The toxicology of fire ant venom is relatively well studied. 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. [4] Some 14 million people are stung annually in the United States, [5] suffering reactions that vary from mild discomfort, to pustule formation, swelling, [6] and in rare cases, systemic reactions followed by anaphylactic shock. [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. [11] On average, however, a worker stores very little venom (only about 0.5 µg at any given time). [12] Newborn workers contain little to no venom within their reservoirs, but workers that are only one day old can produce 1.17 µg/day. However, workers that are 17 days old only produce 0.3 µg/day. Workers deliver 0.66 nl of venom when they sting, which amounts to 3.1% of their supply. Older workers deliver less venom when they sting, but middle-aged workers and nest-defenders deliver much higher quantities. [13] Like all fire ant species, venom is secreted by the venom gland and is stored in the poison sac. [14] When in use, it is ejected through the stinger's main duct. Capacity is between 20 and 40 nl, but this depends on the worker's size. [15] The American entomologist Justin O. Schmidt described it as being "sharp, sudden, mildly alarming", therefore ranking at "1" in the Schmidt sting pain index, a pain scale which ranks the pain intensity of an insect's sting from 0 to 4. [16]
Over 95% of the venom components are water-insoluble piperidine alkaloids. Piperidines include trans-2-methyl-6-n-undecylpiperidines, trans-2-methyl-6-n-tridecylpiperidine, trans-2-methyl-6-(cis-4-tridecenyl) piperidines, trans-2-methyl-6-n-pentadecylpiperidine, trans-2-methyl-6-(cis-6-pentadecenyl)piperidine and 2,6-dialkylpiperidines (the ants' venom is dominated by the trans- stereoisomers of this specific ingredient). [17] [18] [19] trans-2-Methyl-6-n-undecylpiperidine (solenopsin) has been shown to have cytotoxic, hemolytic, necrotic, insecticidal, antibacterial, antifungal, and anti-HIV properties. [20] As well as that, the alkaloid has shown antiangiogenic activity. [21] These components are responsible for the formation of hives, and also for the development of sterile pustules on areas where the ant has stung. [22] Experiments indicate that the median lethal dose (LD50) on tested female rats is 0.36 mg/kg. [23]
Approximately 46 proteins have been identified in the red imported fire ant's venom, [9] although scientists have long believed the venom only contained alkaloids. [24] [25] This assumption was mostly due to the difficulties in obtaining sufficient venom for analysis because of its low protein content, which is only 0.1% of the venom's total weight. [26]
These proteins are experimentally suggested to directly account for the anaphylactic reactions seen in humans sensitive to the venom. [27] Whilst including a number of neurotoxins and potential allergens, not all of these proteins are involved with venom function. [9] At least four protein allergens have been characterised, named Sol i 1-4. Of these, Sol i 3, is part of the antigen 5 family, and Sol i 1 is a phospholipase A1B; Sol i 1 shows a close relation with wasp venom phospholipases. [22] [28] [29] [30] Sol i 2 and 4 are unique, odorant-binding proteins of poorly understood function. Other proteins found in the venom may benefit the colony; some of these proteins can kill off bacteria, which may explain why workers spray venom around their nests by vibrating their gasters. Other proteins also bind pheromones which may assist a worker to lay chemical trails to communicate with other nestmates. [12] [9] [31]
In the United States, more than 40 million people live in areas infested with fire ant populations and 14 million people are stung by them annually. 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. [32] 51% of people who relocated themselves to infested areas report getting stung within three weeks after arrival. [33] In a survey conducted in South Carolina, 33,000 people (or 94 per 10,000 population) received medical attention due to red imported fire ants, and 660 people (1.9 per 10 000 population) were treated for anaphylaxis. [34] In Texas, 79% of participants in a survey stated they had been stung by red imported fire ants, while 20% had not. 61% of West Texans state they had been stung by the ants before, compared to 90% in central Texas, 89% in east Texas, 86% in the gulf coastal regions, 78% in the south and 72% in the north. [35] In separate survey, 87% of individuals classed their reactions as mild, 12% as moderate and 1% as severe. [36] In Australia, 64,000 homes are within red imported fire ant infested areas, and 140,000 consultations and 3,000 anaphylactic reaction cases are predicted every year by 2030 if government efforts to eradicate the ant fail. [37] A survey conducted in China shows that one-third of participants in infested areas were victims of red imported fire ant stings. [38]
