Bulinus Africanus Research Articles

The influence of salinity on certain aspects of the biology of Bulinus (Physopsis) africanus

The hatchability of eggs and the fecundity and survival of adult Bulinus (Physopsis) africanus was investigated in different salinities. Experimental results revealed egg masses and hatchlings to be considerably more sensitive to salinity than the adult snails. Egg-laying was recorded in salinities ⩽ 4·5 ‰ and further increases in salinity resulted in a progressive reduction in the hatching success up to a lethal concentration of 5·25 ‰ Survival of these hatchings was adversely affected by salinities as low as 1·0 ‰ and a salinity of 4·5 ‰ was lethal within 6 days. In contrast, adult survival was unaffected in salinities < 3·5 ‰ while further increases in salinity resulted in significant reductions in survival up to a lethal salinity of 8·7 ‰, which caused 100% mortality within 24 h. The survival of B. africanus infected with Schistosoma haematobium and Schistosoma mattheei was lower in the different salinities and control than that of their uninfected counterparts.

Inheritance of Mantle Pigmentation Patterns in Bulinus (Physopsis) africanus (Basommatophora:Planorbidae)

Two mantle pigmentation patterns of Bulinus (Physopsis) africanus are governed by codominant alleles of one gene. The mantle patterns of the homozygous strains are 1) solid, black pigmentation covering the mantle and 2) mottled, black pigmentation. The mantle pattern of heterozygotes is intermediate between the two homozygous patterns.

A review of the biology and transmission ecology of African bovine species of the genus Schistosoma.

The present paper reviews the information available concerning the biology and transmission ecology of the African bovine species Schistosoma bovis, S. mattheei, S. margrebowiei and S. leiperi. Criteria for species identification (egg morphology, intermediate host spectra, definitive host-parasite relationships, etc.) are listed and the geographical distribution of the four species and factors determining the relative occurrence within their overall distributional ranges are described. S bovis and S. mattheei occur north and south of 10 degrees S, respectively, and S. margrebowiei occurs mainly, and S. leiperi only, in southern central Africa. Definitive host-related factors (susceptibility, water contact pattern, ect.) providing the background for being a primary definitive host and the primary definitive host spectra for the four schistosome species are described. The primary definitive host spectrum for S. margrebowiei and S. leiperi comprise lechwe, puku and waterbuck, for S. mattheei lechwe, puku, waterbuck plus cattle, and for S. bovis cattle and possibly also some of the listed antelope species. In addition, wild bovines and cattle may provide a reservoir of S. mattheei and S. margrebowiei in humans, but wild bovines and domestic stock play no major role in the transmission of other human species of schistosomes. The intermediate snail host spectra of S. mattheei and S. leiperi only comprise members of the Bulinus africanus species complex; S. bovis is transmitted by members of the B. truncatus, B. africanus and B. forskalii species groups, and S. margrebowiei is transmitted by members of the B. forskalii species group and possibly also by members of the B. tropicus and B. truncatus species groups. Factors determining the transmission ecology of the four schistosome species, and thereby the epidemiology of bovine schistosomiasis, are discussed. Influential factors comprise environmental conditions mediated via the effect of these on the size of the snail host population and on the rate of the intramolluscan development, behavioural patterns of the definitive host population and the course of the infection in the definitive host as related to aspects of susceptibility and level of endemicity. The epidemiological pattern (prevalence and intensity of infection, seasonality of transmission, etc.) is described and exemplified, and it is finally concluded that the increasing water conservation and changing methods of husbandry may result in bovine schistosomiasis becoming a major veterinary problem in Africa.

The behaviour of Bulinus africanus: A circadian profile

Six different behaviour patterns have been studied across the circadian spectrum in the tropical freshwater snail Bulinus africanus. Snails entrained to a circadian light/dark regimen show a diurnal rhythm of locomotor activity, and feeding, photokinetic responsiveness, egg laying and hatching all follow a similar pattern. The rhythms are endogenous and persist under constant conditions. In contrast defaecation occurs mainly during the dark period. This antiphase relationship may be due in part to a cycle of absorption and fragmentation in the digestive gland cells, but it is likely that other factors are involved.

