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D Rollinson

Publications and source records attributed to D Rollinson.

At least 91 records · Page 5Linked to original sources
PubMed1986

Differentiation of Schistosoma haematobium from related species using cloned ribosomal RNA gene probes.

The ribosomal RNA (rRNA) gene units of Schistosoma mansoni (lateral spined eggs) and six species of schistosomes with terminal spined eggs (S. haematobium, S. curassoni, S. bovis, S. intercalatum, S. margrebowiei and S. mattheei) have been studied. The schistosome rRNA gene unit consists of a regular interspersion of the two genes encoding the large and small rRNA units with two spacers. The large spacer is not transcribed while the small spacer is part of the transcription unit. Variation in the rRNA gene unit of the species studied is demonstrated and takes three forms: First, variation in DNA sequence leads to both reduced homology in the spacer regions between species and loss or gain of restriction sites. Second, variation in the length of the transcribed spacer is demonstrated and DNA insertions of 0.2 kilobases (kb) and 0.1 kb are observed in S. mattheei and S. margrebowiei, respectively. Third, the length of the non-transcribed spacer region varies between species. S. haematobium has a 0.5 kb deletion in this region, while that of S. margrebowiei contains varying numbers of a 0.4 kb DNA insert. These interspecific variations have been shown to be conserved within species. Analysis of the rRNA genes by DNA hybridisation techniques therefore serves as a means of species identification, whereby it is possible to differentiate S. haematobium from other schistosome species with terminal spined eggs. Similarly, S. margrebowiei and S. mattheei may be clearly distinguished, although no major variation has been detected between S. curassoni, S. bovis and S. intercalatum. All these species differ from S. mansoni by the absence of certain restriction sites in the non-transcribed spacer.

Animals↗
PubMed1986

Schistosoma mansoni from naturally infected Rattus rattus in Guadeloupe: identification, prevalence and enzyme polymorphism.

An enzymatic comparison has been made between isolates of Schistosoma mansoni from rats and humans in Guadeloupe and a Burundi isolate of S. rodhaini. Analyses of LDH, MDH, AcP, PGM, GPI, G6PDH and HK by isoelectric focusing provided no evidence for the involvement of S. rodhaini in the recent evolution of the schistosomes currently endemic in Guadeloupe. No distinction could be made between murine and human isolates of S. mansoni and it is suggested that murine schistosomiasis should not therefore be ignored in control programmes. Rattus rattus were captured at seven sites around the island; of 142 examined, 48 were positive for schistosomes. Differences in prevalence between habitats were marked and only small changes in prevalence were observed in localities sampled in 1982 and 1983. Animals with the greatest worm burdens were associated with areas of high prevalence, and age-related changes in worm burden were observed. Two alleles, a and b, at the MDH-1 locus of S. mansoni from rats were identified. Differences in the overall frequencies of these alleles were observed for schistosomes from different localities. Allelic frequencies representative of schistosomes from rats at four localities were stable from 1982 to 1983. The majority of positive animals, even those with light worm burdens, were found to be infected with a number of different schistosome genotypes.

Alleles↗
PubMed1986

Scanning electron microscopy of the tegument of adult Schistosoma curassoni, and comparison with male S. bovis and S. haematobium from Senegal.

Scanning electron microscopical studies of adult male and female Schistosoma curassoni, male S. haematobium and male S. bovis are reported. The tubercles on the dorsal and dorso-lateral surfaces of male S. bovis are devoid of spines, whereas spines are present on the tubercles of male S. curassoni and S. haematobium. Some of the tubercles of S. curassoni and S. haematobium are completely covered in spines, whereas others have a spine-free apical area. Thus, on the isolates examined from Senegal it is concluded that adult male S. bovis can be easily distinguished from S. curassoni or S. haematobium on the basis of the structure of the tubercles. The surface of female S. curassoni is smooth, with transverse striations and a pitted appearance, apart from the posterior part where anteriorly pointing spines are found.

