The contribution of water contact behavior to the high Schistosoma mansoni Infection rates observed in the Senegal River Basin

Contains fulltext : 97422.pdf (publisher's version ) (Open Access)BACKGROUND: Schistosomiasis is one of the major parasitic diseases in the world in terms of people infected and those at risk. Infection occurs through contact with water contaminated with larval forms of the parasite, which are released by freshwater snails and then penetrate the skin of people. Schistosomiasis infection and human water contact are thus essentially linked, and more knowledge about their relationship will help us to develop appropriate control measures. So far, only few studies have related water contact patterns to infection levels. METHODS: We have conducted detailed direct water contact observations in a village in Northern Senegal during the first years of a massive Schistosoma mansoni outbreak to determine the role of human water contact in the extent of the epidemic.We quantified water contact activities in terms of frequency and duration, and described how these vary with age and sex. Moreover, we assessed the relationship between water contact- and infection intensity patterns to further elucidate the contribution of exposure to the transmission of schistosomiasis. RESULTS: This resulted in over 120,000 recorded water contacts for 1651 subjects over 175 observation days. Bathing was the main activity, followed by household activities. Frequency and duration of water contact depended on age and sex rather than season. Water contacts peaked in adolescents, women spent almost twice as much time in the water as men, and water contacts were more intense in the afternoon than in the morning, with sex-specific intensity peaks. The average number of water contacts per person per day in this population was 0.42; the average time spent in the water per person per day was 4.3 minutes. CONCLUSIONS: The observed patterns of water contact behavior are not unusual and have been described before in various other settings in sub-Saharan Africa. Moreover, water contact levels were not exceptionally high and thus cannot explain the extremely high S. mansoni infection intensities as observed in Northern Senegal. Comparison with fecal egg counts in the respective age and sex groups further revealed that water contact levels did not unambiguously correspond with infection levels, indicating that factors other than exposure also play a role in determining intensity of infection

Use of expressed sequence tags as an alternative approach for the identification of Taenia solium metacestode excretion/secretion proteins

BACKGROUND: Taenia solium taeniasis/cysticercosis is a zoonotic helminth infection mainly found in rural regions of Africa, Asia and Latin America. In endemic areas, diagnosis of cysticercosis largely depends on serology, but these methods have their drawbacks and require improvement. This implies better knowledge of the proteins secreted and excreted by the parasite. In a previous study, we used a custom protein database containing protein sequences from related helminths to identify T. solium metacestode excretion/secretion proteins. An alternative or complementary approach would be to use expressed sequence tags combined with BLAST and protein mapping to supercontigs of Echinococcus granulosus, a closely related cestode. In this study, we evaluate this approach and compare the results to those obtained in the previous study. FINDINGS: We report 297 proteins organized in 106 protein groups based on homology. Additional classification was done using Gene Ontology information on biological process and molecular function. Of the 106 protein groups, 58 groups were newly identified, while 48 groups confirmed previous findings. Blast2GO analysis revealed that the majority of the proteins were involved in catalytic activities and binding. CONCLUSIONS: In this study, we used translated expressed sequence tags combined with BLAST and mapping strategies to both confirm and complement previous research. Our findings are comparable to recent studies on other helminth genera like Echinococcus, Schistosoma and Clonorchis, indicating similarities between helminth excretion/secretion proteomes

Ascariasis, Amebiasis and Giardiasis in Mexican children : distribution and geographical, environmental and socioeconomic risk factors

The aim of this study is to provide an overview of the geographical distribution of Ascariasis, Amebiasis and Giardiasis, and to identify specific geographical, socioeconomic and environmental factors that are associated with the incidence of these infections in Mexican children. We made use of publicly available data that was reported by federal organizations in Mexico for the year 2010. The contribution of geographical, socioeconomic and environmental factors to the incidence of infections was assessed by a multivariable regression model using a backwards selection procedure. A. lumbricoides incidence was associated with mean minimum temperature of the state, the state-wide rate of households without access to piped water and toilet, explaining 77% of the incidence of A. lumbricoides infections. Mean minimum precipitation in the state, the rate of households without access to a toilet, piped water and sewage system best explained (73%) the incidence of E. histolytica infections. G. lamblia infections were only explained by the latitude of the state (11%). In addition to the well-known socioeconomic factors contributing to the incidence of A. lumbricoides and E. histolytica we found that temperature and precipitation were associated with higher risk of infection

Strongyloidiasis - the most neglected of the neglected tropical diseases?

