Intestinal parasitoses and environmental factors in a rural population of Argentina, 2002-2003

We evaluate the prevalence of intestinal parasites in 504 people and the degree of association between environmental variables and parasites found in population, soil and water in a rural area of Argentina during 2002-2003. A structured survey was used to evaluate the environmental variables and fecal-human, soil and water samples were analyzed. The prevalence of parasites was 45.4%. Most prevalent protozoa were Blastocystis hominis (27.2%) and Giardia lamblia (6.9%), while the most prevalent helminth was Ascaris lumbricoides (3.8%). The analyzed environmental variables showing association (p < 0.05) with presence of parasites in population were: cardboard-tin or wooden house, dirt floor, home or communal water pump, faucet outside the house or public faucet and cesspool or latrine. Parasite forms were found in 82.3% of the soil samples and in 84.2% of the water samples. In both samples we found parasites that were also found in people. In this study we have found deficient sanitary conditions associated with presence of parasites in population and we have evidenced that contaminated soil and water were the source of these parasites.

Intestinal parasitism and socio-environmental factors among Mbyá-Guarani indians, Porto Alegre, Rio Grande do Sul, Brazil

Disturbing data reveal the prevalence of intestinal parasites and their relationship with socio-environmental factors among Mbyá-Guarani Indians. The prevalence was determined by spontaneous sedimentation in water, centrifugation-floatation, and Kato-Katz. A socioeconomic questionnaire was submitted to each family. The overall prevalence of intestinal parasites was 88.7%, and 45.5% were polyparasitized. There was 90.5% prevalence of enteric parasites in children (1-12- year-old), and 85% among 13-65-year-old individuals, indicating that both age groups are extensively parasitized. The parasite load was low to moderate for geohelminths and 75% of the families did not have latrine, thus the practice of defecation occurred outdoors. These findings suggest that the multiple intestinal parasitism in the Mbyá-Guarani community is high to the point of being the rule, and that it relates essentially to the traditional lifestyle and health habits. It is urgently necessary to implement the association of anti-parasitic treatment with sanitation improvement. This should be done simultaneously with health education activities for this population.

Effects of environmental factors on community structure of Leptophlebiidae (Insecta, Ephemeroptera) in Cerrado streams, Brazil

We analyzed the effects of environmental factors on abundance, species richness, and functional group richness of Leptophlebiidae in 16 sampling points along four Cerrado streams. Across three periods of 2005, we collected 5,492 larvae from 14 species in stream bed substrate. These species belong to three functional feeding groups: scrapers, filtering collectors and shredders. The abundance and species richness were not affected by water quality, but habitat quality related to presence of riparian vegetation had positive effects on the abundance of shredders. Our results add important information on the natural history of the species and functional groups of aquatic insects and also provide relevant data for the monitoring and conservation of streams in the Brazilian Cerrado.

Age-specific Prevalence of Antibodies to Hepatitis A in Children and Adolescents from Rio de Janeiro, Brazil, 1978 and 1995: Relationship of Prevalence to Environmental Factors

The age-specific prevalence of antibodies to hepatitis A virus (anti-HAV) was determined in two different population groups with low socio-economic status from Rio de Janeiro city, Brazil, whose serum samples were collected 17 years apart (Population 1, 1978; Population 2, 1995). In Population 2, analysis of the anti-HAV prevalence was also carried out with respect to environmental factors. Population 1 was composed of 520 stored sera collected from the umbilical cord of term neonates and children aged 1 month to 6 years. In population 2, 720 serum samples were collected from children and adolescents with ages ranging from 1 to 23 years. The overall prevalence rate of anti-HAV in Population 1 and Population 2 was 65.6% and 32.1%, respectively. In Population 1, the anti-HAV prevalence reached 88% at the age of 3, while in Population 2, it increased from 4.5% in children under the age of 3 to 66% in the group of adolescents over the age of 14. The low exposure to HAV infection in younger children from Population 2 could be a result of improved environmental hygiene and sanitation, as demonstrated by the presence of piped water, waste and sewage disposal systems in most houses from this population group. These findings indicate a possible change in the prevalence of hepatitis A in Rio de Janeiro

Population dynamics of intermediate snail hosts of Fasciola hepatica and some environmental factors in San Juan y Martinez municipality, Cuba

