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Joanne P Webster - One of the best experts on this subject based on the ideXlab platform.
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praziquantel decreases fecundity in schistosoma mansoni adult worms that survive treatment evidence from a Laboratory Life history trade offs selection study
Infectious Diseases of Poverty, 2017Co-Authors: Poppy H L Lamberton, Christina L Faust, Joanne P WebsterAbstract:Mass drug administration of praziquantel is the World Health Organization’s endorsed control strategy for schistosomiasis. A decade of annual treatments across sub-Saharan Africa has resulted in significant reductions of infection prevalence and intensity levels, although ‘hotspots’ remain. Repeated drug treatments place strong selective pressures on parasites, which may affect Life-history traits that impact transmission dynamics. Understanding drug treatment responses and the evolution of such traits can help inform on how to minimise the risk of drug resistance developing, maximise sustainable control programme success, and improve diagnostic protocols. We performed a four-generation Schistosoma mansoni praziquantel selection experiment in mice and snails. We used three S. mansoni lines: a praziquantel-resistant isolate (R), a praziquantel-susceptible isolate (S), and a co-infected line (RS), under three treatment regimens: untreated, 25 mg/kg praziquantel, or 50 mg/kg praziquantel. Life-history traits, including parasite adult-worm establishment, survival, reproduction (fecundity), and associated morbidity, were recorded in mice across all four generations. Predictor variables were tested in a series of generalized linear mixed effects models to determine which factors had a significant influence on parasite Life-history traits in definitive hosts under different selection regimes. Praziquantel pressure significantly reduced adult-worm burdens across all generations and isolates, including within R-lines. However, previous drug treatment resulted in an increase in adult-worm establishment with increasing generation from P1 to F3. The highest worm numbers were in the co-infected RS line. Praziquantel treatment decreased adult-worm burden, but had a larger negative impact on the mean daily number of miracidia, a proxy for fecundity, across all three parasite isolates. Our predicted cost of resistance was not supported by the traits we measured within the murine host. We did not find evidence for negative adult worm density-dependent effects on fecundity. In contrast, of the adult worms that survived treatment, even low doses of praziquantel significantly reduced adult-worm fecundity. Such reductions in worm fecundity post treatment suggest that egg - based measures of drug efficacy, such as Kato-Katz, may overestimate the short-term effect of praziquantel on adult - worm burdens. These findings have important implications for S. mansoni transmission control, diagnostic protocols, and the potential for undetected selection toward drug resistance.
Ross A Black - One of the best experts on this subject based on the ideXlab platform.
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predator induced phenotypic plasticity in daphnia pulex Life history and morphological responses to notonecta and chaoborus
Limnology and Oceanography, 1993Co-Authors: Ross A BlackAbstract:Results from a Laboratory Life-table study show Daphnia pulex has a unique set of rapidly induced responses to waterborne chemicals from each of two predator species. Additionally, Daphnia exhibits a unique set of induced responses when simultaneously exposed to both predators. Daphnids possessed neck teeth and experienced delayed maturity when exposed to waterborne chemicals released from larvae of the phantom midge Chaoborus americanus. Possessing the Chaoborus-induced phenotypic plasticity was not associated with a lower population growth rate relative to that in the control treatment. When exposed to waterborne chemicals released from the backswimmer Notonecta undulata, D. pulex exhibited an unexpected assemblage of responses. The Notonecta-induced phenotypic plasticity included rapid juvenile growth to a large size at first reproduction, little growth beyond maturity, and high reproductive output. Simultaneous exposure to chemical cues from Notonecta and Chaoborus resulted in a Life history and morphologies that agreed with predicted Life history and morphological responses of Daphnia that had been simultaneously exposed to largeand small-size selective predators. Predators are an important evolutionary force shaping the Life histories, morphologies, and behaviors of their prey. Several aquatic taxa possess phenotypically plastic Life histories and morphologies that may be induced by the presence of specific predators (Have1 1987; Dodson 19893; Harvell 1990). Predator-induced phenotypic plasticities can be viewed as being particularly adaptive because any disadvantage incurred by having a predator-resistant form is borne only when the predator is present. Among zooplankton, several species exhibit seasonal variation in morphologies to which the term cyclomorphosis has been applied (Hutchinson 