Toxicology of red imported fire ant venom
The venom plays a central role in the biology of Red imported fire ants, such as in capturing prey,[1] and in defending itself from competitors,[2] assailants,[3] and diseases.
[7] Fire ant venoms are mainly composed (>95%) of a complex mixture of insoluble alkaloids added to a watery solution of toxic proteins.
[8] For the Red imported fire ant Solenopsis invicta Buren there are currently 46 described proteins,[9] of which four are well-characterised as potent allergens.
[10] Venom plays an important role in the biology of fire ants, being used to capture prey items,[1] nest defense,[2] and antimicrobial action.
A quarter of all victims stung by red imported fire ants are expected to develop sensitivity to the venom, and approximately 6,000 will suffer anaphylaxis.
[37] A survey conducted in China shows that one-third of participants in infested areas were victims of red imported fire ant stings.
[45] People who are stung by red imported fire ants may experience intense local burning or flare-ups, followed by reddening of the skin at the sting site.
In most cases, pustules dry up in a matter of weeks and leave brown scars that either remain for several months or become permanent.
Many of them will experience pruritic lumps around areas where the ants stung, known as late-phase responses or cutaneous allergic reactions.
[45][38][51] One case reports a victim feeling strong vertigo 5 to 10 minutes after being stung, followed by glassy eyes, dry mouth, paleness, unconsciousness and severe cramps on the sting sites.
[52] In addition, neuropathy, seizures (even without any evidence of prior systemic reactions), cerebrovascular accidents, and nephrotic syndrome have been associated with red imported fire ant stings.
[45][42][53] A series of neurotoxins have been identified in red imported fire ant venom, which may explain why some victims experience hallucinations after they have been stung.
For minor sting injuries, with symptoms only including pustule formations and pain, over-the-counter products are available to prevent infection.
[42] Epinephrine is the first product for use to treat systemic allergic responses, particularly if a patient is experiencing dyspnoea or hypotension because it is capable of reversing adverse events quickly and is very safe to use.
It is recommended that people who have suffered from anaphylaxis carry an epinephrine autoinjector (EpiPen), should dyspnoea or hypotension begin to occur.
[54] As mentioned, fire ant venom immunotherapy is occasionally used, and studies show it can reduce the risk of systemic reactions.
[64] Fire ant venom immunotherapy is not recommended for children with large local reactions, although an exception may be made for those who live in heavily infested areas.
[54][68] It is recommended that patients going through immunotherapy receive treatment for three to five years, and lifelong therapy, although there is no consensus as to how long an individual should be treated.
[72] In livestock, red imported ants mostly sting animals in regions with no hair, particularly around the ears, eyes, muzzle, the perineum and ventral portion of the abdomen.
[73] Red imported fire ants are known to actively kill vertebrate animals, and cause significant livestock losses.
[75] Animals may trigger major stinging episodes when they disturb active nests, with thousands of ants participating in the attack.
In suckling white tail deer fawns, sting sites have been found in the oesophagus and abomasum; toxins from the ingested ants may cause inflammation of the gastrointestinal lining.