Soil-transmitted helminths of the genus Strongyloides (S. fuelleborni and the more prevalent S. stercoralis) are currently believed to infect an estimated 30-100 million people worldwide. The health consequences of S. stercoralis infections range from asymptomatic light infections to chronic symptomatic strongyloidiasis. Uncontrolled multiplication of the parasite (hyperinfection) and potentially life-threatening dissemination of larvae to all internal organs is found among individuals with compromised immune system functions. This paper provides an overview of the current state of the art in relation to diagnostic methods for detecting the infection, the morbidity caused by the infection and the recommended treatment. It further discusses some of the reasons why this infection is so neglected and the consequence of this for the estimated global prevalence. The paper finally points to the gaps in our knowledge and future research needs related to this infection. As Strongyloides infections have the potential to develop into severe disease in certain population subgroups, untreated infections could cause serious problems in the community. Therefore, we need to carefully investigate this parasite in order to develop and implement effective control programme

Development of a nanobody-based amperometric immunocapturing assay for sensitive and specific detection of Toxocara canis excretory-secretory antigen

Introduction Human Toxocariasis (HT) is a zoonosis that, despite of its wide distribution around the world, remains poorly diagnosed. The identification of specific IgG immunoglobulins against the Toxocara canis Excretory-Secretory antigen (TES), a mix of glycoproteins that the parasite releases during its migration to the target organs in infected patients, is currently the only laboratory tool to detect the disease. The main drawbacks of this test are the inability to distinguish past and active infections together with lack of specificity. These factors seriously hamper the diagnosis, follow-up and control of the disease. Aim To develop an amperometric immunocapturing diagnostic assay based on single domain immunoglobulins from camelids (nanobodies) for specific and sensitive detection of TES. Methods After immunization of an alpaca (Vicugna pacos) with TES, RNA from peripheral blood lymphocytes was used as template for cDNA amplification with oligo dT primers and library construction. Isolation and screening of TES-specific nanobodies were carried out by biopanning and the resulting nanobodies were expressed in Escherichia coli. Two-epitopes amperometric immunocapturing assay was designed using paramagnetic beads coated with streptavidin and bivalent nanobodies. Detection of the system was carried out with nanobodies chemically coupled to horseradish peroxidase. The reaction was measured by amperometry and the limit of detection (LOD) was compared to conventional sandwich ELISA. Results We obtained three nanobodies that specifically recognize TES with no-cross reactivity to antigens of Ascaris lumbricoides and A. suum. The LOD of the assay using PBST20 0.05% as diluent was 100 pg/ml, 10 times more sensitive than sandwich ELISA. Conclusion Sensitive and specific detection of TES for discrimination of active and past infections is one of the most difficult challenges of T. canis diagnosis. The main advantage of our system is the use of two different nanobodies that specifically recognize two different epitopes in TES with a highly sensitive and straightforward readout. Considering that the amounts of TES available for detection in clinical samples are in the range of picograms or a few nanograms maximum, the LOD found in our experiments suggests that the test is potentially useful for the detection of clinically relevant cases of HT

Geospatial and age-related patterns of Taenia solium taeniasis in the rural health zone of Kimpese, Democratic Republic of Congo

Background: Taenia solium infections are mostly endemic in less developed countries where poor hygiene conditions and free-range pig management favor their transmission. Knowledge on patterns of infections in both human and pig is crucial to design effective control strategies. The aim of this study was to assess the prevalence, risk factors and spatial distribution of taeniasis in a rural area of the Democratic Republic of Congo (DRC), in the prospect of upcoming control activities. Methods: A cross-sectional study was conducted in 24 villages of the health zone of Kimpese, Bas Congo Province. Individual and household characteristics, including geographical coordinates were recorded. Stool samples were collected from willing participants and analyzed using the copro-antigen enzyme linked immunosorbent assay (copro-Ag ELISA) for the detection of taeniasis. Blood samples were collected from pigs and analyzed using the B158/660 monoclonal antibody-based antigen ELISA (sero-Ag ELISA) to detect porcine cysticercosis. Logistic regression and multilevel analysis were applied to identify risk factors. Global clustering and spatial correlation of taeniasis and porcine cysticercosis were assessed using K functions. Local clusters of both infections were identified using the Kulldorff s scan statistic. Results: A total of 4751 participants above 5 years of age (median: 23 years; IQR: 11-41) were included. The overall proportion of taeniasis positivity was 23.4% (95% CI: 22.2-24.6), ranging from 1 to 60% between villages, with a significant between-household variance of 2.43 (SE = 0.29, p < 0.05). Taeniasis was significantly associated with age (p < 0.05) and the highest positivity was found in the 5-10 years age group (27.0% (95% CI: 24.4-29.7)). Overall, 45.6% (95% CI: 40.2-51) of sampled pigs were sero-positive. The K functions revealed a significant overall clustering of human and pig infections but no spatial dependence between them. Two significant clusters of taeniasis (p<0.001; n = 276 and n = 9) and one cluster of porcine cysticercosis (p<0.001; n = 24) were found. Conclusion: This study confirms high endemicity and geographical dispersal of taeniasis in the study area. The role of age in taeniasis patterns and significant spatial clusters of both taeniasis and porcine cysticercosis were evidenced, though no spatial correlation was found between human and pig infections. Urgent control activities are needed for this endemic area

