Recommendations for prevention and management of fire ant infestation of health care facilities.

ABSTRACT: The range of imported fire ants now includes most of the southeastern United States, parts of the Southwest, portions of the East and West Coasts, and Puerto Rico. Increasingly, fire ant attacks on patients in health care facilities have been reported. In this paper, we provide recommendations for fire ant control in and around health care facilities that should help prevent building infestation and further attacks. In addition, we provide algorithms detailing fire ant prevention strategies (indoors and outdoors) and patient management after fire ant stings. Physicians in areas endemic for fire ants should be aware of the possibility that patients may be harmed by these insects, and also should be generally familiar with measures used to control fire ants.

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THE TERM IMPORTED FIRE ANT (IFA) refers to several members of the ant genus Solenopsis, including S invicta, S richteri, and a hybrid of the two, often referred to as S invicta x richteri. (1,2) The name derives from the intense burning sensation that occurs when venom is injected. (3) The most widespread species of IFA is S invicta, which infests more than 300 million acres, covering much of the southern United States (Fig 1). (3,4) For various reasons (many of which are poorly understood), two less pugnacious native fire ant species have, for the most part, disappeared. Compared with native ants, both imported species and hybrid fire ants are extremely defensive, and, when disturbed, will sting almost anything with which they are in contact. Fire ant stings induce similar kinds of local cutaneous reactions--sterile pustules--in everyone who is stung. (5,6) Rarely, individuals may become hypersensitive to proteins in fire ant venom and develop allergic reactions upon subsequent stings. These vary from local dermal reactions to generalized allergic reactions, including anaphylaxis. (6,7) Other sequelae, such as dermal infections, have been associated with fire ant stings, particularly in diabetic patients and others with compromised circulation. Very rarely, neurologic effects, such as seizures and neuropathies, occur. (8)

The range of the IFA now includes most of the southeastern United States, irrigated areas in the southwestern United States, parts of the East and West Coasts, and Puerto Rico. The density of these ground-nesting ants has greatly increased in endemic areas. Environmental factors, such as drought, may on occasion be associated with movement of entire ant colonies from the outdoors into dwellings. Increasingly, fire ants have been implicated in indoor attacks on persons in health care facilities. (9-12) At least 10 published cases have been reported to date, and we are aware of additional, unreported cases. In many of these cases, active fire ant colonies were found along the building slab of exterior walls contiguous with rooms where residents have been attacked. What triggers the ants to accumulate on individuals and subsequently sting in large numbers remains unclear. Patients have received hundreds to thousands of stings with sequelae ranging from isolated local reactions to death. Almost all of these attac ks have resulted in lawsuits against the particular health care facility, and physicians have inevitably become involved. In this paper, we present recommendations of how to manage (and prevent) fire ant invasion in health care facilities, including a section on pesticidal control measures. In addition, we provide information in the form of a flow chart concerning patient care after fire ant attack.

RECOMMENDATIONS TO PREVENT INVASION IN HEALTH CARE FACILITIES

Preliminary Guidelines Only

A word of caution before discussing fire ant prevention and control policies in health care facilities: these are preliminary recommendations and not final or legally binding. Insect prevention and management practices are constantly changing, due to new research data and evolving pesticide use restrictions imposed by the United States Environmental Protection Agency. A product appropriately labeled for fire ant control today may be illegal to use in 5 years. Accordingly, readers of this article should check fire ant control recommendations, especially chemical control measures, with their local Department of Agriculture before implementation.

Keeping IFAs Outside and Away From Patients

Extremes in weather may explain the occasional movement of fire ants into inhabited dwellings. During the spring, when soils become saturated, IFA colonies may move inside looking for drier conditions. The same is true for prolonged periods without rain, when the ants will move toward moisture if it is found inside. Another important factor facilitating movement of IFAs to the inside is proximity of ant mounds to the foundation of a building. Foragers from mounds located next to a building's foundation have a greater chance of foraging inside the building than foragers from mounds located some distance away. Special care is required to insure that patients in long term care facilities are not stung by fire ants. Patients in these facilities may not be aware of their surroundings, may be immobilized by disease, or otherwise incapacitated and unable to respond if ants come into contact with them. Once patients have come into contact with foraging ants, a variety of external stimuli, including movement of the pa tient, might trigger a stinging event, leading to multiple stings in a short period of time. Some common-sense suggestions for prevention of indoor and outdoor fire ant infestations are presented in Tables 1 and 2.

Fire ant management also includes a systematic plan for keeping the pests out of facilities, and, if they enter, ways to mitigate their effects. An algorithm is provided to summarize this approach (Fig 2). Once fire ants are found on a patient, clinical evaluation is needed, and possible transport (depending upon findings) to the nearest emergency department (Fig 3).

