Short report: Genetic variation of Echinococcus canadensis (G7) in Mexico.

We evaluated the genetic variation of Echinococcus G7 strain in larval and adult stages using a fragment of the mitochondrial cox1 gen. Viscera of pigs, bovines, and sheep and fecal samples of dogs were inspected for cystic and canine echinococcosis, respectively; only pigs had hydatid cysts. Bayesian inferences grouped the sequences in an E. canadensis G7 cluster, suggesting that, in Mexico, this strain might be mainly present. Additionally, the population genetic and network analysis showed that E. canadensis in Mexico is very diverse and has probably been introduced several times from different sources. Finally, a scarce genetic differentiation between G6 (camel strain) and G7 (pig strain) populations was identified.

Findings related to IL-8 and IL-10 gene polymorphisms in a Mexican patient population with irritable bowel syndrome infected with Blastocystis.

The intestinal protozoan parasite Blastocystis is one of the most common parasites worldwide in humans and, although its ability to cause human disease has been questioned, some reports have demonstrated that this microorganism is associated to the development of irritable bowel syndrome (IBS) and to a proinflammatory response, in which the expression of some cytokines is unregulated. Since inflammatory cytokine gene polymorphisms might have a role in the pathophysiology of IBS, we assessed the role of single nucleotide polymorphisms (SNPs) for interleukin (IL)-8 and IL-10, in previously collected DNA samples from IBS patients and controls, with or without Blastocystis infection. IL-8+396(G) and IL-10-1082 (A) alleles (p=0.0437 and p=0.0267, respectively), as well as their homozygous (p<0.0001 and p=0.0039, respectively) and IL-8+781(CT) (p=0.0248) genotypes were significantly overrepresented in patients with IBS in comparison with controls. IL-8+396(GG) genotype was relevant because it was associated to IBS (p<0.0001), to Blastocystis (p=0.0025), and to IBS­Blastocystis (p=0.0272). In the latter binomial association, this genotype presented a high contribution (etiological fraction =0.452) and a risk >fourfold to develop IBS. IL-8+781 (T) and IL-10-592 (C) alleles were also associated to Blastocystis and to IBS­Blastocystis, respectively (p=0.0448 and p=0.0166). Our results suggest that some IL-8 and IL-10 SNPs could change individual susceptibility increasing the relative risk in the development of IBS in Blastocystis carriers.

Blastocystis infection is associated with irritable bowel syndrome in a Mexican patient population.

In recent times, some common "non-pathogenic" parasites, such as Blastocystis and Dientamoeba fragilis, have been associated to the aetiology of irritable bowel syndrome (IBS), while host pro-inflammatory cytokine gene polymorphisms might have a role in the pathophysiology of the disease. Therefore, Blastocystis subtypes (ST), D. fragilis and gene promoter single nucleotide polymorphisms of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) in IBS patients and controls were studied. After giving written consent, 45 patients with symptoms of IBS according to the Rome III criteria and 45 controls were enrolled. DNA was extracted from peripheral blood for SNP analysis at position -174 for IL-6 as well as -238 and -308 for TNF-α. Blastocystis was more common in the IBS group (p = 0.043). Interestingly, D. fragilis was found more frequently in the control group (p = 0.002); Blastocystis ST1 and 3 were most frequent in both groups. Haploview analysis revealed linkage disequilibrium in TNF-α (p < 0.0001); however, none of the SNPs for IL-6 and TNF-α were found to be significantly related with IBS. The clinical and molecular approaches undertaken for the first time in Latin American IBS patients demonstrated an association with Blastocystis that supports a pathogenic role of this parasite in IBS Furthermore, co-infections with ST1 and ST3 were frequent; thus, the genetic diversity proposed within ST polymorphisms does not rule out that particular strains might be associated with disease. In addition, our results do not support a major contribution of IL-6 and TNF-α gene polymorphisms in the susceptibility to IBS.

Chinchilla laniger can be used as an experimental model for Taenia solium taeniasis.

Chinchilla laniger has been reported as an experimental definitive host for Taenia solium; however no information about its suitability and yield of gravid tapeworm proglottids containing viable and infective eggs has been published. In total 55 outbred female chinchillas were infected with 4 cysticerci each; hosts were immunodeppressed with 6 or 8 mg of methyl-prednisolone acetate every 14 days starting the day of infection and their discomfort was followed. Kinetics of coproantigen ELISA or expelled proglottids was used to define the infection status. Efficiency of tapeworm establishment was 21% and of parasite gravidity was 8%; chinchillas showed some degree of suffering along the infection. Viability of eggs obtained from gravid proglottids was tested comparing methods previously published, our results showed 62% viability with propidium iodide, 54% with trypan blue, 34% with neutral red, 30% by oncosphere activation and 7% with bromide 3-(4,5-dimetil-tiazol-2-il)-2,5-difenil-tetrazolio (MTT) reduction; no statistical differences were obtained between most techniques, except activation. Four piglets were infected with 50,000 eggs each, necropsy was performed 3 months later and, after counting the number of cysticerci recovered, the percentage of infection was similar to data obtained with T. solium eggs recovered from humans. Our results demonstrate that the experimental model of T. solium taeniasis in C. laniger is a good alternative for providing eggs and adult tapeworms to be used in different types of experiments; optimization of the model probably depends on the use of inbred hosts and on the reduction of infected animals' suffering.

What happened after the initial global spread of pandemic human influenza virus A (H1N1)? A population genetics approach.

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.

Geographical widespread of two lineages of Taenia solium due to human migrations: can population genetic analysis strengthen this hypothesis?

In this paper we discuss, with a new analysis of published data, the phylogenetic hypothesis of two genotypes of Taenia solium previously suggested. Sequences of mitochondrial (co1, cob, nad) and nuclear (18S+ITS1+5.8S, LMWA1 and LMWA2) T. solium DNA from Africa, Asia, Latin America, and Oceania deposited in GenBank international databases were analyzed for diversity and genetic structure. Overall, we found that percentages of polymorphic and informative sites were comparatively less in mitochondrial genes, and minimum or null values of nucleotide diversity and nucleotide polymorphism were also observed. Analysis of co1 populations showed two associations of particular interest: Asia/Latin America and Africa/Latin America; with minimal differentiation between them and a constant genetic flow. Bayesian phylogenetic trees built with the available sequences for co1+cob showed two clusters, one for Asia and another one for Africa/Latin America while with ribosomal sequences only one cluster was obtained that grouped Asian and Latin American populations. The haplotype network tree built using co1+cob showed two major clades, one clustering African and Latin American parasite populations and the other grouping Asian populations, hallmarking Mexican/Peruvian and the Indian populations as dispersion centers, respectively. The haplotype network tree built with ribosomal sequences exhibited Philippines and Peru/Mexico/Colombia as the two major dispersion centers, with several Latin American haplotypes diverging from the latter. Our results suggest that the gene flow within the different T. solium populations has the same dispersion pattern than the main maritime trade routes used between the XV and XIX centuries.