scholarly journals Risk of Human Exposure to the Intestinal Schistosome, Schistosoma mansoni, across Seasons along the Senegal River

2021 ◽  
Vol 7 (2) ◽  
pp. 1-9
Author(s):  
Rohr JR
Keyword(s):  
Schistosoma Mansoni ◽  
Rainy Season ◽  
Human Exposure ◽  
Infected Snail ◽  
Life Stage ◽  
Food Resource ◽  
Major Public Health Problem ◽  
Intermediate Hosts ◽  
Dry Seasons ◽  
The Impact

Background: Schistosomiasis is an emerging disease associated with changes to the environment that have increased human contact rates with disease-causing parasites, flatworms that are released from freshwater snails. For example, schistosomiasis remains a major public health problem in Northern Senegal, where prevalence in schoolchildren often reaches 90%. Aim: This study focuses on the impact of seasonality on the risk of human exposure (RHE) to Schistosoma mansoni, defined as the total number of cercariae (the free-living life stage that infects humans) shed from all Biomphalaria pfeifferi snails collected at a site using standardized methods. We focus on RHE because it is rarely quantified and a recent study demonstrated that snails stop shedding cercariae when snail densities increase and thus per capita snail resources become limited [2], suggesting that densities of snails might not be directly proportional to RHE to schistosomes. Method: We sampled four water access points in three villages every other week during the early (Dry1) and later dry seasons (Dry2) and the rainy season, quantifying the abundance of infected and non-infected snail intermediate hosts, cercariae released per infected snail, and water chemistry. We used simple and multiple linear regressions to assess how seasonality and environmental parameters affect non-infected and infected snail abundance and RHE. Results: Although RHE was found across all seasons, the abundance of infected and non-infected snail intermediate hosts and cercariae, as well as prevalence (23.71%), were all highest in the rainy season. In the rainy season, RHE was positively associated with the density of snail hosts and their periphyton food resource. Conclusion: Although previous studies have examined the influence of seasonality on snail densities, few studies have explored the effects of seasonality on cercarial densities, which is the primary source of infection to humans. Our study demonstrates that cercarial densities are greater in the rainy season than in the early or late dry seasons. Given that cercarial densities directly pose risk of infection to humans, unlike non-infected or infected snails, these finding should help to inform decision making and schistosomiasis control efforts in West Africa.

scholarly journals Five-Year Follow-Up on the Prevalence and Intensity of Infections of Schistosoma mansoni in a Hard-to-Reach District of Madagascar

2021 ◽  
Author(s):  
Stephen A. Spencer ◽  
Cortland Linder ◽  
James M. St. J. Penney ◽  
Hannah J. Russell ◽  
Kate Hyde ◽  
...  
Keyword(s):  
Public Health ◽  
Health Education ◽  
Schistosoma Mansoni ◽  
Infection Intensity ◽  
Public Health Problem ◽  
Infection Prevalence ◽  
Major Public Health Problem ◽  
Intermediate Hosts ◽  
Biomphalaria Pfeifferi ◽  
The Impact

Schistosomiasis is a major public health problem in Madagascar. The WHO recommends preventive chemotherapy by mass drug administration (MDA) with praziquantel as the primary approach to control Schistosoma mansoni–related morbidity in endemic populations, alongside complementary interventions such as health education. The impact of annual MDA and health education programs was assessed in the hard-to-reach Marolambo district of eastern Madagascar, an area endemic for S. mansoni. Repeated cross-sectional studies undertaken 2015–2019 examined between 300 and 381 school-aged children (aged 5–14 years) annually. The prevalence and infection intensity of S. mansoni were assessed by urine-circulating cathodic antigen (CCA) dipsticks and coproscopy using Kato–Katz (KK) methodologies. After four rounds of annual MDA, a reduction in S. mansoni prevalence was seen in CCA (93.9% in year 1–87.7% in year 5; P = 0.007) and KK (73.9% in year 1–59.4% in year 5; P < 0.0001). The prevalence of heavy-intensity infections roughly halved from 23.7% to 10.1% (P < 0.0001), and the mean intensity of infection fell by 55.0% (480.2–216.3 eggs per gram of feces). A malacological survey found Biomphalaria pfeifferi snail intermediate hosts in multiple water contact sites including rice paddies, streams, and Nosivolo River. Despite reductions in infection prevalence and intensity, schistosomiasis still poses a significant public health challenge in Marolambo district. Twice yearly MDA cycles and/or community-wide MDA are suggested to better reduce infections. Expanding health education; improving standards of water, sanitation, and hygiene; and attention on snail-related control will also be important, especially in rice paddy irrigated areas.

