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1.
PLoS Negl Trop Dis ; 14(7): e0008417, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32628666

RESUMO

BACKGROUND: Schistosomiasis is responsible for the second highest burden of disease among neglected tropical diseases globally, with over 90 percent of cases occurring in African regions where drugs to treat the disease are only sporadically available. Additionally, human re-infection after treatment can be a problem where there are high numbers of infected snails in the environment. Recent experiments indicate that aquatic factors, including plants, nutrients, or predators, can influence snail abundance and parasite production within infected snails, both components of human risk. This study investigated how snail host abundance and release of cercariae (the free swimming stage infective to humans) varies at water access sites in an endemic region in Senegal, a setting where human schistosomiasis prevalence is among the highest globally. METHODS/PRINCIPAL FINDINGS: We collected snail intermediate hosts at 15 random points stratified by three habitat types at 36 water access sites, and counted cercarial production by each snail after transfer to the laboratory on the same day. We found that aquatic vegetation was positively associated with per-capita cercarial release by snails, probably because macrophytes harbor periphyton resources that snails feed upon, and well-fed snails tend to produce more parasites. In contrast, the abundance of aquatic macroinvertebrate snail predators was negatively associated with per-capita cercarial release by snails, probably because of several potential sublethal effects on snails or snail infection, despite a positive association between snail predators and total snail numbers at a site, possibly due to shared habitat usage or prey tracking by the predators. Thus, complex bottom-up and top-down ecological effects in this region plausibly influence the snail shedding rate and thus, total local density of schistosome cercariae. CONCLUSIONS/SIGNIFICANCE: Our study suggests that aquatic macrophytes and snail predators can influence per-capita cercarial production and total abundance of snails. Thus, snail control efforts might benefit by targeting specific snail habitats where parasite production is greatest. In conclusion, a better understanding of top-down and bottom-up ecological factors that regulate densities of cercarial release by snails, rather than solely snail densities or snail infection prevalence, might facilitate improved schistosomiasis control.


Assuntos
Plantas , Schistosoma/fisiologia , Esquistossomose/epidemiologia , Caramujos/parasitologia , Animais , Cercárias/fisiologia , Ecossistema , Humanos , Perifíton , Esquistossomose/transmissão , Senegal
2.
Infect Dis Poverty ; 9(1): 63, 2020 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-32505216

RESUMO

BACKGROUND: A steady progress on schistosomiasis control in the Peoples' Republic of China (P.R. China) was achieved and broadened into the twelve-year medium and long term national plan (MLNP) which marled the implementation of an integrated control strategy across all endemic areas in P.R. China in 2004. To understand the endemic trends of schistosomiasis to assess the effectiveness of an integrated strategy, we conducted an analysis of schistosomiasis surveillance data spanned from 2005 to 2015. METHODS: The schistosomiasis sentinel surveillance data from sentinel sites were collected and analyzed from 2005 to 2015. In these sentinel sites, residents aged 6 years or above were screened annually by indirect hemagglutination assay (IHA), while only antibody positives were followed by stool examination either Kato-katz method (KK) and/or hatching technique (HT). Domestic animals raised in sentinel sites were examined by HT for confirming the infection of schistosomes. Snail investigation was conducted each year through systematic sampling method combined with environmental sampling method. The snails collected from field were tested by microscopic dissection method. The infection rates of schistosomes in residents, domestic animals and snails, as well as the indicators reflecting the snails' distribution were calculated and analyzed. ANOVA analysis was used to examine the changes of the number of eggs per gram feces in population and Chi-square test was used to examine any change in proportions among groups. RESULTS: A total of 148 902 residents from sentinel sites attended this study and 631 676 blood samples were examined by IHA test during the 11 covered years. The annual average antibody positive rates presented a significant decrease trends, from 17.48% (95% CI: 17.20-17.75%) in 2005 to 5.93% (95% CI: 5.71-6.15%) (χ2 = 8890.47, P < 0.001) in 2015. During 2005-2015, the average infection rate of schistosomes in residents declined from 2.07% (95% CI: 1.96-2.17%) to 0.13% (95% CI: 0.09-0.16%), accompanied by significant decrease of infection intensity in population. In 2015, the stool positives were only found in farmers, fishermen and boatmen with infection rate of 0.16% (95% CI: 0.11-0.20%), 0.17% (95% CI: 0-0.50%) respectively. The infection rate of schistosomes in domestic animals dropped from 9.42% (538/5711, 95% CI: 8.66-10.18%) to 0.08% (2/2360, 95% CI: 0-0.20%) from 2005 to 2015. Infections were found in eight species of domestic animals at the beginning of surveillance while only two cattle were infected in 2015. Totally 98 ha of new snail habitats were found, while 94.90% (93/98) distributed in lake and marshland regions. The percentage of frames with snails decreased from 16.96% (56 884/33 5391, 95% CI: 16.83-17.09%) in 2005 to 4.28% (18 121/423 755, 95% CI: 4.22-4.34%) in 2014, with a slightly increase in 2015. Meanwhile, the infection rate of schistosomes in snails was decreased from 0.26% (663/256 531, 95% CI: 0.24-0.28%) to zero during 2005-2015. CONCLUSIONS: The infection rate of schistosomes declined significantly, providing evidence that the goal of the MLNP was achieved. Elimination of schistosomiasis as a public health problem defined as WHO was also reached in P.R. China nationwide. Surveillance-response system should be improved and strengthened to realize the final goal of schistosomiasis elimination.


