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Background: The purpose of this study was to assess the genetic variation and differentiation of Blastocystis subtypes (STs) recovered from symptomatic children by analysing partial sequences of the small subunit rDNA gene region (SSUrDNA) and internal transcribed spacers (1 and 2) plus the 5.8S region (ITS, ITS1 + 5.8S + ITS2) and comparing with isolates from other countries., Findings: Faecal samples from 47 Blastocystis-infected children with gastrointestinal symptoms and negative for pathogenic enterobacteria were analysed. PCR was performed on DNA from all the samples to identify Blastocystis STs, amplifying a fragment of SSUrDNA and the ITS region. The amplicons were purified and sequenced, and consensus sequences were submitted to GenBank; afterwards, SSUrDNA sequences were analysed for genetic diversity according to geographic area. Regarding the Blastocystis STs found, 51% were ST1, 23% ST2, 19% ST3 and 2% ST7. For ITS, a haplotype network tree and Bayesian inference revealed the presence of two novel variants of ST1, clustering some sequences into ST1A and ST1B. The values of nucleotide diversity (π) and haplotype polymorphism (θ) for ST1, ST2 and ST3 ranged from 0 to 1, whereas the ratio of genetic differentiation (FST)/migration index (Nm) showed the highest differentiation between Libya and Thailand-Philippines for ST2 (0.282/0.63). In contrast, a high flow gene was observed between Czech Republic-Denmark-Holland-Spain and USA-Mexico-Colombia for ST1 (0.003/84)., Conclusion: Our data on genetic differentiation and gene flow might explain the differences for the prevalence of Blastocystis STs. Moreover, the ITS region could be used as a genetic marker to assess genetic variation in this parasite. more...

Background: A large variety of mammals act as natural reservoirs of Trypanosoma cruzi (the causal agent of Chagas disease) across the American continent. Related issues are infection and parasite burden in these reservoirs, and whether they are able to control T. cruzi infections. These parameters can indicate the real role of mammals as T. cruzi reservoirs and transmitters. Here, two species of mammals, white-nosed coati (Nasua narica) and raccoon (Procyon lotor), were examined for to determine: a) T. cruzi presence, and; b) their ability to control T. cruzi infection., Methods: Multiple capture-recaptures of both species were carried out in semi-wild conditions in Villahermosa, Tabasco, Mexico, for 5 years. Two samplings per year (summer and winter) took place. Prevalence and pattern of T. cruzi infection were determined by PCR from both mammals' blood samples., Results: Raccoon samples had a higher relative infection values (26.6%) compared to those of white-nosed coati (9.05%), being this difference significant in summer 2012 (P < 0.00001), summer (P = 0.03) and winter 2013 (P = 0.02). Capture and recapture data indicated three infection dynamics: 1) negative-positive-negative infection; 2) positive-negative-positive infection; and 3) positive at all sampling times., Conclusions: These results indicate that both coati and raccoons may be able to control T. cruzi infection. Thus, the role as efficient reservoirs could be questioned (at least for those times when mammals are able to tolerate the infection). However, while infected, they may also be able to approach human dwellings and play a role important in linking sylvatic and domestic cycles. more...

Background: Human neurocysticercosis (NCC) is a considered public health problem in many underdeveloped and developing countries. Because of the enormous increase in international tourism and migration, NCC nowadays is also found in some developed countries. Our group was the first to demonstrate that tapeworm carriers in the household are the main risk factor for acquiring cysticercosis in humans and pigs, since the disease results from the ingestion of microscopic tapeworm eggs., Findings: We had the opportunity to film the liberation of the embryo from the oncospheral membrane after the hatching of the egg, which is the activation process required for intestinal wall invasion by the onchosphere. Yoshino (J Formosa Med Ass 32:139-142, 1933) described with great detail in diagrams and photographs this process eighty years ago after he infected himself with three living cysticerci in order to study the life cycle of Taenia solium. Other authors further described this process. Nevertheless it has never been filmed before. The purpose of this paper is to shift from stillness to motion since we can now show for the first time a movie of an activated oncosphere and its release from the oncospheral membrane., Conclusion: Oncospheral activation is the requisite for T. solium embryos to invade the intestinal mucosa and develop into cysticerci. This process has been amply described but here it is shown for the first time in motion; thus it may be of interest for readers of the journal and useful for educational purposes towards the control of NCC. more...

