Although the presence of cryptic host specificity has been documented in Blastocystis, differences in infection rates and high genetic polymorphism within and between populations of some subtypes (ST) have impeded the clarification of the generalist or specialist specificity of this parasite. We assessed the genetic variability and host specificity of Blastocystis spp. in wild howler monkeys from two rainforest areas in the southeastern region of Mexico. Fecal samples of 225 Alouatta palliata (59) and A. pigra (166) monkeys, belonging to 16 sylvatic sites, were analyzed for infection with Blastocystis ST using a region of the small subunit rDNA (SSUrDNA) gene as a marker. Phylogenetic and genetic diversity analyses were performed according to the geographic areas where the monkeys were found. Blastocystis ST2 was the most abundant (91.9%), followed by ST1 and ST8 with 4.6% and 3.5%, respectively; no association between Blastocystis ST and Alouatta species was observed. SSUrDNA sequences in GenBank from human and non-human primates (NHP) were used as ST references and included in population analyses. The haplotype network trees exhibited different distributions: ST1 showed a generalist profile since several haplotypes from different animals were homogeneously distributed with few mutational changes. For ST2, a major dispersion center grouped the Mexican samples, and high mutational differences were observed between NHP. Furthermore, nucleotide and haplotype diversity values, as well as migration and genetic differentiation indexes, showed contrasting values for ST1 and ST2. These data suggest that ST1 populations are only minimally differentiated, while ST2 populations in humans are highly differentiated from those of NHP. The host generalist and specialist specificities exhibited by ST1 and ST2 Blastocystis populations indicate distinct adaptation processes. Because ST1 exhibits a generalist profile, this haplotype can be considered a metapopulation; in contrast, ST2 exists as a set of local populations with preferences for either humans or NHP.

This item has no Follow the links below to access the full text.

Toxoplasma gondii is a protozoan parasite with a broad ecological valence, which has been detected in a wide range of hosts and landscapes. Although the genus is considered monospecific, in recent years it has been demonstrated to exhibit more genetic variability than previously known. In Mexico, there are few genotyping studies, which suggest that classical, autochthonous, and atypical strains are circulating. The goal of this study was to describe T. gondii genetic diversity in naturally infected sheep from Colima, Mexico. This is a good site to study ecological aspects of this parasite since it is located between the Nearctic and Neotropical ecozones and it includes domestic and wild risks for transmission. We analyzed 305 tissue samples of semicaptive sheep from six coastal and central zones of Colima and border zones of Michoacán. We used an 803 bp amplicon of the B1 gene to genotype T. gondii and seroprevalence was determined by ELISA. Indexes for genetic diversity and genetic differentiation were calculated and compared with reference strains from North America (NA) and South America (SA). Twenty-three tissue samples were positive for the B1 gene by PCR, which were sequenced. Crude prevalence was 24.4%. The genetic analysis showed 16 variable sites along the 803 bp region that grouped all sequences into 13 haplotypes in the phylogenetic tree. Bayesian and haplotype network analysis showed nine new B1 -types, of which three were frequent and six had unique alleles. Comparisons among sequence sets revealed that the Mexican population had lower differentiation than SA and an intermediate genetic variability between South America and North America. The B1 gene analysis showed new T. gondii haplotypes in naturally infected sheep; therefore, this marker could be initially used in molecular screening studies to identify potentially virulent genotypes of this parasite using natural host samples directly.