Daily emergence of Schistosoma mansoni and S. haematobium cercariae from naturally infected snails under field conditions

2002 ◽  
Vol 76 (3) ◽  
pp. 273-277 ◽  
Author(s):  
C.T. Wolmarans ◽  
K.N. de Kock ◽  
H.D. Strauss ◽  
M. Bornman
Keyword(s):  
Schistosoma Mansoni ◽  
Intermediate Host ◽  
Rainy Season ◽  
Dry Season ◽  
Field Conditions ◽  
Dry Seasons ◽  
Petri Dishes ◽  
Observation Period

AbstractThe daily emergence of Schistosoma mansoni and S. haematobium cercariae was investigated under field conditions. Intermediate host snails of both schistosome species were collected during the rainy season, cold dry season and warm dry season and kept separately in test tubes in habitat water. Shed cercariae were collected from each of the test tubes at two hourly intervals, transferred to Petri dishes and counted. Mice were exposed to these cercariae to establish the identity of the schistosome parasites. Peak shedding for both species was observed at 1100 h during the rainy and warm dry seasons and at 0900 h during the cold dry season. Shedding before 0900 h was found only for S. haematobium in the rainy season while shedding after 1700 h occurred only during this season at both species. Shedding observed during 1900 h observation period was in the low category for both species. No shedding was observed during the 2100 h observation period for any of the species and the investigation was discontinued after this period. Only S. haematobium ova were found in the exposed mice.

scholarly journals Predicting the Future Distribution of Ara rubrogenys, an Endemic Endangered Bird Species of the Andes, Taking into Account Trophic Interactions

Diversity ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 94
Author(s):  
Alain Hambuckers ◽  
Simon de Harenne ◽  
Eberth Rocha Ledezma ◽  
Lilian Zúñiga Zeballos ◽  
Louis François
Keyword(s):  
Food Resource ◽  
Bird Species ◽  
Co2 Concentration ◽  
Distribution Models ◽  
Plant Resources ◽  
Term Survival ◽  
The Andes ◽  
Vegetation Models ◽  
Fertilizing Effect ◽  
The Impact

Species distribution models (SDMs) are commonly used with climate only to predict animal distribution changes. This approach however neglects the evolution of other components of the niche, like food resource availability. SDMs are also commonly used with plants. This also suffers limitations, notably an inability to capture the fertilizing effect of the rising CO2 concentration strengthening resilience to water stress. Alternatively, process-based dynamic vegetation models (DVMs) respond to CO2 concentration. To test the impact of the plant modelling method to model plant resources of animals, we studied the distribution of a Bolivian macaw, assuming that, under future climate, DVMs produce more conservative results than SDMs. We modelled the bird with an SDM driven by climate. For the plant, we used SDMs or a DVM. Under future climates, the macaw SDM showed increased probabilities of presence over the area of distribution and connected range extensions. For plants, SDMs did not forecast overall response. By contrast, the DVM produced increases of productivity, occupancy and diversity, also towards higher altitudes. The results offered positive perspectives for the macaw, more optimistic with the DVM than with the SDMs, than initially assumed. Nevertheless, major common threats remain, challenging the short-term survival of the macaw.