Formulation of an "Ant Policy" at Health Care Facilities

Health care facilities located in geographic areas within the range of the fire ant may choose to develop an "ant policy" to document fire ant activity and establish written guidelines for both patients and staff. Pest control at health care facilities is usually provided by contract with a pest-control company; however, the overall pest-management process involves the watchful eye of health care providers, as well as maintenance and housekeeping staff. Some form of pest documentation should be in place (eg, a pest-sighting log) to inform the pest controller of pest sightings, locations, times, etc. Moreover, sighting of ants in patient rooms should trigger an established plan of action. Management and staff should be aware that not all ants inside health care facilities are fire ants. To be on the safe side, when fire ants are spotted in a room, the patient should be removed until the pest control service has had a chance to investigate and perform adequate control measures. Having an ant policy may reduce l iability in the event of a stinging incident, in effect, showing that the facility was diligent in their efforts to prevent ant invasion. A modified ant policy developed by a nursing home for the prevention of fire ant attacks is provided (Table 3).

FIRE ANT CONTROL MEASURES

Imported fire ants have been in the United States for over 80 years, and during this time, many strategies have been advanced for their control. The mass aerial treatment program between 1950 and 1970 had some success; however, environmental damage from these treatments, plus cost considerations, led to its demise by 1972. (3,13) Although this program fell out of favor, the concept of chemically treating large blocks of infested area still has appeal, albeit on a smaller scale.

There are two treatment techniques widely used in fire ant management. (13,14)

1) Baits. The queen, whose egg production controls the number of ants in each colony, is often located deep within the colony and eats predigested food fed to her by worker ants. Thus, she is relatively protected from pesticides applied directly to the colony. Baits are used to address this problem. Baits are a combination of a slow-acting insecticide or other agent plus a food material attractive to the ants. The most common food attractant is vegetable oil, Ants, attracted to the oil, carry the bait back into the mound, where it is incorporated into the colony's food supply and eventually fed to the queen and developing young. Insecticides formulated as baits are slow-acting in order not to kill foraging ants before they can return to the colony with the baited particle. A nonrepellent bait material is used to ensure that the ants will eat the bait.

A number of insecticides have been formulated as baits for IFA control (Table 4). One of these is hydramethylnon (0.73%). Hydramethylnon is classified as a slow-acting insecticide (metabolic toxin), and kills the queen and colony within 7 to 14 days. Some bait-based products are insect growth regulators (IGRs), and are very-slow-acting materials. These include pyriproxyfen (0.5%), fenoxycarb (1.0%), and s-methophrene (0.5%). This class of bait mimics natural juvenile hormones important in regulating molting and immature insect development. Ant control with one of these IGRs takes a minimum of 6 weeks, with maximal effects usually occurring at 8 to 12 weeks. Interestingly, although it takes longer to get control with the IGRs, ant control tends to last longer with them than with hydramethylnon.

Baits may be broadcast over the ground or placed directly around mounds. They can be applied to areas such as lawns around health care facilities. Broadcast applications are applied at 1.5 pounds per acre (5.5 ounces per 10,000 sq ft). In this method, a seeder or spreader is used to scatter the bait in a uniform pattern over the infested site. Most small areas can be treated with a hand-held device; however, all-terrain-vehicle-mounted spreaders are available. Spreading the bait allows every ant in the treated area an opportunity to pick up baited particles, which gives better overall control.

Treatment of individual mounds may be used on small areas with very few mounds. The bait is applied around the mound (not on top), usually 1 to 2 feet from the base. Then, worker ants foraging for food are more likely to find bait when entering or leaving the mound. Depending on the product, 1 to 5 tablespoons are used per mound. The one disadvantage of this method is that some very small (developing) mounds may be missed.

Baits work extremely well during spring and early summer due to the high number of larval ants in the mound. These larvae require large quantities of food, and foraging ants will immediately pick up available food for them, such as a bait. The bait's active ingredient is ultimately distributed within the mound and will start acting quickly due to the increased need for food by the larvae. As summer temperatures rise, the queen may cut back on egg production, and, although the adults and queen still need food, the amount needed is somewhat reduced. It is during this time that insecticide applications directly to the mound are especially needed.

An IFA-control program would reasonably include one or two bait applications over the infested area during the spring and early summer. The first should be applied when the major lawn grass begins greening, followed with a second application four to five weeks later. Some data suggest that ants will pick up bait even after a moderate rain shower; however, applications are best made to coincide with four to eight hours of dry weather. As hot summer approaches, mounds that might have been missed or new ones that move onto the property can be treated with a mound drench.

Regulations may change on insecticide formulations, so users of pesticides should contact either their State Department of Agriculture or local Cooperative Extension Service agent for the latest product information and use directions.

