Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Biomphalaria”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,675 records · Page 93Linked to original sources
PubMed1966

Trials with N-tritylmorpholine (Shell WL 8008) as a molluscicide in Southern Rhodesia.

In the course of research into the effectiveness of new molluscicides for bilharziasis control, a recently developed compound, Shell WL 8008 (N-tritylmorpholine), has been tested in Southern Rhodesia, both in the laboratory and in the field. It is highly toxic to Bulinus (Physopsis) globosus, Biomphalaria pfeifferi and Lymnaea natalensis, all of which succumbed to the compound at a concentration of 1.0 ppm in a contact time of only 15 minutes. In experiments in reservoirs and natural watercourses, a concentrated aqueous suspension was sprayed on or just under the water surface, forming a white "blanket" that sank at a rate depending on temperature, amount of vegetation, and so on. The period of contact with snails is sufficiently long for the molluscicide to kill them as it sinks; this characteristic is of great importance in the economic treatment of large stagnant water bodies or slow-moving streams. The compound is highly piscicidal, but has little effect on a wide range of microfauna.

Molluscacides↗
PubMed1967

Field trials to evaluate the effectiveness of the molluscicide N-tritylmorpholine in irrigation systems.

In field trials with the molluscicide N-tritylmorpholine (Frescon, WL 8008), a prolonged low-dosage technique has been developed for use in irrigation systems. In Tanzania a dose of 0.025 ppm applied for 30 days to the headworks of a 5000-acre (2025-ha) irrigation system gave effective control of Biomphalaria pfeifferi, the snail host of Schistosoma mansoni, for a period of 3-4 months. This was comparable to the effectiveness of other molluscicides and other dosage regimes but the technique had the advantages of simplicity, lower cost and lack of toxicity towards fish or other aquatic fauna. Similar trials have been carried out in Egypt and Southern Rhodesia. Theoretical and practical considerations involved in the choice of dosage regimes are discussed and a general formula is suggested for choosing dosage regimes in irrigation systems.

Molluscacides↗
PubMed1967

Mathematical simulation of an aquatic snail population.

Techniques for controlling the intermediate snail hosts of schistosomiasis have had to be evaluated by field trials, since the complexity of snail population dynamics has so far made it impossible to predict the effects of these techniques and thereby avoid costly field testing.However, in laboratory studies with Biomphalaria glabrata it was found that the fecundity of these snails was directly proportional to F/NV, where F is the total amount of food in the habitat, N the number of snails, and V the volume of the habitat. The use of this fecundity variable together with data published on snail longevity and fecundity made it possible to construct a mathematical model of a snail population which may eventually be useful for evaluating snail control methods.For preliminary verification of the model, its predictions were compared with a published history of a population of Bulinus globosus in a small pond. The general agreement of the predicted and observed population data indicated that the basic structure of the model was sound.

Animals↗
PubMed1970

Control of schistosomiasis in Guayama and Arroyo, Puerto Rico.

In 1953, a programme to control schistosomiasis mansoni was started in Guayama and Arroyo, Puerto Rico, employing, first, chemical and, later, both biological and chemical methods to control Biomphalaria glabrata, the snail host of Schistosoma mansoni. Sodium pentachlorophenate was the molluscicide, and an ampullarid snail, Marisa cornuarietis, was used for biological control in ponds and reservoirs. In addition some chemotherapy was given to infected persons. The prevalence of intestinal schistosomiasis was measured annually, sampling about one-third of the 6-year-old population in Guayama and Arroyo and in Caguas, an untreated area. Costs of the programme and the results are discussed in relation to similar projects in other parts of Puerto Rico. In Guayama and Arroyo the prevalence of schistosomiasis reached zero in 6-year-olds by 1966 despite the persistence of the disease in a nearby untreated area. Although this decline appeared related to the control effort, it is noted that a large decline also occurred in the untreated area, suggesting the influence of other factors such as economic development or improvements in sanitation.

Child↗
PubMed1970

Cercarial transmission seasons of Schistosoma mansoni in the Nile Delta area.

The cercarial transmission seasons of Schistosoma mansoni in the Nile Delta area were determined by 3 methods: (1) monthly cercarial infection rates in Biomphalaria alexandrina, (2) monthly numbers of infected snails collected by means of a uniform sampling method, and (3) monthly cercarial output and monthly numbers of infected snails collected by means of a uniform sampling method. It was found that the third method is more logical and defines more precisely the transmission seasons of S. mansoni in the area. The paper also includes a discussion on the important factors that influence the timing of mollusciciding operations for the control of schistosomiasis in the Nile Delta area.