Animals↗
PubMed1986

The pathology of experimental Schistosoma curassoni infections in mice and hamsters.

The histopathology of experimental Schistosoma curassoni infections in white mice and hamsters was studied. In mice, hepatic lesions were severe with characteristic extensive perilobular fibrosis and large perilobular granulomas throughout the parenchyma. Only a few granulomas were detected in the lung, small intestine, and rectum of mice. In hamsters, lesions in the liver were limited. Few granulomas were found but the giant cell reaction was pronounced. Lesions in the lung and small intestine were minimal. Many subserosal and submucosal epithelioid cell granulomas were in the colon and rectum of hamsters. Parasites were not detected in the bladder of either mice or hamsters.

Animals↗
PubMed1985

Bulinus tropicus from Central Kenya acting as a host for Schistosoma bovis.

One hundred and twelve snails were collected from two habitats on the Mau Escarpment, Kenya and were provisionally identified as Bulinus tropicus from the characteristics of their shell and soft parts, chromosome number (n = 18), electrophoresis of egg protein on cellulose acetate strip and isoelectric focusing of AcP, GPI, HBDH, MDH and PGM digestive gland enzymes. Of the 55 specimens examined alive in London, 10 were infected with amphistome and schistosome larvae, 9 with amphistome larvae and the remainder were uninfected. The GPI and MDH separations of known infected snails showed two distinct areas of activity: host and parasite. Individual hamsters were exposed to schistosome cercariae emanating from each snail with a double infection (apart from one which died prematurely) and examination of the resulting adult worms showed that all were monomorphic for AcP with a band of enzyme activity at pH 6.45, characteristic of Schistosoma bovis. Examination of eggs found in two infections proved to be S. bovis in shape and size. Exposure of laboratory-bred snails of B. tropicus from the Mau Escarpment and other populations of B. tropicus proved negative. Thus, it is suggested that the presence of the amphistome infection may have a suppressive effect on the immune system of the snail, thereby allowing S. bovis to develop.

Animals↗
PubMed1985

Bulinus tropicus, a natural intermediate host for Schistosoma margrebowiei in Lochinvar National Park, Zambia.

Snails, provisionally identified as Bulinus tropicus, on the basis of chromosome number, egg protein profile, AcP and HBDH enzymes of the digestive gland, and radular morphology, from Lochinvar National Park, Zambia have been demonstrated to transmit Schistosoma margrebowiei naturally. The identification of the unpaired male schistosomes was confirmed by PGM and AcP analyses. The observations confirm earlier epidemiological predictions, and add another species of mollusc to the two, B. forskalii and B. scalaris, known to be natural intermediate hosts of S. margrebowiei.

Animals↗
PubMed1985

Pathology of Schistosoma curassoni infection in sheep.

The gross- and histopathology of natural and experimental Schistosoma curassoni infections in sheep were studied. The data obtained showed that S. curassoni infection in sheep causes only slight clinico-pathological manifestations with preferential involvement of the liver, the lower intestine and the urinary bladder. A variable spectrum of host reaction to the eggs within an individual animal was observed, reflecting the duration of presence of eggs in the organs. In the liver, egg granulomas were most numerous in the perilobular regions, while in the intestine, lesions were most pronounced in the mucosa of the rectum. The presence of eggs in 10% of the urinary bladders examined indicated some bladder involvement.

Animals↗
PubMed1985

The epidemiology of human and animal schistosomiasis in the Senegal River Basin.

