Pattern of cercarial emergence of Schistosoma curassoni from Niger and comparison with three sympatric species of schistosomes.
TL;DR: The emergence pattern of Schistosoma curassoni cercariae from Bulinus umbilicatus, whose adult worms parasitize bovine, caprine, and ovine ungulates in Niger, is of a circadian type with a mean emission time at 0855 hr 1 hr 6 min, characteristic of the schistosome species parasitizing domestic or wild cattle as mentioned in this paper.
Abstract: The emergence pattern of Schistosoma curassoni cercariae from Bulinus umbilicatus, whose adult worms parasitize bovine, caprine, and ovine ungulates in Niger, is of a circadian type with a mean emission time at 0855 hr 1 hr 6 min, characteristic of the schistosome species parasitizing domestic or wild cattle. The comparison of this cercarial emergence pattern with those of the other 3 sympatric species of schistosomes (Schistosoma haematobium, Schistosoma bovis, and Schistosoma mansoni) shows a significant difference between the chronobiology of the cercariae infective for human and those infective for bovine hosts. This difference may improve epidemiological surveys based on snail prevalences by allowing the distinction between bulinids infected with human and bovine parasites.
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TL;DR: The CERMES defined the different patterns of schistosomiasis transmission in Niger and shown the existence of important variability in conditions of transmission of S. haematobium.
Abstract: The Centre de Recherche sur les Meningites et les Schistosomoses (CERMES) a research center in Niamey Niger affiliated with a West African public health organization conducts studies in the areas of parasitology epidemiology and immunology Significant variability in factors related to transmission of Schistosoma haematobium have been noted Experimental research on the Schistosoma-bulinid compatibility and field surveys of the geographic distribution and role of snails in transmission have been essential to the design of parasite control interventions in West Africa A CERMES-sponsored project supported by the European Community is examining urinary schistosomiasis control in the Niger river valley and the impact of treatment on ultrasonically visualized urologic lesions The Experimental Vaccine Unit seeks to improve the route of administration and choice of adjuvant and to propose a vaccine protocol for field testing Recombinant proteins have been found to alter the development of the parasite either by inducing a reduction in the parasite burden or an inhibition of the fecundity of the parasite
5 citations
TL;DR: Une etude ulterieure permettra de mieux apprecier les causes of the modification du rythme circadien au type infradien dans le sens oficiale des processus de transmission du parasite a l’hote vertebre.
Abstract: La schistosomose constitue au Benin un reel probleme de sante publique comme dans la plupart des autres pays africains. L’etude de la chronobiologie des emissions cercariennes horaires de deux populations de Schistosoma mansoni du sud-Benin revele, aussi bien en conditions de laboratoire qu’en conditions naturelles, un rythme particulier d’emission de type infradien avec 3 periodes de production: a l’aube entre 6 heures et 8 heures (Heure Locale, HL), en milieu de journee entre 09 heures et 15 ou 16 heures (HL) et le soir entre 17 heures et 20 heures (HL). Ce rythme d’emission est contraire a celui du type circadien, avec un seul pic d’emission, connu a ce jour pour les schistosomes de ce groupe. Ces deux populations de schistosomes ont ete soumises a une pression selective de meme nature induisant des modifications dans le sens de l’harmonisation des processus de transmission du parasite a l’hote vertebre. Une etude ulterieure permettra de mieux apprecier les causes de la modification du rythme circadien au type infradien. Mots Cles : Schistosoma mansoni , chronobiologie, rythme infradien, sud-Benin
3 citations
Cites background from "Pattern of cercarial emergence of S..."
...…est situé en milieu de journée (S. mansoni, S. haematobium, S. guineensis et S. intercalatum), correspondant aux schistosomes de l’Homme (Combes et Théron, 1977 ; Mouahid et Théron, 1986 ; Mouahid et Combes, 1987 ; Rollinson et Southgate, 1987; Mouchet et al., 1992 ; Thomas et al., 2007)....
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...Ainsi, nous distinguons à ce jour quatre grands types de rythmes à travers les « patterns » chronobiologiques des schistosomes du genre Schistosoma étudiés par différents auteurs : ceux dont le pic d’émergence est matinal (S. bovis, S. curassoni et S. mattheei), correspondant généralement aux schistosomes du bétail domestique, ceux dont le pic d’émergence est tardif, crépusculaire ou nocturne (S. leiperi et S. rodhaini), correspondant aux schistosomes d’animaux sauvages : ruminants (S. leiperi) et rongeurs (S. rodhaini), ceux qui possèdent deux pics d’émergence, l’un au lever du jour, l’autre au crépuscule (S. margrebowiei), correspondant aux schistosomes des antilopes principalement et ceux dont le pic d’émergence est situé en milieu de journée (S. mansoni, S. haematobium, S. guineensis et S. intercalatum), correspondant aux schistosomes de l’Homme (Combes et Théron, 1977 ; Mouahid et Théron, 1986 ; Mouahid et Combes, 1987 ; Rollinson et Southgate, 1987; Mouchet et al., 1992 ; Thomas et al., 2007)....
