Intestinal parasitism in Peruvian children and molecular characterization of Cryptosporidium species

Genomics and molecular epidemiology of Cryptosporidium species

Cryptosporidium is one of the most widespread protozoan parasites that infects domestic and wild animals and is considered the second major cause of diarrhea and death in children after rotavirus. So far, around 20 distinct species are known to cause severe to moderate infections in humans, of which Cryptosporidium hominis and Cryptosporidium parvum are the major causative agents. Currently, ssurRNA and gp60 are used as the optimal markers for differentiating species and subtypes respectively. Over the last decade, diagnostic tools to detect and differentiate Cryptosporidium species at the genotype and subtype level have improved, but our understanding of the zoonotic and anthroponotic transmission potential of each species is less clear, largely because of the paucity of high resolution whole genome sequencing data for the different species. Defining which species possess an anthroponotic vs. zoonotic transmission cycle is critical if we are to limit the spread of disease between animals and humans. Likewise, it is unclear to what extent genetic hybridization impacts disease potential or the emergence of outbreak strains. The development of high resolution genetic markers and whole genome sequencing of different species should provide new insights into these knowledge gaps. The aim of this review is to outline currently available molecular epidemiology and genomics data for different species of Cryptosporidium.

Prevalence of Entamoeba histolytica and other enteral parasitic diseases in the metropolitan region of Belo Horizonte, Brazil. A cross-sectional study

BACKGROUND

Enteral parasitic diseases are a public health problem in nations with low economic development and in settings with poor sanitation. Amebiasis is the second most frequent form of parasitosis, with a high burden of disease. Knowledge of the prevalence of enteroparasitoses in a given region is useful for planning clinical decision-making. Thus, the aim of this study was to estimate the prevalence of enteral parasitic diseases, especially amebiasis, through analysis on stool samples from public and private laboratories in a metropolitan area in southeastern Brazil.

DESIGN AND SETTING

Cross-sectional study conducted in the metropolitan region of Belo Horizonte, Brazil.

METHODS

We evaluated 6,289 fecal samples from one private and one public laboratory. The samples were concentrated by means of spontaneous sedimentation, and those that were positive for Entamoeba histolytica or Entamoeba dispar in optical microscopy analyses were processed to obtain deoxyribonucleic acid, with subsequent identification through the polymerase chain reaction.

RESULTS

Among the stool samples, 942 (15.0%) had parasitic infections; 73 (1.2%) of these were helminthic infections and 847 (13.5%) were protozoan infections, caused mainly by Escherichia coli (6.0%), Endolimax nana (5.2%) and Giardia lamblia (1.2%). Infections due to Entamoeba histolytica or Entamoeba dispar occurred in 36 samples (0.6%) and the polymerase chain reaction revealed five (13.9%) as Entamoeba histolytica.

CONCLUSION

The prevalence of enteral parasitic diseases is high in the metropolitan region of Belo Horizonte, although amebiasis may not be a problem.

Potentially zoonotic helminthiases of murid rodents from the Indo-Chinese peninsula: impact of habitat and the risk of human infection

In this study, we report the potential rodent-borne zoonotic helminths in wild-caught murid rodents from four categorized habitats-forest, nonflooded land, irrigated land, and human settlement in seven localities of Thailand, Cambodia, and Lao PDR. Out of 2478 rodent samples, 735 (29.7%) were infected by at least one of the following zoonotic helminth species: Echinostoma malayanum, Echinostoma ilocanum, Plagiorchis muris, Raillietina spp., Hymenolepis diminuta, Hymenolepis nana, Cyclodontostomum purivisi, and Moniliformis moniliformis. Raillietina spp. showed the highest prevalence (13.8%), followed by H. diminuta (8.6%), H. nana (6.7%), and C. purvisi (1.0%). Habitat affected the intensity of helminth infection in murid rodent hosts. Specific habitats favoring each zoonotic helminth species are discussed in relation to the risk of human infection. Season and host maturity influenced intensity of total zoonotic helminths, but there was no influence of host gender. However, in terms of individual helminth species, female rodents were more infected by E. malayanum, E. ilocanum, and C. purvisi than males. Among the rodent species, Rattus tanezumi seems to play the most important role as a reservoir by hosting seven zoonotic heminth species. This rat is ubiquitously found in all types of the habitats, suggesting that it can act as an important bridge species, carrying parasites across different habitats.