Studies suggest that the rate of systemic reactions to stings may be associated with seasonal variations in the venom's potency. 51% of allergic reactions occurred in summer, and 19% in spring. However, A survey reported a higher incidence during spring (39.9%) than summer (31.9%). [39] Younger people, usually those under 20 years, experience the highest rate of sting attacks (50%), but the rate declines with older people. Among men and women, the rate varies as some studies report more women being attacked than men and vice versa. [36] [38] Deaths from red imported fire ant stings are rare, but may become common the more the ant spreads. Many cases have also been reported in the past. [40] It is reported that more than 80 deaths have been recorded; of these, 22 cases were recorded in Florida and 19 in Texas. However, when duplicate reports are excluded, four deaths were recorded in Alabama, 10 in Florida, two in Georgia and Louisiana, and 14 in Texas. [41] [42] [43] People can be educated and be made aware of the dangers of red imported fire ants. [44]
Reactions seen in humans vary; some are hypersensitive to venom while others show resilience. Hypersensitivity can be attributed to certain medical problems such as heart conditions or diabetes. Bacterial infections attributed to sting injuries also pose a problem and may require further medical attention. Most humans can withstand many stings, but others may suffer from severe reactions such as anaphylaxis. [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. This area will swell into a bump, hive or vesicle within 20 minutes. White fluid-filled sterile pustules begin to form within hours or days after being stung. [45] [38] [46] [47] Pustules on the skin remain for a couple of days, and may become infected which would require medical attention. In most cases, pustules dry up in a matter of weeks and leave brown scars that either remain for several months or become permanent. [45] The formation of pustules occurs in almost every person stung by the ants. In one study, 96% of participants reported the formation of pustules, whereas 2% reported large local reactions. [33] Between 17% and 56% of people stung develop venom-specific IgE. Many of them will experience pruritic lumps around areas where the ants stung, known as late-phase responses or cutaneous allergic reactions. [42] [48] [49]
Pustule formation can only be prevented if the ants are removed before they have a chance to sting. Once venom has been injected, pustules will form and no form of treatment will prevent them from occurring. Medications such as antibiotics, diphenylhydrazines, epinephrines or topical steroids will not affect pustular reactions. [45] [49] [50]
Anaphylaxis occurs in 0.6 to 6% of people who have been stung by the ants, and it can be fatal if left untreated. [40] [42] Typical symptoms of anaphylaxis include dizziness, headaches, fever, severe chest pain, nausea, severe sweating, low blood pressure, loss of breath, serious swelling, and slurred speech. [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. [12]
It is suggested that a conservative approach be used when treating sting injuries; specifically, the kind of treatment used should be based on the symptoms. For minor sting injuries, with symptoms only including pustule formations and pain, over-the-counter products are available to prevent infection. Ants should be removed by washing the area with antiseptic soap, and itchiness. It is rare for ant sting sites to become infected, so the use of antibiotic prophylaxis is not always required. [45] [54]
Victims who show signs of anaphylaxis are treated with antihistamines, epinephrines, and parenteral corticosteroids. [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. [37]
Whole body extract immunotherapy (WBE) to treat victims of anaphylaxis [55] [56] has been in use since 1973. [57] [58] Anyone who has a suspected allergy to the venom is redirected to an allergist for assessment. [45] The treatment uses the entire body of the ant and not just the venom, and unlike fire ant venom immunotherapy (which is occasionally used), WBE contains venom proteins. [59] [56] To reduce a patient's sensitivity to the venom, gradual increases of dose extracts are injected into the body. [60] WBE immunotherapy appears to be very effective in preventing systemic reactions; [55] [56] in one study [61] of participants who completed WBE immunotherapy, two out of fifteen participants suffered from allergic reactions upon being stung 18 months after immunotherapy. [54] As mentioned, fire ant venom immunotherapy is occasionally used, and studies show it can reduce the risk of systemic reactions. [62] [63] In fact, another study claims that fire ant venom immunotherapy is more effective than WBE immunotherapy. [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. There is also an increased risk of systemic allergic reactions to future stings in children who have cutaneous manifestations after getting stung. This makes many experts put some children on fire ant venom immunotherapy, while others do not. [54] [65]
The recommended maintenance dose is between 0.5 mL of a 1:100 w/v 1:10 w/v WBE. [66] For fire ant venom immunotherapy, the most common maintenance dose is 0.5 mL of a 1:200 (wt/vol) dilution. [67] During the build-up phase, it is recommended that dosing is given weekly or biweekly, although some scientists suggest that rush protocols can be successful. [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. [54] [69]
