Biological control of the snail hosts of Schistosoma mansoni in the Caribbean area using Thiara spp.

Background 
In 2012 the World Health Assembly adopted resolution WHA65.21 on elimination of schistosomiasis, calling for increased investment in schistosomiasis control and support for countries to initiate elimination programs. This study aims to analyze prevalence and intensity of Schistosoma mansoni infection in children in Latin America and the Caribbean countries and territories (LAC), at the second administrative level or lower.
Methodology 
A systematic review of schistosomiasis prevalence and intensity of infection was conducted by searching at PubMed, LILACS and EMBASE. Experts on the topic were informally consulted and institutional web pages were reviewed (PAHO/WHO, Ministries of Health). Only SCH infection among children was registered because it can be a ‘proxi-indicator’ of recent transmission by the time the study is conducted.
Principal Findings 
One hundred thirty two full-text articles met the inclusion criteria and provided 1,242 prevalence and 199 intensity of infection data points. Most of them were from Brazil (69.7%). Only Brazil published studies after 2001, showing several 'hot spots' with high prevalence. Brazil, Venezuela, Suriname and Saint Lucia need to update the epidemiological status of schistosomiasis to re-design their national programs and target the elimination of Schistosoma mansoni transmission by 2020. In Antigua and Barbuda, Dominican Republic, Guadeloupe, Martinique, Montserrat and Puerto Rico schistosomiasis transmission may be interrupted. However the compilation of an elimination dossier and follow-up surveys, per WHO recommendations, are needed to verify that status. Hence, the burden of subtle SCH chronic infection may be still present and even high in countries that may have eliminated transmission. Heterogeneity in the methodologies used for monitoring and evaluating the progress of the schistosomiasis programs was found, making cross-national and chronological comparisons difficult.
Conclusions 
There is a need for updating the schistosomiasis status in the historically endemic countries and territories in LAC to address the required public health interventions for control and elimination programs or to verify the elimination of transmission of Schistosoma mansoni. Improved reporting and standardization of the monitoring and evaluation methodologies used are recommended, while using available WHO guidelines. Meeting a regional elimination goal will require additional and improved epidemiological data by age group and sex.

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Schistosomiasis Prevalence and Intensity of Infection in Latin America and the Caribbean Countries, 1942-2014: A Systematic Review in the Context of a Regional Elimination Goal.

In Martinique, intestinal schistosomiasis was discovered at the beginning of this century. The intermediate host snail, Biomphalaria glabrata, was considered in the past as a common species in the different habitats of the island, but during the last decade it has been found only in water-cress beds. Several of these water-cress cultures contained mixed populations of B. glabrata and B. straminea. Moreover, these habitats also constituted transmission sites for Schistosoma mansoni infection. In 1979 the thiarid snail Thiara ( = Melanoides) tuberculata was discovered in Madame river, Fort-de-France, and in the following years at other sites. In 1983 a programme of biological control using this snail was started in two groups of water-cress beds. In 1981-1982 the study site, Roxelane valley, sheltered important populations of B. glabrata (45-256 individuals/m2) and of B. straminea (2-30 ind./m2). In January 1983 the competitor T. tuberculata was introduced into the two groups of water-cress beds (1.3 and 1.7 ind./m2 respectively) and during subsequent years snail population sampling was carried out. The results showed rapid colonization by the competitor snail, whose densities reached 178 and 325 ind./m2 in November 1983 and a maximum of 9941 and 13,388 ind./m2 in October 1984. During that time, B. glabrata populations declined: 153 and 41 ind./m2 in November 1983, 4 and 0 ind./m2 in October 1984, and 0 ind./m2 in the two groups of water-cress beds in October 1985. A similar phenomenon was observed for B. straminea. Since October 1985 neither planorbid species has been found by exhaustive sampling of the habitats.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological control of Biomphalaria glabrata and B. straminea by the competitor snail Thiara tuberculata in a transmission site of schistosomiasis in Martinique, French West Indies

Biological control of Biomphalaria glabrata, the intermediate host of schistosomes, by Marisa cornuarietis in ponds of Guadeloupe: long-term impact on the local snail fauna and aquatic flora

