diagnosed with actual spider bites, 9 patients (4.9%) with bites from other animals, 156 patients (85.7%) with infections, and 6 patients (3.3%) were given other diagnoses. Four patients were given concurrent diagnoses in two categories, and 8 (4.4%) did not have the diagnosis recorded on the data collection instrument. No statistically significant associations were found between the patients' diagnostic categories and the demographic risk factors for CA-MRSA assessed. Conclusion: ED patients reporting a “spider bite” were most frequently diagnosed with skin and soft-tissue infections. Clinically confirmed spider bites were rare, and were caused by black widow spiders when the species could be identified.