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 concept of an age-acquired resistance to reinfection is supported and a predisposition to infection that raises the question of a genetic factor controlling susceptibility/resistance to S. haematobium infection is raised.
Abstract: The effect of age, previous intensity of infection, and exposure on reinfection with Schistosoma haematobium after treatment was studied in a cohort of 468 subjects six years of age and over living in an irrigation scheme area in Mali. Prevalence and intensity of S. haematobium infection were measured each year between 1989 and 1991, but the reinfection study period was restricted to the last year of the follow-up. Observations were made at the principal water contact sites where the number of Bulinus truncatus shedding furcocercous cercariae was recorded. A cumulative index of exposure taking into account time, duration and type of contact, and malacologic data was calculated for each subject. Univariate analysis showed that the reinfection risk decreased with age and increased with exposure and pretreatment intensity. These results were confirmed by fitting a logistic model that showed that this risk was seven times lower among those 15 years of age and older than among the 6–14-year-old children, while linear trends with exposure to infection and pretreatment intensity were significant. This study supports the concept of an age-acquired resistance to reinfection and is in favor of a predisposition to infection that raises the question of a genetic factor controlling susceptibility/resistance to S. haematobium infection.
61 citations
TL;DR: The physicochemical factors that influenced Biomphalaria population and infections are found and greater effort should be placed on reducing environmental contamination by improvement of local water sanitation and hygiene.
Abstract: This study documented the population dynamics of Biomphalaria and associated natural infections with digenetic trematodes, along the shores of Lake Albert and Lake Victoria, recording local physicochemical factors. Over a two-and-a-half-year study period with monthly sampling, physicochemical factors were measured at 12 survey sites and all freshwater snails were collected. Retained Biomphalaria were subsequently monitored in laboratory aquaria for shedding trematode cercariae, which were classified as either human infective (Schistosoma mansoni) or nonhuman infective. The population dynamics of Biomphalaria differed by location and by lake and had positive relationship with pH (P < 0.001) in both lakes and negative relationship with conductivity (P = 0.04) in Lake Albert. Of the Biomphalaria collected in Lake Albert (N = 6,183), 8.9% were infected with digenetic trematodes of which 15.8% were shedding S. mansoni cercariae and 84.2% with nonhuman infective cercariae. In Lake Victoria, 2.1% of collected Biomphalaria (N = 13,172) were infected with digenetic trematodes with 13.9% shedding S. mansoni cercariae, 85.7% shedding nonhuman infective cercariae, and 0.4% of infected snails shedding both types of cercariae. Upon morphological identification, species of Biomphalaria infected included B. sudanica, B. pfeifferi, and B. stanleyi in Lake Albert and B. sudanica, B. pfeifferi, and B. choanomphala in Lake Victoria. The study found the physicochemical factors that influenced Biomphalaria population and infections. The number and extent of snails shedding S. mansoni cercariae illustrate the high risk of transmission within these lake settings. For better control of this disease, greater effort should be placed on reducing environmental contamination by improvement of local water sanitation and hygiene.
36 citations
TL;DR: The results showed that the chronobiological life-history trait is useful for the detection of new hosts and also may reveal the possible presence of introgressive hybridization in schistosomes.
Abstract: Schistosomiasis remains a parasitic infection which poses serious public health consequences around the world, particularly on the African continent where cases of introgression/hybridization between human and cattle schistosomiasis are being discovered on a more frequent basis in humans, specifically between Schistosoma haematobium and S. bovis. The aim of this paper is to analyze the occurrence of S. bovis in cattle and its relationship with S. haematobium in an area where cattle and humans share the same site in Benin (West Africa). We used the chronobiology of cercarial emergence as an ecological parameter and both molecular biology (COI mtDNA and ITS rDNA) of the larvae and morphology of the eggs as taxonomic parameters. The results showed a chronobiological polymorphism in the cercarial emergence rhythm. They showed for the first time the presence of S. bovis in Benin, the presence of introgressive hybridization between S. bovis and S. haematobium in domestic cattle, and the presence of atypical chronobiological patterns in schistosomes from cattle, with typical S. haematobium shedding pattern, double-peak patterns, and nocturnal patterns. Our results showed that the chronobiological life-history trait is useful for the detection of new hosts and also may reveal the possible presence of introgressive hybridization in schistosomes. Our results, for the first time, place cattle as reservoir host for S. haematobium and S. bovis x S. haematobium. The consequences of these results on the epidemiology of the disease, the transmission to humans, and the control of the disease are very important.