Animals↗
PubMed1970

Attempts to eradicate snails from impounded water by the use of N-tritylmorpholine.

This paper records attempts to overcome the problems of using a powerful but non-ovicidal molluscicide (N-tritylmorpholine) in eradicating snails from a dam by treating the water twice in 14 days. The first treatment was aimed at the existing snail population and the second at snails hatched from eggs that survived the first application. At each treatment an over-all concentration of 0.25 ppm was applied by spraying a 16% emulsifiable concentrate of N-tritylmorpholine from shore and boat to the water surface. The snails, Biomphalaria pfeifferi and Lymnaea natalensis, were first seen again 8 weeks from the start of the application in the region of 2 inlet furrows. When pretreatment levels of snails were again reached, a second double treatment was applied, again at an over-all concentration of 0.25 ppm but using a 50% paste formulation applied over 3 days for 3 hours per day to the inlet furrows. The snail kill was again 100% as measured by the sampling technique used but again young snails appeared 9 weeks later. The author concludes that single treatments at 5-week intervals probably represent the best means of control with N-tritylmorpholine.

Animals↗
PubMed1970

The development of snail control methods on an irrigated sugar-cane estate in northern Tanzania.

In an attempt to prevent the transmission of Schistosoma mansoni on an irrigated sugar-cane estate, molluscicide experiments were carried out to find the optimum methods for controlling the intermediate-host snails, Biomphalaria pfeifferi. The ease of application of N-tritylmorpholine led to its adoption as the molluscicide of choice for the two separate irrigation systems on the estate. Experiments on the frequency and duration of molluscicide treatments were carried out, and from these it was concluded that 5-day applications of N-tritylmorpholine at 0.025 ppm every 7 weeks might lead to a break in transmission by control of the snails.In another set of trials, drainage ditches were treated alternately with N-tritylmorpholine and niclosamide ethanolamine salt, and although the chemicals differed only slightly in their effect, the latter-being ovicidal-was chosen to be applied at approximately 4 ppm by knapsack sprayer every 8 weeks. Extra treatment of small pools with the same compound was carried out during the long rains when irrigation was unnecessary and most of the canals were dry.It is pointed out that the effect of the control methods on S. mansoni transmission will need to be evaluated by studying the incidence of the disease in the population.

Agriculture↗
PubMed1977

Failure of irradiated Echinostoma audyi and Hypoderaeum dingeri to sensitize Lymnaea rubiginosa snails.

Attempts to induce acquired resistance in Lymnaea rubiginosa snails against the echinostomes Echinostoma audyi and Hypoderaeum dingeri by means of irradiated miracidia were unsuccessful, although Lie and coworkers using similar methods had recently sensitized Biomphalaria glabrata against Echinostoma lindoense (1975a). In contrast to the B. glabrata-E. lindoense system, in Lymnaea rubiginosa the amebocytic response to irradiated parasites was slow: irradiated E. audyi sporocysts were encapsulated 15 to 28 days and H. dingeri sporocysts 20 to 27 days postexposure. No obvious enlargement of the amebocyte-producing organ was seen. No resistance was demonstrable to subsequent homologous challenge. Development of acquired resistance to a trematode infection in snails may be related to the speed with which the snails destroy the irradiated sporocysts.

Animals↗
PubMed1983

A study of some factors influencing the epidemiology of urinary schistosomiasis at Ifakara (Kilombero District, Morogoro Region, Tanzania).

Some factors influencing the epidemiology of urinary schistosomiasis were studied at Ifakara between 1978 and 1980. Ifakara is situated in the fertile plain of the Kilombero river in the south-eastern part of Tanzania. The overall prevalence of Schistosoma haematobium infection among primary school children (6-19 years) in the Ifakara agglomeration was 21% (730/3478). The highest prevalence was observed in both sexes in the age group 15-19 years. Distinct variations in prevalence were found between the individual schools examined, ranging from 5 to 71% and indicating a focal transmission of the disease. The intensity of S. haematobium infection in the individual schools was relatively low, ranging from 5 to 36 eggs/10 ml urine. However, the frequency of microhaematuria among infected subjects was high, reaching 100% from an egg output of 50 eggs/10 ml onwards. Forty-nine waterbodies--most of them man-made--with Bulinus (Ph.) globosus and/or B. (Ph.) nasutus were found, 12 of them harboured B. (Ph.) globosus shedding cercariae of the mammalian type. These waterbodies were mainly localized in the northern and north-eastern areas of Ifakara where the primary schools with the highest prevalence of S. haematobium were found. Most of these waterbodies were known to be bathing places for the children. Susceptibility experiments with B. (Ph.) globosus and B. (Ph.) nasutus indicated that B. (Ph.) globosus is possibly the only intermediate host for S. haematobium in the areas examined. No Biomphalaria, the intermediate hosts for S. mansoni, were found. In addition, the knowledge and awareness of the local population about urinary schistosomiasis were assessed by a questionnaire survey.