BARBOSA, F. S. & BARBOSA, C. S. The Bioecology of Snail Vectors for Schistosomiasis inBrazil. Cad. Saude Publ., Rio de Janeiro, 10 (2): 200-209, Apr/Jun, 1994.This paper describes the ecology of two species of Biomphalaria: B.glabrata and B. straminea.These species have been intensively studied in Brazil and in other countries since the 1950s. Theliterature in this area can be broadly subdivided into three categories, linked to three distinct historicalperiods: 1) an accumulated store of early studies carried out in the laboratory and in the field; 2) thedevelopment of quantitative ecological models; and 3) the development of an alternative methodologyfor breeding snails under seminatural conditions.Key words: Snail Ecology; Biomphalaria sp.; SchistosomiasisINTRODUCTIONInvestigations into the ecology of freshwatersnails have shown that the populationdynamics of these animals depend on thephysical geography of a given region. Landcontours, soil composition, hydrography, andclimate all have a significant effect on snailpopulation dynamics.Further factors that effect the distributionand abundance (biogeography) of snails, andthat will be addressed at a secondary level inthis paper, include: the biotic and non-bioticenvironment, behavior, reproduction,genetics, interactions within and betweenspecies, and human influences. Therelationship between the snail host and itsparasites will not be discussed.Although any physical, chemical, orbiological factor can have a significant effecton population dynamics, a few factors –especially those related to climate

The Bioecology of Snail Vectors for Schitosomiasis in Brazil Bioecologia dos Caramujos Vetores da Esquistossomose no Brasil

For the development of laboratory experiments on the competitive interacitons between freshwater snail populations, special snail rooms were set up in the main building of the Research Center "Aggeu Magalhaes". In the current paper, the first of a series on this subject, the general methodology of the laboratory work is described in detail. Using indoor cement channels in which a uniform seminatural environment was created, interactions of freshwater snail populations can be studied with minimal interference of the usual variables. Controlled indoor environmental techniques, as described in the current paper, may also be utilized in different types of experiments in malacology, and represent a substantial technical advance in malacological work.

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Competitive interactions between species of freshwater snails: I. Laboratory: Ia. General methodology

Nesta primeira serie de um conjunto de tres trabalhos, foram estudados, do ponto de vista epidemiologico, 23 perimetros de irrigacao do Departamento Nacional de Obras Contra as Secas (DNOCS), com vistas a determinacao da presenca de esquistossomose. Os resultados indicaram que, alem do perimetro de Sao Goncalo, PB (onde a esquistossomose ja era conhecida), casos autoctones da doenca foram encontrados no perimetro de Moxoto, PE.

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A esquistossomose e o Nordeste semi-árido: I - o estudo preliminar

Foi realizado estudo transversal sobre a esquistossomose mansonica em nove engenhos da usina Catende localizada na Zona da Mata sul do Estado de Pernambuco (Brasil). A prevalencia foi 43,8% para a populacao geral dos engenhos e 64,6% para os trabalhadores de campo. A prevalencia das formas hepato-esplenicas foi 4,1% sendo que em dois engenhos chegou a 8,7% e 9,1%. Biomphalaria straminea foi o unico molusco transmissor encontrado na area; sua taxa de infeccao natural por S. Mansoni foi 0,07%. A esquistossomose pode ser considerada como doenca grave na regiao estudada.

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Esquistossomosse em trabalhadores da Usina Catende, Pernambuco, Brasil

A prospective study of the effect of schistosomiasis on the productivity of canecutters was carried out in northeastern Brazil during the harvest season 1977-1978. This study revealed that field workers bearing the hepatosplenic form of the disease produce significantly less in terms of cane tons cut than their pairs (intestinal form, used as controls). Futhermore, the productivity is gradually reduced the period of the sugar-cane cut season. Two workers (cases) with the hepatosplenic form had to leave field work during the experiment due to visible deterioration of their general health.

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Dirceu P. Pereira da Costa

Papers

Competitive interactions between species of freshwater snails: I. Laboratory: Ia. General methodology

A esquistossomose e o Nordeste semi-árido: I - o estudo preliminar

Esquistossomosse em trabalhadores da Usina Catende, Pernambuco, Brasil

Efeito da esquistossomose na produtividade do cortador de cana ao longo da safra de açúcar da usina catende, Pernambuco