Survey of 2144 cases of red-back spider bites: Australia and New Zealand, 1963--1976.

An analysis has been made of 2144 consecutive cases of latrodectism (envenomation by the red-back spider, Latrodectus mactans hasselti) reported to the Commonwealth Serum Laboratories. In the last eight years, notifications have averaged 240 cases per annum. Bites, usually on the extremities (74%), occurred most frequently in the summer months, and in the afternoon or evening. Most victims (79%) were aged between 18 and 50 years and 64.4% of them were males. Males are still often bitten on the genitals or buttocks (9.7% of cases). Local pain, redness and swelling were the most common symptoms, although significant pain was felt at other sites in 39% of the cases. The regional lymph nodes often became swollen and tender within 30 minutes. General effects included nausea, vomiting and sweating, but coma and respiratory failure were very uncommon, probably because of use of specific antivenom. This was administered within 24 hours of the bite in 92% of cases, and within two hours in 70%. Although 11 anaphylactic reactions (0.54%) were reported, no deaths resulted either from the venom or from reactions to the antivenom. Few delayed serum reactions (1.7%) were recorded. The action of the venom is described and the management of red-back spider bite is outlined.