Showing posts with label foodborne transmission. Show all posts
Showing posts with label foodborne transmission. Show all posts

Monday, July 28, 2014

This Month In Blastocystis Research (JUL 2014)

For Spanish-speaking Blastocystis geeks, this summer must have been a real treat: Londoño-Franco and colleagues published a paper in Biomédica on Blastocystis in children and Colombia. But not only did they look for Blastocystis in faecal samples, they also sampled from finger nails, house floors, toys, tap water,  vegetables, other food items, etc... It is extremely rare to see studies aiming to identify sources of potential transmission, and I thought that this study would merit a blog post (unfortunately, I will have to rely on the Google translated version with all its potential limitations; I excuse for any misunderstandings).

Of course one of the big questions still remaining in Blastocystis research is: From where do we get this parasite? With more than one billion people colonised on the globe, the transmission pressure must be massive, and it's tempting to expect infectious cysts (or other stages) being more or less ubiquitous. There is some evidence accumulating that the parasite can be water-borne, and we also know that zoonotic transmission can occur (although relatively rarely, supposedly). However, this study takes things way further:

The authors carried out their study in Calarcá where they identified a prevalence of Blastocystis (based on microscopy of stool concentrates) of 57.5% in 275 children less than 5 years old; children aged 48 months or more were more prone to be positive than those who were younger. This is something we see a lot, and it either suggests a cumulative effect of colonisation (once established, colonisation is chronic), or that the behaviour (~exposure) or intestinal microbiota of older children favours colonisation.
Agua de panela (source).

Blastocystis was also found in dogs (63.3%), cats (56.3%), and poultry (35.7%). Moreover, it was found in tap water (38.5%), on toys (29.9%), baby bottles (18.5%), and under the nails of infected children (42.2%), their siblings (44.8%), and their mothers (34.2%). Among the vegetables that are typically consumed raw, it was found most frequently in lettuce (66.7%), and, in descending order, in tomato (44.4%), carrots (37.5%), cabbage (28.6%) and onion (25%). A high occurrence was seen in containers used to store 'aqua de panela', which is allegedly some kind of sugar water (haven't had the opportunity to sample it myself), with 47.7% of the samples positive. I believe that this drink is used as a sweetener and possibly also as a refreshment/energy drink, and maybe served with for instance cheese (image). Taken into account that Blastocystis is not exactly fussy about growth medium requirements, it may not be surprising at all to learn that this type of drink serves as a perfect stronghold for Blastocystis

The authors also explored a number of other things, among them i) the relative occurrence of cysts and vacuolar stages in the different types of samples and ii) whether any symptoms experienced over the past month could be attributed to Blastocystis, and iii) risk factors for colonisation. However, Google translate plays tricks on me on some of these bits, so I won't try to go more into detail with these findings. Suffice to say that the approach of distinguishing between different stages should help researchers find out more about which stage(s) that is/are responsible for transmission. Also, if for instance vacuolar stages are found in agua de panela and not cysts, then this might indicate that Blastocystis is actually growing in the drink? Which again is interesting because this would mean that Blastocystis capable of infecting humans can grow at temperatures lower than 37 degrees C.

Now, I could only have great confidence in the diagnostic work carried out by this team; however, I would have absolutely loved molecular confirmation of all of these findings. Also, maybe it would have been an idea to try and culture some of the Blastocystis found on fomites and in food/water to test for viability, or, as mentioned by the authors themselves, to test for viability using trypan blue. However, the authors should be praised for their perseverance and ingenuity, and I hope that this study will inspire other colleagues to pursue and expand on these initiatives and ideas.

This month saw a number of different Blastocystis-related papers, among them a paper from Klimes et al. on issues with Blastocystis genome annotation and polyadenylation-mediated termination codon creation in nuclear mRNA transcripts. Moreover, there's a paper on population structure analysis of seven eukaryotic microbial lineages, including Blastocystis, that apparently makes it possible to infer variable impacts of genetic exchange in populations of predominantly clonal micro-pathogens  (in fact the authors used our MLST data for ST3 in their analyses!). Finally, our colleagues in České Budějovice have produced an interesting review on self-infections with parasites; in the paper they point to the traditional focus on sussing out the pathogenic potential of parasites instead of trying to identify the potentially positive effects of parasite colonisation. Definitely worth a read!


Londoño-Franco AL, Loaiza-Herrera J, Lora-Suárez FM, & Gómez-Marín JE (2014). [Blastocystis sp. frequency and sources among children from 0 to 5 years of age attending public day care centers in Calarcá, Colombia]. Biomedica : Revista del Instituto Nacional de Salud, 34 (2), 218-27 PMID: 24967927 

Klimeš V, Gentekaki E, Roger AJ, & Eliáš M (2014). A large number of nuclear genes in the human parasite Blastocystis require mRNA polyadenylation to create functional termination codons. Genome Biology and Evolution PMID: 25015079 

Lukeš J, Kuchta R, Scholz T, & Pomajbíková K (2014). (Self-) infections with parasites: re-interpretations for the present. Trends in Parasitology PMID: 25033775

Tomasini N, Lauthier JJ, Ayala FJ, Tibayrenc M, & Diosque P (2014). How often do they have sex? A comparative analysis of the population structure of seven eukaryotic microbial pathogens. PLoS One, 9 (7) PMID: 25054834 

Sunday, November 3, 2013

This Month in Blastocystis Research (OCT 2013)

Thanks to Google Scholar and PubMed feeds I can keep myself relatively up-to-date with emerging Blastocystis data and 'breaking news' in the field.