Factors associated with parasitic infection amongst street children in orphanages across Lima, Peru

Infection caused by intestinal parasites has significant public health consequences amongst children in the developing world. Street children are an under-studied group of society subjected to increased health risks when compared to their peers. To estimate the prevalence of intestinal parasitic infection and ascertain risk factors for parasitosis amongst this population, stool samples were collected from 258 children across four orphanages in three districts of Lima, Peru. Surveys were used to determine associations between risk factors and infection status. The prevalence of parasitic infection within the study sample was 66·3%, with 30·6% testing positive for pathogenic species. Entamoeba coli was the most commonly detected parasite (41·9%) and Giardia lamblia was the most commonly detected pathogenic parasite (17·1%). Of the group 15·1% had helminth infection. When testing for association, age and BMI were risk factors for infection. A notable difference in prevalence (P < 0·00001) based on orphanage was observed, but the duration of residence in an orphanage was not a predictor for infection. A sub-analysis conducted amongst children who were given anti-parasitic treatment 5 months beforehand found no significant difference in parasitosis between those who had been given treatment and those who had not (P = 0·218). It is suggested that a single dose of albendazole alone may not be effective in combating long-term infection rates.

Epidemiology of Cyclospora cayetanensis: A review focusing in endemic areas

Cyclospora cayetanensis is an intestinal coccidian protozoon that has emerged as an important cause of endemic or epidemic diarrhoeal illness in children and adults worldwide. Humans appear to be the only natural hosts. However, the role of animals as natural reservoirs is uncertain but of increasing concern. Human-to-human spread of the parasite occurs indirectly via the environment through oocysts in contaminated water, food or soil. In endemic areas, risk factors associated with the infection include contaminated water or food, contact with soil or animals, type of sanitation and low socioeconomic status. Infections linked to soil contact provide reasons to believe that this route of spread may be more common than realised in disadvantaged community settings. C. cayetanensis is an important cause of traveller's diarrhoea and numerous large foodborne outbreaks associated with the globalisation of the food supply and importation of fruits and vegetables from developing countries have occurred. Waterborne outbreaks have also been reported. Implementation of measures to prevent or control the spread of Cyclospora oocysts in the environment is critical. In endemic areas, the most important steps to prevent infection are improving environmental sanitation and health education. Significant gaps remain in our understanding of the epidemiology of human cyclosporiasis that highlight the need for continued research in several aspects of C. cayetanensis.

Update on Cyclospora cayetanensis, a food-borne and waterborne parasite

The coccidian parasite Cyclospora cayetanensis is recognized as an emerging pathogen that causes protracted diarrhea in humans. The first cases of Cyclospora infection were reported in the late 1970s and were observed among expatriates and travelers in regions where infections are endemic. Since then, Cyclospora has been considered a cause of traveler's diarrhea. Epidemiological investigations were reported and examined in areas of endemicity even before the true identity of Cyclospora was elucidated. Cyclospora was fully characterized in the early 1990s, but it was not until the 1995 Cyclospora outbreak in the United States and Canada that it caught the attention of the public and physicians. The biology, clinical presentation, epidemiology, diagnosis, treatment, and control of cyclosporiasis are reviewed, with a focus on diagnostic assays currently being used for clinical and environmental samples. Challenges and limitations in working with Cyclospora are also discussed.