Adolescent↗
PubMedDate not supplied

[A survey of schistosomiasis in Ivory Coast (author's transl)].

S. intercalatum has not yet been observed in Ivory Coast whereas S. mansoni and S. haematobium are frequent. S. mansoni schistosomiasis is distributed in limited foci as a consequence of the vital requirements of Biomphalaria. Its clinical detection is uneasy and stool control is necessary. Kato's technique is recommended. Prevalence has great topographic variations with an average value of 0,7 p. 100. Complications are not frequent, and can be detected only with rather sophisticated techniques available only in hospital. S. haematobium schistosomiasis is much more widespread according to the strong resistence of the mollusc host. Its clinical syndrome is significant and the diagnosis is easily controlled by a microscopic examination of the urine centrifugation deposit. The average prevalence is about 20-25 p. 100. Detection of complication requires hospital equipments.

Adult↗
PubMedDate not supplied

Is Planorbarius metidjensis compatible with Schistosoma haematobium and S. bovis?

On the basis of laboratory snail infection experiments it is concluded that Planorbarius metidjensis is unimportant in the epidemiology of Schistosoma haematobium in North West Africa. 410 P. metidjensis Spain were exposed to 8 isolates of S. haematobium from Ghana, Kenya, Madagascar, Mauritius, Morocco, Tanzania, South Africa and Sudan. 50 P. metidjensis Morocco and 50 P. metidjensis Algarve were exposed to S. haematobium Morocco. All infections failed to develop to maturity. Serial sections of P. metidjensis Morocco infected with S. haematobium Morocco at 24 h, 48 h and 72 h post infection showed that 34% of the miracidia penetrated the snail epithelium, but young sporocysts were encapsulated and killed by an ameobocytic host response. Two hypotheses are postulated to explain the reports in the literature that P. metidjensis transmits S. haematobium. The dual infectivity of B. truncatus and B. africanus by S. haematobium from Guinea Bissau suggests that this isolate is probably an infraspecific hybrid with enhanced intermediate host infectivity. By analogy with work on Biomphalaria glabrata and S. mansoni, field observations of P. metidjensis transmitting S. haematobium could be explained if the snail had been previously infected with a compatible digenean, thus rendering a refractory snail into a susceptible snail. S. bovis Spain is compatible with P. metidjensis Morocco, Portugal and Spain with 14.3%, 29.2% and 73.3% of the snails respectively surviving the prepatent period becoming infected. P. metidjensis Spain is refractory to S. bovis Iran and Sudan. Thus, P. metidjensis may be important in the epidemiology of S. bovis in the Iberian Peninsula and North West Africa.

Animals↗
PubMedDate not supplied

[An epidemiological study of intestinal bilharziasis and roundworm infections in Bafia (Cameroon)].

The prevalence of intestinal helminthiasis is measured by means of stool examinations. In Bafia eggs are passed in the feces of 69.1% of the inhabitants for Ascaris lumbricoides, 70.1 % for Trichuris trichiura, 59.6 % for Necator americanus and 14.8% for Enterobius vermicularis. A small focus of intestinal bilharziasis exists in Bafia and eggs of Schistosoma mansoni are found in the feces of 18.6% of the persons studied. Biomphalaria pfeifferi is the intermediate host of the parasite and transmission occurs in the town itself, in the fish-culture pool and in the rivers Guen and Rutop.

Adolescent↗
PubMed1982

[Evaluation of 10 years of research on S. mansoni schistosomiasis A in the French West Indies].

From 1971 until 1982, we studied the ecological factors which stead fast a perennial schistosomiasis in Guadeloupe on an exhaustive mode. More recently, we start a similar investigation in Martinique. In Guadeloupe the single vector of Schistosoma mansoni is the snail Biomphalaria glabrata which is an ubiquist species. But the transmission to man is restricted to the "canal-sewers" where faeces are dropped and not in the rivers of Basse-Terre or the ponds of Grande-Terre. Moreover, the infection is possible only during the hottest hours of the day, when the cercariae get out of the snail. We built a "cercariometer" with which we are able to know the number of cercariae per litre in a given place at every hour of day and night. The black rat (and not the grey rat!) seems, alone, able to maintain the life-cycle of the parasite, at least in the mangrove forests. It is now possible to "clone" S. mansoni by sporocysts transplantation in non-infected snails. The biological control of B. glabrata populations is possible by sterilizating Trematodes such as Ribeiroia guadeloupensis. A new built irrigation reservoir in Grande-Terre give a chance of spread for the endemy in an area which was, till now, unharmed.