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...Dans la littérature, les études expérimentales ont montré que dans le cas d’une double infestation d’un mollusque par deux espèces de schistosomes appartenant au même groupe (Rollinson et Southgate, 1987), l’expression chronobiologique est individuelle comme cela fut observer avec Biomphalaria glabrata doublement infecté par S. mansoni à émission diurne et S. rodhaini à émission nocturne (Northon et al., 2008 ; Steinauer et al., 2008)....
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TL;DR: In this article, the authors quantified the contributions of exposure, hazard, and vulnerability to the presence and intensity of Schistosoma haematobium re-infection.
Abstract: Background Infectious disease risk is driven by three interrelated components: exposure, hazard, and vulnerability. For schistosomiasis, exposure occurs through contact with water, which is often tied to daily activities. Water contact, however, does not imply risk unless the environmental hazard of snails and parasites is also present in the water. By increasing reliance on hazardous activities and environments, socio-economic vulnerability can hinder reductions in exposure to a hazard. We aimed to quantify the contributions of exposure, hazard, and vulnerability to the presence and intensity of Schistosoma haematobium re-infection. Methodology/Principal findings In 13 villages along the Senegal River, we collected parasitological data from 821 school-aged children, survey data from 411 households where those children resided, and ecological data from all 24 village water access sites. We fit mixed-effects logistic and negative binomial regressions with indices of exposure, hazard, and vulnerability as explanatory variables of Schistosoma haematobium presence and intensity, respectively, controlling for demographic variables. Using multi-model inference to calculate the relative importance of each component of risk, we found that hazard (Ʃwi = 0.95) was the most important component of S. haematobium presence, followed by vulnerability (Ʃwi = 0.91). Exposure (Ʃwi = 1.00) was the most important component of S. haematobium intensity, followed by hazard (Ʃwi = 0.77). Model averaging quantified associations between each infection outcome and indices of exposure, hazard, and vulnerability, revealing a positive association between hazard and infection presence (OR = 1.49, 95% CI 1.12, 1.97), and a positive association between exposure and infection intensity (RR 2.59–3.86, depending on the category; all 95% CIs above 1) Conclusions/Significance Our findings underscore the linkages between social (exposure and vulnerability) and environmental (hazard) processes in the acquisition and accumulation of S. haematobium infection. This approach highlights the importance of implementing both social and environmental interventions to complement mass drug administration.
2 citations
TL;DR: Cercarial rhythmicity can be reflected in health education, and the reproduction and survival rate of infected snails can be used as parameters for developing disease modeling.
Abstract: Background: The epidemiology of schistosomiasis transmission varies depending on the circumstances of the surrounding water bodies and human behaviors. We aimed to explore cercarial emergence patterns from snails that are naturally affected by human schistosomiasis and non-human trematodes. In addition, this study aimed to explore how schistosomiasis infection affects snail survival, reproduction, and growth. Methods: We measured the survival rate, fecundity, and size of Biomphalaria pfeifferi snails and the cercarial rhythmicity of S. haematobium and S. mansoni. The number of egg masses, eggs per egg mass, and snail deaths were counted for 7 weeks. The survival rate and cumulative hazard were assessed for infected and non-infected snails. Results: S. haematobium and S. mansoni cercariae peaked at 9:00–11:00 a.m. Infection significantly reduced the survival rate of B. pfeifferi, which was 35% and 51% for infected and non-infected snails, respectively (p = 0.02), at 7 weeks after infection. The hazard ratio of death for infected snails compared to non-infected snails was 1.65 (95% confidence interval: 1.35–1.99; p = 0.01). Conclusions: An understanding of the dynamics of schistosomiasis transmission will be helpful for formulating schistosomiasis control and elimination strategies. Cercarial rhythmicity can be reflected in health education, and the reproduction and survival rate of infected snails can be used as parameters for developing disease modeling.
2 citations
Dissertation•
01 Aug 2008
TL;DR: A thesis submitted in partial fulfillment of the requirement for the award of the degree of Master of Science in Infectious Disease Diagnosis in the School of Pure and Applied Sciences at Kenyatta University.
Abstract: A thesis submitted in partial fulfillment of the requirement for the award of the degree of Master of Science in Infectious Disease Diagnosis in the School of Pure and Applied Sciences at Kenyatta University, QL 391 .P7N52
1 citations
Cites background from "Pattern of cercarial emergence of S..."