Assuntos
Animais Domésticos , Esquistossomose , Vigilância de Evento Sentinela , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Criança , China/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Saúde Pública , Esquistossomose/epidemiologia , Esquistossomose/prevenção & controle , Esquistossomose/transmissão , Esquistossomose/veterinária , Caramujos/parasitologia , Adulto Jovem
3.
Parasitol Res ; 119(8): 2531-2537, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32562067

RESUMO

Human cercarial dermatitis is a parasitic disease that causes an allergic reaction in the skin (swimmer's itch) as a consequence of contact with cercariae of bird schistosomes present in water, mainly of the genus Trichobilharzia Skrjabin et Zakarow, 1920. The main objective of the study was to confirm the presence of the zoonotic disease agent following reports of human infections in recreational water in Slovakia. We identified two species of freshwater snails at Kosice Lake, Radix auricularia (Linnaeus, 1758) and Physa acuta (Draparnaud, 1805). Trematode infections were observed only in R. auricularia. Of the 62 snails collected, 11 (17.7%) were infected with 5 different species of larval stages of trematodes. The blood fluke Trichobilharzia franki was found in 2 (3.2%) of the examined snails. The present record provides the first evidence that T. franki from the pulmonate snail R. auricularia represents a source of human cercarial dermatitis in recreational water in Slovakia. Our finding complements the easternmost records of both swimmer's itch and the confirmed occurrence of a bird schistosome in a waterbody in Europe. The present work suggests that the health risks associated with trichobilharziasis need to be further studied by detailed monitoring of the occurrence of the major causative agent of human cercarial dermatitis, T. franki.


Assuntos
Dermatite/parasitologia , Lagos/parasitologia , Schistosomatidae/isolamento & purificação , Esquistossomose/transmissão , Dermatopatias Parasitárias/parasitologia , Infecções por Trematódeos/parasitologia , Zoonoses/parasitologia , Animais , Dermatite/epidemiologia , Surtos de Doenças , Humanos , Schistosomatidae/classificação , Schistosomatidae/genética , Esquistossomose/epidemiologia , Esquistossomose/parasitologia , Dermatopatias Parasitárias/transmissão , Eslováquia/epidemiologia , Caramujos/parasitologia , Infecções por Trematódeos/epidemiologia , Infecções por Trematódeos/transmissão , Zoonoses/epidemiologia , Zoonoses/transmissão
4.
Infect Dis Poverty ; 9(1): 31, 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32241298

RESUMO

BACKGROUND: Schistosomiasis is one of the neglected tropical diseases (NTDs) selected for worldwide elimination in the near future. Egypt has made strong progress against its two endemic species of Schistosoma mansoni and S. haematobium. The former is prevalent in the Nile Delta with the latter dominating in the Nile south of Cairo. Innovative efforts are needed to reach the goal as further reduction of the prevalence has stalled due to ongoing transmission. In this study we aimed to explore the difference between low and high prevalence villages with regard to knowledge attitude and practice about schistosomiasis, utilization of health services, infection and transmission indices. METHODS: A hybrid cross-sectional longitudinal study was conducted with three annual follow-ups conducted during 1994-1996. We used a representative systematic random sampling technique investigating 993 individuals from the high prevalence village and 614 from the low prevalence village. Data were analyzed using SPSS, comparing proportions with the Chi square test and means with the Student t test, and ANOVA. RESULTS: Compliance of faecal sampling and chemotherapy was above 70% in both villages over the whole study period. Selective praziquantel treatment resulted in a significant reduction of prevalence and intensity of infection in both villages, dropping from 35.8% prevalence to 20.6%, in the low-prevalence village, and from 69.5 to 45.9% in the high-prevalence one. Intensity of infection at the base line was 30 eggs per gram (EPG) of stool in the low-prevalence village versus 105 EPG in the high-prevalence village. However, after the second round, reinfection rebounded by 22% in the high-prevalence village, while a slight improvement of the infection indices was demonstrated in the low-prevalence one. The level of knowledge was modest in both villages: people knew about self-protection and treatment, but not much about the role of human excreta for schistosomiasis transmission. While all participants maintained that using the water from the canals was inevitable, inhabitants in the high-prevalence village showed significantly lower scores reflecting higher water contact compared to the low-prevalence one. Many of them (67%) did not utilize the health centre at all compared to 26% of the people in the low-prevalence village. Interestingly, private clinics were seen as the primary source of health care by both villages, but more frequently so in the high-prevalence village (used by 87.2% of the inhabitants) compared to the low-prevalence one (59.8%). CONCLUSIONS: Even if chemotherapy works well as reflected by the observed downregulation of intensity of infection in both villages, reinfection continued due to difficulties to avoid water contact. Efforts must be made to make people understand the role of human excreta for transmission. There is also a need to make people better trust the medical services available.


Assuntos
Conhecimentos, Atitudes e Prática em Saúde , Serviços de Saúde/estatística & dados numéricos , Schistosoma haematobium/isolamento & purificação , Schistosoma mansoni/isolamento & purificação , Esquistossomose/diagnóstico , Adolescente , Adulto , Animais , Anti-Helmínticos/uso terapêutico , Criança , Estudos Transversais , Egito/epidemiologia , Fezes , Feminino , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Praziquantel/uso terapêutico , Prevalência , Saúde da População Rural , Schistosoma haematobium/efeitos dos fármacos , Schistosoma mansoni/efeitos dos fármacos , Esquistossomose/tratamento farmacológico , Esquistossomose/epidemiologia , Esquistossomose/transmissão , Resultado do Tratamento
5.
Am J Trop Med Hyg ; 102(4): 827-831, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32043449

