Monday, November 10, 2014

Intestinal Parasites: Friends, Foes and Shades of Gray


Parasite is a bad word with negative connotations. Yet, "bad things" can be good for you - and every situation is different.

About one third of people in the world carry at least one parasite in their gastrointestinal tract (the numbers reported vary from 2-4% in Japanese residing in developing countries to 6% in patients of a specialized private hospital in Saudi Arabia, 7% among individuals with mental retardation in New York, 17% in HIV patients with low CD4 counts in France, 30% in households of USA, Saudi Arabia and Turkey, 40% in Pakistan and Brasil, to over 50% in Nigeria, 50-70% in Morocco and almost 100% in Senegal). Prevalence varies between countries and within communities. Women and children appear to harbor larger numbers of parasites. But men, in general, may be less healthy than women, so the relationship between health and intestinal parasites is not as straightforward as one might think.

Let's take a look at three studies published this year.

Paper by Lukeš and co-authors (2014) suggests that intestinal parasites such as Blastocystis (single celled protozoa closely related to algae and molds) and nematodes (e.g., tapeworms or hookworms) can be actually beneficial to human health. To prove the point, Julius Lukeš even ingested  a handful of tapeworms called Diphyllobothrium latum. After more than a year with the tapeworms, which might have grown to be as long as four meters each by now, he still feels healthy and convinced that we should rethink our views of organisms that live off our bodies.

According to a Danish study (Krogsgaard et al, 2014), Blastocystis could be rare in individuals with low microbial diversity, disturbed by antibiotic treatment, inflammation, infection and diet, while common in the healthy population. Healthy individuals are more likely to carry intestinal parasites (50% vs 36%) than those with IBS and IBD. Protozoa Blastocystis and Dientamoeba were the most common parasites found. D fragilis was detected in a greater proportion of fecal samples from controls than cases (35% vs 23%; P = .03), and so was Blastocystis (22% of controls vs 15% of cases; P = .09), and combinations of parasite species (16% of controls vs 8% of cases; P = .05). D fragilis infection was more likely among those with low frequency of defecation and those having children 5 to 18 years old in the household. Blastocystis was associated with high income, increasing age, no animals in the household and drinking bottled water. These results are drawn from analyzing hundreds of individuals - 124 cases/204 controls.

Smaller and more focused studies, however, do find association between Blastocystis and IBS.

A recent French study compared the prevalence of Blastocystis among 56 IBS patients and  56 control and found that Blastocystis species are likely to couse IBS symptoms in men (prevalence was 37% in IBS sufferers vs 5% in healthy men; difference in women was not statistically significant). One of the older smaller studies that indicated possible relation between Blastocytes and IBS (Funda Dogruman-Al et al., 2009) suggested that Blastocystis don't really attack the body, it's the human organism that attacks the microbes first and the outcome is the result of defensive actions by the microbes. Obviously, symptoms do depend on many other health factors. Nourrisson and co-authors identified them as the prevalence of certain "good" bacteria. Men are more likely to get constipated when their Blastocystis leads to a significant decrease in Bifidobacterium species. On the other hand, they are doing just fine if Blastocystis causes decrease in Faecalibacterium prausnitzii - relatively good bacteria known for its anti-inflammatory properties,

Another interesting insight into the impact of a complex interplay of environmental factors on our health. Still a long way to go to understand how we interact with microbes that call us home.


REFERENCES

Lukeš J, Kuchta R, Scholz T, & Pomajbíková K (2014). (Self-) infections with parasites: re-interpretations for the present. Trends in parasitology, 30 (8), 377-85 PMID: 25033775
press release

Krogsgaard LR, Engsbro AL, Stensvold CR, Nielsen HV, & Bytzer P (2014). The Prevalence of Intestinal Parasites Is Not Greater Among Individuals With Irritable Bowel Syndrome: a Population-Based Case-Control Study. Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association PMID: 25229421

Nourrisson C, Scanzi J, Pereira B, NkoudMongo C, Wawrzyniak I, Cian A, Viscogliosi E, Livrelli V, Delbac F, Dapoigny M, & Poirier P (2014). Blastocystis Is Associated with Decrease of Fecal Microbiota Protective Bacteria: Comparative Analysis between Patients with Irritable Bowel Syndrome and Control Subjects. PloS one, 9 (11) PMID: 25365580

El Safadi D, Gaayeb L, Meloni D, Cian A, Poirier P, et al. (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.

