Arthropods

• 2.3.5.1.1 Red Back Spiders
• 2.3.5.1.2 Funnel Web Spiders
• 2.3.5.1.3 Other Spiders

Exposure to insects is a common occurrence in Australia. In the past year there were over 2800 calls to the NSW Poison Information Centre regarding exposure to insects (not including spiders). Clinical effects of insects can vary significantly from envenomation (eg scorpions), dermatitis (eg caterpillars) and allergic reactions (eg bees & wasps). Generally the clinical effects are not life-threatening but can cause distress to the patient. Often in these scenarios it is impossible to know what the exact culprit was as often the insects are not seen at the time of the sting.

General first aid for insect stings consists of:

• Removal of contact with the insect
• Application of ice pack
• Early identification of allergic reactions.
• Symptomatic treatment eg analgesia, antihistamines
• If pain is severe may require medical input for analgesia

Life threatening allergic reactions to arthropods stings occurs in between 0.5-4% of an exposed population. Insect venom anaphylaxis almost always begins within half an hour of exposure with life-threatening allergy usually manifesting within minutes but may rarely occur as long as 24 hours after sting.

The areas to be covered in this topic are:

• Insect order that contains bees, wasp and ants
• Major cause of insect sting allergy
• Reactions range from localised effects such as swelling to generalised urticaria & systemic effects (anaphylaxis), Localised swelling can often by delayed.
• Treatment consists of topical application of ice & supportive therapy such as antihistamines.

• Includes over 3000 species which are grouped into 4 orders: Scolopendromorpha (Tropical or giant centipedes – the most medically significant group), Scutigeramorpha (House of feather centipedes), Geophilomorpha (soil centipedes), Lithiobiomorpha (rock or garden centipedes)
• Clinical effects range from mild to severe local pain associated with erythema
• Treatment consists of ice and analgesia.

• Reactions to caterpillars is vary varied & can consist of:
• Dermatitis (hairy caterpillars): present as itch, rash,
• Envenomation (venom mediated): Main feature is pain
• Mechanical injury: mechanism here is large amounts of caterpillar spines embedded into the skin causing pain.
• Treatment consists of removal of contact with the caterpillar which consists of various methods depending on the type of caterpillar involved.

• Stings generally occur at night & outdoors
• Clinical effects range from local pain which can be severe for several hours usually without local tissue injury
• Treatment consists of ice pack & analgesia

• Most important are the Ixodes species of hard ticks.
• An adult female attached to a child and feeding for several days may introduce enough toxin to cause paralysis.
• An antivenom is available but it is currently unclear if it alters the course of envenomation.