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D Rollinson

Publications and source records attributed to D Rollinson.

At least 55 records · Page 3Linked to original sources
PubMed1997

Some molecular insights into schistosome evolution.

Robust phylogenies based on molecular data for species within the genus Schistosoma have been generated in recent years. The considerable progress made in understanding the relationships between many of the 19 recognised species of Schistosoma is reviewed with particular attention being given to the detection and analysis of parasite variation as shown by studies on ribosomal RNA genes, mitochondrial DNA and RAPDs. For the most part, molecular phylogenies agree with observations based on morphological or life-history characteristics. It is clear that the parasites of man do not form a monophyletic group and that close relationships exist between parasites within species groups, especially in the S. haematobium group of species. The S. japonicum group appears to be the most divergent of the species groups and yet little DNA sequence variation has been observed between various isolates of S: japonicum. Some of the less studied schistosomes have yet to be examined at the molecular level and may prove to be interesting links between the species groups as has recently been shown with S. hippopotami. The power of molecular approaches for the analysis of schistosomes at the population and individual level is now apparent, especially for S. mansoni. Important questions remain concerning the maintenance of parasite diversity and how schistosomes respond to selection pressures imposed either during natural progression through the life-cycle or through drug treatment or vaccination. Gene discovery and gene mapping projects are leading to a better understanding of the schistosome genome and can be expected to contribute significantly to future comparative evolutionary studies.

Animals↗
PubMed1997

Observations on compatibility between Bulinus truncatus and Schistosoma haematobium in the Senegal River Basin.

In experiments to determine the compatibility between isolates of Schistosoma haematobium and Bulinus truncatus from Mali and Senegal, the parasite isolates were shown to differ in their intermediate host specificity. Bulinus truncatus from the Lower and Middle Valleys (Senegal) and the Upper Valley (Mali) of the Senegal River Basin (SRB) were all susceptible to S. haematobium isolated from the urines of children living in Tenegue, Office du Niger, Mali. However, none of the B. truncatus tested was susceptible to a parasite isolated from children living in Mbodiene, a village in the Lower Valley of the SRB, where natural transmission is normally associated with B. globosus. As B. truncatus is widely distributed in the SRB, the possible appearance of a Bulinus-truncatus-borne parasite in the Middle and Lower Valleys should be carefully monitored.

Animals↗
PubMed1996

Variation within the internal transcribed spacer (ITS) of ribosomal DNA genes of intermediate snail hosts within the genus Bulinus (Gastropoda: Planorbidae).

Species within the genus Bulinus are responsible for transmission of schistosomes within the Schistosoma haematobium group. In order to provide a molecular insight into the species relationships within the genus, genetic variation between species representing the four species groups was assayed by Polymerase Chain Reaction (PCR) amplification of the ribosomal Internal Transcribed Spacer (ITS) region followed by Restriction Fragment Length Polymorphism (RFLP) analysis of this product with six restriction enzymes. This PCR-RFLP methodology detected considerable variation within the ITS region indicating that restriction profiles will be useful as genetic markers for identification purposes. The complete ITS1 spacer was sequenced for B. globosus, B. cernicus and B. truncatus. There were numerous nucleotide differences between taxa mainly insertions and deletions. Nucleotide divergence was calculated between species from the restriction profiles: the B. truncatus/tropicus complex and B. reticulatus group were most similar which were in turn more closely related to the B. africanus group than to the B. forskalii group. The nucleotide divergence between the species groups is substantial and questions the placement of these groups within the same genus.

Animals↗
PubMed1996

Morphometric variability of Schistosoma intercalatum eggs: a diagnostic dilemma.

Variability of Schistosoma intercalatum eggs in shape and size, and their similarity to those of S. haematobium presented a problem of species identification when egg morphology was the diagnostic criterion used in a study of human schistosomiasis conducted on São Tomé and Principe. More than 2500 egg measurements were obtained by light micoscopy to gather data relating to size variability of S. intercalatum eggs, to evaluate whether factors such as age of host, sex of host and intensity of infection are correlated with variability, and the data were compared with previously published measurements on different isolates and strains of S. intercalatum: the range in length (104-203 microns) embraces most of the measurements reported in other studies of S. intercalatum eggs. There was no correlation either between age and sex of the host, or intensity of infection with variability of egg size. Comparison between measurements of the eggs of S. haematobium, S. intercalatum and S. bovis eggs are presented.

Adolescent↗
PubMed1995

Schistosoma mattheei infections in cattle: changes associated with season and age.

