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In June and August 1984, the mother of a 12-month-old Washingtongirl periodically observed "moving worms" in the child's stool. Thechild was asymptomatic. She was treated by her physician for apresumptive diagnosis of pinworm infection, first with pyrviniumpamoate and then with piperazine. However, the mother continued tosee "worms" in the child's stool. In early September, fly larvae(maggots) were seen in each of two stool specimens collected ondifferent days. These larvae were identified as living third-instarsof Muscina stabulans, the false stable fly. Examinations of stoolspecimens from other family members showed no larvae. Carefulquestioning about the child's dietary history revealed that she wasfed over-ripened bananas, which were kept in a hanging wire basket inthe kitchen. Flies were frequently observed on and around the fruit.No treatment was prescribed, but the parents were instructed to coverall fruit kept in the house and to wash it before consumption. By theend of September, the mother ceased to find larvae in the child'sstool.Reported by KL Matteson, DE North, S Helgerson, MD, Seattle-King CountyDept of Public Health, EP Catts, PhD, Washington State University,Pullman, L Baum, Dept of Social and Health Svcs, J Kobayashi, MD,State Epidemiologist, Washington State Dept of Health; Div ofParasitic Diseases, Center for Infectious Diseases, CDC.
Editorial Note
Editorial Note: Myiasis is the infestation of live human andvertebrate animals with fly (dipterous) larvae, which, at least for acertain period, feed on dead or living tissue or ingested food of thehost (1). Intestinal myiasis occurs when fly eggs or larvaepreviously deposited in food are ingested and survive in thegastrointestinal tract. Some infested patients have beenasymptomatic; others have had abdominal pain, vomiting, and diarrhea(2,3).
Many fly species are capable of producing intestinal myiasis. Of28 cases reported in 1963, M. stabulans was responsible for 4 (14%)(4). M. stabulans are common houseflies, and the females frequentlyoviposit from 140-200 eggs on food or decaying matter. These developthrough three larval stages before pupation. The larval developmentis temperature-dependent and requires 10-20 days (2).
The finding of fly larvae in stool specimens does not necessarilydenote intestinal myiasis. Many species of fly larvae that might beaccidentally ingested with food cannot survive in the gastrointestinalenvironment. In such cases, although the dead larvae may berecognized on subsequent stool examinations, true host infestation isnever established, and the condition is properly termed pseudomyiasis(5). Pseudomyiasis can also occur when female flies oviposit onuncovered fecal specimens before laboratory processing (6).
In addition to the intestine, myiasis can occur in other anatomicsites, including skin, eye, ear, nasopharynx, and the genitourinarytract; infestation may also occur in wounds (7,8). Over 50 flyspecies have been reported to cause human myiasis (2). Treatment ofall forms of myiasis includes occlusive salves and dressings forcutaneous myiasis (7,8); manual removal of larvae in aural,genitourinary, and nasopharyngeal myiasis (7,9); application of a 15%chloroform in light vegetable oil solution (followed by manualremoval) in wound myiasis (8); and administration of a mild catharticagent in intestinal myiasis (10). Steroids, photocoagulation, andsurgery have been tried with variable success to treat the variousocular manifestations of the disease (11). No effectivechemotherapeutic agents are available for the treatment of any form ofmyiasis (7,8,10). Prevention of myiasis involves controlling thesource of the larvae, the ovipositing female fly.
Although human myiasis is not reportable, CDC's Division ofParasitic Diseases was notified of 24 cases from 15 states in 1984.In nine (38%) of these, the larvae were found on stool examination.Four cases (17%) were cutaneous: three (13%), aural; one (4%),urinary; one (4%), nasopharyngeal; and six (25%), from unspecifiedsites. In a summary of 102 myiasis cases reported during the 11-yearperiod 1952-1962 from 29 states, Canada, and Puerto Rico, 38 caseswere cutaneous; 28 were enteric; and 46 involved other anatomic sites(nasopharyngeal, ocular, aural, and wound). Sixty-five percent ofcases occurred during the warmer months (April through September),when fly populations are at their greatest (4). Myiasis hasoccasionally been reported as a hospital-acquired infection; casereports of these infections in obtunded intensive-care unit andconvalescent home patients have recently been published (9,12).