1967; Black and Slobodkin 1987). Dodson (1974a) suggested zooplankton change shape as an adaptive strategy to foil the efforts of specific size-selective predators. An abundance of recent evidence supports his hypothI Present address: Water Resources Laboratory, University of Louisville, Louisville, Kentucky 40292. Acknowledgments I thank Stanley I. Dodson, John E. Havel, Nina Hemphill, and an anonymous reviewer for comments on the interpretation of the results presented and on the preparation of this manuscript. Daniel D. Wiegmann provided statistical advice. I received financial support through a Henry Freeman Vilas Graduate Fellowship from the University of Wisconsin-Madison Graduate School and an NSF grant (BSR 88-05805) to S. I. Dodson. esis. Several of the morphological changes seen in common cyclomorphic species of zooplankton can be induced by waterborne chemicals released from invertebrate predators (see Havel 1987; Stemberger and Gilbert 1987). Also, several predators are each capable of inducing a different morphological response in a prey species (Dodson 1989a). In practically every reported case of predator-induced morphological shifts, possession of the induced morphology is coupled with shifts in Life history traits (for Daphnia, Black and Dodson 1990; Riessen and Sprules 1990; for rotifers, Stemberger 1988; for Bryozoa, Harvell 1986). When Life history traits of the induced form result in lower fitness relative to the uninduced form, in the absence of the predator, investigators have interpreted the Life history shifts as the cost of the induced morphology (Stemberger 1988; Walls and Matti 1989; Black and Dodson 1990; Riessen and Sprules 1990). In this study, Life-table experiments were used to collect survivorship, fecundity, and morphological data from Daphnia pulex individuals that were exposed to chemical cues from two invertebrate predators, the backswimmer Notonecta undulata (Insecta, Hemiptera) and larvae of the phantom midge Chaoborus americanus (Insecta, Diptera). Both are common predators of Daphnia and often co-occur (Dodson and Have1 1988), although
Poppy H L Lamberton - One of the best experts on this subject based on the ideXlab platform.
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praziquantel decreases fecundity in schistosoma mansoni adult worms that survive treatment evidence from a Laboratory Life history trade offs selection study
Infectious Diseases of Poverty, 2017Co-Authors: Poppy H L Lamberton, Christina L Faust, Joanne P WebsterAbstract:Mass drug administration of praziquantel is the World Health Organization’s endorsed control strategy for schistosomiasis. A decade of annual treatments across sub-Saharan Africa has resulted in significant reductions of infection prevalence and intensity levels, although ‘hotspots’ remain. Repeated drug treatments place strong selective pressures on parasites, which may affect Life-history traits that impact transmission dynamics. Understanding drug treatment responses and the evolution of such traits can help inform on how to minimise the risk of drug resistance developing, maximise sustainable control programme success, and improve diagnostic protocols. We performed a four-generation Schistosoma mansoni praziquantel selection experiment in mice and snails. We used three S. mansoni lines: a praziquantel-resistant isolate (R), a praziquantel-susceptible isolate (S), and a co-infected line (RS), under three treatment regimens: untreated, 25 mg/kg praziquantel, or 50 mg/kg praziquantel. Life-history traits, including parasite adult-worm establishment, survival, reproduction (fecundity), and associated morbidity, were recorded in mice across all four generations. Predictor variables were tested in a series of generalized linear mixed effects models to determine which factors had a significant influence on parasite Life-history traits in definitive hosts under different selection regimes. Praziquantel pressure significantly reduced adult-worm burdens across all generations and isolates, including within R-lines. However, previous drug treatment resulted in an increase in adult-worm establishment with increasing generation from P1 to F3. The highest worm numbers were in the co-infected RS line. Praziquantel treatment decreased adult-worm burden, but had a larger negative impact on the mean daily number of miracidia, a proxy for fecundity, across all three parasite isolates. Our predicted cost of resistance was not supported by the traits we measured within the murine host. We did not find evidence for negative adult worm density-dependent effects on fecundity. In contrast, of the adult worms that survived treatment, even low doses of praziquantel significantly reduced adult-worm fecundity. Such reductions in worm fecundity post treatment suggest that egg - based measures of drug efficacy, such as Kato-Katz, may overestimate the short-term effect of praziquantel on adult - worm burdens. These findings have important implications for S. mansoni transmission control, diagnostic protocols, and the potential for undetected selection toward drug resistance.
Volodymyr V Tkach - One of the best experts on this subject based on the ideXlab platform.
