Cercarial emergence of Schistosoma mansoni from Biomphalaria glabrata and Biomphalaria straminea

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Compatibility between Schistosoma mansoni and Biomphalaria straminea when exposed to the parasite on the first four months of age was assessed for five parasitological aspects: indices of infection and mortality, duration of precercarial and cercarial periods, and rate of cercarial emission. Infections were made on molluscs from laboratory colonies, at the following ages: 8, 13, 18, 21, 53, 83 and 114 days. Two B. straminea colonies were used (Camorim, PE and Picos, PI)

Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 97%

mentioning

confidence: 96%

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Infection by Schistosoma mansoni sambon 1907 in the first four months of life of Biomphalaria straminea (Dunker, 1848) in Brazil

Fernandez¹,

Pieri

2001

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“…However, infection indices up 10% were obtained by some investigators: Paraense (1967) obtained 3 positive snails of 28 specimens from Fordlândia, Pará (index of 10.7%); Souza et al (1983) found 11 out of 100 specimens from Jequitibá, Minas Gerais (11%); and Fernandez and Pieri (2001) found 217 positive snails among 1,691 specimens from Camorim, Pernambuco (12.8%). The lengthening of the precercarial period is also in accordance with that described by Favre et al (1995) and Fernandez and Pieri (2001) for this species.…”

supporting

confidence: 91%

Susceptibility of Biomphalaria straminea (Dunker, 1848) from Serra da Mesa Dam, Goiás, Brazil to infection with three strains of Schistosoma mansoni Sambon, 1907

Fernandez

Thiengo

2002

“…They were kept in glass containers with 4 l of non-chlorinated water and fresh lettuce. Screening for the identification of positive snails was carried out at weekly intervals, over a period of one month (Favre et al 1995). The containers were inspected twice a day to detect snails with signs of distress or imminent death.…”

Section: Methodmentioning

confidence: 99%

Longitudinal Study on the Natural Infection of Biomphalaria straminea and B. glabrata by Schistosoma mansoni in an Endemic Area of Schistosomiasis in Pernambuco, Brazil

Favre

Pieri

Zani

et al. 2002

In the Brazilian state of Pernambuco, schistosomiasis exhibits an epidemiological profile of chronic infection and persistent reinfection in the rainforest area (Zona da Mata). Heavy infections are also frequent in the coastal area (Barbosa et al. , 2001. Despite the amount of data amassed over the years and the advances in immunological and therapeutic clinical research, control of schistosomiasis transmission still represents a challenge for government institutions (Barbosa & Coimbra 2000). Although morbidity indices remain low, the prevalence of infection and the rate of reinfection have remained high in rural areas despite repeated treatment with oxamniquine , Favre 1999.Longitudinal studies of infected snails in critical areas, in parallel with application of control measures may shed light on why control measures fail. Nevertheless, few have been carried out (Dazo et al. 1976, Gundersen et al. 1990).In Pernambuco, there are two intermediate host species of Schistosoma mansoni: Biomphalaria straminea and B. glabrata. The first species is widespread over the Agreste, a zone of transitional vegetation, and the Zona da Mata, where it maintains high endemicity levels despite the low rates of natural and experimental infection (Paraense & Corrêa 1989). The second species, with infection rates reaching up to 20%, is mainly found in coastal areas, and remains responsible for several active foci of transmission .The present study aims to assess, on a monthly basis over a period of four years, the relative abundance and the natural infection of B. straminea and B. glabrata by S. mansoni in two representative localities in an endemic area in the state of Pernambuco, where infected persons were treated periodically with oxamniquine. In addition, tests were carried out to ascertain the susceptibility of snail species found in these localities to local parasite strains. MATERIALS AND METHODSTwo rural localities sharing similar sociodemographic characteristics and displaying medium levels of endemicity in relation to schistosomiasis (prevalence ranging from 30% to 40%), populated by distinct intermediate host species, were chosen after a preliminary stool survey and the application of a home questionnaire as described by Moza et al. (1998). Nine stool surveys by the Kato-Katz method (Katz et al. 1972) were undertaken every three months in both localities and individuals who tested positive for S. mansoni were treated with oxamniquine ), in March 1995, June 1995, March 1997 and March 1998 Characterization of the study area -Ecological features relevant to schistosomiasis transmission were recorded, including water-contact habits and rainfall. As recommended by Olivier (1973), sketch maps were used to display the location of houses, land use and water resources of each locality.Malacological survey -Snail breeding sites regarded as potential of transmission foci were identified in both localities. Snails were collected monthly from predetermined stations over the four years of the follow-up sur-+ Corresponding