Showing papers on "Bulinus truncatus published in 1990"

Genetic variability in the compatibility between Schistosoma haematobium and its potential vectors in Niger. Epidemiological implications.

Abstract: A populational study of the compatibility be- tween Scliistosoma lzaematobiurn and its potential vectors has been carried out in the Niger, confronting samples of S. haeinatohiunz populations from three epidemiologic foci with Bulinus populations originating from the same focus (sympatric infection) and with Bulinus populations from other foci (allopatric infections). The three transmis- sion foci selected were irrigation canals in ricefields along the Niger river where one finds: Bulinus truncatus rohlfsi, Bidinus globosus, Bulinus forskalii and Bulinus senegalensis; temporary pools in the Sahel area where one finds B. trzmca- tus and B. senegalensis; permanent pools of the "guelta" type in Sahara area where only B. truncatus occurs. As a compatibility test, the snail infection test was selected, with particular emphasis on optimising its reliability. Snail-in- fection experiments showed that B. trzmcatus.and B. sene- galensis are very good potential vectors, with infection rates ranging between 71.5 and 85.9%. B. globosus and B. forska- Zii, on the other hand, are totally incompatible. The mean in- fection percentages in the sympatric and allopatric combi- nations carried out with the S. haenzatobiuin-B. truncatus couple were very similar. This character strongly suggests a lack of isolation in schistosome populations and a circula- tion of the parasite genome through the mobility of infected human populations (Peuls and Touaregs) in Sahel zone. This study, in relation with snail surveys carried out in par- allel, shows that the main types of aquatic environments on the Niger act as high risk areas for schistosome transmis- sion.

The effect of Schistosoma haematobium infection on the growth and fecundity of three sympatric species of bulinid snails.

Abstract: Three species of bulinid snails were monitored to determine the effect of infection with 2 sympatric strains of Schistosoma haematobium on longevity, growth, and reproductive output, from the onset of cercarial production until death. Bulinus senegalensis was least affected by infection, with total fecundity reduced by less than 34%. Infected Bulinus truncatus showed an acceleration in growth accompanied by a 63% reduction in fecundity, although the majority of snails continued to oviposit at a low level. The longest-lived snails in this study, Bulinus globosus, showed decreased growth and survival when infected. In addition a significant proportion of infected individuals of this species failed to oviposit, and those that retained some reproductive capacity produced fewer embryos than controls. Total fecundity of B. globosus was reduced almost 90% by infection with S. haematobium, yet long-term monitoring of individuals showed that reproductive activity recovered when parasite productivity was low. Results from this and similar studies indicate that the time of infection by a trematode in relation to reproductive maturity of the molluscan host is important in determining the subsequent effects on host growth and fecundity.

Allozyme comparisons and ploidy levels among species of the Bulinus truncatus/tropicus complex (Gastropoda: Planorbidae) in Cameroon.

Abstract: Afin d'identifier avec plus de precision le complexe B. truncatus/tropicus, des electrophoreses des allozymes, le niveau de ploidie et les caracteristiques morphologiques ont ete utilises. Le polymorphisme des allozymes parmi les populations de ce groupe a ete examine

Interference of Echinoparyphium elegans with the host-parasite system Bulinus truncatus-Schistosoma bovis in natural conditions.

Abstract: Histological observations of Bulinus truncatus naturally infected by both Schistosoma bovis and Echinoparyphium elegans in Sardinia (Italy) have shown that E. elegans is pathogenic to the mollusc and dominant to the schistosome. The larval stages, rediae and metacercariae, acted as compressors. Rediae, mainly the young and very motile ones, also behaved as predators. The organs of the mollusc were variably affected; the ovotestis totally disappeared. The larval development of the schistosome was disturbed; cercariogenesis was strongly inhibited and gave way to high sporocystogenesis. The intensity of this interference depended on the density of echinostome larvae present.

The effect of sodium chloride concentration on growth and egg laying of Helisoma duryi, Biomphalaria alexandrina and Bulinus truncatus (Gastropoda : Planorbidae)

Abstract: L'effet a long terme de la salinite du milieu sur la croissance et la ponte est etudie chez 3 especes de planorbe, hotes intermediaires de la Schistosomiase. Des concentrations de 0,6 a 32 mM de NaCl sont utilisees

Schistosomiasis Control in Saudi Arabia with Special Reference to the Period 1983-1988

Abstract: Schistosomiasis control operations carried out between 1983 and 1988 are described, together with information of the impact of schistosomiasis. The prevalence of schistosomiasis has declined from 9.5% in 1983 to 1.8% in 1988 (P<0.05). Bulinus truncatus, B. beccarii, and B. reticulatus wrighti are the intermediate hosts of S. haematobium in Saudi Arabia and are distributed unevenly in the different regions. Biomphalaria arabica is the intermediate host of S. mansoni and is found wherever the disease is endemic. The influx of expatriate workers from countries where schistosomiasis is endemic, inaccessible water sources, the constant movement of large numbers of bedouins in some regions, and manpower shortages in some regions are considered to be the main obstacles for schistosomiasis control programmes in Saudi Arabia.

Urinary schistosomiasis in the Saharan mountain plateau of Air (Republic of Niger)

Abstract: In two villages of the Air (Republic of Niger) the authors have found a Schistosoma haematobium overall prevalence of 24.1% at Timia and 43.5% at El Meki. At El Meki, the distribution of prevalences by age group accords to that which is usually found. The maximum is found in the 5-14 years age group and highest in men than in women. At Timia, the prevalence among young pupils is low, this seems to be due to the application of sanitary education measures. At El Meki, Bulinus truncatus rohlfsi, present in a permanent pool ("guelta") is the intermediate host of schistosomes. The role of this snail in the transmission of urinary schistosomiasis at Timia has not been demonstrated. The role of Bulinus senegalensis, found in both villages has yet to be proved.