Molecular epidemiology of cryptosporidiosis: an update

Molecular tools have been developed to detect and differentiate Cryptosporidium at the species/genotype and subtype levels. These tools have been increasingly used in characterizing the transmission of Cryptosporidium spp. in humans and animals. Results of these molecular epidemiologic studies have led to better appreciation of the public health importance of Cryptosporidium species/genotypes in various animals and improved understanding of infection sources in humans. Geographic, seasonal and socioeconomic differences in the distribution of Cryptosporidium spp. in humans have been identified, and have been attributed to differences in infection sources and transmission routes. The transmission of C. parvum in humans is mostly anthroponotic in developing countries, with zoonotic infections play an important role in developed countries. Species of Cryptosporidium and subtype families of C. hominis have been shown to induce different clinical manifestations and have different potential to cause outbreaks. The wide use of a new generation of genotyping and subtyping tools in well designed epidemiologic studies should lead to a more in-depth understanding of the epidemiology of cryptosporidiosis in humans and animals.

Molecular and epidemiological investigations of cryptosporidiosis in Cuban children

Molecular and epidemiological studies of Cryptosporidium infections amongst 28 Cuban children (aged 2-8 years) with diarrhoea are described. As few of the younger infected children but most of the older infected children had been breastfed, short-term protection from maternal antibodies passed to infants during breastfeeding may result in a lack of cryptosporidial infection in infancy. This protection of breastfeeding children may, however, result in such children developing less anti-Cryptosporidium immunity of their own (than their bottle-fed counterparts), so that, by school age, the children who had been breastfed are those most likely to be found infected. In the present study, in contrast with the observations made during a previous study of cryptosporidiosis in Cuban children, vomiting was rare (7%) whereas abdominal pain was common (57%). These differences in expression of symptoms between studies may be age-related. As seen in other studies from similar countries, including those of the Caribbean and Latin America, C. hominis was found to predominate, the results of the successful molecular analyses revealing 10 C. hominis infections but no C. parvum. Subgenotyping (at the gp60 locus) indicated that the C. hominis infections included a wide range of subtypes, with isolates from three subtype families (Ia, Ib and Id) being detected.

Cyclosporiasis: an update

Cyclosporiasis is a food- and water-borne infection that affects healthy and immunocompromised individuals. Awareness of the disease has increased, and outbreaks continue to be reported among vulnerable hosts and now among local residents in endemic areas. Advances in molecular techniques have improved identification of infection, but detecting food and water contamination remains difficult. Further understanding of the biology, pathogenesis, and control of infection and transmission has been hindered by the difficulty of propagating the organism, lack of reliable oocyst viability and infectivity assays, and inability to experimentally infect animals and human volunteers. This article provides a general review and presents recent insights into the organism and disease.

Prevalence of enteroparasites and genotyping of Giardia lamblia in Peruvian children

Enteroparasites in children from three marginal urban districts of Trujillo (Peru) were studied to treat these children and to design a prevention and control programme. A total of 845 children were examined. The general prevalence of enteroparasites was of 66.3%, and 45.6% were multiparasitized. The pathogenic enteroparasite prevalence were 23.8% (Giardia lamblia), 4.6% (Iodamoeba buschlii), 2.6% (Cyclospora cayetanensis), 2.2% (Hymenolepis nana), and 2% (Cryptosporidium spp.). G. lamblia was the most frequent parasite both in diarrheic children (28.1%) as well as in nondiarrheic ones (19.5%). The G. lamblia genotypes were molecularly characterized by sequence analysis of the glutamate dehydrogenase (gdh) gene using PCR and RFLP. Sequence analysis revealed both Assemblage A (AI and AII) and Assemblage B (BIV), with the predominance of Assemblage AI. All the samples with Assemblage A were diarrheic but not those with Assemblage B. This is the first study of molecular characterization of G. lamblia in Peruvian children and confirms the importance of asymptomatic patients in the transmission of the giardiosis, especially in places with poor hygiene and sanitation.