The life cycle of Taenia pisiformis includes canines as definitive hosts and rabbits as intermediate hosts. Golden hamster (Mesocricetus auratus) is a rodent that has been successfully used as experimental model of Taenia solium taeniosis. In the present study we describe the course of T. pisiformis infection in experimentally infected golden hamsters. Ten females, treated with methyl-prednisolone acetate were infected with three T. pisiformis cysticerci each one excised from one rabbit. Proglottids released in faeces and adults recovered during necropsy showed that all animals were infected. Eggs obtained from the hamsters' tapeworms, were assessed for viability using trypan blue or propidium iodide stains. Afterwards, some rabbits were inoculated with eggs, necropsy was performed after seven weeks and viable cysticerci were obtained. Our results demonstrate that the experimental model of adult Taenia pisiformis in golden hamster can replace the use of canines in order to study this parasite and to provide eggs and adult tapeworms to be used in different types of experiments., (© 2011 Toral-Bastida et al; licensee BioMed Central Ltd.) more...

Taenia solium life cycle includes humans as definitive hosts and pigs as intermediate hosts. One of the measures to stop the life cycle of this parasite is by vaccination of pigs. In experiments performed in pigs with TSOL18 and TSOL45-1A, two recombinant T. solium proteins, 99.5% and 97.0% protection was induced, respectively. The purpose of this paper was to localize these antigens in all stages of the parasite (adult worms, oncospheres and cysticerci) by immunofluorescence, with the use of antibodies against TSOL18 and TSOL45-1A that were obtained from the pigs used in the vaccination experiment. Results show that TSOL18 and TSOL45-1A are expressed on the surface of T. solium oncospheres and not in tapeworms or cysticerci, indicating that they are stage-specific antigens. This, therefore, might explain the high level of protection these antigens induce against pig cysticercosis. more...

One hundred and fifteen patients with symptoms suggestive of irritable bowel syndrome (IBS) according to Rome III criteria and 209 patients with gastrointestinal symptoms different from IBS (control) were identified through medical records from the Gastroenterology Clinic of the "Dr. Manuel Gea Gonzalez General Hospital" from January 2008 to March 2010. No statistical differences in IBS data as compared with control groups were observed except in bloating, that was more frequent in the IBS group (P = 0.043). Although the pathogenicity of specific intestinal protozoa could not be demonstrated due to lack of association with the development of gastrointestinal symptoms, Blastocystis spp, in the IBS group, exhibited a trend of association to diarrhoea (odds ratio = 2.73, 95% confidence interval = 0.84-8.80, P = 0.053), while having any parasite and diarrhoea was significant (odds ratio = 3.38, 95% confidence interval = 1.33-8.57, P = 0.008). The association between Blastocystis and diarrhoea in IBS patients although not conclusive is an interesting finding; nonetheless more extensive case-controlled studies are required to clearly define the role of some "non-pathogenic" parasites in intestinal disease and IBS. more...

Viral population evolution dynamics of influenza A is crucial for surveillance and control. In this paper we analyzed viral genetic features during the recent pandemic caused by the new influenza human virus A H1N1, using a conventional population genetics approach based on 4689 hemagglutinin (HA) and neuraminidase (NA) sequences available in GenBank submitted between March and December of 2009. This analysis showed several relevant aspects: a) a scarce initial genetic variability within the viral isolates from some countries that increased along 2009 when influenza was dispersed around the world; b) a worldwide virus polarized behavior identified when comparing paired countries, low differentiation and high gene flow were found in some pairs and high differentiation and moderate or scarce gene flow in others, independently of their geographical closeness, c) lack of positive selection in HA and NA due to increase of the population size of virus variants, d) HA and NA variants spread in a few months all over the world being identified in the same countries in different months along 2009, and e) containment of viral variants in Mexico at the beginning of the outbreak, probably due to the control measures applied by the government. more...