Abstract
BackgroundSeveral species of protozoa cause acute or chronic gastroenteritis in humans, worldwide. The burden of disease is particularly high among children living in developing areas of the world, where transmission is favored by lower hygienic standards and scarce availability of safe water. However, asymptomatic infection and polyparasitism are also commonly observed in poor settings. Here, we investigated the prevalence of intestinal protozoa in two small fishing villages, Porto Said (PS) and Santa Maria da Serra (SM), situated along the river Tietê in the State of São Paolo, Brazil. The villages lack basic public infrastructure and services, such as roads, public water supply, electricity and public health services.MethodsMultiple fecal samples were collected from 88 individuals in PS and from 38 individuals in SM, who were asymptomatic at the time of sampling and had no recent history of diarrheal disease. To gain insights into potential transmission routes, 49 dog fecal samples (38 from PS and 11 from SM) and 28 river water samples were also collected. All samples were tested by microscopy and PCR was used to genotype Giardia duodenalis, Blastocystis sp., Dientamoeba fragilis and Cryptosporidium spp.ResultsBy molecular methods, the most common human parasite was Blastocystis sp. (prevalence, 45% in PS and 71% in SM), followed by D. fragilis (13.6% in PS, and 18.4% in SM) and G. duodenalis (18.2% in PS and 7.9% in SM); Cryptosporidium spp. were not detected. Sequence analysis revealed large genetic variation among Blastocystis samples, with subtypes (STs) 1 and 3 being predominant, and with the notable absence of ST4. Among G. duodenalis samples, assemblages A and B were detected in humans, whereas assemblages A, C and D were found in dogs. Finally, all D. fragilis samples from humans were genotype 1. A single dog was found infected with Cryptosporidium canis. River water samples were negative for the investigated parasites.ConclusionsThis study showed a high carriage of intestinal parasites in asymptomatic individuals from two poor Brazilian villages, and highlighted a large genetic variability of Blastocystis spp. and G. duodenalis.
Highlights
Several species of protozoa cause acute or chronic gastroenteritis in humans, worldwide
The large genetic variability observed among isolates of intestinal protozoan species has lead to the description of many genotypes and subtypes that have been found to differ in host range, zoonotic potential and clinical significance [2,3,4] strongly impacting on our knowledge of the epidemiology of parasitic infection
Microscopic detection of intestinal parasites All individuals (n = 126) were considered asymptomatic, since stools were scored as formed at the time of collection and no episode of diarrhea was reported during the two months prior to sample collection
Summary
Several species of protozoa cause acute or chronic gastroenteritis in humans, worldwide. Human infection with gastrointestinal parasites is common worldwide, but a significantly higher morbidity and mortality is observed in developing countries, among children, where many communities still lack access to improved sanitation facilities [1]. Species of Cryptosporidium, Blastocystis and Entamoeba, as well as Giardia duodenalis and Dientamoeba fragilis are the most common etiological causes of intestinal infections. The large genetic variability observed among isolates of intestinal protozoan species has lead to the description of many genotypes and subtypes that have been found to differ in host range, zoonotic potential and clinical significance [2,3,4] strongly impacting on our knowledge of the epidemiology of parasitic infection
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