The Schistosoma mattheei egg output was monitored in 31 cattle over a 18-month period on a dairy farm near Lusaka (Zambia). The animals were kept on pasture with free access to two streams which were suitable for the intermediate host, Bulinus globosus. Individual faecal egg excretion reached an average peak of 130 eggs per gram, around 9 months after birth and decreased markedly before the age of 18 months. Average counts declined significantly with age, down to less than five eggs per gram in adult cows. A seasonal increase in B. globosus snails and S. mattheei transmission during the rainy season had no effect on the egg output of animals older than 18 months. Two calves and two adult cows were necropsied to compare fluke and tissue egg counts in young and old infections. There was a marked decline in tissue egg accumulation in older cows, in spite of an increase in the numbers of adult female flukes, as compared with young animals. A shift of egg accumulation from the large intestine towards the liver was also observed as infection progressed. It is concluded from the results of faecal egg counts that cattle reared under conditions of continuous challenge develop acquired resistance to S. mattheei infection within the first year following primary infection. Comparison of fluke and tissue egg counts in farm animals of different ages suggests the acquisition of an anti-fecundity effect as infection progresses.

Age Factors↗
PubMed1995

Transvaginal small-bowel evisceration: a case report.

Transvaginal small-bowel evisceration is rare. Only 47 case reports appear in the literature in English. Review of this literature shows that vaginal evisceration occurs mainly in women who are older, multiparous, and have undergone vaginal surgery. The immediate cause of evisceration is either sudden, increased intraabdominal pressure, trauma, or a spontaneous event. The small bowel and omentum are most commonly involved. Surgical repair is performed vaginally, abdominally, or by both methods. We present a case of transvaginal small bowel evisceration caused by inadvertent self-induced trauma, a heretofore unreported cause of this complication, in a 79-year-old woman with known weakness of her pelvic structural support. She experienced sudden evisceration of small bowel following manual decompression of her cystocele during voiding. We used a combined abdominal and vaginal approach to examine the small and large intestines and mesentery for trauma, attach the vaginal vault to the shortened uterosacral ligament, obliterate the cul-de-sac using the Moschowitz procedure, and repair the defect in the levator plate. To limit risk, patients should be evaluated for predisposing conditions. We recommend a combined abdominal and vaginal surgical approach to adequately evaluate the involved tissues and to effect repair.

Aged↗
PubMed1994

A phylogenetic analysis of Schistosoma haematobium group species based on randomly amplified polymorphic DNA.

Randomly amplified polymorphic DNA (RAPD) profiles were produced using four oligonucleotide primers with genomic DNA from 15 isolates of schistosome. Both inter- and intraspecific variation were noted. Intraspecific variation was greater for two species of the S. haematobium group (S. haematobium and S. intercalatum) than for S. mansoni. The inferred phylogeny placed S. curassoni and S. bovis as sister groups to S. mansoni-S. rodhaini group. S. mattheei and S. leiperi formed a separate lineage. The results confirm that RAPD profiles may be used for both strain and species differentiation and for the generation of phylogenetic trees.

Animals↗
PubMed1994

Cattle schistosomiasis in Zambia.

A total of 358 cattle was examined for schistosome infection in Zambian slaughterhouses. A total of 542 worms collected from 104 infected individuals was examined for glucose-6-phosphate dehydrogenase and phosphoglucomutase using isoelectric focusing. The overall prevalence of infection was 51%. Ninety three percent of the infected animals had less than 100 worm pairs in the mesenteric veins. Schistosoma mattheei was the predominant species (75%); S. leiperi (12%) and S. margrebowiei (2%) were also identified. The remaining 11% of the worms showed one of two distinct heterozygote patterns. Pattern A is identical to that of a laboratory-produced F1 S. mattheei x S. haematobium hybrid, but could also represent a S. mattheei x S. leiperi hybrid. Further studies are required to elucidate the origins of pattern B.

Animals↗
PubMed1994

Effects of Schistosoma haematobium infection on reproductive success and male outcrossing ability in the simultaneous hermaphrodite, Bulinus truncatus (Gastropoda: Planorbidae).

The schistosome intermediate snail host, Bulinus truncatus (Mollusca: Planorbidae), has two reproductive (phally) morphs. Both aphallics and euphallics can self-fertilize, but aphallics cannot donate sperm because they do not develop a functional penis and prostate. This study investigated the interactions between phally and fitness consequences of Schistosoma haematobium infection in B. truncatus. Snails which developed patent infections produced 26% fewer eggs than controls and 35% fewer eggs than exposed snails which did not develop infections. This reduction was due to a lower lifetime production of egg masses and a smaller mean number of eggs/mass in infected snails relative to control or exposed snails. However, there was no evidence of increased mortality in infected snails. Contrary to reports of fecundity compensation in other intermediate host snails, egg production post-exposure during the pre-patent period did not increase relative to that of controls in either infected or exposed snails. Phally did not influence susceptibility to infection or length of the prepatent period. Furthermore, lifetime egg, egg mass and hatchling production, as well as mean eggs/mass and number of hatchlings reaching maturity, did not differ significantly between aphallics and euphallics within control of exposed experimental groups. However, within the infected group euphallics produced 38% fewer eggs, smaller egg masses, and fewer hatchlings reaching maturity than aphallics, supporting the prediction of a cost to the growth and maintenance of a full male tract. This cost was detectable only when snails were under the stress of infection. The proportion of euphallic offspring produced did not differ across experimental groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

Cross-protection between species of the Schistosoma haematobium group induced by vaccination with irradiated parasites.

