Microsporidiosis
Microsporidiosis is a protozoan infection. Patients with AIDS have symptomatic disease: diarrhea, keratitis, disseminated and muscle infections. Little is known about routes of transmission or reservoirs.
CASES/YEAR
5,000 (US); 3,530,000 (Global)
INCUBATION
Little known about routes of transmission or reservoirs: [Merck Manual, p. 1649] Estimated: days to years;
INITIAL SYMPTOMS
Symptomatic disease primarily in patients with AIDS: diarrhea, keratitis, disseminated and muscle infections; [Merck Manual, p. 1649]
COMMENTS
EPIDEMIOLOGY:
Microsporidia are obligate intracellular protozoan parasites that are characterized by resistant spores and a unique organelle, the polar filament, used to inject sporoplasm into the host cells. New spores then develop in the cytoplasm of the host cell and are released when the cell ruptures. At least 14 microsporidian species have been identified as human pathogens. Some of these microsporidia also infect other domestic and wild animals. Parrots, parakeets, love birds, and budgies are naturally infected with 3 species known to be human pathogens. Spores have also been found in surface waters. [www.dpd.cdc.gov/dpdx] How microsporidiosis is acquired is not completely understood--presumed ingestion or inhalation of spores. [Harrison ID, p. 1121-2]
FINDINGS:
Microsporidia infections occur mainly in severely immunocompromised AIDS patients who suffer chronic diarrhea and wasting. Other common infections are keratoconjunctivitis and infections of the skin and muscle. Disseminated infections in immunocompetent patients have been reported. [www.dpd.cdc.gov/dpdx] Rarely causes disease in immunocompetent hosts; [Harrison ID, p. 1211] In disseminated infections, respiratory tract infection may result in rhinitis, sinusitis, and nasal polyposis. Two cases of pneumonia have been reported in AIDS patients. A pediatric case with seizures and hepatomegaly was reported. [PPID, p. 3262-4] Cerebral microsporidiosis was reported in two children who presented with seizures. AIDS patients may present with seizures and ring-like brain lesions; [Cohen, p. 1741] Renal failure is a complication in AIDS patients. [Guerrant, p. 717]
DIAGNOSTIC
Transmission electron microscopy is the gold standard for identifying species. Chromotrope 2R is the most widely used staining method for light microscopy. A faster version is the Quick-Hot Gram Chromotrope technique. [www.dpd.cdc.gov/dpdx]
SIGNS & SYMPTOMS
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>fever
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>myalgia
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E rhinitis
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G abdominal pain
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G diarrhea
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G hepatomegaly
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G liver function test, abnormal
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G nausea, vomiting
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N lethargy
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N muscle weakness
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N seizure
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O conjunctivitis, acute
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R cough
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R dyspnea
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R wheezing
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S skin or subcutaneous nodule
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U hematuria
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X lung infiltrates
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*acute renal failure
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*brain abscess or lesion
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*encephalitis
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*hepatitis
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*osteomyelitis
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*pneumonia
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*pneumonitis
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*weight loss
SOURCE
Waterborne (Ingesting, Inhaling, or Swimming)
RESERVOIR
Birds and Poultry
RISK FACTORS
- AIDS patients
- Ingest infectious agents in food/water
REFERENCES FOR CASES/YEAR
1. (US) Assume 10% of AIDS patients are infected; 10% X 50,000 (US AIDS patients) = 5000;
2. (Global) Initially considered rare, now believed to be a common enteric pathogen, most likely causing asymptomatic or self-limited diarrheal infections in immunocompetent hosts; Prevalence studies found a range of 2% to 70% of AIDS patients infected before the widespread used of cART; [PPID, p. 3259] Guesstimate: Assume 10% of AIDS patients are infected; Calculate: 10% X 35.3 million = 35,300,000;