The relative influence of polyparasitism, environment, and host factors on schistosome infection.
(17/92)
Where prevalence of geohelminths and schistosomes is high, co-infections with multiple parasite species are common. Previous studies have shown that the presence of geohelminths either promotes or is a marker for greater prevalence and intensity of Schistosoma mansoni infections. Some of this apparent synergy may simply represent shared conditions for exposure, such as poor sanitation, and may not suggest a direct biologic interaction. We explored this question in a study of 13,279 school children in Jequie, Bahia, Brazil, with a survey of demographic characteristics and stool examinations. Cross-sectional analysis revealed a statistically significant increase in the prevalence and intensity of S. mansoni infection with increasing numbers of geohelminth species (OR 2.5, 95% CI 1.38-3.64). Less than 20% of the strength of this association was contributed by socioeconomic status or environmental conditions. Thus, polyparasitism itself, as well as intrinsic host factors, appears to produce greater susceptibility to additional helminth infections. (+info)
The bandit, a new DNA transposon from a hookworm-possible horizontal genetic transfer between host and parasite.
(18/92)
BACKGROUND: An enhanced understanding of the hookworm genome and its resident mobile genetic elements should facilitate understanding of the genome evolution, genome organization, possibly host-parasite co-evolution and horizontal gene transfer, and from a practical perspective, development of transposon-based transgenesis for hookworms and other parasitic nematodes. METHODOLOGY/PRINCIPAL FINDINGS: A novel mariner-like element (MLE) was characterized from the genome of the dog hookworm, Ancylostoma caninum, and termed bandit. The consensus sequence of the bandit transposon was 1,285 base pairs (bp) in length. The new transposon was flanked by perfect terminal inverted repeats of 32 nucleotides in length with a common target site duplication TA, and it encoded an open reading frame (ORF) of 342 deduced amino acid residues. Phylogenetic comparisons confirmed that the ORF encoded a mariner-like transposase, which included conserved catalytic domains, and that the bandit transposon belonged to the cecropia subfamily of MLEs. The phylogenetic analysis also indicated that the Hsmar1 transposon from humans was the closest known relative of bandit, and that bandit and Hsmar1 constituted a clade discrete from the Tc1 subfamily of MLEs from the nematode Caenorhabditis elegans. Moreover, homology models based on the crystal structure of Mos1 from Drosophila mauritiana revealed closer identity in active site residues of the catalytic domain including Ser281, Lys289 and Asp293 between bandit and Hsmar1 than between Mos1 and either bandit or Hsmar1. The entire bandit ORF was amplified from genomic DNA and a fragment of the bandit ORF was amplified from RNA, indicating that this transposon is actively transcribed in hookworms. CONCLUSIONS/SIGNIFICANCE: A mariner-like transposon termed bandit has colonized the genome of the hookworm A. caninum. Although MLEs exhibit a broad host range, and are identified in other nematodes, the closest phylogenetic relative of bandit is the Hsmar1 element of humans. This surprising finding suggests that bandit was transferred horizontally between hookworm parasites and their mammalian hosts. (+info)
Wastewater-irrigated vegetables: market handling versus irrigation water quality.
(19/92)
OBJECTIVE AND METHODS: Vegetables irrigated with untreated domestic wastewater were, at the time of harvest, analysed for the presence of the faecal indicator, Escherichia coli, and helminth eggs in Faisalabad, Pakistan. Vegetables from the same harvested batch were collected approximately 12 h later from the local market. RESULTS: The survey found relatively low concentrations of E. coli (1.9 E. coli per gram), but relatively high concentrations of helminths (0.7 eggs per gram) on vegetables collected from agricultural fields. Higher concentration of both E. coli (14.3 E. coli per gram) and helminths (2.1 eggs per gram) were recovered from the vegetables collected from the market. CONCLUSIONS: The results of the survey suggest that unhygienic post harvest handling was the major source of produce contamination. Interventions at the market, such as the provision of clean water to wash produce in, are better ways to protect public health and more cost effective than wastewater treatment. (+info)
A 6 year Geohelminth infection profile of children at high altitude in Western Nepal.
(20/92)
Bayesian risk maps for Schistosoma mansoni and hookworm mono-infections in a setting where both parasites co-exist.
(21/92)
There is growing interest in the use of Bayesian geostatistical models for predicting the spatial distribution of parasitic infections, including hookworm, Schistosoma mansoni and co-infections with both parasites. The aim of this study was to predict the spatial distribution of mono-infections with either hookworm or S. mansoni in a setting where both parasites co-exist. School-based cross-sectional parasitological and questionnaire surveys were carried out in 57 rural schools in the Man region, western Cote d'Ivoire. A single stool specimen was obtained from each schoolchild attending grades 3-5. Stool specimens were processed by the Kato-Katz technique and an ether concentration method and examined for the presence of hookworm and S. mansoni eggs. The combined results from the two diagnostic approaches were considered for the infection status of each child. Demographic data (i.e. age and sex) were obtained from readily available school registries. Each child's socio-economic status was estimated, using the questionnaire data following a household-based asset approach. Environmental data were extracted from satellite imagery. The different data sources were incorporated into a geographical information system. Finally, a Bayesian spatial multinomial regression model was constructed and the spatial patterns of S. mansoni and hookworm mono-infections were investigated using Bayesian kriging. Our approach facilitated the production of smooth risk maps for hookworm and S. mansoni mono-infections that can be utilized for targeting control interventions. We argue that in settings where S. mansoni and hookworm co-exist and control efforts are under way, there is a need for both mono- and co-infection risk maps to enhance the cost-effectiveness of control programmes. (+info)
Hookworm-related anaemia among pregnant women: a systematic review.
(22/92)
The potential impact of density dependent fecundity on the use of the faecal egg count reduction test for detecting drug resistance in human hookworms.
(23/92)
Spatial distribution of soil-transmitted helminths, including Strongyloides stercoralis, among children in Zanzibar.
(24/92)
A programme periodically distributing anthelminthic drugs to school-aged children for the control of soiltransmitted helminthiasis was launched in Zanzibar in the early 1990s. We investigated the spatial distribution of soiltransmitted helminth infections, including Strongyloides stercoralis, in 336 children from six districts in Unguja, Zanzibar, in 2007. One stool sample per child was examined with the Kato-Katz, Koga agar plate and Baermann methods. The point prevalence of the different helminth infections was compared to the geological characteristics of the study sites. The observed prevalences for Trichuris trichiura, Ascaris lumbricoides, hookworm and S. stercoralis were 35.5%, 12.2%, 11.9% and 2.2%, respectively, with considerable spatial heterogeneity. Whilst T. trichiura and hookworm infections were found in all six districts, no A. lumbricoides infections were recorded in the urban setting and only a low prevalence (2.2%) was observed in the South district. S. stercoralis infections were found in four districts with the highest prevalence (4.0%) in the West district. The prevalence of infection with any soil-transmitted helminth was highest in the North A district (69.6%) and lowest in the urban setting (22.4%). A. lumbricoides, hookworm and, with the exception of the North B district, S. stercoralis infections were observed to be more prevalent in the settings north of Zanzibar Town, which are characterized by alluvial clayey soils, moist forest regions and a higher precipitation. After a decade of large-scale administration of anthelminthic drugs, the prevalence of soil-transmitted helminth infections across Unguja is still considerable. Hence, additional measures, such as improving access to adequate sanitation and clean water and continued health education, are warranted to successfully control soil-transmitted helminthiasis in Zanzibar. (+info)