RESUMO

Saint Lucia at one time had levels of schistosomiasis prevalence and morbidity as high as many countries in Africa. However, as a result of control efforts and economic development, including more widespread access to sanitation and safe water, schistosomiasis on the island has practically disappeared. To evaluate the current status of schistosomiasis in Saint Lucia, we conducted a nationally representative school-based survey of 8-11-year-old children for prevalence of Schistosoma mansoni infections using circulating antigen and specific antibody detection methods. We also conducted a questionnaire about available water sources, sanitation, and contact with fresh water. The total population of 8-11-year-old children on Saint Lucia was 8,985; of these, 1,487 (16.5%) provided urine for antigen testing, 1,455 (16.2%) provided fingerstick blood for antibody testing, and 1,536 (17.1%) answered the questionnaire. Although a few children were initially low positives by antigen or antibody detection methods, none could be confirmed positive by follow-up testing. Most children reported access to clean water and sanitary facilities in or near their homes and 48% of the children reported contact with fresh water. Together, these data suggest that schistosomiasis transmission has been interrupted on Saint Lucia. Additional surveys of adults, snails, and a repeat survey among school-age children will be necessary to verify these findings. However, in the same way that research on Saint Lucia generated the data leading to use of mass drug administration for schistosomiasis control, the island may also provide the information needed for guidelines to verify interruption of schistosomiasis transmission.


Assuntos
Anticorpos Anti-Helmínticos/sangue , Esquistossomose/epidemiologia , Esquistossomose/transmissão , Criança , Feminino , Humanos , Masculino , Fatores de Risco , Santa Lúcia/epidemiologia , Saneamento , Esquistossomose/prevenção & controle , Testes Sorológicos , Inquéritos e Questionários
6.
Acta Trop ; 204: 105323, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31891706

RESUMO

Chronic infection with Schistosoma mekongi may result in severe hepatosplenic morbidity. We report on eight patients with severe morbidity due to S. mekongi infection. The patients were diagnosed, treated and followed-up between 2007 and 2010 in Khong district, Southern Lao People's Democratic Republic (Lao PDR), eight years after the end of a control intervention. S. mekongi control programmes aimed to prevent morbidity and mortality associated with infection. The patients were visited and interviewed annually. In addition, clinical and abdominal ultrasound examinations were performed and faecal and blood samples were examined. The patients' ages ranged from 6 to 66 years. Of the eight patients, three were children and five were adults. The four youngest patients (aged 6-27 years) significantly improved after praziquantel treatment. One patient (age 46 years) worsened between 2007 and 2010. Two patients died due to bleeding of the oesophageal varices. One patient was lost to follow-up. The leading clinical signs were ascites, splenomegaly, collateral veins on the abdomen and a poor general nutrition status. Ultrasonography disclosed advanced liver fibrosis patterns in all patients; in seven patients, fibrosis pattern E or F was revealed, as per the Niamey protocol (pattern A normal, pattern B to F pathological with increasing severity). Stool microscopy revealed that five patients were co-infected with hookworm and Opisthorchis viverrini. The youngest patient (aged 6 years) was born after the schistosomiasis control program had ended. From her severe morbidity, we can conclude that S. mekongi transmission was on-going in Khong district, and that even in areas with low S. mekongi transmission intensities, severe morbidity from schistosomiasis can develop quickly. Early diagnosis and treatment are imperative, and close monitoring is required.


Assuntos
Schistosoma/classificação , Esquistossomose/patologia , Esquistossomose/transmissão , Adolescente , Adulto , Idoso , Animais , Anti-Helmínticos/uso terapêutico , Criança , Fezes , Feminino , Humanos , Laos/epidemiologia , Masculino , Pessoa de Meia-Idade , Praziquantel/uso terapêutico , Prevalência , Esquistossomose/tratamento farmacológico , Esquistossomose/epidemiologia , Adulto Jovem
7.
Acta Trop ; 202: 105244, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31669533

RESUMO

Mekong schistosomiasis caused by Schistosoma mekongi is a public health problem that occurs along the border between southern Laos and northern Cambodia. Given its restricted distribution and low prevalence, eventual eradication via an effective control program can be expected to be successful. To achieve this goal detailed knowledge of its basic biology, molecular biology, biochemistry, and pathology is urgently required. In this regard, recent studies on transcriptome analysis of adult male and female S. mekongi worms, and proteome analysis of developmental stages have been reported and are discussed here. The biology, habitat, and distribution of the snail intermediate host Neotricula aperta, which are factors in disease transmission, are discussed in this review. These have initiated renewed interest in S. mekongi research and contributed promising data that will be utilized in the generation of effective control and prevention strategies.


Assuntos
Reservatórios de Doenças/parasitologia , Schistosoma/parasitologia , Esquistossomose , Caramujos/parasitologia , Animais , Camboja/epidemiologia , Ecossistema , Perfilação da Expressão Gênica , Humanos , Laos/epidemiologia , Estágios do Ciclo de Vida , Prevalência , Proteômica , Esquistossomose/diagnóstico , Esquistossomose/prevenção & controle , Esquistossomose/transmissão
8.
Elife ; 82019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31845890

RESUMO

Human disease agents exist within complex environments that have underappreciated effects on transmission, especially for parasites with multi-host life cycles. We examined the impact of multiple host and parasite species on transmission of the human parasite Schistosoma mansoni in Kenya. We show S. mansoni is impacted by cattle and wild vertebrates because of their role in supporting trematode parasites, the larvae of which have antagonistic interactions with S. mansoni in their shared Biomphalaria vector snails. We discovered the abundant cattle trematode, Calicophoron sukari, fails to develop in Biomphalaria pfeifferi unless S. mansoni larvae are present in the same snail. Further development of S. mansoni is subsequently prevented by C. sukari's presence. Modeling indicated that removal of C. sukari would increase S. mansoni-infected snails by two-fold. Predictable exploitation of aquatic habitats by humans and their cattle enable C. sukari to exploit S. mansoni, thereby limiting transmission of this human pathogen.


