RESUMO
BACKGROUND AND AIMS: Grasses of the Festuca genus have complex phylogenetic relations due to morphological similarities among species and interspecific hybridization processes. Within Patagonian fescues, information concerning phylogenetic relationships is very scarce. In Festuca pallescens, a widely distributed species, the high phenotypic variability and the occurrence of interspecific hybridization preclude a clear identification of the populations. Given the relevance of natural rangelands for livestock production and their high degradation due to climate change, conservation actions are needed and knowledge about genetic variation is required. METHODS: To unravel the intraspecific phylogenetic relations and to detect genetic differences, we studied 21 populations of the species along its natural geographical distribution by coupling both molecular [internal transcribed spacer (ITS) and trnL-F markers] and morpho-anatomical analyses. Bayesian inference, maximum likelihood and maximum parsimony methods were applied to assemble a phylogenetic tree, including other native species. The morphological data set was analysed by discriminant and cluster analyses. KEY RESULTS: The combined information of the Bayesian tree (ITS marker), the geographical distribution of haplotype variants (trnL-F marker) and the morpho-anatomical traits, distinguished populations located at the margins of the distribution. Some of the variants detected were shared with other sympatric species of fescues. CONCLUSIONS: These results suggest the occurrence of hybridization processes between species of the genus at peripheral sites characterized by suboptimal conditions, which might be key to the survival of these populations.
Assuntos
Festuca , Filogenia , Festuca/genética , Teorema de Bayes , Variação Genética , Poaceae/genética , Análise de Sequência de DNARESUMO
We conducted a prospective, longitudinal study in a cohort of 36 Peace Corps volunteers (PCVs) in Guatemala to study the incidence and natural history of intestinal parasitic infections during the PCVs' >2-year overseas stay. PCVs collected stool specimens at least monthly and when ill with gastrointestinal symptoms. Of the 1,168 specimens tested, 453 (38.8%) were positive for at least one parasite and 48 (4.1%) were positive for a pathogenic parasite. A median interval of 187 days (range, 14 to 752 days) elapsed before the first documented parasitic infection, and the median intervals from arrival until subsequent infections (e.g., second or third) were >300 days. The PCVs had 116 episodes of infection with 11 parasites, including up to 4 episodes per PCV with specific nonpathogens and Blastocystis hominis. The incidence, in episodes per 100 person-years, was highest for B. hominis (65), followed by Entamoeba coli (31), Cryptosporidium parvum (17), and Entamoeba hartmanni (17). The PCVs' B. hominis episodes lasted 6,809 person-days (28.7% of the 23,689 person-days in the study), the E. coli episodes lasted 2,055 person-days (8.7%), and each of the other types of episodes lasted <2% of the person-days in the study. Gastrointestinal symptoms were somewhat more common and more persistent, but not significantly so, in association with pathogen episodes than with B. hominis and nonpathogen episodes. Although infections with pathogenic parasites could account for only a minority of the PCVs' diarrheal episodes, the continued acquisition of parasitic infections throughout the PCVs' >2-year stay in Guatemala suggests that PCVs repeatedly had fecal exposures and thus were at risk for infections with both parasitic and nonparasitic pathogens throughout their overseas service.
Assuntos
Órgãos Governamentais , Enteropatias Parasitárias/epidemiologia , Enteropatias Parasitárias/parasitologia , Intestinos/parasitologia , Infecções por Protozoários/epidemiologia , Voluntários , Adulto , Animais , Blastocystis hominis/isolamento & purificação , Estudos de Coortes , Cryptosporidium parvum/isolamento & purificação , Diarreia/epidemiologia , Diarreia/parasitologia , Entamoeba/isolamento & purificação , Fezes/parasitologia , Feminino , Guatemala/epidemiologia , Humanos , Incidência , Estudos Longitudinais , Masculino , Estudos Prospectivos , Infecções por Protozoários/parasitologia , Estudos SoroepidemiológicosRESUMO
In a Mexican village in which Taenia solium infection was known to be endemic, we selected a cluster sample of 368 households (21% of the total) for demographic, environmental, and diagnostic surveys, and medical histories for taeniasis and cysticercosis. Coproparasitologic studies of 1,531 participants revealed infection by Taenia sp. in four (0.3%) individuals; however, 5.8% of the respondents reported a history of having passed tapeworm proglottids in feces. Of 1,552 human serum specimens, 10.8% tested positive in the cysticercosis immunoblot assay. Seropositivity increased with age and reached a maximum in subjects ages 46-55 years. Risk factors associated with seropositivity included a history of passing tapeworm proglottids, frequent consumption of pork, and poor personal and household hygiene (P less than 0.05). A history of seizures was also significantly associated with seropositivity (P less than 0.05); approximately one-third of persons with such histories were seropositive. Of 571 pigs examined by tongue inspection, 23 (4.0%) had cysticerci; infection rates increased with the age of pigs, and were higher in pigs that habitually ran loose or were fed human feces (P less than 0.05). Goodness of fit analysis confirmed that seropositive persons (but not infected pigs) were significantly clustered within households, particularly, in households in which a member reported a history of having passed tapeworm proglottids. The results of this study have identified community behavioral and environmental practices that must be modified to prevent continued transmission of cysticercosis and taeniasis.