Observations on an isolate of Schistosoma bovis from Tanzania.

The eggs of Schistosoma bovis isolated from Misungwi, Tanzania measure 211.1 micrometer +/- 18.4 long and 66.7 micrometer +/- 5.4 wide. The parasite is naturally transmitted by Bulinus africanus and is compatible in the laboratory with snails belonging to the B. truncatus. B. forskali, and B. reticulatus groups. The compatibility with B. africanus group snails is shared with isolates from Kenya and Sudan but not with S. bovis from more northern distributions. Enzyme analyses were carried out by isoelectric focusing. In adult worms, phosphoglucomutase (PGM), hexokinase (HK), malate dehydrogenase (MDH), and lactate dehydrogenase (LDH) proved to be monomorphic whereas two types of glucosephosphate isomerase (GPI), three types of glucose-6-phosphate dehydrogenase (G6PDH), and two types of acid phosphatase (AcP) were identified. Differences in the pI values of gPI and MDH of snail digestive glands and of larval parasites allowed the intramolluscan stages to be characterised. The GPI heterogeneity encountered was common both to the larval and adult parasites. The enzyme types identified in S. bovis are discussed both from an intra- and interspecific viewpoint.

Analysis of enzymes in theBulinus africanusgroup (Mollusca: Planorbidae) by isoelectric focusing

Summary Four enzyme systems have been analysed in digestive gland extracts of snails of the Bulinus africanus group. Forty population samples, representing eight of the ten nominal species recognized in the group, have been examined. Three distinct enzyme types were recognized in each of three of the systems and ten types in the fourth. Few of the individual enzyme types show marked restriction in either their taxonomic or geographic distributions. However, certain combinations of types appear to be associated with some nominal taxa and others with regional distributions.

Enzyme analyses of Bulinus africanus group snails (Mollusca: Planorbidae) from Tanzania

38 population samples of snails of the Bulinus africanus group, collected from three separate areas of Tanzania, have been examined. Enzymes in crude digestive gland extracts of individual snails have been analysed by isoelectric focusing in polyacrylamide gels. The enzymes studied were: malate dehydrogenase (MDH); phosphoglucomutase (PGM); glucosephosphate isomerase (GPI); acid phosphatase (AcP) and hydroxybutyrate dehydrogenase (HBDH). Samples of B. nasutus were clearly differentiated from other species and enzyme differences were apparent between samples from the lake and coastal areas. Similarly, although clear distinctions could not always be made, samples of B. africanus, B. globosus and B. ugandae were characterized by their enzyme types. Individual variation was detected within populations and the significance of enzyme polymorphisms in relation to identification has been considered. No correlation was found between snail enzyme type and susceptibility to Schistosoma haematobium or S. bovis.

Intermediate host antigens associated with the cercariae of Schistosoma haematobium.

Bulinus (Physopsis) africanus antigens were shown to be associated with the cercarial glycocalyx of Schistosoma haematobium using immunofluorescence and the Cercarienhüllen Reaktion. It is proposed that this snail antigen may sensitise the definitive host and that resistance to further invasion by cercariae could be induced in this manner.

A NOTE ON THE EFFECTS OF DRASTIC CHANGES IN TOTAL DISSOLVED SOLIDS ON THE AQUATIC PULMONATE SNAILBULINUS (PHYSOPSIS) AFRICANUSKRAUSS

SUMMARY THE transfer of a sample of Bulinus (Physopsis) africanus from water in their natural habitat containing 490 ppm TDS to a laboratory culture medium of 126 ppm TDS was found to be accompanied by a marked increase in the variability of the rate of oxygen consumption among individuals, and resulted in a 46% mortality. Transfer through the same gradient, but through two acclimatory stages of intermediate dissolved solid content, eliminated both these effects, suggesting an ability to acclimate and therefore to cope with the more gradual changes which may be expected to occur under field conditions.

