Effects of envenoming by comb-footed spiders of the genera Steatoda and Achaearanea (family Theridiidae: Araneae) in Australia.
BACKGROUND
The family Theridiidae (comb-footed spiders) contains the well-known and medically important widow spider group (Latrodectus spp.). Little is known about the effects of envenoming by other common members of this family.


OBJECTIVE
The objective of this study was to determine the clinical effects of bites by common theridiid spiders of the genera Steatoda and Achaearanea.


METHODS
This was a prospective cohort study of calls to Australian poison information centers and presentations to emergency departments. Twenty-eight persons with a definite bite by a spider of the family Theridiidae, excluding Latrodectus spp., were included where the spider was immediately collected and expertly identified from February 1999 to April 2002.


RESULTS
There were 23 bites by Steatoda spp. and five bites by Achaearanea spp. Steatoda bites occurred across Australia, throughout the year, and the majority during waking hours. Seventy-eight percent of bites occurred indoors and 48% while dressing indoors. Pain was universal and was severe in six (26%). Increasing pain in the first hour occurred in 30%, and the median duration of pain was 6 hr (interquartile range: 1-12 hr). Local or regional diaphoresis did not occur. Systemic effects occurred in 30% and included nausea, headache, lethargy, and malaise. The majority received no treatment: seven patients presented to a hospital (two patients received opiates for analgesia) and 1 patient inadvertently received intravenous redback spider (RBS) antivenom because the spider was initially misidentified as a RBS (Latrodectus). The pain and symptoms responded over 1 hr following antivenom administration. Bites by Achaeranea spp. caused moderate to severe persistent pain, but no systemic effects.


CONCLUSIONS
Steatoda spp. bites or "steatodism" may cause prolonged pain and systemic effects similar to Latrodectus bites, but less severe. In severe cases, the clinical effects were almost indistinguishable from Latrodectus, except diaphoresis was absent, and the spiders were often mistaken for Latrodectus. Intravenous RBS antivenom appears to be an effective treatment in isolated severe cases, consistent with in vitro work. Achaearanea bites caused pain similar to Latrodectus bites.
Isbister
Geoffrey K
GK
University of Newcastle, Newcastle, Australia. gsbite@ferntree.com
Gray
Michael R
MR
D000818:Animals; D000997:Antivenins / Q000627:therapeutic use; D001315:Australia / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D010146:Pain / Q000188:drug therapy / Q000209:etiology; D011446:Prospective Studies; D012621:Seasons; D001098:Spider Bites / Q000453:epidemiology / Q000473:pathology* / Q000628:therapy; D013112:Spiders / Q000145:classification
D000997:Antivenins