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Journal ArticleDOI

Pattern of cercarial emergence of Schistosoma curassoni from Niger and comparison with three sympatric species of schistosomes.

01 Feb 1992-Journal of Parasitology (J Parasitol)-Vol. 78, Iss: 1, pp 61-63
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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Citations
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Journal ArticleDOI
TL;DR: Cercarial emergence patterns were used to analyse the intraspecific variability within and between nine populations of Schistosoma haematobium collected along a transect line from the north to the South of the Ivory Coast using Bulinus truncatus or Bulinus globosus as intermediate snail hosts.

26 citations

Journal ArticleDOI
TL;DR: A better understanding of top-down and bottom-up ecological factors that regulate densities of cercarial release by snails, rather than solely snail densities or snail infection prevalence, might facilitate improved schistosomiasis control.
Abstract: Author(s): Haggerty, Christopher JE; Bakhoum, Sidy; Civitello, David J; De Leo, Giulio A; Jouanard, Nicolas; Ndione, Raphael A; Remais, Justin V; Riveau, Gilles; Senghor, Simon; Sokolow, Susanne H; Sow, Souleymane; Wolfe, Caitlin; Wood, Chelsea L; Jones, Isabel; Chamberlin, Andrew J; Rohr, Jason R | Abstract: BACKGROUND:Schistosomiasis is responsible for the second highest burden of disease among neglected tropical diseases globally, with over 90 percent of cases occurring in African regions where drugs to treat the disease are only sporadically available Additionally, human re-infection after treatment can be a problem where there are high numbers of infected snails in the environment Recent experiments indicate that aquatic factors, including plants, nutrients, or predators, can influence snail abundance and parasite production within infected snails, both components of human risk This study investigated how snail host abundance and release of cercariae (the free swimming stage infective to humans) varies at water access sites in an endemic region in Senegal, a setting where human schistosomiasis prevalence is among the highest globally METHODS/PRINCIPAL FINDINGS:We collected snail intermediate hosts at 15 random points stratified by three habitat types at 36 water access sites, and counted cercarial production by each snail after transfer to the laboratory on the same day We found that aquatic vegetation was positively associated with per-capita cercarial release by snails, probably because macrophytes harbor periphyton resources that snails feed upon, and well-fed snails tend to produce more parasites In contrast, the abundance of aquatic macroinvertebrate snail predators was negatively associated with per-capita cercarial release by snails, probably because of several potential sublethal effects on snails or snail infection, despite a positive association between snail predators and total snail numbers at a site, possibly due to shared habitat usage or prey tracking by the predators Thus, complex bottom-up and top-down ecological effects in this region plausibly influence the snail shedding rate and thus, total local density of schistosome cercariae CONCLUSIONS/SIGNIFICANCE:Our study suggests that aquatic macrophytes and snail predators can influence per-capita cercarial production and total abundance of snails Thus, snail control efforts might benefit by targeting specific snail habitats where parasite production is greatest In conclusion, a better understanding of top-down and bottom-up ecological factors that regulate densities of cercarial release by snails, rather than solely snail densities or snail infection prevalence, might facilitate improved schistosomiasis control

23 citations


Cites background from "Pattern of cercarial emergence of S..."

  • ...Thus, we could focus our shedding period to one hour because we targeted the emergence period of human schistosomes [37], and shedding for longer periods i....

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  • ...bovis (also common in this region) are generally shed in the morning from 07:00 to 10:00 [37]....