Isoenzymes of snail livers—I. Hydrolysing enzymes and peroxidase

1. 1. The separation of acid and alkaline phosphatases, esterases, leucine amino peptidase, β-glucosidase, β-glucuronidase and peroxidase on polyacrylamide gels from the livers of the amphibious ampulariid snail Pila ovata and the pulmonate snails Lymnaea natalensis, Biomphalaria sudanica, Bulinus africanus and Bulinus nasutus is described. 2. 2. All of the enzymes occur in multiple forms in some or all of the snail livers. 3. 3. The effect of the presence of daughter sporocysts of a plagiorchioid cercaria on the above-mentioned enzymes of the liver of B. sudanica is reported. The only detected effect was on alkaline phosphatase which is reduced.

L'extension geographique de la bilharziose a Schistosoma intercalatum en Afrique tropicale

The specificity of S. intercalatum as a cause of intestinal schistosomiasis, and the separate identity of this infection, were established by Fisher in 1934. The original geographical distribution was in Equatorial Africa (Congo, Gabon), and the classical intermediate snail host is Bulinus (Physopsis) africanus. Since 1966 there has been a spread of this infection from the original foci in the Congo and Gabon as far as Cameroun, where, between 1966 and 1969, 9 foci have been discovered. These are, in South Cameroun (3° to 6° N.) the foci of Eséka, Edea, Mbalmayo, Yaoundé, Obala and Bokito; in West Cameroun the focus of Penja (50 km. northwest of Douala); in North Cameroun the foci of Garoua (Benoué) and Maroua (Diamare). The number of cases discovered in Cameroun is now 700. Details are given of the numbers of cases found during 1966-68 in various areas of the region, the rates of infection ranging from 5.71 in Obala to 24.3% in Yaoundé Severe infections are common, particularly in young people, presumably as a result of massive infections. Treatment with niridazole is fairly satisfactory, though relapses have been observed in the absence of opportunity for reinfection. A new intermediate host, Bulinus (Pyrgophysa) forskali, has now been recognized in Cameroun and Gabon; this snail is present in practically the whole of tropical Africa. The importation of S. intercalatum into Cameroun runs parallel with the movements of infected labourers and nomadic peoples from Gabon or the Congo. Such movements are favourable to the spread of parasitic diseases. Extension within Cameroun, from the south northwards, follows the traditional nomad route from south Cameroun to the Tchad basin, across the Adamoua massif. African nomadism and the exchange of African labourers, which have followed the great increase in the facilities of transport, as well as the very wide geographical distribution of Pyrgophysa forskali and Physopsis africanus in equatorial and tropical Africa, suggest that this infection may continue to spread on a large scale. The sanitary services of the République Centrafricaine and Tchad have not discovered evidence of foci introduced from outside, but have shown that introduction is possible. We suggest that in Nigeria, the Sudan, Tanzania and Angola the situation should be studied.

The Protective Action of Chaetogaster limnaei on Snails Exposed to Schistosoma mansoni

The Protective Action of Chaetogaster limnaei on Snails Exposed to Schistosoma mansoni

Possible occurrence of strains in species of schistosomes.

IN a recent paper Cridland1 has stated among his conclusions that there is no evidence for the occurrence of strains in human schistosomes and also that he had found that certain species of snail did not appear to act as carriers. For example, he states that Bulinus africanus ovoideus (Bgt.) will not act as a carrier of Schistosoma haematobium in Uganda, on the evidence that he had not been able to infect it in the laboratory. In the Kitui area of Kenya Bulinus (Physopsis) africanus ovoideus (Bgt.) and B. (P.) nasutus (von Marts.) both occur in ponds, dams and streams. The latter snail is common also in the coastal regions of north-east Tanganyika and is, in my opinion, quite different from the snail occurring in the Great Lakes which Mandahl–Barth2 recorded as nasutus. He agrees with me that different sub-species are involved.