Assuntos
Biomphalaria/parasitologia , Interações Hospedeiro-Parasita , Parasitos/fisiologia , Esquistossomose/transmissão , Animais , Biodiversidade , Bovinos , Humanos , Quênia/epidemiologia , Modelos Biológicos , Schistosoma mansoni/fisiologia , Esquistossomose/epidemiologia , Trematódeos/fisiologia
9.
Pan Afr Med J ; 34: 19, 2019.
Artigo em Francês | MEDLINE | ID: mdl-31762888

RESUMO

Introduction: The purpose of this study was to determine the knowledge, attitudes and practices of the populations relating to schistosomal infestation. Methods: We conducted a cross-sectional descriptive and analytical study of knowledges, attitudes and practices of the population of the township of Légbassito relating to schistosomiasis. The sampling calculated on the basis of the population of the township by the software DosBox 0.74 of Epi Info 3.5.4 allowed to investigate 380 subjects. Results: The study highlighted that out of 380 people investigated, 57,30% were not aware of the symptoms of the disease, 40,10% did not know the mode of transmission of the disease, 26.40% knew that avoiding any contact with contaminated surface water could prevent the disease, 18,20% came into contact with fresh waters of the area in which 46,40% of them went to bathe. Regarding sewage disposal, 90,80% used latrines, 1.30% urinated sometimes in the streams, 85,80% used wells water for domestic needs, 48.40% didn't think they could live with an individual whose urine or stool contains blood, 24.5% were not often involved in mass treatment. Conclusion: The township of Légbassito is an endemic area for schistosomiasis infestation. Population attitudes and practices are unfavorable to the elimination of the disease, such as bathing during the hot hours, urinating in fresh waters and coming into contact with other water courses. These practices could lead to new cases of infestation.


Assuntos
Conhecimentos, Atitudes e Prática em Saúde , Esquistossomose/prevenção & controle , Adolescente , Adulto , Criança , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Esquistossomose/epidemiologia , Esquistossomose/transmissão , Togo/epidemiologia , Adulto Jovem
10.
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi ; 31(5): 538-540, 2019 Jul 25.
Artigo em Chinês | MEDLINE | ID: mdl-31713389

RESUMO

OBJECTIVE: To understand the potential risk of schistosomiasis transmission in Xiuzhou District of Jiaxing City, so as to provide the scientific evidence for consolidating schistosomiasis control achievements. METHODS: Fixed and mobile surveillance sites were set up in Xiuzhou District of Jiaxing City from 2013 to 2015. Oncomelania hupensis snails was surveyed historical snail habitats, current snail habitats, and suspected snail habitats. The schistosome infections were identified using serological and parasitological testing among local residents and mobile populations. In addition, the survival and reproduction of snails imported into Xiuzhou District was observed, and the schistosome infection in wild reservoir hosts was detected. RESULTS: A total of 540.14 hm2 of settings were surveyed in Xiuzhou District, Jiaxing City from 2013 to 2015, and 1.65 hm2 of snail habitats were identified. The snail habitats were mainly located in dry lands, and no infected snails or importation of snails were found. During the period from 2013 to 2015, a total of 7 668 local residents and mobile populations were examined in Xiuzhou District, and no new local infections were detected; however, three imported schistosomiasis cases were identified. Field simulation experiment showed that the imported snails laid eggs and reproduced in Xiuzhou District, and no schistosome infections were found in wild animals. CONCLUSIONS: There are still residual Oncomelania snails and imported schistosomiasis patients in Xiuzhou District of Jiaxing City; therefore, the surveillance and management of local Oncomelania snails and imported schistosomiasis should be intensified to reduce the risk of schistosomiasis transmission.


Assuntos
Esquistossomose , Caramujos , Animais , China , Ecossistema , Humanos , Vigilância da População , Fatores de Risco , Schistosoma , Esquistossomose/transmissão , Caramujos/parasitologia , Caramujos/fisiologia , Inquéritos e Questionários
11.
Parasit Vectors ; 12(1): 499, 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31647019

RESUMO

BACKGROUND: Schistosomiasis is a neglected tropical disease, targeted by the World Health Organization for reduction in morbidity by 2020. It is caused by parasitic flukes that spread through contamination of local water sources. Traditional control focuses on mass drug administration, which kills the majority of adult worms, targeted at school-aged children. However, these drugs do not confer long-term protection and there are concerns over the emergence of drug resistance. The development of a vaccine against schistosomiasis opens the potential for control methods that could generate long-lasting population-level immunity if they are cost-effective. METHODS: Using an individual-based transmission model, matched to epidemiological data, we compared the cost-effectiveness of a range of vaccination programmes against mass drug administration, across three transmission settings. Health benefit was measured by calculating the heavy-intensity infection years averted by each intervention, while vaccine costs were assessed against robust estimates for the costs of mass drug administration obtained from data. We also calculated a critical vaccination cost, a cost beyond which vaccination might not be economically favorable, by benchmarking the cost-effectiveness of potential vaccines against the cost-effectiveness of mass drug administration, and examined the effect of different vaccine protection durations. RESULTS: We found that sufficiently low-priced vaccines can be more cost-effective than traditional drugs in high prevalence settings, and can lead to a greater reduction in morbidity over shorter time-scales. MDA or vaccination programmes that target the whole community generate the most health benefits, but are generally less cost-effective than those targeting children, due to lower prevalence of schistosomiasis in adults. CONCLUSIONS: The ultimate cost-effectiveness of vaccination will be highly dependent on multiple vaccine characteristics, such as the efficacy, cost, safety and duration of protection, as well as the subset of population targeted for vaccination. However, our results indicate that if a vaccine could be developed with reasonable characteristics and for a sufficiently low cost, then vaccination programmes can be a highly cost-effective method of controlling schistosomiasis in high-transmission areas. The population-level immunity generated by vaccination will also inevitably improve the chances of interrupting transmission of the disease, which is the long-term epidemiological goal.