The stings of the red imported fire ant in animals are painful, and may prove life-threatening. [70] In dogs, stings from the red imported fire ant can cause pustular dermatosis, a condition where pustules appear in crops as a result of the ant sting. [71] After getting stung, the immediate response consists of erythema and swelling. The pustules remain for approximately 24 hours, whereas in humans they can last for several days. [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. Newborn or young livestock can be blinded or killed when attacked by the ants. [73] [74] Healthy individuals are less likely to be attacked than weak or sick animals. Red papule and mild swelling occur, followed by vesicopustule with a red halo developing within 24 to 48 hours. The eyes and eyelids are commonly damaged from the stings; in sheep and goats, ophthalmic ointment containing antibiotics and corticosteroids can be used to treat the eyes of sheep and goats, but this treatment is not recommended for horses. In non-domestic animals, cases of red imported fire ants stings in animals such as ferrets, moles squirrels, white-tailed deer, cottontail rabbits, and newborn blackbucks have been reported, as well as lizards and screech owl nestlings. The aftermath of the injuries is like those in domestic animals. [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. During such episodes, an animal may suffer from hundreds to thousands of individual stings. It is suspected that many victims of the red imported fire ants may be depressed as a result of the effects of the toxin. Some animals may swallow red imported fire ants as they lick or bite around the sites they are stinging. This can cause additional injuries inside the animal itself, especially in the upper gastrointestinal tract. 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. [73]
Allergies, also known as allergic diseases, are various conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis. Symptoms may include red eyes, an itchy rash, sneezing, coughing, a runny nose, shortness of breath, or swelling. Note that food intolerances and food poisoning are separate conditions.
An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies.
Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the following: an itchy rash, throat closing due to swelling that can obstruct or stop breathing; severe tongue swelling that can also interfere with or stop breathing; shortness of breath, vomiting, lightheadedness, loss of consciousness, low blood pressure, and medical shock. These symptoms typically start in minutes to hours and then increase very rapidly to life-threatening levels. Urgent medical treatment is required to prevent serious harm and death, even if the patient has used an epipen or has taken other medications in response, and even if symptoms appear to be improving.
Most ants are capable of biting, stinging, and spraying irritant chemicals. However, only relatively few species can harm humans; among which some can cause significant injury or, in rare cases, death. Like wasps, individual ants are capable of stinging multiple times as they do not lose their stingers.
Fire ants are several species of ants in the genus Solenopsis, which includes over 200 species. Solenopsis are stinging ants, and most of their common names reflect this, for example, ginger ants and tropical fire ants. Many of the names shared by this genus are often used interchangeably to refer to other species of ant, such as the term red ant, mostly because of their similar coloration despite not being in the genus Solenopsis. Both Myrmica rubra and Pogonomyrmex barbatus are common examples of non-Solenopsis ants being termed red ants.
Solenopsis invicta, the fire ant, or red imported fire ant (RIFA), is a species of ant native to South America. A member of the genus Solenopsis in the subfamily Myrmicinae, it was described by Swiss entomologist Felix Santschi as a variant of S. saevissima in 1916. Its current specific name invicta was given to the ant in 1972 as a separate species. However, the variant and species were the same ant, and the name was preserved due to its wide use. Though South American in origin, the red imported fire ant has been accidentally introduced in Australia, New Zealand, several Asian and Caribbean countries, Europe and the United States. The red imported fire ant is polymorphic, as workers appear in different shapes and sizes. The ant's colours are red and somewhat yellowish with a brown or black gaster, but males are completely black. Red imported fire ants are dominant in altered areas and live in a wide variety of habitats. They can be found in rainforests, disturbed areas, deserts, grasslands, alongside roads and buildings, and in electrical equipment. Colonies form large mounds constructed from soil with no visible entrances because foraging tunnels are built and workers emerge far away from the nest.
Immunoglobulin E (IgE) is a type of antibody that has been found only in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains and two light chains, with the ε chain containing four Ig-like constant domains (Cε1–Cε4). IgE is thought to be an important part of the immune response against infection by certain parasitic worms, including Schistosoma mansoni, Trichinella spiralis, and Fasciola hepatica. IgE is also utilized during immune defense against certain protozoan parasites such as Plasmodium falciparum. IgE may have evolved as a defense to protect against venoms.
A food allergy is an abnormal immune response to food. The symptoms of the allergic reaction may range from mild to severe. They may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressure. This typically occurs within minutes to several hours of exposure. When the symptoms are severe, it is known as anaphylaxis. A food intolerance and food poisoning are separate conditions, not due to an immune response.