2) Conventional insecticides. Chemicals used for conventional or traditional IFA control are available formulated as liquids, powders, or dusts, and are applied directly to the mound as a water-based application (usually referred to as a mound drench), a powder, or a dust. Products used in this manner may be consumer based (over-the-counter) or available only to a professional pest-control company. A brief description of each method follows.

Mound Drench. When using a product formulated as a liquid or a wettable powder, a specified amount is mixed with water, and the solution slowly poured into the mound. It generally takes a gallon of solution to give adequate penetration into a large mound. Lesser volumes can be mixed for smaller mounds. A sprinkling can (like those used by gardeners) may be used for this treatment. The solution should be poured slowly over and around the mound so it will seep in as deeply as possible. This technique can be labor intensive if a number of mounds are present.

Powder Application. Powder applications are generally convenient and not labor intensive. In this technique, a measured amount of pesticide concentrate is sprinkled over the mound, with some also being applied to the perimeter. Powders work well if the canopy of the mound is moist; however, if it is dry and crusted over, effectiveness is limited because insecticide will remain on the surface and ultimately be broken down by ultraviolet light.

Dust Application. A few dusts are registered for IFA control, and this technique has the same limitations as powders. Dusts are easy to use and do not require large volumes of water. If the mound canopy is moist, dusting will give good control.

CONCLUSIONS

Fire ants will likely continue to be a problem in. the United States and for all health care facilities for many years to come. Current management practices and new methodologies under development have little chance of eradicating fire ants. In the case of some insect pests, nonchemical control methods are fairly effective in reducing pest populations. This is not the case with fire ants, however, and pesticides are an integral part of prevention/control. We must learn to live with the pests, wisely using pesticides and prevention/management strategies to minimize interactions between humans and ants and the subsequent health problems associated with ant stings.

TABLE 1. Recommendations for Prevention of Outdoor Fire Ant Infestation at Health Care Facilities

* The first 25 to 50 feet around the outside of a building should be considered a critical zone and regularly surveyed for fire ant infestation.

* Allow 18 to 20 inches of clear air space between the building and the mature height and width of ornamental plants.

* If irrigation is used, make sure that sprinkler heads are pointed away from the building and not positioned so as to wet the building, thus providing moisture for insect infestation.

* Keep the soil grade sloping away from the building to prevent accumulation of water against the foundation.

* If rain gutters are used, make sure that downspouts are clear and water runs freely away from the facility.

* Contract with a pest-control service to routinely inspect and, if appropriate, apply insecticides to keep the perimeter of health care facilities free of fire ant infestation.

TABLE 2. Recommendations for Prevention of Indoor Fire Ant Infestation in Health Care Facilities

* Determine if facility's pest service contract covers fire ants.

* Increase vigilance in order to identify fire ant infestation during weather extremes.

* Do not allow beds or linens to touch the wall or floor.

* Limit food in the bed as much as possible.

* Check mattresses for food accumulation.

* Place food left in the room in a well-sealed (air-tight) container.

* Keep the outside of intravenous inserts as dry as possible.

* Make sure that catheters are functioning properly.

* Avoid accumulation of water or food particles under base plates during floor sweeping or mopping.

TABLE 3. Sample of Fire Ant Policy for a Health Care Facility *

1. This facility maintains an ongoing pest control program. Pest-control services, including those providing surveillance for and extermination of fire ants, are provided by a licensed pest exterminator on a monthly basis and as needed. The contract for pest-control services is maintained in the business office.

2. Nursing staff will inspect each room daily for evidence of fire ants and other insects. Sightings will be recorded in an insect-sighting log.

3. In the event that ants are detected in the facility, the pest-control service will be contacted and the area treated.

4. If fire ants are noted in a patient's room, the patient will be removed from the room until the pest-control specialist has had a chance to investigate and perform adequate control measures.

5. If ants are detected on a resident, the patient will be assessed immediately and appropriate care provided. The patient's family and physician will also be notified immediately. The area will he treated for ant infestation. All other residents and their rooms will be checked for ants. An incident form will be completed.

6. The housekeeping/maintenance supervisor or his/her designee will make daily rounds on the grounds of the facility to inspect for ants and other pests. Lawns will be carefully inspected weekly during ant season and treated (when ants are found) with an ant insecticide and/or bait by the housekeeping/maintenance department and monthly by a licensed pest exterminator. Logs will be kept for dates of lawn treatments.

7. Garbage and trash are to be removed from the facility daily.

8. Maintenance staff will look for and correct any water leaks within the facility on a regular basis.

9. Families bringing food to residents must use air-tight containers for the food.

* This is a guideline only, and not intended to be an all-inclusive approach to fire ant control.

