Microsporidiosis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Ogheneochuko Ajari, MB.BS, MS [2];Associate Editor(s)-in-Chief: Ahmed Younes M.B.B.CH [3]

Overview

Microsporidia are a group of obligate intracellular parasitic fungi with more than 1,200 species belonging to 143 genera that infect a wide range of vertebrate and invertebrate hosts. They are characterized by the production of resistant spores that vary in size, depending on the species.

Pathophysiology

Life Cycle

The infective form of microsporidia is the resistant spore and it can survive for an extended period of time in the environment.

Life cycle of microsporoidosia - Public Domain, </nowiki>https://commons.wikimedia.org/w/index.php?curid=2740681
Life cycle of microsporoidosia - Public Domain, </nowiki>https://commons.wikimedia.org/w/index.php?curid=2740681
  1. The spores enter the body via ingestion or inhalation.
  2. Spores penetrate host cell using its polar tubule
  3. The spore uses its polar tubule for injecting its sarcoplasm into the infected cell.
  4. The sarcoplasm multiplies either by binary fission or multiple fission
  5. The sarcoplasm of microsporidia develops into mature spores either free in the cytoplasm or inside a vacuole.
  6. The process of development involves acquiring a thick capsule. This capsule provides protection against environmental stressors and is thought to play a role in its infectivity.
  7. After their number reach a certain limit, the host cell ruptures releasing the spores to continue the life cycle.

Pathogenesis

  • Microsporidia cause distortion of the villi without profound inflammatory findings.
  • With the progression of the disease, the microsporidia interfere with the intestinal absorption causing various symptoms of malabsorption (weight loss, chronic diarrhea, and vitamin deficiencies).
  • Disseminated disease can cause symptoms in the biliary tract, respiratory system, the urinary tract or the eye.

Microscopic pathology

  • Intestinal biopsy shows crypt hyperplasia and decrease in the absorptive surface of the intestine.
  • Stool examination using “Quick-Hot Gram Chromotrope technique” reveals the spores staining dark violet and containing gram-positive granules.
  • Enterocytozoon bieneusi spores measure 0.8-1.4 µm while spores of Anncaliia algerae, Encephalitozoon spp., Vittaforma corneae, and Nosema spp measure 1.5-4 µm.
Sporoblast of the Microsporidium Fibrillanosema crangonycis - By No machine-readable author provided. Javier martin assumed (based on copyright claims). - No machine-readable source provided. Own work assumed (based on copyright claims)., CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=919796
Dictyocoela diporeiae.A, meront and spore; B, spore wall; C, polar filament - By Andrew David Winters & Mohamed Faisal - Winters, A. D., Faisal, M. 2014. Molecular and ultrastructural characterization of Dictyocoela diporeiae n. sp. (Microsporidia), a parasite of Diporeia spp. (Amphipoda, Gammaridea). Parasite, 21, 26 doi:10.1051/parasite/2014028, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=33448743
A hyperparasitic microsporidian, Nosema podocotyloidis - By Bhen Sikina Toguebaye, Yann Quilichini, Papa Mbagnick Diagne and Bernard Marchand - Toguebaye, B. S., Quilichini, Y., Diagne, P. M. & Marchand, B. 2014: Ultrastructure and development of Nosema podocotyloidis n. sp. (Microsporidia), a hyperparasite of Podocotyloides magnatestis (Trematoda), a parasite of Parapristipoma octolineatum (Teleostei). Parasite, 21, 44. doi:10.1051/parasite/2014044, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=35088476

Diseases caused by the different species

The clinical manifestations vary according to the causative species with diarrhea being the most common presentation.[1]

Microsporidian species Clinical manifestation
Anncaliia algerae Keratoconjunctivitis, skin and deep muscle infection
Enterocytozoon bieneusi* Diarrhea, acalculous cholecystitis
Encephalitozoon cuniculi and Encephalitozoon hellem Keratoconjunctivitis, infection of respiratory and genitourinary tract, disseminated infection
Encephalitozoon intestinalis (syn. Septata intestinalis) Infection of the GI tract causing diarrhea, and dissemination to ocular, genitourinary and respiratory tracts
Microsporidium (M. ceylonensis and M. africanum) Infection of the cornea
Nosema sp. (N. ocularum), Anncaliia connori Ocular infection
Pleistophora sp. Muscular infection
Trachipleistophora anthropophthera Disseminated infection
Trachipleistophora hominis Muscular infection, stromal keratitis, (probably disseminated infection)
Tubulinosema acridophagus Disseminated infection
Vittaforma corneae (syn. Nosema corneum) Ocular infection, urinary tract infection

*Two reports of E. bieneusi in respiratory samples have also been published, one in 1992 and the other in 1997.

References

  1. "CDC - DPDx - Microsporidiosis".

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