Mice vaccinated with irradiated cercariae of Schistosoma haematobium, S. bovis and S. margrebowiei showed good levels of resistance (38-62%) against an homologous challenge, and varying degrees of resistance (19-46%), against challenges with closely related species. No protection against S. mansoni was induced by vaccination with any of these species. This restricted cross-protection reflects the close phylogenetic relationship between species of the S. haematobium group and indicates that immunologically important epitopes are conserved within this species complex.

Animals↗
PubMed1994

Studies on transmission and schistosome interactions in Senegal, Mali and Zambia.

The transmission and interaction of schistosomes in the Senegal River Basin in Mali and Zambia are reviewed and some preliminary field data are presented. In the Senegal River Basin four species of schistosomes are prevalent: Schistosoma mansoni, S. haematobium, S. bovis and S. curassoni as well as the following potential intermediate hosts: Biomphalaria pfeifferi, Bulinus globosus, B. umbilicatus, B. truncatus, B. senegalensis and B. forskalii. The role of each of these species in the transmission of schistosomes in man and domestic stock is discussed. Recent ecological changes caused by the construction of dams at Diama and Mananatali on the Senegal River, such as reduction in salinity, more stable water flow, creation of irrigation canals and development and extension of rice culture, have contributed towards the occurrence of new outbreaks of both intestinal and urinary schistosomiasis in the Senegal River Basin. In Mali, the four main areas of high prevalence of S. haematobium are Office du Niger (irrigation areas), Bandiagara (small dams), Selingué (dam areas) and Baguineda (irrigation areas). Apart from the Office du Niger, S. mansoni infections are rare. Surveys were carried out in the Dogon Country (Bandiagara District) in an attempt to confirm the recent independent reports of the presence of S. intercalatum. Data based on egg morphology and Ziehl Neelsen staining of egg shells suggested the possible occurrence of S. haematobium x S. intercalatum hybrids. Potential factors affecting the focal endemicity of S. haematobium in Mali are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The use of RAPDs for the study of the genetic diversity of Schistosoma mansoni and Trypanosoma cruzi.

Arbitrary primers have been used for the production of complex, PCR generated DNA profiles in order to undertake a preliminary random amplified polymorphic DNA (RAPD) analysis of strains (and related species) of two parasitic organisms that are responsible for important diseases endemic in Brazil: Schistosoma mansoni that causes schistosomiasis, and Trypanosoma cruzi that causes Chagas' disease. A relatively low level of polymorphism was found in S. mansoni when strains isolated from different regions of Brazil were compared, with less than 10% of bands exhibiting polymorphism. Comparison of different schistosome species, on the other hand, showed them to be distantly related with very few bands shared by even the more closely related species. Trypanosome strains were found to be much more variable. When strains were compared between zymodemes (groups of parasite strains with the same isoenzyme profiles), a maximum of 7% of bands were found to be common whereas among strains in the same zymodeme a clear characteristic pattern was observed. In the zymodeme most thoroughly studied, it was found that 59% of bands were shared. Band sharing analysis showed that the relationships of strains within a zymodeme correlate with their geographical origin and that the relationship between zymodemes correlates closely with that previously determined by isoenzyme analysis. These preliminary data indicate the ready applicability of RAPD analysis to the study of parasites where largely unexplored genetic variations may have an important bearing on the complexity and diversity of diseases.

Animals↗
PubMed1993

The random amplification of polymorphic DNA allows the identification of strains and species of schistosome.

The use of arbitrarily selected primers (10-24 nucleotides) and very low stringency annealing conditions (30 degrees C followed by 40 degrees C) for the polymerase chain reaction amplification of 1.0 ng of schistosome DNA resulted in relatively complex patterns of products. Amongst the primers tested some, for example 5'-TCGTAGCCAA, produced patterns that included bands that were polymorphic between strains of Schistosoma mansoni. Other primers, for example 5'-TCACGATGCA, produced apparently identical products using DNA from 5 S. mansoni strains but highly variable patterns when DNA from different schistosome species was used. The results indicate that the random amplification of polymorphic DNA (RAPD) may be an extremely useful approach to the identification of schistosome strains and species.

Animals↗
PubMed1993

Opening the can of worms: molecular analysis of schistosome populations.

The Schistosomatidae are dioecious digenean parasites of the blood vascular system of vertebrates. Of the 13 genera within the family, only Sehistosoma is associated with humans and, of the mammalian blood flukes, this genus has achieved the greatest geographical distribution and diversification in terms of recognized species and definitive hosts parasitized. In this review, Dave Johnston, Emmanuel Dias Neto, Andy Simpson and David Rollinson consider some recent molecular research that either sheds light on the micro-evolutionary changes occurring within schistosome populations or provides insights into broader, macro-evolutionary questions.

Journal Article↗