Assuntos
Administração Massiva de Medicamentos/economia , Doenças Negligenciadas/prevenção & controle , Esquistossomose/prevenção & controle , Vacinação/economia , Adolescente , Animais , Benchmarking , Criança , Pré-Escolar , Estudos de Coortes , Análise Custo-Benefício , Reservatórios de Doenças/parasitologia , Humanos , Lactente , Administração Massiva de Medicamentos/normas , Modelos Animais , Modelos Econômicos , Doenças Negligenciadas/tratamento farmacológico , Doenças Negligenciadas/economia , Esquistossomose/tratamento farmacológico , Esquistossomose/economia , Esquistossomose/transmissão , Processos Estocásticos , Fatores de Tempo , Vacinação/normas , Vacinas/administração & dosagem , Vacinas/economia
12.
Parasit Vectors ; 12(1): 498, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31640811

RESUMO

BACKGROUND: Sound knowledge of the abundance and distribution of intermediate host snails is key to understanding schistosomiasis transmission and to inform effective interventions in endemic areas. METHODS: A longitudinal field survey of freshwater snails of biomedical importance was undertaken in the Niger River Valley (NRV) between July 2011 and January 2016, targeting Bulinus spp. and Biomphalaria pfeifferi (intermediate hosts of Schistosoma spp.), and Radix natalensis (intermediate host of Fasciola spp.). Monthly snail collections were carried out in 92 sites, near 20 localities endemic for S. haematobium. All bulinids and Bi. pfeifferi were inspected for infection with Schistosoma spp., and R. natalensis for infection with Fasciola spp. RESULTS: Bulinus truncatus was the most abundant species found, followed by Bulinus forskalii, R. natalensis and Bi. pfeifferi. High abundance was associated with irrigation canals for all species with highest numbers of Bulinus spp. and R. natalensis. Seasonality in abundance was statistically significant in all species, with greater numbers associated with dry season months in the first half of the year. Both B. truncatus and R. natalensis showed a negative association with some wet season months, particularly August. Prevalences of Schistosoma spp. within snails across the entire study were as follows: Bi. pfeifferi: 3.45% (79/2290); B. truncatus: 0.8% (342/42,500); and B. forskalii: 0.2% (24/11,989). No R. natalensis (n = 2530) were infected. Seasonality of infection was evident for B. truncatus, with highest proportions shedding in the middle of the dry season and lowest in the rainy season, and month being a significant predictor of infection. Bulinus spp. and Bi. pfeifferi showed a significant correlation of snail abundance with the number of snails shedding. In B. truncatus, both prevalence of Schistosoma spp. infection, and abundance of shedding snails were significantly higher in pond habitats than in irrigation canals. CONCLUSIONS: Evidence of seasonality in both overall snail abundance and infection with Schistosoma spp. in B. truncatus, the main intermediate host in the region, has significant implications for monitoring and interrupting transmission of Schistosoma spp. in the NRV. Monthly longitudinal surveys, representing intensive sampling effort have provided the resolution needed to ascertain both temporal and spatial trends in this study. These data can inform planning of interventions and treatment within the region.


Assuntos
Caramujos/fisiologia , Caramujos/parasitologia , Irrigação Agrícola , Animais , Biomphalaria/parasitologia , Bulinus/parasitologia , Clima , Humanos , Gado , Estudos Longitudinais , Níger , Rios , Esquistossomose/transmissão , Estações do Ano
13.
PLoS Biol ; 17(10): e3000485, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31622335

RESUMO

Schistosomes are parasitic flatworms that infect over 200 million people, causing the neglected tropical disease, schistosomiasis. A single drug, praziquantel, is used to treat schistosome infection. Limitations in mass drug administration programs and the emergence of schistosomiasis in nontropical areas indicate the need for new strategies to prevent infection. It has been known for several decades that rotifers colonizing the schistosome's snail intermediate host produce a water-soluble factor that paralyzes cercariae, the life cycle stage infecting humans. In spite of its potential for preventing infection, the nature of this factor has remained obscure. Here, we report the purification and chemical characterization of Schistosome Paralysis Factor (SPF), a novel tetracyclic alkaloid produced by the rotifer Rotaria rotatoria. We show that this compound paralyzes schistosome cercariae and prevents infection and does so more effectively than analogous compounds. This molecule provides new directions for understanding cercariae motility and new strategies for preventing schistosome infection.


Assuntos
Alcaloides/farmacologia , Anti-Helmínticos/farmacologia , Cercárias/efeitos dos fármacos , Rotíferos/química , Schistosoma mansoni/efeitos dos fármacos , Esquistossomose/prevenção & controle , Alcaloides/química , Alcaloides/isolamento & purificação , Animais , Anti-Helmínticos/química , Anti-Helmínticos/isolamento & purificação , Cercárias/patogenicidade , Cercárias/fisiologia , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Feminino , Fígado/efeitos dos fármacos , Fígado/parasitologia , Masculino , Camundongos , Movimento/efeitos dos fármacos , Movimento/fisiologia , Rotíferos/isolamento & purificação , Rotíferos/metabolismo , Schistosoma mansoni/crescimento & desenvolvimento , Schistosoma mansoni/patogenicidade , Esquistossomose/parasitologia , Esquistossomose/transmissão , Pele/efeitos dos fármacos , Pele/parasitologia , Caramujos/parasitologia , Solubilidade , Relação Estrutura-Atividade
14.
Proc Natl Acad Sci U S A ; 116(46): 23182-23191, 2019 11 12.
Artigo em Inglês | MEDLINE | ID: mdl-31659025