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The numbers game: quantitative analysis of Neorickettsia sp. propagation through complex Life cycle of its digenean host using realtime qPCR
Parasitology Research, 2016Co-Authors: Stephen E Greiman, Volodymyr V TkachAbstract:Bacteria of the genus Neorickettsia are obligate intracellular endosymbionts of parasitic flukes (Digenea) and are passed through the entire complex Life cycle of the parasite by vertical transmission. Several species of Neorickettsia are known to cause diseases in domestic animals, wildLife, and humans. Quantitative data on the transmission of the bacteria through the digenean Life cycle is almost completely lacking. This study quantified for the first time the abundance of Neorickettsia within multiple stages of the Life cycle of the digenean Plagiorchis elegans . Snails Lymnaea stagnalis collected from a pond in North Dakota were screened for the presence of digenean cercariae, which were subsequently tested for the presence of Neorickettsia . Three L. stagnalis were found shedding P. elegans cercariae infected with Neorickettsia . These snails were used to initiate three separate Laboratory Life cycles and obtain all Life cycle stages for bacterial quantification. A quantitative real-time PCR assay targeting the GroEL gene was developed to enumerate Neorickettsia sp. within different stages of the digenean Life cycle. The number of bacteria significantly increased throughout all stages, from eggs to adults. The two largest increases in number of bacteria occurred during the period from eggs to cercariae and from 6-day metacercariae to 48-h juvenile worms. These two periods seem to be the most important for Neorickettsia propagation through the complex digenean Life cycle and maturation in the definitive host.
Stephen E Greiman - One of the best experts on this subject based on the ideXlab platform.
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The numbers game: quantitative analysis of Neorickettsia sp. propagation through complex Life cycle of its digenean host using realtime qPCR
Parasitology Research, 2016Co-Authors: Stephen E Greiman, Volodymyr V TkachAbstract:Bacteria of the genus Neorickettsia are obligate intracellular endosymbionts of parasitic flukes (Digenea) and are passed through the entire complex Life cycle of the parasite by vertical transmission. Several species of Neorickettsia are known to cause diseases in domestic animals, wildLife, and humans. Quantitative data on the transmission of the bacteria through the digenean Life cycle is almost completely lacking. This study quantified for the first time the abundance of Neorickettsia within multiple stages of the Life cycle of the digenean Plagiorchis elegans . Snails Lymnaea stagnalis collected from a pond in North Dakota were screened for the presence of digenean cercariae, which were subsequently tested for the presence of Neorickettsia . Three L. stagnalis were found shedding P. elegans cercariae infected with Neorickettsia . These snails were used to initiate three separate Laboratory Life cycles and obtain all Life cycle stages for bacterial quantification. A quantitative real-time PCR assay targeting the GroEL gene was developed to enumerate Neorickettsia sp. within different stages of the digenean Life cycle. The number of bacteria significantly increased throughout all stages, from eggs to adults. The two largest increases in number of bacteria occurred during the period from eggs to cercariae and from 6-day metacercariae to 48-h juvenile worms. These two periods seem to be the most important for Neorickettsia propagation through the complex digenean Life cycle and maturation in the definitive host.
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Laboratory maintenance of the bacterial endosymbiont, Neorickettsia sp., through the Life cycle of a digenean, Plagiorchis elegans
Experimental parasitology, 2015Co-Authors: Stephen E Greiman, Jefferson A Vaughan, Maksym Tkach, Vasyl V TkachAbstract:The Digenea (Platyhelminthes: Trematoda) are a diverse and complex group of internal metazoan parasites. These parasites can serve as hosts to obligate intracellular bacteria belonging to the genus Neorickettsia (Family: Anaplasmataceae). Neorickettsiae persist within all stages of the fluke Life cycle and thus are maintained through vertical transmission. However, the low prevalence of Neorickettsia in nature limits study of their transmission biology at different steps of digenean Life cycles. To resolve this dilemma, we have developed for the first time a Laboratory model allowing to maintain Neorickettsia sp. through the whole Life cycle of a digenean, Plagiorchis elegans. The Laboratory Life cycle of P. elegans consists of a snail first intermediate host, Lymnaea stagnalis, an aquatic arthropod second intermediate host, Culex pipiens (mosquito larva), and a vertebrate definitive host, Mesocricetus auratus (Syrian hamster). This paper focuses on the development of the Laboratory Life cycle, as well as outlines its potential uses in studying the transmission biology of Neorickettsia and its evolutionary relationship within its digenean host.
