Basic Infection Control: Mice and Maggots
June 1, 2002 3 minutes read
Abstract & Commentary
Synopsis: Nasal myiasis was detected in 2 ICU patients subsequent to a hospitalwide rodent population explosion.
Source: Beckendorf R, et al. Nasal myiasis in an intensive care unit linked to hospital-wide mouse infestation. Arch Intern Med. 2002;162:638-640.
Beckendorf and associates report 2 instances of maggots discovered in the nares of intensive care patients in a large city hospital in Kansas City. The first case was noted shortly before demise and ignored, but the second was investigated and a series of problems were discovered, yieding a scenario not unlike a story from the Middle Ages.
It seems there was a cutback in expenses in the hospital, which led to outside contracting for food services and a laxity in pest control. The number of mice was noted to increase but this was not initially considered a cause for concern. Some of the nursing staff treated the furry little creatures more as pets than enemies. When there was finally a crackdown the vermin were poisoned with coumadin and trapped with glue boards. The number of mice was apparently reduced in the hospital but unexpected consequences occurred. Large, slow-flying, iridescent flies began to appear throughout the hospital, including the ICU. Not long after that, maggots were discovered in the mouth and nasopharynx of a patient who had been in the unit for 10 days. This unusual event was thought to be related to flies from outside the hospital as there was some construction going on, but several months later maggots were again discovered—from around a nasotracheal tube which had been inserted in a patient 8 days prior. This time the maggots were sent off to the laboratory for further identification and the flies taken seriously.
Further investigations led to the discovery of extensive mice infestations of the cafeteria and the canteen, which had not been attended to for more than a year. Numerous carcasses were found and felt to be the feeding ground for the green blowfly (Phaenicia sericata) larvae. The literature suggests one mouse carcass can provide sustenance for 100 larvae to grow to maturity.
Steps were then taken to clean out the food service areas, remove as many dead mice as possible, and use traps rather than poisons or glue boards so the dead mice could be removed from the hospital rather than serving as food for more larvae. The traps brought in 184 mice in the first 2 months of the mouse control campaign. The number of flies was also dramatically reduced, although a year later a number were recovered in the operating room, likely related to 7 mouse carcasses discovered on glue boards nearby that had been overlooked the year before.
Comment by Alan D. Tice, MD, FACP
It is hard to believe there was not more concern about the cases of myiasis in patients who had been in the intensive care unit for more than a week, or that mice and blowflies were not seen as harbingers of disease. It reminds one of how devastating plague was before it was recognized as related to rodents. Perhaps the rats of London were seen as pets there as well. The Walt Disney portrayal of rodents in such stories as "The Secret of NIMH" shed some light on the human qualities of mice but they must be seen as potential enemies and purveyors of numerous diseases as well. Flies are also a marker of environmental hazards and can easily carry disease. While it is a rarity to have problems with these creatures in modern hospital facilities, they are a part of health care in impoverished countries and should be treated aggressively. While human myiasis is possible with only a few species of flies, such as the green blowfly, the risk of spreading infections is clearly present, especially in an ICU where patients may not be aware of the flies and unable to protect themselves from them.
The basic point of the report is to emphasize the need for infection control and prevention by knowledgeable people. Infection control applies not only to antimicrobial-resistant bacteria, viruses, fungi, and parasites but to flies and mice as well. There must not be laxity in cleaning and inspection of medical facilities with adequate regular measures to control of pests as well as antimicrobial resistance.
Dr. Tice, Infections Limited, PS, Tacoma, WA; Infectious Disease Consultant, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, is Associate Editor of Infectious Disease Alert.
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