Tuesday, September 30, 2014

This Month in Blastocystis Research (SEP 2014)

Before leaving for Venice and Padova to introduce Blastocystis to the XXX National Congress of The Italian Society of Protistology (ONLUS), allow me to kick in just a few words for the September issue of 'This Month in Blastocystis Research'.

I will highlight two papers.

The first is a study from the US (Yes, - US data! How rare is that?). The team investigated the prevalence and subtype distribution of Blastocystis among client-owned and shelter-resident cats and dogs. Studies of Blastocystis in companion animals are actually quite rare. The authors used nested PCR for detection, followed by sequencing of PCR products. Interestingly, Blastocystis was not detected in any of the >100 fecal samples from client-owned animals. By comparison, Blastocystis was detected in 10/103 (9.7%) shelter-resident canines, and 12/103 (11.65%) shelter-resident felines. There was no significant difference in Blastocystis spp. carriage rates between the shelter-resident dogs and cats. It is likely that differences in diet and other types of exposure account for Blastocystis being found in shelter-resident animals and not in domestic animals. As for cats and dogs, we don't really know much about what to expect subtype-wise. These animals harboured ST10 mostly, a subtype that has only been found in artiodactyls, NHPs, and lemurs, so far, and - taking these new data into account - with little apparent host preference.

Viktor - an avid fox hunter (in 2007).
Other subtypes included ST1 and one case of ST3, and one case of what was most likely a new subtype - maybe! But then, few animals were positive, and given the different data on subtypes in cats and dogs, it's much too early to speculate on host specific subtypes... for now, it appears that there are none, and that maybe cats and dogs are not really natural hosts? A study by Wang and colleagues identified a plethora of subtypes in dogs: Among 22 positive dogs, most of which were from India, ST1, ST2, ST4, ST5, and ST6 were found. Again, nested PCR was used, and I might have a slight concern that this type of PCR approach is so sensitive that it will pick up the smallest quantity of Blastocystis, maybe even dead Blastocystis or other stages of Blastocystis not necessarily colonising the host (contamination, etc.). But I don't know. The authors of the US study noted that Blastocystis was unlikely to be associated with disease of the animals and were unable to establish a reservoir for human colonisation/infection in these animals.

I never got around to checking Viktor (our cat, pictured above) for Blastocystis. Now it's too late.

I would like to move on to another study. This time the data is from a paper that has just appeared in press in Clinical Gastroenterology and Hepatology. We  analysed faecal DNAs from patients diagnosed with irritable bowel syndrome and healthy individuals. The reason for doing this was due to the fact that intestinal parasite have been speculated to play a role in the development of IBS, a disease affecting about 16% of the adult Danish population. And so we thought that the prevalence of common parasites such as Blastocystis and Dientamoeba fragilis might be higher in IBS patients than in healthy individuals. The study was led by Dr Laura R Krogsgaard, who took a quite unusual approach to collecting questionnaires and faecal samples, namely by collaborating with the company YouGov Zapera.  
We obtained faecal samples from 483 individuals, of whom 186 were cases – ie. patients with IBS – and 297 were healthy controls. DNA was extracted directly from the stool using the easyMag protocol, and the faecal DNAs were submitted to real-time PCR based screening for Blastocystis, Dientamoeba, Entamoeba histolytica and E. dispar, Cryptosporidium, and Giardia.

Above you see the results of the various analyses. Blue columns represent healthy individuals, and orange columns represent IBS patients. Fifty percent of the healthy controls were positive for one or more parasites, while this proportion was significantly lower in IBS patients, 36%. Also for each individual parasite, the number of positive cases was higher among controls than among patients with IBS. Dientamoeba was the most common parasite among healthy controls and IBS patients. In terms of Blastocystis subtypes, the distribution of subtypes between the two groups was non-significant (data not shown).We ended up by concluding that our findings indicated that these parasites are not likely to play a direct role in the pathogenesis of IBS. Longitudinal studies are required to understand their role in gastrointestinal health. 

Still, the role of Blastocystis in human health and disease remains ambiguous, although lots of interesting data is emerging. In order to try and understand the theories behind Blastocystis' potential able to generate disease, I would like to point the readers' attention to a new review, developed by Ivan Wawrzyniak and his prolific colleauges.



Krogsgaard LR, Engsbro AL, Stensvold CR, Vedel Nielsen H, & Bytzer P (2014). The Prevalence of Intestinal Parasites is not Greater Among Individuals with IBS: a Population-Based Case-Control Study. Clinical Gastroenterology and Hepatology : the official clinical practice journal of the American Gastroenterological Association PMID: 25229421

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

Ruaux CG, & Stang BV (2014). Prevalence of Blastocystis in Shelter-Resident and Client-Owned Companion Animals in the US Pacific Northwest. PloS One, 9 (9) PMID: 25226285  

Wang W, Cuttell L, Bielefeldt-Ohmann H, Inpankaew T, Owen H, & Traub RJ (2013). Diversity of Blastocystis subtypes in dogs in different geographical settings. Parasites & Vectors, 6 PMID: 23883734

Wawrzyniak I, Poirier P, Viscogliosi E, Dionigia M, Texier C, Delbac F, & Alaoui HE (2013). Blastocystis, an unrecognized parasite: an overview of pathogenesis and diagnosis. Therapeutic Advances in Infectious Disease, 1 (5), 167-78 PMID: 25165551