The results of four field surveys in Senegal are reported. 1. A snail survey in various parts of the Senegal River Basin, including the Senegal River, temporary rain-fed pools, swamps, irrigation canals and drains, ricefields and Lac de Guier was carried out. Three species of snails were commonly found: Bulinus guernei was the most common, occurring in permanent habitats, Bulinus senegalensis occurring in laterite pools in the eastern part of the Middle Valley, and also in the ricefields of Guédé Chantier and Lampsar; B. forskalii was found in small numbers in Lac de Guier and Richard Toll. Three B. guernei were found to be naturally infected with S. bovis. Neither B. jousseaumei, B. globosus nor B. umbilicatus were found in our surveys. 2. A survey for urinary schistosomiasis was carried out in 100 villages (walo, near the Senegal River) and 11 villages (diéré, away from the river) by delivering questionnaires in schools and by direct examinations of haematuria samples. The prevalence of haematuria varied between 0 and 33%. Generally, walos showed low rates of haematuria with the exception of Lampsar and Guédé Chantier, and diérés showed higher rates of haematuria. 3. Examination of 400 cattle at the abattoir St. Louis, revealed a prevalence of 80% of schistosome infection. Two species were present, S. bovis and less commonly S. curassoni. Sometimes high worm burdens were seen, but lesions appeared to be minimal because of high ratio of male to female worms. 4. Examinations of 5722 sheep and 1752 goats in the abattoir, Dakar revealed an overall prevalence of 2.1%. Of the infected animals, 97.3% were infected with S. curassoni and 2.7% with S. curasonni and S. bovis. Laboratory snail infection experiments showed that S. curassoni is marginally compatible with B. senegalensis, but incompatible with B. guernei.

Animals↗
PubMed1984

[Selection of genotypes of Schistosoma mansoni and their maintenance by sporocyst transplantation].

Schistosoma mansoni was isolated by hatching eggs obtained from a naturally infected Rat in Grand Etang, Guadeloupe; fifty Biomphalaria glabrata were exposed to five miracidia each. The resulting cercariae were used to infect laboratory mice which were later sacrificed to provide worms for enzyme analyses and eggs for further infections. Seven enzymes in extracts of individual worms were examined by isoelectric focusing in polyacrylamide gels: AcP, G6PDH, PGM, GPI and HK showed no variation, whereas MDH and LDH proved to be polymorphic. Two MDH loci were recognised, MDH-2 was invariant whereas two alleles were assumed at the MDH-1 locus. It was not possible to make a genetic interpretation of the complex banding pattern of LDH, although 4 types (LDH-A, -B, -C, -D) were observed. Of the snail infections, one batch of snails was exposed to 5 miracidia per snail in the normal way whereas other snails were each exposed to a single miracidium. The latter were sacrificed to provide sporocysts to transplant into further groups of recipient snails. Cercariae from the recipient snails were used to infect mice and the adult worms were analysed and compared with the normally passaged material. In this way, three lines, defined by the possession of particular MDH and LDH types, were selected from the originally polymorphic population; two were identical. The combination of single miracidium infections and enzyme typing has illustrated the possibility of selecting parasite lines of known genotype; transplantation of sporocysts from snail to snail has demonstrated that such lines can be maintained exclusively in the intermediate host.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

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.

Acid Phosphatase↗
PubMed1979

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.

Acid Phosphatase↗
PubMed1979

Parasites in Bulinus senegalensis (Mollusca: Planorbidae) and their detection.

Isoelectric focusing studies on enzyme variation between populations of the snail Bulinus senegalensis revealed that parasitic infections in the snails contributed additional bands of enzyme activity, particularly in the glucose phosphate isomerase (GPI) and malate dehydrogenase (MDH) systems. The patterns due to the parasite enzymes were, in most cases, clearly distinct from those of the host and different from each other. Parasites encountered included Schistosoma haematobium, S. bovis, Paramphistomum microbothrium, another amphistome probably belonging to the group which infect amphibians, Echinostoma revolutum, another echinostome (probably Echinoparyphium sp.), strigeids, xiphidiocercariae (these were resolved into 3 distinct types by the enzyme data) and ciliate protozoa. The 7 host populations which were examined showed marked differences in both the prevalence and variety of their parasitic infections and these variations were tentatively related to environmental differences in their respective habitats and to the nature of human contact patterns. Seasonal changes in the parasite fauna were also noted and some of the implications of the parasite load on the host population are briefly mentioned.

Animals↗