RESUMO

Recently, the World Health Organization recognized that efforts to interrupt schistosomiasis transmission through mass drug administration have been ineffective in some regions; one of their new recommended strategies for global schistosomiasis control emphasizes targeting the freshwater snails that transmit schistosome parasites. We sought to identify robust indicators that would enable precision targeting of these snails. At the site of the world's largest recorded schistosomiasis epidemic-the Lower Senegal River Basin in Senegal-intensive sampling revealed positive relationships between intermediate host snails (abundance, density, and prevalence) and human urogenital schistosomiasis reinfection (prevalence and intensity in schoolchildren after drug administration). However, we also found that snail distributions were so patchy in space and time that obtaining useful data required effort that exceeds what is feasible in standard monitoring and control campaigns. Instead, we identified several environmental proxies that were more effective than snail variables for predicting human infection: the area covered by suitable snail habitat (i.e., floating, nonemergent vegetation), the percent cover by suitable snail habitat, and size of the water contact area. Unlike snail surveys, which require hundreds of person-hours per site to conduct, habitat coverage and site area can be quickly estimated with drone or satellite imagery. This, in turn, makes possible large-scale, high-resolution estimation of human urogenital schistosomiasis risk to support targeting of both mass drug administration and snail control efforts.


Assuntos
Bulinus , Vetores de Doenças , Ecossistema , Esquistossomose/transmissão , Animais , Humanos , Densidade Demográfica , Imagens de Satélites , Esquistossomose/epidemiologia , Senegal/epidemiologia , Análise Espacial
15.
Parasit Vectors ; 12(1): 503, 2019 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-31665080

RESUMO

BACKGROUND: National deworming programmes rely almost exclusively on mass drug administration (MDA) to children to control morbidity caused by these parasitic infections. The provision of other interventions, consisting of preventive chemotherapy at high population level coverage together with water, sanitation and hygiene (WaSH) and changes in risk behaviour, should enable sustainable control of soil-transmitted helminths (STH) and schistosomiasis and ultimately interrupt transmission. METHODS/DESIGN: Two interventions will be implemented by the project: (i) community-wide biannual albendazole and annual praziquantel treatment with a target of 80-90% treatment coverage ("expanded MDA"); and (ii) provision of WaSH with behaviour change communication (BCC), within the Wolaita zone, Ethiopia. The project has three study arms: (i) expanded community-wide MDA, WaSH and BCC; (ii) expanded community-wide MDA only; and (iii) annual school-based MDA (the current National STH/schistosomiasis Control Programme). The impact of these interventions will be evaluated through prevalence mapping at baseline and endline (after four rounds of MDA), combined with annual longitudinal parasitological surveillance in defined cohorts of people to monitor trends in prevalence and reinfection throughout the project. Treatment coverage and individual compliance to treatment will be monitored by employing fingerprint biometric technology and barcoded identification cards at treatment. WaSH utilisation will be evaluated through school and household level observations and annual WaSH assessment survey. Complementary qualitative surveys will explore practices, cultural and social drivers of risk behaviours, uptake of WaSH and treatment, and assessing the impact of the BCC. DISCUSSION: The study has the potential to define an 'End Game' for STH and schistosomiasis programmes through provision of multiple interventions. Interrupting transmission of these infections would eliminate the need for long-term repeated MDA, lead to sustained health improvements in children and adults, thereby allowing health systems to focus on other disease control priorities.


Assuntos
Albendazol/administração & dosagem , Anti-Helmínticos/administração & dosagem , Helmintíase/prevenção & controle , Praziquantel/administração & dosagem , Esquistossomose/prevenção & controle , Adolescente , Criança , Pré-Escolar , Análise Custo-Benefício , Estudos Transversais , Demografia , Etiópia/epidemiologia , Comportamentos Relacionados com a Saúde , Helmintíase/epidemiologia , Helmintíase/transmissão , Humanos , Higiene/normas , Lactente , Estudos Longitudinais , Administração Massiva de Medicamentos/economia , Modelos Biológicos , Doenças Negligenciadas/prevenção & controle , Prevalência , Saneamento/normas , Esquistossomose/epidemiologia , Esquistossomose/transmissão , Instituições Acadêmicas , Solo/parasitologia , Inquéritos e Questionários , Abastecimento de Água/normas
16.
PLoS Negl Trop Dis ; 13(10): e0007740, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31603908

RESUMO

Schistosomiasis is a serious worldwide parasitic disease. One of the best ways to control schistosomiasis is to control the population of Oncomelania hupensis snails. We sought to identify a high-efficiency biogenic molluscicide against Oncomelania with low toxicity, to avoid chemical molluscicide contamination and toxicity in aquatic organisms. We extracted quaternary benzo[c]phenanthridine alkaloids (QBAs) from Macleaya cordata fruits. Molluscicidal activity of the QBAs against Oncomelania was determined using bioassay. Our results showed that the extracted QBAs had a strong molluscicidal effect. In treatment of O. hupensis with QBAs for 48 h and 72 h, the lethal concentration (LC50) was 2.89 mg/L and 1.29 mg/L, respectively. The molluscicidal activity of QBAs was close to that of niclosamide (ethanolamine salt), indicating that QBAs have potential development value as novel biogenic molluscicides. We also analyzed physiological toxicity mechanisms by examining the activity of several important detoxification enzymes. We measured the effect of the extracted QBAs on the activities of glutathione S-transferase (GST), carboxylesterase (CarE), acid phosphatase (ACP), and alkaline phosphatase (AKP) in the liver of O. hupensis. We found that the effects of QBAs on detoxification metabolism in O. hupensis were time and concentration dependent. The activities of GST, CarE, AKP, and ACP in the liver of snails increased significantly in the early stage of treatment (24 h), but decreased sharply in later stages (120 h), compared with these activities in controls. GST, CarE, AKP, and ACP activity in the liver of snails treated with LC50 QBAs for 120 h decreased by 62.3%, 78.1%, 59.2%, and 68.6%, respectively. Our results indicate that these enzymes were seriously inhibited by the extracted QBAs and the detoxification and metabolic functions of the liver gradually weakened, leading to poisoning, which could be the main cause of death in O. hupensis snails.