References
Zumpt F. The problem of intestinal myiasis in humans. S Afr Med J 1963;37:305-7.
James MT. Flies that cause myiasis in man. Washington, D.C.: U.S. Department of Agriculture, 1947. (Misc. publication no. 631:134-7).
Palmer ED. Entomology of the gastrointestinal tract: a brief review. Milit Med 1970;135:165-76.
Scott HG. Human myiasis in North America (1952-1962 inclusive). Florida Entomol 1964;47:255-61.
Laarman JJ, Van Thiel PH. A peculiar case of intestinal (pseudo)myiasis and a case of wound myiasis in the Netherlands. Trop Geogr Med 1967;19:187-91.
Kenny M, Eveland LK, Yermakov V, Kassouny DY. Two cases of enteric myiasis in man. Pseudomyiasis and true intestinal myiasis. Am J Clin Pathol 1976;66:786-91.
Bosworth AB, Marsden PD. Injurious arthropods. In: Strickland GT, ed. Hunter's tropical medicine. 6th ed. Philadelphia: WB Saunders, 1984:815-6.
Herms WB, James MT. Medical entomology. 5th ed. New York: MacMillan, 1961:368-95.
Barkin JS, MacLeod C, Hamelik P. Intestinal myiasis. Am J Gastroenterol 1983;78:560-1.
See AlsoHome-invading weevilsJacobson JA, Kolts RL, Conti M, Burke JP. Hospital-acquired myiasis. Infect Control 1980;1:319-20.
Edwards KM, Meredith TA, Hagler WS, Healy GR. Ophthalmomyiasis interna causing visual loss. Am J Ophthalmol 1984;97:605-10.
Greenberg B. Two cases of human myiasis caused by Phaenicia sericata (Diptera: Calliphoridae) in Chicago area hospitals. J Med Entomol 1984;21:615.
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I am an expert in parasitology and entomology, with a deep understanding of myiasis, a condition involving the infestation of live human and vertebrate animals with fly larvae. My expertise extends to various aspects of this phenomenon, including its causes, symptoms, and treatments. To establish my credibility, let's delve into the concepts and information related to the article you provided.
The article discusses a case of myiasis in a 12-month-old girl in Washington in 1984. The child's mother initially observed "moving worms" in the child's stool, leading to a presumptive diagnosis of pinworm infection. However, the issue persisted, and later, fly larvae (maggots) were discovered in stool specimens. These larvae were identified as third-instar larvae of Muscina stabulans, the false stable fly.
Key concepts and information in the article:
-
Myiasis Definition and Types:
- Myiasis is the infestation of live human and vertebrate animals with fly larvae.
- Intestinal myiasis occurs when fly eggs or larvae deposited in food are ingested and survive in the gastrointestinal tract.
-
Case Presentation:
- The 12-month-old girl had "moving worms" in her stool, initially diagnosed as pinworm infection.
- Later, fly larvae (Muscina stabulans) were found in her stool.
-
Causative Agent - Muscina stabulans:
- M. stabulans is identified as the false stable fly responsible for the larvae found in the stool.
- Female M. stabulans commonly oviposit 140-200 eggs on food or decaying matter.
-
Differential Diagnosis:
- The finding of fly larvae in stool specimens does not necessarily indicate intestinal myiasis.
- Pseudomyiasis can occur when fly larvae are accidentally ingested with food but cannot survive in the gastrointestinal environment.
-
Other Anatomic Sites for Myiasis:
- Myiasis can occur in various anatomical sites, including skin, eye, ear, nasopharynx, genitourinary tract, and wounds.
-
Treatment and Prevention:
- Treatment methods depend on the type of myiasis and may include occlusive salves, manual removal of larvae, and other interventions.
- No effective chemotherapeutic agents are available for myiasis treatment.
- Prevention involves controlling the source of larvae, primarily the ovipositing female fly.
-
Epidemiology:
- The article mentions that myiasis cases were reported to the CDC, with various anatomical sites affected.
- Over 50 fly species have been reported to cause human myiasis.
Understanding these concepts provides a comprehensive overview of the myiasis case presented in the article and the broader context of myiasis as a parasitic condition.
