Blastocystis

For the disease, see Blastocystosis. For the structure formed in the early embryogenesis of mammals, see Blastocyst.

Blastocystis
Blastocystis sp.
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Stramenopiles
Phylum: Bigyra
Subphylum: Opalozoa
Infraphylum: Placidozoa
Superclass: Opalinata
Class: Blastocystea
Zierdt et al. 1967
Order: Blastocystida
Zierdt 1978
Family: Blastocystidae
Jiang & He 1988
Genus: Blastocystis
(Alexieff 1911) Brumpt 1912[1]

Blastocystis is a genus of single-celled parasites belonging to the Stramenopiles that includes algae, diatoms, and water molds. There are several species, living in the gastrointestinal tracts of species as diverse as humans, farm animals, birds, rodents, reptiles, amphibians, fish, and cockroaches.[2] Blastocystis has low host specificity, and many different species of Blastocystis can infect humans,[3] and by current convention, any of these species would be identified as Blastocystis hominis.

Blastocystis is one of the most common human parasites in the world and has a global distribution.[4][5][6][7] It is the most common parasitic infection in the United States, where it infected approximately 23% of the total population during year 2000.[6][7] In less developed areas, infection rates as high as 100% have been observed.[4][5] High rates of infection are found in individuals in developed countries who work with animals.[5][8] Although the role of Blastocystis hominis in human disease is often referred to as controversial, a systematic survey of research studies conducted by 11 infectious disease specialists from nine countries, found that over 95% of papers published in the 10 years prior identified it as causing illness in immunocompetent individuals.[7] The paper attributed confusion over pathogenicity to the existence of asymptomatic carriers, a phenomenon the study noted is common to all gastrointestinal protozoa.[7] However, Blastocystis has never fulfilled Koch's postulate that infection of a healthy individual with Blastocystis leads to disease. The fact that Blastocystis' infection route is oral-anal indicates that carriers have been in contact with faecal contaminated matter which might have included other intestinal pathogens that explain the observed symptoms. A more likely explanation is the presence of virulent and non-virulent strains since there exists an enormous genetic variation between different strains (or genotypes). See the genotype paper by Rune Stensvold[9] and the 2017 Blastocystis genome paper[10] expanding on this diversity. An alternative theory that Blastocystis is not a pathogen at all has recently been strengthened based on its biochemistry.[11][12]