Assuntos
Alcaloides/toxicidade , Frutas/química , Gastrópodes/efeitos dos fármacos , Moluscocidas/toxicidade , Papaveraceae/química , Fenantridinas/toxicidade , Extratos Vegetais/toxicidade , Fosfatase Ácida/efeitos dos fármacos , Fosfatase Ácida/metabolismo , Fosfatase Alcalina/efeitos dos fármacos , Fosfatase Alcalina/metabolismo , Animais , Carboxilesterase/efeitos dos fármacos , Carboxilesterase/metabolismo , China , Glutationa Transferase/efeitos dos fármacos , Glutationa Transferase/metabolismo , Inativação Metabólica/efeitos dos fármacos , Fígado/metabolismo , Esquistossomose/prevenção & controle , Esquistossomose/transmissão
17.
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi ; 31(4): 374-381, 2019 Sep 25.
Artigo em Chinês | MEDLINE | ID: mdl-31612671

RESUMO

OBJECTIVE: To investigate the spatial distribution of Oncomelania hupensis snail habitats at the administrative village scale in schistosomiasis-endemic areas of Hubei Province, so as to provide scientific bases for precise control of O. hupensis snails in the province. METHODS: Data regarding snail distribution at the village level in Hubei Province in 2017 were collected to create a spatial analysis database of snail distribution in Hubei Province. The spatial aggregations of O. hupensis distribution were analyzed using Moran's I index and Local Moran's I index. In addition, the distances from schistosomiasis-endemic villages to the Yangtze River were captured using the software ArcGIS 13.0, and their correlations with area of snail habitats were examined with the Spearman correlation method. RESULTS: O. hupensis snails were mainly distributed in 5 450 endemic villages from 63 counties of 13 cities in Hubei Province in 2017. The global spatial autocorrelation analysis showed spatial aggregations in the areas of historically accumulated snail habitats, current areas of snail habitats, areas of snail habitats outside the embankment and snail habitats inside the embankment (all Z Scores > 0, all P values < 0.05), and no spatial aggregation was seen in the areas of snail habitats in hilly areas (Z Score > 0, P > 0.05). There were four types of spatial distribution of historically accumulated areas of snail habitats, areas of current snail habitats, areas of snail habitats outside the embankment and snail habitats inside the embankment, including the high-high type (H-H type), high-low type (H-L type), low-high type (L-H type) and random distribution type, and a high percentage of the H-H type was found. There were 340, 125 and 110 endemic villages with the H-H type of areas of historically accumulated snail habitats, current areas of snail habitats and areas of snail habitats outside the embankment, and these villages were mainly concentrated in Wuhan and Jingzhou cities, with almost consistent spatial aggregation locations. There were 319 endemic villages with the H-H type of distribution of snail habitats inside the embankment, which were mainly distributed in Jingzhou, Xiaogan and Huangshi cities. In addition, the areas of historically accumulated snail habitats, current areas of snail habitats and areas of snail habitats outside the embankment negatively correlated with the distance from the endemic villages to the Yangtze River (r = -0.094, P < 0.01; r = -0.225, P < 0.01; r = -0.177, P < 0.01). CONCLUSIONS: The clustering areas of snail habitats along the Yangtze River Basin, notably the villages near the Yangtze River are key regions for snail monitoring and control in Hubei Province.


Assuntos
Distribuição Animal , Rios , Esquistossomose , Caramujos , Animais , China/epidemiologia , Ecossistema , Humanos , Rios/parasitologia , Schistosoma/fisiologia , Esquistossomose/epidemiologia , Esquistossomose/prevenção & controle , Esquistossomose/transmissão , Caramujos/parasitologia , Caramujos/fisiologia , Análise Espacial
18.
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi ; 31(3): 251-257, 2019 Aug 13.
Artigo em Chinês | MEDLINE | ID: mdl-31544402

RESUMO

OBJECTIVE: To build a schistosomiasis transmission risk surveillance system in Sichuan Province, so as to provide technical support for facilitating the progress towards schistosomiasis elimination in the province. METHODS: The surveillance sites for schistosomiasis transmission risk were assigned in 63 endemic counties (districts) of 11 cities (prefectures) in Sichuan Province. During the period from 2015 through 2018, wild feces contamination, the sources of Schistosoma japonicum infections (fever patients, livestock and wild animals), water infectivity in key settings, snail distribution in key settings, and snail breeding risk (snail importation and spread, floating debris carrying snails and snail breeding in ecological wetlands) were monitored in the surveillance sites. RESULTS: From 2015 to 2018, a total of 1 636 wild faces were detected in Sichuan Province, and 3 faces were positive for S. japonicum, with a 0.18% positive rate; among 3 995 livestock and 59 wild mice monitored, no S. japonicum infection was detected. A total of 49 414 fever patients were monitored in 2018, and 493 were seropositive for S. japonicum infection; then, 445 seropositives were subjected to stool examinations, and no egg-positives were found. From 2010 to 2018, a total of 93 sentinel sites were assigned, and 3 994 sentinel mice were placed for monitoring the water infectivity, with one S. japonicum-infected mouse detected. Between 2015 and 2018, a total of 4 156 key settings were investigated covering an area of 1 998.46 hm2, and 668 settings were detected with snails (16.07%), covering an area of 193.26 hm2; 497 suspected settings with a likelihood of snail importation with plant introduction were monitored from 2017 to 2018, and 65 settings with snails were found with 2 673 snails captured; 593 sites were assigned to collect the floating debris from 2017 to 2018, and 9 191.39 kg floating debris were collected with 186 snails captured; 4 wetlands were monitored for the risk of schistosomiasis transmission from 2013 to 2015, and snail breeding was found in 2 wetlands. No S. japonicum infection was identified in snails captured from all surveillance sites. CONCLUSIONS: A sensitive and effective schistosomiasis transmission risk surveillance system has been successfully established in Sichuan Province. There is still a risk of schistosomiasis transmission risk in local areas of Sichuan Province. Therefore, the integrated schistosomiasis control measures with emphasis on the control of the source of S. japonicum infections should be further intensified, and snail monitoring and control and monitoring and control of schistosomiasis in wetlands should be also intensified.