scholarly journals Measuring capability wellbeing in adults at different stages of life for use in economic evaluation of health and care interventions: a qualitative investigation in people requiring kidney care

2021 ◽  
Author(s):  
Paul Mark Mitchell ◽  
Samantha Husbands ◽  
Sabina Sanghera ◽  
Fergus John Caskey ◽  
Jemima Scott ◽  
...  
Keyword(s):  
Life Stage ◽  
Structured Interview ◽  
Health Conditions ◽  
Economic Evaluations ◽  
Qualitative Investigation ◽  
Key Factors ◽  
Younger Adults ◽  
Patient Groups ◽  
The Life Course ◽  
The Impact

Abstract Purpose Capability wellbeing measures, such as the ICECAP measures, have been proposed for use in economic evaluations to capture broader outcomes of health and care interventions. The ICECAP measures have been developed to reflect capabilities at different stages of life. Some patient groups include patients of different ages and at different stages of life, so it is not always apparent which ICECAP measure is most relevant. This study explores the impact of age and life stage on completion, where both ICECAP-A and ICECAP-O were completed by the same patient. Methods A think-aloud study, and an associated semi-structured interview were conducted with people receiving kidney care as a renal outpatient, kidney transplant outpatient, or through receiving facility-based haemodialysis. Qualitative analysis focused on (1) differences in responses across measures by individuals, where attributes had conceptual overlap, (2) key factors in self-reported capability levels, and (3) measure preference. Results Thirty participants were included in the study, with a mix of older and younger adults. Attributes with similar wording across measures produced similar responses compared to attributes where wording differed. Age and health were key factors for self-reported capability levels. ICECAP-A was slightly preferred overall, including by older adults. Conclusion This study suggests use of ICECAP-A in patients with certain chronic health conditions that include a mix of adults across the life course. This study highlights the importance of considering the stage of life when using capability measures and in economic evaluations of health and care interventions more generally.

scholarly journals The Early Days of Personal Solar Ultraviolet Dosimetry

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 125 ◽  
Author(s):  
Brian Diffey
Keyword(s):  
Uv Radiation ◽  
Human Exposure ◽  
Ground Level ◽  
Uv Exposure ◽  
Population Exposure ◽  
Atmospheric Ozone ◽  
Quantitative Understanding ◽  
Solar Uv ◽  
The Impact ◽  
Solar Ultraviolet

In the early 1970s, environmental conservationists were becoming concerned that a reduction in the thickness of the atmospheric ozone layer would lead to increased levels of ultraviolet (UV) radiation at ground level, resulting in higher population exposure to UV and subsequent harm, especially a rise in skin cancer. At the time, no measurements had been reported on the normal levels of solar UV radiation which populations received in their usual environment, so this lack of data, coupled with increasing concerns about the impact to human health, led to the development of simple devices that monitored personal UV exposure. The first and most widely used UV dosimeter was the polymer film, polysulphone, and this review describes its properties and some of the pioneering studies using the dosimeter that led to a quantitative understanding of human exposure to sunlight in a variety of behavioral, occupational, and geographical settings.

scholarly journals Facilitation Effects of Haloxylon salicornicum Shrubs on Associated Understory Annuals, and a Modified “Stress-Gradient” Hypothesis for Droughty Times

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1726
Author(s):  
Nasr H. Gomaa ◽  
Ahmad K. Hegazy ◽  
Arafat Abdel Hamed Abdel Latef
Keyword(s):  
Species Richness ◽  
Water Availability ◽  
Stress Gradient ◽  
Growing Season ◽  
Annual Species ◽  
Negative Effects ◽  
Growing Seasons ◽  
Dry Seasons ◽  
The Impact ◽  
Haloxylon Salicornicum

