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… And Now Microsporidiosis

Louis M. Weiss, MD, MPH
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From Albert Einstein College of Medicine Bronx, NY 10461. Grant Support: By National Institutes of Health grant AI31788. Requests for Reprints: Louis M. Weiss, MD, MPH, Division of Infectious Diseases, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Room 504 Forchheimer Building, Bronx, NY 10461.

Copyright ©2004 by the American College of Physicians

Ann Intern Med. 1995;123(12):954-956. doi:10.7326/0003-4819-123-12-199512150-00012
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This is the decade of emerging infectious diseases. It seems that a “new” disease or an infectious cause for old diseases is being announced at astounding rates. Microsporidiosis is one such infection. Microsporidian infection in humans, usually those with immune deficiencies, were infrequently reported before the acquired immunodeficiency syndrome (AIDS) epidemic [12]. Microsporidia are now being increasingly recognized as important opportunistic pathogens in human immunodeficiency virus (HIV) infection. Microsporidiosis has also been described in immunocompetent hosts [3]. Diseases caused by the different microsporidia that infect humans include diarrhea, keratoconjunctivitis, disseminated disease, hepatitis, myositis, kidney and urogenital infection, ascites, cholangitis, and asymptomatic carriage [12]. Knowledge of the epidemiology of microsporidiosis in humans is limited, but as with cryptosporidiosis, microsporidiosis is probably a common, self-limited or asymptomatic infection in immunocompetent hosts. The high prevalence of antibodies to microsporidia (such as Encephalitozoon) in many serosurveys supports this view [12].

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Figure 1.
Structure of a microsporidian spore.Nosema

Depending on the species, the size of the spore can vary from 1 to 10 µm and the number of polar tubule coils can vary from a few to 30 or more. A equals the anchoring disk (the extrusion apparatus consists of the polar tube [Pt], tubular polaroplast [Tp], lamellar polarplast [Lp], and the anchoring disk and is used to identify microsporidia); D equals the nucleus, which may be single (such as in Encephalitozoonae and Enterocytozoonae) or a pair of abutted nuclei called a diplokaryon (such as in ); En equals the endospore, an inner thicker electron-lucent region; Ex equals the exospore, an outer electron-dense region; P equals the plasma membrane separating the spore coat from the sporoplasm (Sp); Pv equals posterior vacuole, a membrane-bound structure; R equals ribosomes, present in a coiled helical array. Reproduced with permission from Cali A, Owen RL. Microsporidiosis. In: Ballows A, Hausler W Jr, Lennette EH, eds. The Laboratory Diagnosis of Infectious Diseases: Principles and Practice. New York: Springer-Verlag; 1988:928-49.

Grahic Jump Location




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