The variation of abundances of intermediate snail hosts of Fasciola hepatica in Cuba (Fossaria cubensis and Pseudosuccinea columella) was studied during one year under natural conditions at five sampling sites in San Juan y Martinez municipality, Pinar del Rio province, Cuba. The effect of some environmental variables on the lymnaeid abundances was also studied. A canonical correspondence analysis showed that both species do not generally occur together in the same habitat and that most factors affect them in an opposite fashion, although both of them correlate positively through time to the diversity of the habitats. F. cubensis prefers the sites that are in or closer to the city whereas P. columella is more abundant in rural sites. Lymnaeid abundances are mainly affected by nitrite and nitrate concentrations as well as by the abundance of the thiarid Tarebia granifera. F. cubensis is more abundant in polluted habitats with low densities (or absence) of T. granifera whereas P. columella prefers cleaner habitats and can coexist with the thiarid, even at its higher densities. The implications of divergent preferences of the two lymnaeids for the control of fasciolosis are discussed.

Habitat preference of freshwater snails in relation to environmental factors and the presence of the competitor snail Melanoides tuberculatus (Müller, 1774)

Our objective is to evaluate the habitat preference of freshwater snails in relation to environmental factors and the presence of the competitor snail Melanoides tuberculatus. In the first phase, snails was collected at 12 sites. This sampling sites presented a degree of organic input. In the second phase 33 sampling sites were chosen, covering a variety of lotic and lentic environments. The snail species found at Guapimirim, state of Rio de Janeiro, displayed a marked habitat preference, specially in relation to the physical characteristics of each environment. Other limiting factors for snail distribution at the studied lotic environments were the water current velocity and the amount of organic matter, mainly to Physa marmorata, M. tuberculatus, and Biomphalaria tenagophila. The absence of interactions between M. tuberculatus and another snails could be associated to the distinct spatial distribution of those species and the instability of habitats. This later factor may favor the coexistence of M. tuberculatus with B. glabrata by reduction of population density. In areas of schistosomiasis transmission some habitat modification may add to the instability of the environment, which would make room for the coexistence of M. tuberculatus and Biomphalaria spp. In this way, some of the usual measures for the control of snail hosts would prevent the extinction of populations of Biomphalaria spp. by M. tuberculatus in particular habitats.

Coliform density in oyster culture waters and its relationship with environmental factors

The objective of this work was to evaluate the total and thermotolerant coliform densities in the oyster culture water of Cananeia, SP, Brazil, correlating these densities with environmental variables and tidal variations. Superficial water samples were collected in two tide conditions (spring and neap) from three areas of Cananéia municipality (Mandira, Itapitangui and Cooperostra). The three studied areas showed good conditions for the culture regarding coliform densities. The two tidal conditions differed significantly as to total coliform concentration; however, the same procedure was not performed for thermotolerant coliforms. No correlation was observed between water temperature, pH, and concentrations of total and thermotolerant coliforms. Coliform density was positively correlated with rainfall and negatively correlated with salinity. Spring and neap tides differed significantly as to coliform number. Simple diagnosis of environmental conditions of the crop fields is insufficient to assess water quality of shellfish cultivation. A continuous monitoring program of planted areas is necessary both for the assessment of water quality potential for marine culture and for ensuring safe consumption of seafood, besides constituting an important tool to understand the relationships between contamination and the involved environmental variables.

Influence of environmental factors on seed germination and seedling emergence of yellow sweet clover (Melilotus officinalis)

Laboratory and greenhouse experiments were conducted to determine the effects of drought and salinity stress, temperature, pH and planting depth on yellow sweet clover (Melilotus officinalis) germination and emergence. Base, optimum and ceiling germination temperatures were estimated as 0, 18.47 and 34.60 ºC, respectively. Seed germination was sensitive to drought stress and completely inhibited at a potential of -1 MPa, but it was tolerant to salinity. Salinity stress up to 90 mM had no effect over the M. officinalis seed germination, but the germination decreased by increasing the salt concentration. The drought and salinity required for 50% inhibition of maximum germination were 207 mM and -0.49 MPa, respectively. High percentage of seed germination (>92%) was observed at pH = 5-6 and decreased to 80% at acidic medium (pH 4) and to 42% at alkaline medium (pH 9) pH. Maximum seedling emergence occurred when the seeds were placed at 2 cm depth and decreased when increasing the depth of planting; no seed emerged from depths of 10 cm.