Perennial shrub-annual plant interactions play key roles in desert regions influencing the structure and dynamics of plant communities there. In the present study, carried out in northwestern Saudi Arabia, we examined the effect of Haloxylon salicornicum shrubs on their associated understory annual species across four consecutive growing seasons, along with a record of the seasonal rainfall patterns. We measured density and species richness of all the annual species in permanent quadrats located beneath individual shrubs, as well as in the spaces between shrubs. During wet growing season H. salicornicum shrubs significantly enhanced the density and species richness of sub-canopy species, whereas in the relatively dry seasons they exerted negative effects on the associated species. In all growing seasons, the presence of shrubs was associated with enhanced soil properties, including increased organic carbon content, silt + clay, and levels of nutrients (N, P and K). Shrubs improved soil moisture content beneath their canopies in the wet growing season, while in the dry seasons they had negative effects on water availability. Differences in effects of H. salicornicum on understory plants between growing seasons seem due to the temporal changes in the impact of shrubs on water availability. Our results suggest the facilitative effects of shrubs on sub-canopy annuals in arid ecosystems may switch to negative effects with increasing drought stress. We discuss the study in light of recent refinements of the well-known “stress-gradient hypothesis”.

Susceptibilities of Various Snail Intermediate Hosts of Schistosoma mansoni to Different Strains of the Parasite

1965 ◽  
Vol 39 (4) ◽  
pp. 363-376 ◽  
Author(s):  
M.F.A. Saoud
Keyword(s):  
Puerto Rico ◽  
Schistosoma Mansoni ◽  
Intermediate Hosts ◽  
Considerable Evidence ◽  
The Past ◽  
Host Parasite Relationship ◽  
Parasite Relationship ◽  
Different Strains ◽  
Host Parasite ◽  
Comprehensive Studies

In the past two decades, considerable evidence has accumulated in the literature about the differences in the susceptibility of various intermediate hosts of Schistosoma mansoni to different strains of the parasite. Comprehensive studies on this aspect of host-parasite relationship have been published by Files & Cram (1949), Abdel-Malek (1950) and Files (1951). The results of more recent studies have been reported by Wright (1962) and Saoud (1964).In the present paper, the writer has studied the susceptibility of four intermediate hosts of S. mansoni from Brazil, Puerto Rico, Egypt and Tanganyika to some strains of the parasite.

scholarly journals Spatio-temporal dynamics of schistosomiasis in Rwanda between 2001 and 2012: impact of the national Neglected Tropical Disease control programme

2017 ◽  
Vol 12 (1) ◽  
Author(s):  
Elias Nyandwi ◽  
Tom Veldkamp ◽  
Frank Badu Osei ◽  
Sherif Amer
Keyword(s):  
Temporal Dynamics ◽  
Public Health Problem ◽  
Incidence Rates ◽  
Control Programme ◽  
Scan Statistics ◽  
Major Public Health Problem ◽  
Implementation Phase ◽  
Incidence Data ◽  
Spatio Temporal ◽  
The Impact

Schistosomiasis is recognised as a major public health problem in Rwanda. We aimed to identify the spatio-temporal dynamics of its distribution at a fine-scale spatial resolution and to explore the impact of control programme interventions. Incidence data of Schistosoma mansoni infection at 367 health facilities were obtained for the period 2001-2012. Disease cluster analyses were conducted using spatial scan statistics and geographic information systems. The impact of control interventions was assessed for three distinct sub-periods. Findings demonstrated persisting, emerging and re-emerging clusters of schistosomiasis infection across space and time. The control programme initially caused an abrupt increase in incidence rates during its implementation phase. However, this was followed by declining and disappearing clusters when the programme was fully in place. The findings presented should contribute to a better understanding of the dynamics of schistosomiasis distribution to be used when implementing future control activities, including prevention and elimination efforts.

scholarly journals Wolbachia-Mediated Antiviral Protection in Drosophila Larvae and Adults following Oral Infection

2015 ◽  
Vol 81 (23) ◽  
pp. 8215-8223 ◽  
Author(s):  
Aleksej L. Stevanovic ◽  
Pieter A. Arnold ◽  
Karyn N. Johnson
Keyword(s):  
Virus Infection ◽  
Oral Delivery ◽  
Life Stage ◽  
Potential Effect ◽  
Oral Exposure ◽  
Viral Dynamics ◽  
Content Type ◽  
Viral Spread ◽  
Infected Insect ◽  
The Impact

