History
In Australia, most bites occur during the warmer months between December and April. Bites to the limbs comprise approximately three quarters of cases, and bites to the distal limbs are twice as common as to the proximal limbs; 46% in distal extremity and 26% in proximal limb. In areas without indoor plumbing, bites to the genitalia and buttocks are often seen. [10]
There is usually immediate pain at the site of the bite with or without erythema, which can progress over hours to involve the entire limb and draining lymph nodes in the axilla or groin. The pain may persist longer than 24 hours, with a median duration of 36 hours.
Local inflammation and swelling is more prominent in redback envenomations than in envenomations by other Latrodectus species, for which local symptoms are usually minimal.
Some patients then develop painful spasms of the large muscle groups; when involving the abdominal muscles, it may mimic an acute abdomen. [11]
Other common complaints include nausea, vomiting, abdominal pain, headache, and migratory arthralgias. [6]
Infants and toddlers may present with nonspecific symptoms such as irritability, inconsolable crying, and refusal to eat. [12]
Most cases are mild or unrecognized and do not receive antivenom.
Physical Examination
Common physical findings in a patient with redback spider envenomation include tenderness and erythema at the bite site. Occasionally, one can see generalized or localized sweating, which may be remote from the bite site. Local piloerection may also be present. [4]
Systemic findings in redback spider envenomation, seen in approximately 35% of all bites, include fever, hypertension, and tachycardia. [4]
Spasms of large muscle groups are seen in some patients. Priapism may be seen in young male children. [13]
Neurological symptoms may include restlessness and insomnia, muscle weakness and twitching, and paralysis. The median duration of all effects is 48 hours.
Rare complications include myocarditis, rhabdomyolysis, and death.
Complications
Complications of redback spider envenomation are as follows:
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Paralysis
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Death
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Female redback spider showing a distinctive red stripe over the abdomen. Image courtesy of John Paterson.
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Female redback spider with egg sacs. Image courtesy of John Paterson.
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Female redback spider. Image courtesy of John Paterson.
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Female redback spider. Image courtesy of John Paterson.