Soil seed bank variation patterns according to environmental factors in a natural grassland

This research aimed to determine the soil seed bank and its relationship with environmental factors that have an influence in the distribution of the vegetation above the ground in an excluded area of natural grassland in the South of Brazil. Most of the 122 identified species in the seed bank were perennials. Data analysis indicated three distinct community groups, according to the size and composition of the soil seed bank in lowlands with permanent wet soils, in lowlands and in other areas. In general, lowlands were characterized by low-fertility soils, high moisture and aluminum contents, being spatially homogeneous habitats and, therefore, more restricted to vegetation heterogeneity than other parts of the relief. Environmental factors most associated with soil seed bank size and composition were relief position and their co-related soil variables such as: soil moisture content, potassium content, organic matter, basic saturation of cation exchange soil capacity, exchangeable basics sum of the soil and clay soil content. According to that, relief position, associated with combined effects of soil chemical properties related to it, determines the observed variation pattern of the soil seed bank, as a reflection of the vegetation above the area.

Environmental and physiological factors that affect the efficacy of herbicides that inhibit the enzyme protoporphyrinogen oxidase: a literature review

Herbicides that inhibit the enzyme protoporphyrinogen oxidase (PROTOX) are usually effective to control dicotyledonous weeds and their agronomic efficacy is affected by environmental and physiological factors. The objective of this review is to summarize the knowledge of those factors available in the scientific literature in the last decade. Environmental factors that influence PROTOX inhibitors include temperature, irradiance and relative humidity. The most relevant physiological factors are the activity of enzymes that can detoxify herbicides and also of enzymes that mitigate the effects of oxidative stress in plants. The study also suggests some possible management strategies that could optimize the activity of PROTOX-inhibiting herbicides.

Prevalence of Trypanosoma cruzi and Leishmania chagasi infection and risk factors in a Colombian indigenous population

This study was carried out in order to obtain base-line data concerning the epidemiology of American Visceral Leishmaniasis and Chagas’ Disease in an indigenous population with whom the government is starting a dwelling improvement programme. Information was collected from 242 dwellings (1,440 people), by means of house to house interviews about socio-economic and environmental factors associated with Leishmania chagasi and Trypanosoma cruzi transmission risk. A leishmanin skin test was applied to 385 people and 454 blood samples were collected on filter paper in order to detect L. chagasi antibodies by ELISA and IFAT and T. cruzi antibodies by ELISA. T. cruzi seroprevalence was 8.7% by ELISA, L. chagasi was 4.6% and 5.1% by IFAT and ELISA, respectively. ELISA sensitivity and specificity for L. chagasi antibodies were 57% and 97.5% respectively, as compared to the IFAT. Leishmanin skin test positivity was 19%. L. chagasi infection prevalence, being defined as a positive result in the three-immunodiagnostic tests, was 17.1%. Additionally, 2.7% of the population studied was positive to both L. chagasi and T. cruzi, showing a possible cross-reaction. L. chagasi and T. cruzi seropositivity increased with age, while no association with gender was observed. Age (p<0.007), number of inhabitants (p<0.05), floor material (p<0.03) and recognition of vector (p<0.01) were associated with T. cruzi infection, whilst age ( p<0.007) and dwelling improvement (p<0.02) were associated with L. chagasi infection. It is necessary to evaluate the long-term impact of the dwelling improvement programme on these parasitic infections in this community.

Factors associated with Leishmania chagasi infection in domestic dogs from Teresina, State of Piauí, Brazil

INTRODUCTION: Many studies have evaluated risk factors for human visceral leishmaniasis, but few have focused on the infection among dogs. The objective of this study was to assess the association between peridomestic socioeconomic and environmental factors and the presence of dogs seropositive for Leishmania chagasi in the City of Teresina, Brazil. METHODS: This case-control study was based on the results of a routine seroepidemiological survey among domestic dogs carried out in 2007. Serological tests were performed by means of indirect immunofluorescence antibody test. All dwellings in which at least one seropositive dog was detected were considered cases, and controls were a random sample of dwellings in which only seronegative dogs were identified. Associations between variables were expressed as odds ratios (OR) and their respective 95% confidence intervals (95%CI) estimated using multivariate logistic regression. RESULTS: Dwellings with a history of dogs removed by the visceral leishmaniasis control program in the last 12 months had five-fold higher odds of having at least one seropositive dog as compared with dwellings having no history of dog removal (OR = 5.19; 95%CI = 3.20-8.42). Dwellings with cats had 58% increased odds of dog infection as compared with those having no cats (OR = 1.58; 95%CI = 1.01-2.47). CONCLUSIONS: Identification of factors associated with canine visceral leishmaniasis might be used for the delimitation of areas of higher risk for human visceral leishmaniasis, since infection in dogs generally precedes the appearance of human cases.