One of things that have caught my attention recently, is the string of foodborne outbreaks in Sweden, due to Cryptosporidium, Cyclospora and microsporidia stemming from (presumably) imported produce. A few of my colleagues (Robertsen et al., in press) have just published a large review on the impact of globalisation on foodborne parasites - a resource that has been a long time coming, and which I hope will be read and contemplated by many. The review includes a table on parasites isolated from fresh produce (for some reason the Swedish data was not included), and among these is Blastocystis, which was identified in fresh produce from Saudi Arabia (original data published by Al-Binali et al., 2006). Apart from this, hardly any data is out there on Blastocystis in the environment, and we therefore still know very little about potential sources of transmission and how we are exposed.

In Clinical Microbiology and Infection there is a paper out by Mass et al. on detection of intestinal protozoa in paediatric patients with gastrointestinal symptoms by multiplex real-time PCR. Not surprisingly, the study is from The Netherlands, the cradle of real-time PCR-based parasite diagnostics in clinical microbiology. It's a great paper despite all its limitations, but I couldn't figure out which Blastocystis PCR they used for the study, - I think the authors failed to provide a reference for it. Anyway, the authors found 30% of the children colonised by Blastocystis, while Dientamoeba fragilis was found in a staggering 62%, which is more or less equivalent to what we see in Denmark in this type of cohort (please refer to previous blog post on Dientamoeba fragilis). It appeared that symptom resolution was just as common in patients who were treated with different antibiotics as in patients who were not treated, and the authors end up by highlighting the fact that it is still difficult to know whom and when to test for these parasites, and when to treat them.

In Mexico, Sanchez-Aguillon and colleagues have documented a very nice study on parasitic infections in a Mexican HIV/AIDS cohort. Quite a few of the patients had Cryptosporidium, Cyclospora or Cystoisospora, the presence of which was - not surprisingly - associated with diarrhoea. Table 1 in the paper is a bit confusing, but I believe that Blastocystis was found in about 30%; of note, only ST1 and ST3 were found, adding further support to the hypothesis that ST1 and ST3 are common in most parts of the world, while especially ST4 exhibits vast differences in geographic 'affinity'. The authors end their paper by saying
"Other molecular markers for Blastocystis ST should be studied to elucidate the complexity of this heterogeneous genus and its role in human disease."
Let me just add that subtype identification is a valid proxy for intra-generic diversity in Blastocystis, - we have been looking at mitochondrial genomes and found that analyses based on mitochondrial markers and ribosomal genes reveal similar phylogenetic relationships. So, in terms of transmission and epidemiology in general, the subtyping system ('barcoding') is highly applicable and robust. It is true, however, that we need to see if we can identify specific genes potentially responsible for pathogenesis. The Mexican paper can be accessed here.

There's a very nice paper out now from the Swiss Tropical and Public Health Institute and University of Basel on differential diagnoses of common dermatological problems in returning travellers. Blastocystis has been included in the list (in the section on allergic skin reactions/urticaria) together with a plethora of other infectious agents. Lots of informative images there, and the paper has a nice structure.

Despite loads of daily feeds, a lot of papers relevant to Blastocystis research still escape my attention. I realise that there was a paper out in PLoS Genetics in June on Saprolegnia parasitica (an oomocyte parasitising on fish) which appears to be a good and interesting read. Maybe I'll come back to this one!

For me personally, this month in Blastocystis research has been a month of putting together grant proposals - more so now than usual -, many initiatives are being taken, networks are being expanded, and interesting data are accumulating from various projects... I hope to be back with details on some of this soon!


Maas L, Dorigo-Zetsma JW, de Groot CJ, Bouter S, Plötz FB, & van Ewijk BE (2013). Detection of intestinal protozoa in paediatric patients with gastrointestinal symptoms by multiplex real-time PCR. Clinical Microbiology and Infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases PMID: 24131443

Fabiola Sanchez-Aguillon, Eduardo Lopez-Escamilla, Francisco Velez-Perez, Williams Arony Martinez-Flores, Patricia Rodriguez-Zulueta, Joel Martinez-Ocaña, Fernando Martinez-Hernandez, Mirza Romero-Valdovinos, Pablo Maravilla (2013). Parasitic infections in a Mexican HIV/AIDS cohort. The Journal of Infection in Developing Countries PMID: 24129632 

Neumayr A, Hatz C, Blum J. In Press. Not be missed! Differential Diagnoses of Common Dermatological Problems in Returning Travellers. Travel Medicine and Infectious Disease.

Robertson LJ, Sprong H, Ortega YR, van der Giessen JW, Fayer R. In Press. Impact of globalisation on foodborne parasites. Trends in Parasitology