Assuntos
Vigilância da População , Esquistossomose Japônica , Esquistossomose , Animais , Cruzamento , China/epidemiologia , Cidades , Fezes/parasitologia , Humanos , Gado , Camundongos , Vigilância da População/métodos , Prevalência , Esquistossomose/epidemiologia , Esquistossomose/prevenção & controle , Esquistossomose/transmissão
19.
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi ; 31(3): 258-263, 2019 Aug 12.
Artigo em Chinês | MEDLINE | ID: mdl-31544403

RESUMO

OBJECTIVE: To understand the current distribution of Oncomelania snails in Sichuan Province, so as to provide scientific evidence for formulating the schistosomiasis elimination strategy and implementing the precision schistosomiasis control measures in the province. METHODS: According to the National Scheme on Oncomelania hupensis Snails in China and the Scheme on Oncomelania hupensis Snails in Sichuan Province, snail surveys were performed in current snail habitats, historical snail habitats and suspected snail habitats using systematic sampling in Sichuan Province from 2016 to 2017, and the survey results were analyzed. RESULTS: From 2016 to 2017, a total of 88 346 settings were surveyed in schistosomiasis-endemic areas of Sichuan Province, and 19 314 settings were detected with snails, covering an area of 4 829.25 hm2, with no Schistosoma japonicum infection identified in snails. A total of 3 017 915 frames were investigated in Sichuan Province, and 1 041 417 frames were found to have living snails, with totally 1 791 115 living snails captured. The mean density of living snails was 0.59 snails/0.1 m2, and the mean percentage of frames with living snails was 34.51% in Sichuan Province. The current snail habitats were mainly distributed in 1 704 villages, 377 townships, 54 counties (districts) of 9 cities (prefectures) across the schistosomiasis-endemic areas of Sichuan Province. Snail habitats were mainly found in ditches (70.22%), and weeds were the predominant vegetation in snail habitats (66.45%). Snails were firstly discovered in Sichuan Province in 1913, and S. japonicum-infected snails were firstly identified in 1956, with the latest identification of S. japonicum-infected snails in 2008. CONCLUSIONS: There are many settings suitable for snail breeding in Sichuan Province, and snail monitoring and control should be intensified in the future.


Assuntos
Distribuição Animal , Erradicação de Doenças , Doenças Endêmicas , Esquistossomose , Caramujos , Animais , China , Cidades , Doenças Endêmicas/prevenção & controle , Densidade Demográfica , Esquistossomose/prevenção & controle , Esquistossomose/transmissão , Esquistossomose Japônica , Caramujos/parasitologia , Caramujos/fisiologia
20.
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi ; 31(3): 269-274, 2019 Aug 28.
Artigo em Chinês | MEDLINE | ID: mdl-31544405

RESUMO

OBJECTIVE: To explore the spatial-temporal clustering distribution of schistosomiasis transmission risk in Yunnan Province from 2004 to 2015, so as to provide scientific evidence for the future schistosomiasis control and consolidation of the control achievements. METHODS: All data pertaining to endemic situation of human and bovine schistosomiasis and snail survey at a township level in Yunnan Province from 2004 to 2015 were collected. A descriptive epidemiological method and Joinpoint model were used to describe the changing trends of Schistosoma japonicum infections in humans, bovine and snails, and the hotspots and clusters of schistosomiasis transmission risk were identified using spatial autocorrelation analysis, hotspots analysis and retrospective space-time scan statistic in Yunnan Province from 2004 to 2015. RESULTS: The prevalence of S. japonicum infections appeared a continuous decline in humans, bovine and snails in Yunnan Province from 2004 to 2015, and the estimated number of schistosomiasis cases reduced from 43 056 in 2004 to 756 in 2015, with a decline rate of 98.24%. There were no acute cases since 2008 and no infected snails since 2014 in Yunnan Province. There were significant differences in the changing trends of human and bovine S. japonicum infections in Yunnan Province between 2012 and 2015 and between 2013 and 2015, respectively using the Joinpoint model (P < 0.05). In addition, there was a spatial autocorrelation in human S. japonicum infections in Yunnan Province from 2004 to 2013 (P < 0.01), and the hotspots areas for human S. japonicum infections were mainly distributed in some townships from Dali City, Weishan County and Eryuan County. Retrospective spatial-temporal scanning revealed that S. japonicum human, bovine and snail infections were clustered in 23, 15, 4 townships from Dali City, Weishan County, Eryuan County, Nanjian County and Heqing County, respectively, with relative risks of 6.25 to 28.75 (P < 0.01), which was almost consistent with the cluster areas detected by hotspots analysis. CONCLUSIONS: The endemic situation of schistosomiasis significantly reduced in Yunnan Province from 2004 to 2015; however, there is still a risk of schistosomiasis transmission. The monitoring and control of schistosomiasis should be intensified in the future in Yunnan Province.


Assuntos
Esquistossomose Japônica , Esquistossomose , Animais , Bovinos , China , Humanos , Estudos Retrospectivos , Fatores de Risco , Esquistossomose/epidemiologia , Esquistossomose/prevenção & controle , Esquistossomose/transmissão , Caramujos , Análise Espaço-Temporal
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