Recommendations for Prevention and Management of Fire Ant Infestation of Health Care Facilities

Jerome Goddard, PhD, James Jarratt, PhD, and Richard D. deShazo, MD


South Med J. 2002;95(6) 

In This Article

Abstract and Introduction

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.

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]

Imported fire ant quarantine map, reflecting current geographic distribution of the ant (courtesy of the US Department of Agriculture).

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.[9,10,11,12] 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 attacks 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.