Transmission of Schistosoma mansoni from man to snail: laboratory studies on the influence of snail and miracidial densities on transmission success

Parasitology ◽  
1982 ◽  
Vol 85 (2) ◽  
pp. 361-372 ◽  
Author(s):  
N. P. Carter ◽  
R. M. Anderson ◽  
R. A. Wilson
Keyword(s):  
Schistosoma Mansoni ◽  
Biomphalaria Glabrata ◽  
Snail Host ◽  
Transmission Dynamics ◽  
Laboratory Studies ◽  
Infection Rates ◽  
Snail Infection ◽  
Transmission Success ◽  
Laboratory Infection ◽  
The Relationship

SUMMARYThe relationship between infection success, the density of Schistosoma mansoni miracidia and the density of the snail host Biomphalaria glabrata was examined experimentally. Within laboratory infection arenas, the distribution of miracidial infections/snail was approximately uniform and the net rate of snail infection was directly positive binomial to miracidial density. In contrast, however, the rate of infection declined exponentially as snail density increased. Mathematical models are developed to aid in the estimation of infection rates and experimental results are discussed in the context of the transmission dynamics of schistosomiasis.

Exposure of Caged Biomphalaria glabrata (Say) to Investigate Dispersion of Miracidia of Schistosoma mansoni Sambon in Outdoor Habitats in St. Lucia

1972 ◽  
Vol 46 (4) ◽  
pp. 297-306 ◽  
Author(s):  
Edward Suchart Upatham
Keyword(s):  
Schistosoma Mansoni ◽  
Field Experiments ◽  
Natural Habitat ◽  
Biomphalaria Glabrata ◽  
Field Conditions ◽  
Laboratory Studies ◽  
Infection Rates ◽  
Random Fashion ◽  
Simulated Field ◽  
Transmission Studies

1. Laboratory studies showed two types of cages to be suitable for exposing uninfected B. glabrata in field habitats as a means of locating S. mansoni miracidial infestations.2. Tests conducted in tanks under simulated field conditions showed that miracidia moved away from the point of inoculation in non-random fashion and congregated at the margins of the tanks.3. In a natural habitat, miracidia located and infected caged snails at distances of 33 cm vertically and 106·7 cm horizontally.4. The pattern of infection was similar in the simulated field and field experiments, but field infection rates were lower.5. For transmission studies in field habitats, caged laboratorybred snails should be placed at the margin of the habitat to ensure the maximum snail-miracidium interaction.

Energy constraint exerted by the parasite Schistosoma mansoni on the locomotion of its snail host, Biomphalaria glabrata

1996 ◽  
Vol 74 (4) ◽  
pp. 594-598 ◽  
Author(s):  
Claudia Gérard
Keyword(s):  
Resource Allocation ◽  
Schistosoma Mansoni ◽  
Biomphalaria Glabrata ◽  
Snail Host ◽  
Locomotory Activity ◽  
Patent Period ◽  
Energy Constraint

The consequences of the constraint caused by the parasite Schistosoma mansoni on the locomotory activity of its snail host, Biomphalaria glabrata, were studied during the patent period. Rates of locomotion were determined 6 times per 24-h period for juvenile and adult snails with single-miracidium infections, then compared with those of healthy snails of the same age. The locomotory activity of infected snails was the same during the day and at night, whereas control snails moved less at night than during the day. The locomotion of snails infected when immature was similar to that of the controls during the day and superior at night. The locomotion of snails infected when mature decreased regularly during patency and clearly decreased in comparison with that of healthy snails. The results are interpreted in terms of energy constraint on the mode of resource allocation of the host due to the parasite.

scholarly journals Behaviour of albino and melanic variants of Biomphalaria glabrata Say, 1818 (Mollusca: Planorbidae) following infection by Schistosoma mansoni Sambon, 1907

2009 ◽  
Vol 69 (1) ◽  
pp. 217-222 ◽  
Author(s):  
SM. Allegretti ◽  
JF. Carvalho ◽  
LA. Magalhães ◽  
EM. Zanotti-Magalhães
Keyword(s):  
Mortality Rate ◽  
Schistosoma Mansoni ◽  
Cross Sections ◽  
Biomphalaria Glabrata ◽  
Infection Rates ◽  
Susceptibility To Infection ◽  
Belo Horizonte

The behaviour of the albino and melanic variants of Biomphalaria glabrata of Belo Horizonte (MG. Brazil) was studied comparatively, in terms of their respective susceptibilities to infection by Schistosoma mansoni of the same origin, through observation of the elimination of cercariae for a three-month period and the calculation of mortality and infection rates, in control and in infected snails. The number of amoebocytes, granulocytes and hyalinocytes in the circulating hemolymph during different periods of infection was analyzed. The evolution of the infection in the tissues was observed by means of histological cross-sections. The melanic variant showed greater susceptibility to infection and a higher mortality rate. The albino variant showed a higher number of circulating amoebocytes, both granulocytes and hyalinocytes. A higher number of degenerated sporocysts were seen in the histological cross-sections of the albino variant. The results suggest that the melanic variant of B. glabrata was more susceptible to infection by S. mansoni than was the albino variant.

scholarly journals Experimental infection with Schistosoma mansoni of Biomphalaria straminea from different parts of the Northeast of Brazil