Latex allergy is a medical term encompassing a range of allergic reactions to the proteins present in natural rubber latex. It generally develops after repeated exposure to products containing natural rubber latex. When latex-containing medical devices or supplies come in contact with mucous membranes, the membranes may absorb latex proteins. In some susceptible people, the immune system produces antibodies that react immunologically with these antigenic proteins. Many items contain or are made from natural rubber, including shoe soles, pen grips, hot water bottles, elastic bands, rubber gloves, condoms, baby-bottle nipples, and balloons; consequently, there are many possible routes of exposure that may trigger a reaction. People with latex allergies may also have or develop allergic reactions to some fruits, such as bananas.
The black imported fire ant, or simply BIFA, is a species of ant in the genus Solenopsis. It was long thought to either be a subspecies or a color variation of Solenopsis invicta, but is now recognized as its own species with a demonstratively different range and living habits. BIFA seem to be more tolerant of cold and a less dominant species than RIFA. Due to the BIFA higher body content of water than the RIFA conclusions demonstrate the certain factor plays a role in their differences of living regions.
Allergen immunotherapy, also known as desensitization or hypo-sensitization, is a medical treatment for environmental allergies, such as insect bites, and asthma. Immunotherapy involves exposing people to larger and larger amounts of allergens in an attempt to change the immune system's response.
A hypoallergenic dog breed is a dog breed that is purportedly more compatible with allergic people than are other breeds. However, prominent allergen researchers have determined that there is no basis to the claims that certain breeds are hypoallergenic and, while allergen levels vary among individual dogs, the breed is not a significant factor.
The jack jumper ant, also known as the jack jumper, jumping jack, hopper ant, or jumper ant, is a species of venomous ant native to Australia. Most frequently found in Tasmania and southeast mainland Australia, it is a member of the genus Myrmecia, subfamily Myrmeciinae, and was formally described and named by British entomologist Frederick Smith in 1858. This species is known for its ability to jump long distances. These ants are large; workers and males are about the same size: 12 to 14 mm for workers, and 11 to 12 mm for males. The queen measures roughly 14 to 16 mm long and is similar in appearance to workers, whereas males are identifiable by their perceptibly smaller mandibles.
Peanut allergy is a type of food allergy to peanuts. It is different from tree nut allergies, because peanuts are legumes and not true nuts. Physical symptoms of allergic reaction can include itchiness, hives, swelling, eczema, sneezing, asthma attack, abdominal pain, drop in blood pressure, diarrhea, and cardiac arrest. Anaphylaxis may occur. Those with a history of asthma are more likely to be severely affected.
Allergies to cats are one of the most common allergies among human individuals. Among the eight known cat allergens, the most prominent allergen is secretoglobin Fel d 1, which is produced in the anal glands, salivary glands, and, mainly, in sebaceous glands of cats, and is ubiquitous in the United States, even in households without cats. The second most common is Fel d 2, this type is triggered by the cats dead skin flakes (dander) that are floating in the air as well as in the smell of cat urine.
Milk allergy is an adverse immune reaction to one or more proteins in cow's milk. Symptoms may take hours to days to manifest, with symptoms including atopic dermatitis, inflammation of the esophagus, enteropathy involving the small intestine and proctocolitis involving the rectum and colon. However, rapid anaphylaxis is possible, a potentially life-threatening condition that requires treatment with epinephrine, among other measures.
A tree nut allergy is a hypersensitivity to dietary substances from tree nuts and edible tree seeds causing an overreaction of the immune system which may lead to severe physical symptoms. Tree nuts include almonds, Brazil nuts, cashews, chestnuts, filberts/hazelnuts, macadamia nuts, pecans, pistachios, shea nuts and walnuts.
Insect sting allergy is the term commonly given to the allergic response of an animal in response to the bite or sting of an insect. Typically, insects which generate allergic responses are either stinging insects or biting insects. Stinging insects inject venom into their victims, whilst biting insects normally introduce anti-coagulants into their victims.
Laboratory animal allergy (LAA) is an occupational disease of laboratory animal technicians and scientists. It manifests as an allergic response to animal urine, specifically the major urinary proteins (Mups) of rodents, and can lead to the development of asthma. A study of 5641 workers in Japan who were exposed to laboratory animals found 23.1% had one or more allergic symptoms; globally the prevalence among at risk workers is estimated between 11 and 30% According to the National Institutes of Health, prevention of animal allergy depends on the control of allergens in the work environment. This involves a combination of measures to eliminate or control allergen exposure, including engineering controls, administrative controls, and personal protective equipment.
Exercise-induced anaphylaxis is a rare condition in which anaphylaxis, a serious or life-threatening allergic response, is brought on by physical activity. Approximately 5–15% of all reported cases of anaphylaxis are thought to be exercise-induced.
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