Life Span and Monthly Mortality Rate of Bulinus truncatus and Planorbis boissyi, the Intermediate Hosts of Schistosomiasis in Egypt

Barlow, Claude H.; Muench, H.

doi:10.2307/3273448

Cited by 11 publications

(8 citation statements)

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“…Analysis of laboratory data, however, is an important first step in examining species-specific trends in mortality patterns. The studies of Barlow & Muench (1951), for example, clearly portray age-dependence in the survival of Bulinus Muench, 1951). Open circles: observed proportions surviving to age t (P(t)); solid circles and solid line: predictions of exponential decay survival model where P(t) = exp (-fit), ft = 0-514/month.…”

Section: Snail Mortality Uninfected Snailsmentioning

confidence: 95%

Prevalence of schistosome infections within molluscan populations: observed patterns and theoretical predictions

1979

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SUMMARYThe paper draws together a large and scattered body of empirical evidence concerning the prevalence of snail infection with schistosome parasites in field situations, the duration of the latent period of infection in snails (and its dependence on temperature), and the mortality rates of infected and uninfected snails in field and laboratory conditions. A review and synthesis of quantitative data on the population biology of schistosome infections within the molluscan host is attempted and observed patterns of infection are compared with predictions of a schistosomiasis model developed by May (1977) which incorporates differential snail mortality (between infected and uninfected snails) and latent periods of infection. It is suggested that the low levels of prevalence within snail populations in endemic areas of schistosomiasis are closely associated with high rates of infected snail mortality and the duration of the latent period of infection within the mollusc. In certain instances, the expected life-span of an infected snail may be less than the duration of the latent period of infection. Such patterns generate very low levels of parasite prevalence. A new age prevalence model for schistosome infections within snail populations is developed and its predictions compared with observed patterns.The implications of this study of observed and predicted patterns of snail infection within molluscan populations are discussed in relation to the overall transmission dynamics of schistosomiasis.

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Section: Snail Mortality Uninfected Snailsmentioning

confidence: 95%

Prevalence of schistosome infections within molluscan populations: observed patterns and theoretical predictions

1979

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“…Many infected snails lived for a year but only a few survived longer than a year. It seems that this increase in mortality was not due to infection but was Parasitology 20 a natural process, for observations on the life span of Bulinus truncatulus made by Barlow & Muench (1951) in Egypt show that the mortality rises sharply when the snails reach the age of 8 months, and none survives over 14 months.…”

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confidence: 99%

The life cycle of Paramphistomum microbothrium Fischoeder, 1901 (Trematoda, Paramphistomidae)

Dinnik

1954

Parasitology

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The whole life cycle of Paramphistomum microbothrium Fischoeder, 1901, found in cattle of Kenya, East Africa, has been established experimentally.In laboratory conditions, the eggs hatched miracidia on the 14th to 16th day, if they were kept in water at a temperature of 26–28° C.In a snail, Bulinus alluaudi (Dautzenberg), kept at the temperature of 18–20° C., the miracidium developed into a sporocyst, the elongated body of which, containing young rediae, reached a length of 3·6 mm. in about 2 weeks.The first rediae which emerged from a sporocyst were observed on the 14th day, and on the 20th day the first generation rediae began to produce second-generation rediae. From the 28th day onward the first-generation parent rediae ceased to produce daughter rediae and began to develop cercariae only. This period of production of cercariae by the redia lasted about 30 days, and when the life of the first-generation rediae drew to its close, the old rediae developed a few daughter rediae again.Cercariae began to emerge from the first-generation rediae 30 days after exposure of the snail to miracidia. The cercariae left the parent redia in a very immature state and further development occurred in the liver of the snail. The emergence of cercariae from the infected snail began on the 43rd day after exposure to miracidia. Shortly after emerging from the snail, the cercariae attached themselves to vegetation and encysted.Development of rediae of the second, third, fourth and apparently more successive generations followed an identical course to that outlined for the rediae of the first generation. As a result the successive generations of rediae maintain the infection going in an intermediate host and the infected snails were continually shedding cercariae as long as they lived. In the laboratory experiments the life span of some of the infected snails exceeded a year.In cattle infected experimentally P. microbothrium reached maturity and began passing out the eggs about a 100 days after the encysted cercariae were fed to the animals.

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“…Such disparities among population survival rates have been observed in previous studies investigating resistance of Bulinus sp. at low and high temperatures [34][35][36]. More recently, 100% survival rates have been reported in B. truncatus snails from Cameroon maintained at temperatures of 16°C and 24°C for periods up to 25 weeks [37].…”

Section: Discussionmentioning

confidence: 99%

Spatial variation of life-history traits in the freshwater snail Bulinus truncatus, the intermediate host of human and cattle schistosomiasis, in relation to field application of niclosamide in northern and central Côte d’Ivoire

Konan¹,

Tian-Bi²,

Diakité³

et al. 2021

Preprint

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Background: Control of intermediate host snails using molluscicides for the control and/or elimination of schistosomiasis is strategy in the line with WHO recommendations. Niclosamide is the main chemical molluscicide recognized by WHO. However, the extent of the application of molluscicide outside the immediate killing of the snail such as the impact on the evolution of life-history traits; in relation to recolonization of treated sites is less or not known. This study aimed to characterize the spatial variation of life-history traits in Bulinus truncatus populations in north and central Côte d’Ivoire, in relation to niclosamide spraying in the field.From 2016 to 2018, we conducted a trial to control the intermediate host snails for interrupting seasonal transmission urinary schistosomiasis in northern and central Côte d’Ivoire, using niclosamide. The molluscicide was sprayed three times per year in habitats harboring the freshwater snail B. truncatus. Snails were collected before niclosamide application and 2-3 months after the sites were treated, and also from some untreated sites. Families from six natural populations of snails were monitored for several life-history traits, including growth, fecundity and survival, under laboratory conditions, over one generation (G1).Results: Survival rate varied among populations with the highest rates observed in northern populations. No significant difference was detected between populations before and after treatment, for this trait. Numbers of eggs and eggs per capsule at first reproduction, fecundity and growth were significantly lower in treated than untreated groups. Similar finding was observed for populations of before and after treatment. Egg production also varied across populations with the highest values found in northern populations. Within treated group, a significant difference for survival rate was detected between northern and central populations. Almost all parameters of reproduction and growth varied significantly, except for the number of egg capsules.Conclusions: Our study shows a spatial variation of life-history traits in B. truncatus snails. Lower values of these traits were observed in populations from recolonized sites after treatment with niclosamide. This trend was much more perceptible in populations from central Côte d’Ivoire. Investigations should be carried out over several generations of snails in order to clarify the impact of niclosamide on their life-history traits.

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Life Span and Monthly Mortality Rate of Bulinus truncatus and Planorbis boissyi, the Intermediate Hosts of Schistosomiasis in Egypt

Cited by 11 publications

References 0 publications

Prevalence of schistosome infections within molluscan populations: observed patterns and theoretical predictions

Prevalence of schistosome infections within molluscan populations: observed patterns and theoretical predictions

The life cycle of Paramphistomum microbothrium Fischoeder, 1901 (Trematoda, Paramphistomidae)

Spatial variation of life-history traits in the freshwater snail Bulinus truncatus, the intermediate host of human and cattle schistosomiasis, in relation to field application of niclosamide in northern and central Côte d’Ivoire

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