ABSTRACTUnderstanding viral dynamics in arthropods is of great importance when designing models to describe how viral spread can influence arthropod populations. The endosymbiotic bacteriumWolbachiaspp., which is present in up to 40% of all insect species, has the ability to alter viral dynamics in bothDrosophilaspp. and mosquitoes, a feature that in mosquitoes may be utilized to limit spread of important arboviruses. To understand the potential effect ofWolbachiaon viral dynamics in nature, it is important to consider the impact of natural routes of virus infection onWolbachiaantiviral effects. Using adultDrosophilastrains, we show here thatDrosophila-Wolbachiaassociations that have previously been shown to confer antiviral protection following systemic viral infection also confer protection against virus-induced mortality following oral exposure to Drosophila C virus in adults. Interestingly, a different pattern was observed when the same fly lines were challenged with the virus when still larvae. Analysis of the fourDrosophila-Wolbachiaassociations that were protective in adults indicated that only the w1118-wMelPop association conferred protection in larvae following oral delivery of the virus. Analysis ofWolbachiadensity using quantitative PCR (qPCR) showed that a highWolbachiadensity was congruent with antiviral protection in both adults and larvae. This study indicates thatWolbachia-mediated protection may vary between larval and adult stages of a givenWolbachia-host combination and that the variations in susceptibility by life stage correspond withWolbachiadensity. The differences in the outcome of virus infection are likely to influence viral dynamics inWolbachia-infected insect populations in nature and could also have important implications for the transmission of arboviruses in mosquito populations.

scholarly journals Structure of pond vegetation of a vereda in the Brazilian Cerrado

Rodriguésia ◽  
2011 ◽  
Vol 62 (4) ◽  
pp. 721-729 ◽  
Author(s):  
Suzana Neves Moreira ◽  
Arnildo Pott ◽  
Vali Joana Pott ◽  
Geraldo Alves Damasceno-Junior
Keyword(s):  
Water Depth ◽  
Rainy Season ◽  
Life Form ◽  
Mato Grosso ◽  
Relative Cover ◽  
Dry Seasons ◽  
The Relationship ◽  
Measured Water ◽  
Mato Grosso Do Sul ◽  
New Occurrences

Abstract This is the first report on aquatic macrophytes in ponds of veredas (palm swamps) in the Cerrado (Brazilian savanna). We studied a pond in a vereda in Terenos, Mato Grosso do Sul state, central-western Brazil, during drought and flood periods to assess plant community structure and the relationship between species distribution and water depth. Sampling was carried out in five permanent transects, along which we placed sampling units of 1 m2 quadrats every 5 m. We estimated visually the relative cover of each species, bare ground, dead matter, and exposed water. We also measured water depth. We recorded 77 species of 49 genera and 31 families. The number of species varied between seasons, and in the rainy season the amphibious life form was predominant. The richest families were Poaceae (15 species), Cyperaceae (11), Asteraceae (4) and Lentibulariaceae (4). The richest genera were Rhynchospora (4), Utricularia (4), Eleocharis (4), Aeschynomene (3), Bacopa (3), Ludwigia (3) and Panicum (3). We found six new occurrences for the cerrado. Eleocharis acutangula had the highest relative cover (rainy and dry seasons), followed by Bacopa reflexa (rainy season), Paspalum lenticulare (rainy and dry seasons), Leersia hexandra (rainy and dry seasons), and Sagittaria rhombifolia (rainy season). Some species were distributed mainly at shallower depths, others occurred in deeper water, whereas some species varied greatly in terms of depth. Heliotropium filiforme and Ludwigia nervosa were found only in the dry season. In the rainy season, as expected, the exclusive species were mostly true aquatics.

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