Although Phoneutria species (Ctenidae) occur throughout South America and Costa Rica, most reports of significant bites are from Brazil by P. nigriventer, the South American wandering spider or armed spider.1 Phoneutria spiders are nocturnal and wander large distances to catch prey and in doing this occasionally enter human dwellings. Their venom contains peptide neurotoxins that mainly affect ion channels and can cause neurotransmitter release. Most reports are from Brazil (southern and central regions) and occur when the spiders are encountered in shoes, piles of building materials or rubbish outdoors.

Bites cause immediate pain at the site which is associated with diaphoresis, erythema and piloerection, often without fang marks, which may radiate proximally and can be associated with mild agitation and tachycardia. Severe envenomation occurs in about 10% of cases and is more common in children. Systemic envenomation includes nausea, vomiting, autonomic effects (tachycardia, hypertension, diaphoresis and salivation) and priapism. Rarely pulmonary edema and shock occur, and deaths have been reported.2
In most cases symptomatic treatment is all that is required including oral analgesia. Opioid analgesia and sedatives may be required with more severe pain and symptoms. A polyvalent antivenom is available in Brazil for Phoneutria and Loxosceles spiders, as well as for Tityus scorpions. In severe envenomation administration within 3 hours of the bite has been associated with improvement by 24 hours.

1. Isbister, G.K. & Fan, H.W. Spider bite. Lancet 378, 2039-2047 (2011).
2. Bucaretchi, F., et al. A clinico-epidemiological study of bites by spiders of the genus Phoneutria. Revista do Instituto de Medicina Tropical de Sao Paulo 42, 17-21 (2000).