1986 ◽  
Vol 28 (3) ◽  
pp. 160-165 ◽  
Author(s):  
E. A. Malek ◽  
M. Z. Rouquayrol
Keyword(s):  
Schistosoma Mansoni ◽  
Puerto Rican ◽  
Experimental Infection ◽  
Snail Host ◽  
The State ◽  
Infection Rates ◽  
Biomphalaria Straminea ◽  
Albino Strain ◽  
Very High ◽  
Different Parts

In the western part of the State of Bahia Biomphalaria straminea and B. glabrata both occur, but in the majority of cases they do not share the same habitat. In the State of Ceará, however, B. straminea is the sole snail host of Schistosoma mansoni. In this survey, no naturally infected B. straminea was found among snails collected from Bahia and Ceará, evidently because of the very low infection rates. The susceptibility of laboratory-reared specimens to infection with a Puerto Rican strain of S. mansoni was then tested experimentally. In general, the snails showed very low susceptibility. The infection rates were 1.1% among snails from Redenção (Ceará); 2.3% in those from Pentecoste (Ceará); 2.9% in snails from São Desidério (Bahia), while they were very high among an albino strain (NIH) of B. glabrata used as control. Another group of B. straminea from São Desidério was exposed to a Bahian strain of S. mansoni and the infection rate was still very low (3.6%) Apparently, the very low susceptibility of B. straminea, despite high snail density, is correlated with moderate infection rates with S. mansoni among humans, as shown by the results of stool examinations conducted by SUCAM in the municipalities of Redenção and Pentecoste, in Ceará.

Observations on the field transmission dynamics of Schistosoma mansoni and S. mattheei in southern Natal, South Africa

Parasitology ◽  
1985 ◽  
Vol 91 (2) ◽  
pp. 281-290 ◽  
Author(s):  
Fiona A. Donnelly ◽  
C. C. Appleton
Keyword(s):  
South Africa ◽  
Schistosoma Mansoni ◽  
Transmission Dynamics ◽  
Small Rivers ◽  
Seasonal Patterns ◽  
Infection Rates ◽  
Intermediate Hosts ◽  
Low Oxygen ◽  
Transmission Season ◽  
Extensive Growth

Cercarial transmission of Schistosoma mansoni and S. mattheei was monitored in two small rivers near Durban, South Africa. The seasonal patterns recorded corresponded to those already documented for these parasites. Tn the case of S. mansoni, however, this was interrupted at the height of the transmission season. The reason for this was believed to be very low oxygen concentrations in the snail habitat due to unusually extensive growth of the plant Ludwigia stolonifera over the water. The failure of the spring rains, which would normally have flushed the system is seen as contributing to this phenomenon. Infection rates in the snail intermediate hosts were low ( > 10%). A preponderance of male worms of both schistosome species was noted.

scholarly journals Molluscicidal and parasiticidal activities of Eryngium triquetrum essential oil on Schistosoma mansoni and its intermediate snail host Biomphalaria glabrata, a double impact

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Ronaldo de Carvalho Augusto ◽  
Nadjiya Merad ◽  
Anne Rognon ◽  
Benjamin Gourbal ◽  
Cédric Bertrand ◽  
...  
Keyword(s):  
Essential Oil ◽  
Schistosoma Mansoni ◽  
Vector Control ◽  
Biological Effects ◽  
Biomphalaria Glabrata ◽  
Snail Host ◽  
Intermediate Hosts ◽  
Egg Hatching ◽  
Toxic Activity ◽  
Oil Extract

Abstract Background Freshwater snails are the intermediate hosts of a large variety of trematode flukes such as Schistosoma mansoni responsible for one of the most important parasitic diseases caused by helminths, affecting 67 million people worldwide. Recently, the WHO Global Vector Control Response 2017–2030 (GVCR) programme reinforced its message for safer molluscicides as part of required strategies to strengthen vector control worldwide. Here, we present the essential oil from Eryngium triquetrum as a powerful product with molluscicide and parasiticide effect against S. mansoni and the snail intermediate host Biomphalaria glabrata. Methods In the present study, we describe using several experimental approaches, the chemical composition of E. triquetrum essential oil extract and its biological effects against the snail B. glabrata and its parasite S. mansoni. Vector and the free-swimming larval stages of the parasite were exposed to different oil concentrations to determine the lethal concentration required to produce a mortality of 50% (LC50) and 90% (LC90). In addition, toxic activity of this essential oil was analyzed against embryos of B. glabrata snails by monitoring egg hatching and snail development. Also, short-time exposure to sublethal molluscicide concentrations on S. mansoni miracidia was performed to test a potential effect on parasite infectivity on snails. Mortality of miracidia and cercariae of S. mansoni is complete for 5, 1 and 0.5 ppm of oil extract after 1 and 4 h exposure. Results The major chemical component found in E. triquetrum oil determined by GC-FID and GC/MS analyses is an aliphatic polyacetylene molecule, the falcarinol with 86.9–93.1% of the total composition. The LC50 and LC90 values for uninfected snails were 0.61 and 1.02 ppm respectively for 24 h exposure. At 0.5 ppm, the essential oil was two times more toxic to parasitized snails with a mortality rate of 88.8 ± 4.8%. Moderate embryonic lethal effects were observed at the concentration of 1 ppm. Severe surface damage in miracidia was observed with a general loss of cilia that probably cause their immobility. Miracidia exposed 30 min to low concentration of plant extract (0.1 ppm) were less infective with 3.3% of prevalence compare to untreated with a prevalence of 44%. Conclusions Essential oil extracted from E. triquetrum and falcarinol must be considered as a promising product for the development of new interventions for schistosomiasis control and could proceed to be tested on Phase II according to the WHO requirements.

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