Hospitals Misidentify Types of Maggot Infestations

Released: 12-Jul-2000 12:00 AM EDT
Embargo expired: 11-Jul-2000 4:00 PM EDT
Source Newsroom: University of California, Irvine
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EMBARGOED UNTIL 1 P.M. PDT, TUESDAY, JULY 11, 2000

HOSPITAL STAFFS PRONE TO MISIDENTIFY TYPES OF MAGGOT INFESTATIONS, UC IRVINE RESEARCHER FINDS

National Study Warns That Not All Maggots Are Alike

Irvine, Calif. -- Health care professionals may misidentify the maggots that infest patients' wounds if they do not follow through with proper study of the organisms, according to a national study led by a UC Irvine College of Medicine researcher.

Maggots are the larvae of flies and often infest untreated, open wounds. The study, one of the first to classify the types of maggots found in hospital infections, found that most infestations were caused by the same noninfectious species of maggots that are used sometimes to treat wounds. In addition, most of the patients studied were infested before admission to the hospital, and many of them were homeless. The study appears in the July 10, 2000 issue of Archives of Internal Medicine.

Dr. Ronald A. Sherman, assistant professor of medicine and an authority on maggots and disease, studied 20 health care centers and found that--contrary to previous studies on maggots--most infestations were caused by a maggot known for its inability to invade healthy tissue and that hospital infestations took place in wounds the patients had before being admitted.

"Knowing the species of a maggot can be crucial for determining the type and history of an infestation," said Sherman. "Unfortunately, when health care professionals clean a wound, they rarely save the maggots for further pathological analysis. Only by analyzing the larvae can we determine whether or not it is invading fresh, healthy tissue or infesting dead, diseased areas of the body."

Sherman and colleagues from 20 hospitals nationwide found that in 42 cases of maggot infestation, no fresh tissue invasion occurred because most larvae were those of the green blowfly, which do not invade fresh tissue. Two patients were hospitalized at the time of infestation. At least 16 of these cases involved homeless patients, and the clothing of most of these patients was soiled, encouraging the infestation of fly larvae.

Noninvasive species like the green blowfly were the predominant maggot species found in these infestations, which contradicted most published accounts of infestations that cited more dangerous species of fly larvae. Sherman and his team suggest that since most health professionals do not keep maggot samples from infested patients, they can delay the identification of maggot infestations.

"Traditionally, health care workers often assume that maggot infestations are caused by invasive larvae, and do not even identify the species of larvae," said Sherman. "While our study found that most maggot infestations are caused by noninvasive species, it is still necessary to identify the maggots in each case. Dangerous species like the screw-worm are returning to the United States, and the sooner we discover them, the sooner we can respond appropriately."

Sherman and his group noted that only a minority of infestations occur in hospitals after a patient has been admitted and that these infestations are not necessarily due to hospital neglect. The study recommends such preventive measures for hospitals as screening windows, tightly covering garbage and submitting all patient-associated flies and maggots for identification.

Sherman's colleagues in this study included researchers at UCI Medical Center; the Long Beach Veterans Affairs Medical Center; Los Angeles County-USC Medical Center; Bellevue Hospital, New York; UCLA-Harbor Medical Center, Torrance, Calif.; Dallas Veterans Affairs Medical Center; Denver General Hospital; Maricopa Medical Center, Phoenix, Ariz.; Augusta Veterans Affairs Medical Center, Augusta, Ga.; University Medical Center, Albuquerque, N.M.; University Medical Center, Fresno, Calif., and White River Indian Health Service Hospital, White River, Ariz.

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Contact:
Andrew Porterfield
(949) 824-3969
amporter@uci.edu

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