Integration of schistosomiasis control activities within the primary health care system: a critical review.

Schistosomiasis is a chronic disease linked to poverty and is widely endemic, particularly in sub-Saharan Africa. For decades, the World Health Organization has called for a larger role of the primary health care system in schistosomiasis control, and its integration within the routine activities of primary health care facilities. Here, we reviewed existing studies on the integration of schistosomiasis control measures within the primary health care system, more precisely at the health centre, and we analysed their outcomes. An online search of studies published via PubMed and Embase databases was carried out until December 2017. Keywords were used to identify articles related to the integration of schistosomiasis control within the primary health care system, especially at the health centre level. Studies on integration of the following control measures were included: diagnosis and treatment, supplemented or not with (i) health education; (ii) snail control; and (iii) clean water supply and sanitation. A qualitative review was undertaken. To conclude on the effectiveness of an intervention, intermediate outcomes (knowledge, attitude and practice, coverage, access to health care) and distal outcomes (prevalence, incidence, mortality) were considered, and pre/post-intervention results were compared. Of 569 records found, 11 met the inclusion criteria. Studies were classified in three groups, according to the control measures they included. Integration of diagnosis and treatment, and health education in the first group resulted in an improvement of knowledge level of care providers, access to health care and health care seeking behaviour of the community. However, no positive effect was observed on the knowledge level of symptoms and modes of transmission at the community level. Most studies in the second group (with snail control as additional measure) and the third group (with clean water supply and sanitation as additional measure) showed a positive effect on schistosomiasis prevalence and incidence post-intervention, independent of the additional control measures implemented. The results of this review suggest a positive impact of integration of schistosomiasis control within the primary health care system. However, more robust studies are needed, especially in resource-limited regions, for conclusive evidence on the effectiveness and the sustainability of this strategy

Ultrasensitive detection of toxocara canis excretory-secretory antigens by a nanobody electrochemical magnetosensor assay.

peer reviewedHuman Toxocariasis (HT) is a zoonotic disease caused by the migration of the larval stage of the roundworm Toxocara canis in the human host. Despite of being the most cosmopolitan helminthiasis worldwide, its diagnosis is elusive. Currently, the detection of specific immunoglobulins IgG against the Toxocara Excretory-Secretory Antigens (TES), combined with clinical and epidemiological criteria is the only strategy to diagnose HT. Cross-reactivity with other parasites and the inability to distinguish between past and active infections are the main limitations of this approach. Here, we present a sensitive and specific novel strategy to detect and quantify TES, aiming to identify active cases of HT. High specificity is achieved by making use of nanobodies (Nbs), recombinant single variable domain antibodies obtained from camelids, that due to their small molecular size (15kDa) can recognize hidden epitopes not accessible to conventional antibodies. High sensitivity is attained by the design of an electrochemical magnetosensor with an amperometric readout with all components of the assay mixed in one single step. Through this strategy, 10-fold higher sensitivity than a conventional sandwich ELISA was achieved. The assay reached a limit of detection of 2 and15 pg/ml in PBST20 0.05% or serum, spiked with TES, respectively. These limits of detection are sufficient to detect clinically relevant toxocaral infections. Furthermore, our nanobodies showed no cross-reactivity with antigens from Ascaris lumbricoides or Ascaris suum. This is to our knowledge, the most sensitive method to detect and quantify TES so far, and has great potential to significantly improve diagnosis of HT. Moreover, the characteristics of our electrochemical assay are promising for the development of point of care diagnostic systems using nanobodies as a versatile and innovative alternative to antibodies. The next step will be the validation of the assay in clinical and epidemiological contexts