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Journal ArticleDOI
TL;DR: Findings clarify ecological and behavioral components necessary to the adaptation of S. mansoni to the water-rat as a non human definitive host and the existence of a transmission cycle involving this animals as a reservoir.
Abstract: Due to the semi aquatic habits and the overlap of the geographical distribution of the water-rat, Nectomys spp., with schistosomiasis endemic areas, these wild rodents are very likely to acquire Schistosoma mansoni infection in their daily activities. The role of the water-rat in the S. mansoni cycle would be substantiated if one could prove that these rodents acquire the parasite during their own activity time, a completely independent time schedule of human activities. To pursue this goal, we performed two field experiments in the municipality of Sumidouro, State of Rio de Janeiro, Brazil, a schistosomiasis endemic area where N. squamipes is found naturally infected. One experiment was devised as a series of observations of activity time of the water-rat. The other experiment was a test of the occurrence of late transmission of S. mansoni to the water-rat. The daily activity pattern showed that the water-rat is active chiefly just after sunset. At both diurnal and late exposition essays the water-rat sentinels got infected by S. mansoni. These findings clarify ecological and behavioral components necessary to the adaptation of S. mansoni to the water-rat as a non human definitive host and the existence of a transmission cycle involving this animals as a reservoir.

20 citations


Additional excerpts

  • ...(Mouchet et al. 1992)....

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Journal ArticleDOI
TL;DR: The data suggest that species-specific biological traits may exist in relation to co-infections, snail-schistosome compatibility and intramolluscan schistosomes development in the Niger River Valley region.
Abstract: Urogenital schistosomiasis, caused by infection with Schistosoma haematobium, is endemic in Niger but complicated by the presence of Schistosoma bovis, Schistosoma curassoni and S. haematobium group hybrids along with various Bulinus snail intermediate host species. Establishing the schistosomes and snails involved in transmission aids disease surveillance whilst providing insights into snail-schistosome interactions/compatibilities and biology. Infected Bulinus spp. were collected from 16 villages north and south of the Niamey region, Niger, between 2011 and 2015. From each Bulinus spp., 20–52 cercariae shed were analysed using microsatellite markers and a subset identified using the mitochondrial (mt) cox1 and nuclear ITS1 + 2 and 18S DNA regions. Infected Bulinus spp. were identified using both morphological and molecular analysis (partial mt cox1 region). A total of 87 infected Bulinus from 24 sites were found, 29 were molecularly confirmed as B. truncatus, three as B. forskalii and four as B. globosus. The remaining samples were morphologically identified as B. truncatus (n = 49) and B. forskalii (n = 2). The microsatellite analysis of 1124 cercariae revealed 186 cercarial multilocus genotypes (MLGs). Identical cercarial genotypes were frequently (60%) identified from the same snail (clonal populations from a single miracidia); however, several (40%) of the snails had cercariae of different genotypes (2–10 MLG’s) indicating multiple miracidial infections. Fifty-seven of the B. truncatus and all of the B. forskalii and B. globosus were shedding the Bovid schistosome S. bovis. The other B. truncatus were shedding the human schistosomes, S. haematobium (n = 6) and the S. haematobium group hybrids (n = 13). Two B. truncatus had co-infections with S. haematobium and S. haematobium group hybrids whilst no co-infections with S. bovis were observed. This study has advanced our understanding of human and bovid schistosomiasis transmission in the Niger River Valley region. Human Schistosoma species/forms (S. haematobium and S. haematobium hybrids) were found transmitted only in five villages whereas those causing veterinary schistosomiasis (S. bovis), were found in most villages. Bulinus truncatus was most abundant, transmitting all Schistosoma species, while the less abundant B. forskalii and B. globosus, only transmitted S. bovis. Our data suggest that species-specific biological traits may exist in relation to co-infections, snail-schistosome compatibility and intramolluscan schistosome development.

19 citations

01 Jan 1993
TL;DR: La caracterisation de schistosomes par la morphologie des oeufs intra-uterins des vers femelles and l'analyse des phenotypes des parasites observes pour la phosphatase acide apres separation electrophoretique suggere la presence de genes de S. bovis.
Abstract: La caracterisation de schistosomes par la morphologie des oeufs intra-uterins des vers femelles et l'analyse des phenotypes des parasites observes pour la phosphatase acide apres separation electrophoretique suggere la presence de genes de S. bovis, parasite du betail domestique, chez des schistosomes issus de l'homme dans la region est du Niger et presumes appartenir a l'espece S. haematobium

16 citations

References
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Book
01 Jan 1981

4,608 citations

Journal ArticleDOI
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.

59 citations

Journal ArticleDOI
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.

53 citations

Journal ArticleDOI
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