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, 1:40 2

Krogsgaard LR, Engsbro AL, & Bytzer P (2013). The epidemiology of irritable bowel syndrome in Denmark. A population-based survey in adults ≤50 years of age. Scandinavian Journal of Gastroenterology, 48 (5), 523-9 PMID: 23506174

(2004) Intestinal parasites prevalence and related factors in school children, a western city sample--Turkey. BMC Public Health. 2004 Dec 22;4:64.

Houmsou R.S., Amuta E.U., Olusi T.A. (2010) Prevalence of intestinal parasites among primary school children in Makurdi, Benue State- Nigeria. Internet Journal of Infectious Diseaes. vol.8, 1, p.2

Schupf N, Ortiz M, Kapell D, Kiely M, Rudelli RD. Prevalence of intestinal parasite infections among individuals with mental retardation in New York State. Ment Retard. 1995 Apr;33(2):84–8

Sah, Ram; Bhattarai, Sailesh; Yadav, Satish; Baral, Ratna; Nilambar; Pokharel, Paras (2013) A study of prevalence of intestinal parasites and associated risk factors among the school children of Itahari, Eastern Region of Nepal. Tropical Parasitology, 3, 2, 140-144, DOI 10.4103/2229-5070.122143

Oman Med J. May 2011; 26(3): 182–185. doi: 10.5001/omj.2011.44 PMCID: PMC3191688 Dina AM Zaglool,1 Yousif AW Khodari,2 Zohair J. Gazzaz,3 Khalid O. Dhafar,4 Hani AS Shaker,5 and Mian U. Farooq
nt J Infect Dis. 2012 Sep;16(9):e677-9. doi: 10.1016/j.ijid.2012.05.1022. Epub 2012 Jul 6.

Prevalence of opportunistic intestinal parasitic infections among HIV-infected patients with low CD4 cells counts in France in the combination antiretroviral therapy era. Pavie J1, Menotti J, Porcher R, Donay JL, Gallien S, Sarfati C, Derouin F, Molina JM.

Jeevitha Dhanabal, Pradeep Pushparaj Selvadoss, and Kanchana Muthuswamy (2014) Comparative Study of the Prevalence of Intestinal Parasites in Low Socioeconomic Areas from South Chennai, India. Journal of Parasitology Research Volume 2014 (2014), Article ID 630968, 7 pages http://dx.doi.org/10.1155/2014/630968

Blagburn BL1, Schenker R, Gagne F, Drake J.(2008) Vet Ther. 2008 Fall;9(3):169-75. Prevalence of intestinal parasites in companion animals in Ontario and Quebec, Canada, during the winter months.

Hamada A1, Okuzawa E, Kawabuchi Y, Nishikawa T. (1998) Kansenshogaku Zasshi. 1998 Dec;72(12):1283-8. [Prevalence of intestinal parasites among Japanese residents in developing countries]. [Article in Japanese]

Hirata, T., Nakamura, H., Kinjo, N., Hokama, A., Kinjo, F., Yamane, N. et al. (2007) Prevalence of Blastocystis hominis and Strongyloides stercoralis infection in Okinawa, Japan. Parasitol Res 101: 17171719.

Javed Yakoob, Wasim Jafri, Nadim Jafri, Rustam Khan, Muhammad Islam, M. Asim Beg, and Viqar Zaman (2004) Irritable bowel syndrome: in search of an etiology: role of Blastocystis hominis Am. J. Trop. Med. Hyg., 70(4), pp. 383–385

2 comments:

Aurametrix said...

Another benefit of parasitic worms - they are increasing women's fertility.
New study ( published in Science on November 20, 2015) of 986 indigenous women in Bolivia indicated a lifetime of Ascaris lumbricoides, a type of roundworm, infection led to an extra two children

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