Table 4 Some Common Examples of Insecticides Used to Control Fire Ants

Treatment       Chemical Name

Outdoors Baits  Abamectin

                Boric acid
                Fenoxycarb
                Hydramethylnon
                Methroprene
                Pyriproxyfen
                Spinosad
                Fipronil
Drenches,       Acephate
sprays, dusts,  Bifenthrin
granules        Carbaryl
                Deltamethrin
                Diazinon *
                Cypermethrin
                Cyfluthrin
                Tralomethrin
                Cyhalothrin
                Permethrin
                Fipronil

Indoors Baits   Abamectin

                Hydramethylnon
                Sulfluramid

                Orthoboric acid
Sprays, dusts,  Cypermethrin
aerosols

Treatment       Trade / Brand Name and Manufacturer

Outdoors Baits  PT Ascend fire ant bait, Whitmire
                Micro-Gen Corp.; Clinch, Novartis Corp
                Bushwhacker, The Bushwhacker Assoc.
                Award (Logic), Novartis Corp.
                Amdro (Seige), BASF Corp.
                Extinguish, Wellmark International
                Distance, Valent USA Corp.
                Conserve/Justice, Dow Agrosciences
                Chipco FireStar bait, Aventis Corp.
Drenches,       Orthene, Valent USA
sprays, dusts,  Talstar, FMC
granules        Sevin, Rhone-Poulenc Ag Co
                DeltaGard G, Aventis Corp.; Ultradust, Bengal Corp.
                Diazinon, Novartis Corp.
                Demon, Zeneca Corp.
                Countdown WP, Bayer Corp.; Talstar, FMC Corp.
                Saga, Aventis
                Demand, Aventis
                Various brand names and packagers
                Over'nOut, Kelly Products Inc.;
                Chipco Top Choice, Aventis Corp.
Indoors Baits   PT Ascend fire and bait, Advance,
                Whitmire Micro-Gen Corp.
                Maxforce, Clorox Co.; Seige, BASF Corp.
                Raid Ant Bait Plus, S.C. Johnson Inc.; Dual-Choise
                Whitmire Micro-Gen Corp.; FluorGuard, FMC Corp.
                DRAX, Waterbury Co.
Sprays, dusts,  Demon, Zeneca Inc.
aerosols

* Currently being phased out.

References

(1.) Buren WF: Revisionary studies on the taxonomy of the imported fire ants. J Georgia Entomol Soc l972; 7:1-26

(2.) Trager JC: A revision of the fire ants, Solenopsis geminata group. J New York Entomol Soc 1991; 99:141-198

(3.) Vinson SB, Sorensen AA: Imported Fire Ants: Life History and Impact. Texas Department of Agriculture, 1986

(4.) Goddard J: Physician's Guide to Arthropods of Medical Importance. 3rd ed. Boca Raton, Fla, CRC Press, 2000

(5.) Baer H, Liu TY, Anderson M, et al: Protein components of fire ant venom. Toxicon 1979; 17:397-405

(6.) Lofgren CS, Banks WA, Glancey BM: Biology and control of imported fire ants. Ann Rev Entomol 1975; 20:1-30

(7.) Levy AL, Wagner JM, Schuman SH: Fire ant anaphylaxis: two critical cases in South Carolina. J Agromed 1998; 5:49-54

(8.) Fox RW, Lockey RF, Bukantz SC: Neurologic sequelae following the imported fire ant sting. J Allergy Clin Immunol 1982; 70:120-124

(9.) deShazo RD, Williams DF, Moak ES: Fire ant attacks on residents in health care facilities: a report of two cases. Ann Intern Med 1999; 131:424-429

(10.) deShazo RD, Williams DF: Multiple fire ant stings indoors. South Med J 1995; 88:712-715

(11.) deShazo RD, Banks WA: Medical consequences of multiple fire ant stings occurring indoors. J Allergy Clin Immunol 1994; 93:847-850

(12.) Kemp SF, deShazo RD, Moffitt JE, et al: Expanding habitat of the imported fire ant: a public health concern. f Allergy Clin Immunol 2000; 105:683-691

(13.) Collins H: Control of imported fire ants. U.S. Department of Agriculture, 1992. Technical Bulletin No. 1807.

(14.) Horton PM, Gorsuch CS: Fire Ant Management in the Home Lawn. Cooperative Extension Service, Clemson University, February 1998, Entomology Insect Information series

RELATED ARTICLE: KEY POINTS

* Fire ant attacks on patients inside health care facilities are increasingly being reported.

* Physicians in areas endemic for fire ants should be aware of the possibility that patients may be harmed by these insects, and should be generally familiar with measures used to control fire ants.

* Knowledge of fire ant biology and behavior, combined with implementation of common-sense prevention strategies, may protect patients from attack.

From the Mississippi Department of Health; the University of Mississippi Medical center, Jackson; and Mississippi State University, Starkville.

Reprint requests to Jerome Goddard, PhD. PO Box 1700, Jackson, MS 39215.