30 citations
Cites background or result from "Pattern of cercarial emergence of S..."
...The second pattern, midday to late diurnal, was new for cercarial emission in cows while it was similar to what has been published on S. haematobium in humans from Algeria (Kéchemir and Théron 1997), Morocco (Mouahid et al. 1991), Niger (Pagès and Théron 1990; Mouchet et al. 1992), and Gabon (Mintsa-Nguema et al. 2014)....
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...This is interesting given that all of Benin’s neighboring countries including Togo, Burkina Faso, Niger, and Nigeria were known to harbor this bovine species (Moné et al. 1999)....
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...Platt et al. (2019) studied the exomes of miracidia coming from humans in Niger and Zanzibar and their data did not reveal any evidence for contemporary hybridization....
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...1991), Niger (Pagès and Théron 1990; Mouchet et al. 1992), and Gabon (Mintsa-Nguema et al....
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...Pagès and Théron (1990) conducted crossing experiments between S. bovis from Spain and S. haematobium from Niger and the F1 hybrids harbored the same chronobiological pattern as the parental S. bovis, i.e., with an early peak....
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TL;DR: This review gathers the knowledge and unresolved issues about the synchronization of these rhythms, their genetic support and the role of the host physiology or activity, and focuses on how cercarial rhythmicity influences cercariae densities in waters of transmission sites and then the risk of host infection in case of schistosomiasis.
Abstract: One major challenge for parasites with complex cycles consists to succeed in the transmission from one host to the next host. To maximize the probability of encountering the right host, numerous trematode species have selected various emergence rhythms occurring during the escape of the short-lived cercariae from the mollusc host. Cercarial shedding patterns are beautiful examples of adaptation of the parasite for a successful rendezvous with its subsequent host. In this review, after an analysis of the technical and statistical aspects specific to such studies, we compile the knowledge and unresolved issues we have about the synchronization of these rhythms, their genetic support and the role of the host physiology or activity. We are also interested on how cercarial rhythmicity influences cercarial densities in waters of transmission sites and then the risk of host infection in case of schistosomiasis. Ecological significance of the inter- and intra-specific diversity of these rhythms is emphasized as well as the evolutionary implication of new chronotypes resulting from the capture of new host species and promoting reproductive isolation and alloxenic speciation. Currently, genome sequence data now available for some trematodes such as the schistosomes provide an unprecedented resource for new research approaches that should contribute identification of the genes and mechanisms involved in determining the cercarial shedding rhythms observed.
29 citations
TL;DR: The production and the chronobiology of emergence of the cercariae of Euparyphium albuferensis from Gyraulus chinensis experimentally infected with a single miracidium were established, and the effect of a sudden change in light-dark cycling resulted in corresponding alterations in emergence patterns, which shows that cercarial emergence was correlated to light- dark alternation.
Abstract: The production and the chronobiology of emergence of the cercariae of Euparyphium albuferensis from Gyraulus chinensis experimentally infected with a single miracidium were established during 28 consecutive days from the first day of cercarial shedding. Moreover, the effect of a sudden change in light-dark cycling was investigated. Although the daily cercarial shedding rates show great variability, a progressive increase in cercarial production was observed in the first weeks of the cercarial shedding periods, probably in relation to the demography of intramollusean larval stages. Under 12:12 light-dark cycling condition;, it, albuferensis cercariae emerged in the light, and the rhythm was circadian. The sudden change in the light-dark cycle resulted in corresponding alterations in emergence patterns, which shows that cercarial emergence was correlated to light-dark alternation. The ecological consequences of daily y emergence by mobile cercariae whose target hosts are organisms that regularly occur in the same habitat with the molluscan emitting host, such as those of E. albuferensis, are discussed with reference to the hypotheses proposed to date, and an alternative hypothesis is proposed.
26 citations
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.
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.
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