Immigrant spiders – a cause for concern? [Abstract]

Objective: ‘ Steatoda nobilis ’ , commonly known as the false black widow spider, is an immigrant spider originating from the Canary Islands. Closely related to the black widow species but lacking its distinctive red spot, this spider was fi rst reported in the UK in 1879. It has since become acclimatised along the south coast of England although National Poisons Information Service (NPIS) call records indicate that it has been witnessed as far north as Yorkshire. While the spider is not considered aggressive, it possesses large venomous fangs that can instigate ‘ instant ’ severe pain, described as being worse than a wasp sting. Methods: A case study is reported and enquiries to NPIS concerning false black widow spider bites between August 2007 and August 2011 were analysed with regard to location and features. Case report: A 41-year-old male presented to the accident and emergency department two days after being bitten on the calf by a spider subsequently identifi ed as ‘ Steatoda nobilis ’ . He was treated prophylactically with co-amoxiclav. The skin around the bite was warm and discoloured with acute swelling at the puncture site. NPIS advised that apart from appropriate analgesia further treatment was unlikely to be required and that localised features from the envenomation would subside with time. Other than mild cellulitis in the calf and a raised CRP (31 mg/L), this patient exhibited no systemic complications and was discharged the same day. Results: NPIS received 21 enquiries involving ‘ Steatoda nobilis ’ throughout the study period. The majority of enquiries were from southern England with a few as far north as Yorkshire and Suffolk. Localised oedema was the most signifi cant feature along with hypoaesthesia, paraesthesia and skin rash. Systemic features such as tachycardia, chest tightness, vomiting, anxiety with increased sweating and fever were also reported in fi ve cases. Conclusion: It has been reported that ‘ Steatoda nobilis ’ bites may be neurotoxic and affect the parasympathetic nervous system. 1 Nevertheless, NPIS experience suggests that these bites, although sometimes medically signifi cant, can be managed successfully with supportive care and analgesia. Reference: 1. Warrell DA, Shaheen J, Hillyard PD, et al. Neurotoxic envenoming by an immigrant spider (Steatoda Nobilis) in southern England. Toxicon 1991; 29:1263 – 5