...Mammalian schistosome cercariae can be distinguished by the pattern they exhibit as they are released by the snail intermediate host by examining eggs or adult worms recovered from lab rodents several weeks after cercariae exposure (Prentice and Ouma, 1984; Kimura et aI., 1994; Yousif et aI., 1996; Pitchford and Dutoit, 1976; Theron, 1984; Mouahid and Theron, 1986; Mouchet et al., 1992), by analysis of isoenzyme markers (Mahon and Shiff, 1978; Boissezon and Jelnes, 1982; Fletcher et al....
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..., 1996), studying cercariae emergence patterns (pitchford and Dutoit, 1976; Theron, 1984; Mouahid and Theron, 1986; Mouchet et al., 1992), 'or analysis of cercariae isoenzyme patterns (Mahon and Shiff, 1978; Boissezon and Jelnes, 1982) tend to be long, cumbersome, and are considered impractical for routine use....
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References
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TL;DR: Viable hybrid parasites were produced in the laboratory and were maintained up until the F4 generation, Comparisons of egg morphology, surface structure of adult male worms and enzyme profiles have been made between experimental hybrid lines and field isolates.
Abstract: Surveys of 332 naturally infected bovines at eight abattoirs in Senegal, The Gambia and Mali were carried out to determine the prevalence of infection with Schistosoma bovis and S. curassoni and to pinpoint areas where the distribution of the species overlap. S. bovis was the commonest schistosome of cattle in Senegal and Mali being found in animals at seven abattoirs, the highest prevalance of 85.1% occurred at Mopti in Mali. S. bovis was the only bovine schistosome observed in The Gambia. S. curassoni was isolated from a cow at Bamako and shown to have similar glucose-6-phosphate dehydrogenase, phosphoglucomutase and acid phosphatase profiles to those described for a Senegalese isolate. Evidence of interaction of S. bovis with S. curassoni was found in cattle from Senegal, at Tambacounda and Kolda, and from Mali, at Bamako and Mopti. A mixed experimental infection of both species in a sheep showed the lack of any specific mate recognition system: identification of the worms was facilitated by analysis of acid phosphatase by isoelectric focusing in polyacrylamide gels. Viable hybrid parasites were produced in the laboratory and were maintained up until the F4 generation. Comparisons of egg morphology, surface structure of adult male worms and enzyme profiles have been made between experimental hybrid lines and field isolates. Possible mechanisms maintaining species integrity are discussed.
59 citations
TL;DR: Experimental crossbreeding between schistosomes with an early and those with a late cercarial shedding pattern demonstrates that the cercaria emergence rhythms of schistOSomes are genetically determined.
Abstract: Using two chronobiological variants ofSchistosoma mansoni (a blood fluke infecting man) from Guadeloupe (French West Indies), we carried out experimental crossbreeding between schistosomes with an early and those with a late cercarial shedding pattern. The results obtained on the F1 (intermediate shedding patterns) and F2 generations (early, intermediate, and late patterns) demonstrate that the cercarial emergence rhythms of schistosomes are genetically determined. This genetic variability is interpreted as a consequence of the selective pressure exerted by the two different hosts (man and rat) implicated in the life cycle ofS. mansoni from the Guadeloupean focus of schistosomiasis.
54 citations
Journal Article•
TL;DR: A snail survey in various parts of the Senegal River Basin, including the SenegalRiver Basin, temporary rain-fed pools, swamps, irrigation canals and drains, ricefields and Lac de Guier was carried out, finding Bulinus guernei was the most common, occurring in permanent habitats, and Bulinus senegalensis occurring in laterite pools in the eastern part of the Middle Valley.
Abstract: 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 Guede 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 (diere, 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 Guede Chantier, and dieres 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.
53 citations
TL;DR: A comparative study on the development of Senegalese isolates of Schistosoma curassoni, S. haematobium and S. bovis in hamsters is reported, together with the compatibility of these parasites with Bulinus spp.
Abstract: A comparative study on the development of Senegalese isolates of Schistosoma curassoni, S. haematobium and S. bovis in hamsters is reported, together with the compatibility of these parasites with Bulinus spp. and enzymes of adult worms. The mean worm return from 35 hamsters exposed to 100 cercariae each of S. curassoni was 11·5%, and of these 54% were paired, the remainder were single males. The growth and maturation of the worms were recorded from 40 to 100 days. The cross-over point (when paired females are of the same length as paired males) was reached at 42 days post-infection when the worms averaged 13·7 mm in length. The majority of tissue eggs (84·5%) were recovered from the liver, compared with 11% in the colon, 2·5% in the caecum and 1·6% in the small intestine. Estimates of the fecundity of paired females averaged 167 eggs/day per female worm. Snail-infection experiments showed S. curassoni to be compatible with B. umbilicatus, marginally compatible with B. senegalensis and incompatible with B...
37 citations