Epidemiological and environmental aspects of visceral leishmaniasis in children under 15 years of age between 2007 and 2012 in the City of Araguaína, State of Tocantins, Brazil

Introduction Visceral leishmaniasis (VL) stands out as a zoonosis observed on four continents and also in urban expansion zones in several regions of Brazil. Methods A cross-sectional epidemiological study of VL cases in children under 15 years of age in the period from 2007 to 2012. Clinical data were gathered from medical reports; meteorological data were obtained at the Meteorological Measurement Department of UFT. Environmental variables were divided into two periods, rainy and dry. Results The study revealed no difference by gender (p=0.67) among the 821 patients. However, the most affected age group was between one and five years of age (58.6%; p<0.01); the highest prevalence of the disease (99.03%; p<0.01) occurred in urban zones; and the most affected ethnic group (85.5%; p<0.01) was mixed race. The highest incidence coefficients in this population occurred in 2007 and 2008 (578.39/100,000 inhabitants; 18.5/100,000 inhabitants, respectively), whereas the highest lethality coefficients occurred in 2008 and 2011 (0.85/100 deaths). There was no significant correlation between average rainfall and the number of VL cases. The correlation between temperature and number of VL cases was negative (r = -0.4039; p<0.01). Conclusions In Araguaína, visceral leishmaniasis in children under 15 years is an urban-based endemic disease distributed across all districts of the city wherein temperature as an environmental factor, a higher prevalence in mixed race children between one and five years of age, and a high incidence coefficient all strongly contribute to child mortality.

Factors conditioning the habitat and the density of Biomphalaria tenagophila (Orbigny, 1835) in an isolated schistosomiasis focus in Rio de Janeiro city

The present work was carried out in a watercress garden in Alto da Boa Vista, in the city of Rio de Janeiro, Brazil. The investigation was carried out in two phases. The first one (1985-86) involved the sampling of Biomphalaria tenegophila in two areas to determine its relative populational densities. The results showed that the populations presented similar densities and dynamics. The second phase (1988-89) involved the study of the influence of some environmental factors on the establishment of B. tenagophila in watercress garden. Two factors were identified as responsible for the establishment of B. tenagophila in the garden: (1) the quality of the water entering the irrigation system, to which domestic sewage is added, and (2) alterations in the nature of the substrate, due to inadequate fertilization techniques, which employ organic matter from adjacent pigsties. Aquatic plants and hydrological parameters of the irrigation system were subsidiary factors to the establishment of B. tenagophila in the garden.

The distribution of Biomphalaria spp. in different habitats in relation to physical, biological, water contact and cognitive factors in a rural area in Minas Gerais, Brazil

A total of 256 sites in 11 habitats were surveyed for Biomphalaria in Melquiades rural area (State of Minas Gerais) in August and November 1999 and in March 2000. Of the 1,780 Biomphalaria collected, 1,721 (96.7%) were B. glabrata and 59 (3.3%) B. straminea. Snails were found in all habitats except in wells, with the largest mean numbers in tanks, seepage ponds and canals, and the smallest numbers in springs, rice fields and fishponds. People's knowledge of the occurrence of Biomphalaria at the collection sites and the presence of Biomphalaria ova were strongly correlated with the occurrence of snails, and distance between houses and collection sites, as well as water velocity were inversely correlated with Biomphalaria occurrence (p < 0.001). The strongest predictor o f Biomphalaria occurrence was the presence of tilapia fish in fishponds. Fourteen Biomphalaria (0.8% of all snails) found at 6 sites were infected with Schistosoma mansoni. Suggestions are made for the utilization of local people's knowledge in snail surveys and further studies are recommended on the possible use of tilapia for biological control of Biomphalaria in fishponds, as well as modeling of S. mansoni transmission and reinfection.