Animals↗
PubMed1982

[Comparison of the cercarial chaetotaxy of 10 species of schistosomes].

The cercarial chaetotaxy permits the differenciation of four groups of Schistosomatinae. --Schistosomatium douthitti, parasite of Stagnicola and Lymnaea (Lymnaeidae); --Schistosoma japonicum, parasite of Oncomelania (Melaniidae); --Schistosoma mansoni and S. rodhaini, parasites of Biomphalaria (Planorbiinae, Bulinidae); --Schistosoma haematobium, S. bovis, S. margrebowiei, S. mattheei, S. leiperi and S. intercalatum, parasites of Isidora, Physopsis and Bulinus (Bulininae, Bulinidae). For the third group, cercaria of Schistosoma mansoni and S. rodhaini may be distinguished. In the fourth group, small statistical differences in the topography of the sensillae can be shown between the various species.

Schistosoma↗
PubMed1977

Lectin and human blood group determinants of Schistosoma mansoni: alteration following in vitro transformation of miracidium to mother sporocyst.

A mixed agglutination assay method was employed to detect the presence of surface determinants for various lectins and human blood group antibodies on Schistosoma mansoni miracidia and cultured mother sporocysts. Miracidia were found to possess surface receptors for the lectins Con A (concanavalin A), anti-Heel (eel serum agglutinin), and anti-ADb (Dolichos seed extract), as well as human anti-A antibodies. Following in vitro transformation of the miracidium to mother sporocyst, anti-Heel and human anti-A receptors were no longer detectable on the sporocyst surface, while determinants for Con A and anti-ADb remained essentially unaltered. It is concluded that transition of the miracidium to the sporocyst results in the alteration of surface molecular structures on schistosome larve. Furthermore, since determinants for Con A, anti-Heel, anti ADb, and human anti-A have been found associated with macromolecules in the hemolymph of the snail Biomphalaria glabrata (Stnislawski et al., 1976), there is now evidence that miracidia and mother sporocysts of S. mansoni and their snail host share molecules with common lectin and human blood group determinants.

Agglutination Tests↗
PubMedDate not supplied

[Specificity and active principle of Bacillus thuringiensis var. israelensis].

Bio-assays of B. thuringiensis var. israelensis on larvae of Drosophila melanogaster, Musca domestica, Culicoides sp. and Chironomus plumosus are negative except in the last case, but only with doses much higher than those which are lethal for mosquito larvae. Tests on mollusks (Biomphalaria glabrata) and golden fishes are also negative. The specificity of action of the H 14 serotype, limited to a few Diptera families, should be mainly related to the special characteristics of its crystals, which are proved to be the only active material by studying the larvicidal power of isolated crystals and of spore-free or crystal-free mutants. The amino-acid composition is one of these characteristics, being similar qualitatively but different quantitatively, when compared with the composition of the other studied H serotypes.

Animals↗
PubMedDate not supplied

[Chaetotaxic variations of the cercaria Schistosoma mansoni from a human strain during successive transmissions through mice (author's transl)].

The "cercarian chaetotaxic index" from the human strain of Schistosoma mansoni from West Africa is conspicuously modified during the third transmission Biomphalaria pfeifferi-white mouse only. This might be the explanation why Planorbs collected in Guadeloupe discharge slightly different cercariae whether they come from stations where the infestation is predominantly from human origin or from stations where the infestation is predominantly from murine origin. On the contrary, the "Grand Etang" station is significatively different from all the others and seems to be exclusively murine transmitted.

Africa, Western↗
PubMedDate not supplied

[Recent detection of a schistosomiasis focus with S. mansoni in a high region of Rwanda (author's transl)].

A schistosomiasis focus infested by S. mansoni has been recently detected in the North-Western region of Rwanda (average altitude 1800 m). The soil is rich. The small homesteads are scattered. Only a part of the population, living on the bank of the lakes Bulera and Ruhondo, is mainly concerned with fishery. The endemy is not negligible, in spite of unfavourable climatic conditions, and of lakes water temperature never reaching 25 degrees C. But all other conditions required for the growth and the transmission of the parasite are present: mollusks are abundant, mainly Biomphalaria pfeifferi. An epidemiologic study carried out through stool exams among the water-side population (11.857 persons) demonstrated a low incidence of the disease. It is possible to conclude that there is no evident correlation between the schistosoma infestation and the disease incidence.

Adolescent↗