  1. ^ Alexeieff A (1911). "Sur la nature des formations dites "kystes de Trichomonas intestinalis"". CR Soc Biol. 71: 296–298.
  2. ^ Yoshikawa H, Wu Z, Howe J, Hashimoto T, Geok-Choo N, Tan KS (2007). "Ultrastructural and phylogenetic studies on Blastocystis isolates from cockroaches". The Journal of Eukaryotic Microbiology. 54 (1): 33–37. doi:10.1111/j.1550-7408.2006.00141.x. PMID 17300516. S2CID 45995362.
  3. ^ Noël C, Dufernez F, Gerbod D, et al. (January 2005). "Molecular Phylogenies of Blastocystis Isolates from Different Hosts: Implications for Genetic Diversity, Identification of Species, and Zoonosis". Journal of Clinical Microbiology (in Chinese). 43 (1): 348–55. doi:10.1128/JCM.43.1.348-355.2005. PMC 540115. PMID 15634993.
  4. ^ a b El Safadi D, Gaayeb L, Meloni D, Cian A, Poirier P, Wawrzyniak I, Delbac F, Dabboussi F, Delhaes L, Seck M, Hamze M, Riveau G, Viscogliosi E (March 2014). "Children of Senegal River Basin show the highest prevalence of Blastocystis sp. ever observed worldwide". BMC Infect. Dis. 14: 164. doi:10.1186/1471-2334-14-164. PMC 3987649. PMID 24666632.
  5. ^ a b c Roberts T, Stark D, Harkness J, Ellis J (May 2014). "Update on the pathogenic potential and treatment options for Blastocystis sp". Gut Pathog. 6: 17. doi:10.1186/1757-4749-6-17. PMC 4039988. PMID 24883113. Blastocystis is one of the most common intestinal protists of humans. ... A recent study showed that 100% of people from low socio-economic villages in Senegal were infected with Blastocystis sp. suggesting that transmission was increased due to poor hygiene sanitation, close contact with domestic animals and livestock, and water supply directly from well and river [10]. ...
  6. ^ a b Amin OM (2002). "Seasonal prevalence of intestinal parasites in the United States during 2000" (PDF). Am. J. Trop. Med. Hyg. 66 (6): 799–803. doi:10.4269/ajtmh.2002.66.799. PMID 12224595. S2CID 3767711. Archived from the original (PDF) on 27 May 2020. Retrieved 3 January 2016. Parasitologic investigations of large patient populations are rarely conducted in the United States, where the illusion of freedom from parasitic infections still predominates. Such investigations are considerably more common in third-world countries where endemic parasitoses are more readily documented.1 In an attempt to address this problem we reported the results of routine examination of fecal specimens for parasites from 644 patients in the United States during the summer of 1996. ...
    Prevalence. Nine hundred sixteen (32%) of 2,896 tested patients were infected with 18 species of intestinal parasites in the year 2000 (Table 1) in 48 states and the District of Columbia as follows ... Blastocystis hominis was the most frequently detected parasite in single and multiple infections, with Cryptosporidium parvum and Entamoeba histolytica/E. dispar ranking second and third, respectively.
  7. ^ a b c d Boorom KF, Smith H, Nimri L, Viscogliosi E, Spanakos G, Parkar U, Li LH, Zhou XN, Ok UZ, Leelayoova S, Jones MS (2008). "Oh my aching gut: irritable bowel syndrome, Blastocystis, and asymptomatic infection". Parasit Vectors. 1 (1): 40. doi:10.1186/1756-3305-1-40. PMC 2627840. PMID 18937874. Blastocystis is now by far the most prevalent mono-infection in symptomatic patients in the United States [14] and was found 28.5 times more often than Giardia lamblia as a mono-infection in symptomatic patients in a 2000 study [14].
  8. ^ Parkar U, Traub RJ, Vitali S, et al. (April 2010). "Molecular characterization of Blastocystis isolates from zoo animals and their animal-keepers". Vet. Parasitol. 169 (1–2): 8–17. doi:10.1016/j.vetpar.2009.12.032. PMID 20089360.
  9. ^ Stensvold, C. R.; Suresh, G. K.; Tan, K. S.; Thompson, R. C.; Traub, R. J.; Viscogliosi, E.; Yoshikawa, H.; Clark, C. G. (2007). "Terminology for Blastocystis subtypes—a consensus". Trends in Parasitology. 23 (3): 93–6. doi:10.1016/j.pt.2007.01.004. PMID 17241816.
  10. ^ Gentekaki, E.; Curtis, B. A.; Stairs, C. W.; Klimeš, V.; Eliáš, M.; Salas-Leiva, D. E.; Herman, E. K.; Eme, L.; Arias, M. C.; Henrissat, B.; Hilliou, F.; Klute, M. J.; Suga, H.; Malik, S. B.; Pightling, A. W.; Kolisko, M.; Rachubinski, R. A.; Schlacht, A.; Soanes, D. M.; Tsaousis, A. D.; Archibald, J. M.; Ball, S. G.; Dacks, J. B.; Clark, C. G.; Van Der Giezen, M.; Roger, A. J. (2017). "Extreme genome diversity in the hyper-prevalent parasitic eukaryote Blastocystis". PLOS Biology. 15 (9): e2003769. doi:10.1371/journal.pbio.2003769. PMC 5608401. PMID 28892507.
  11. ^ Stensvold, Christen Rune; Van Der Giezen, Mark (2018). "Associations between Gut Microbiota and Common Luminal Intestinal Parasites". Trends in Parasitology. 34 (5): 369–377. doi:10.1016/j.pt.2018.02.004. hdl:10871/32596. PMID 29567298.
  12. ^ Tsaousis, Anastasios D.; Hamblin, Karleigh A.; Elliott, Catherine R.; Young, Luke; Rosell-Hidalgo, Alicia; Gourlay, Campbell W.; Moore, Anthony L.; Van Der Giezen, Mark (2018). "The Human Gut Colonizer Blastocystis Respires Using Complex II and Alternative Oxidase to Buffer Transient Oxygen Fluctuations in the Gut". Frontiers in Cellular and Infection Microbiology. 8: 371. doi:10.3389/fcimb.2018.00371. PMC 6204527. PMID 30406045.