Spatio-temporal genetic variability in the schistosome intermediate host Biomphalaria pfeifferi

Webster, Joanne P.; Davies, C. S. L.; Ndamba, J.; Noble, Leslie R.; Jones, Catherine S.; Woolhouse, Mark

doi:10.1080/00034980120072239

Cited by 15 publications

(13 citation statements)

References 32 publications

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“…Severe bottlenecks or extinction occurred during the rainy season in open habitats and during the dry season in closed ones. This is direct evidence that B. pfeifferi populations go through limited numbers (confirming previous results; Woolhouse and Chandiwana 1989;Webster et al 2001aWebster et al , 2001bCharbonnel et al 2002) and likely experience genetic drift. The genetic approach also revealed the action of genetic drift.…”

Section: Genetic Driftsupporting

confidence: 87%

“…Habitat openness (closed vs. open) and season (end of dry vs. rainy season) are factors that may affect population size, migration, and mode of colonization, and we propose some predictions here based on field observations and previous genetic studies (e.g., Viard et al 1997;Webster et al 2001aWebster et al , 2001b. First, strong genetic drift is expected in closed habitats during the hot and dry season.…”

Section: Predictions About Population Dynamics According To Habitat Amentioning

confidence: 95%

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A Spatial and Temporal Approach to Microevolutionary Forces Affecting Population Biology in the Freshwater SnailBiomphalaria pfeifferi

Charbonnel

Quesnoit

Razatavonjizay³

et al. 2002

The American Naturalist

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The limitations of both population demography and genetics highlight the need to combine these approaches when inferring the influence of demographic processes and modes of migration on genetic structure. The aim of this study was to use spatiotemporal genetic and demographic surveys to reveal the microevolutionary forces acting on the metapopulation dynamics of the freshwater snail Biomphalaria pfeifferi. We also analyzed the consequences of population turnover on temporal genetic differentiation, an aspect that has been little explored. Genetic drift was revealed by both the demographic survey, which indicated severe bottlenecks or extinction during the rainy (resp. dry) season in open (resp. closed) habitats, and the genetic approach, which indicated high selfing rates and strong temporal differentiation. Genetic reassignments and temporal differentiation both confirmed the results of the demographic survey, which suggests that migration occurs in closed (resp. open) habitats during the hot and dry (resp. rainy) season, and indicated that source-sink functioning may be envisaged. A propagule pool mode of colonization was inferred in the open habitats during the rainy season and a migrant pool in the closed habitats during the dry season. Our study also suggests that selection might be inferred from patterns of neutral genetic markers when recombination is limited.

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Section: Genetic Driftsupporting

confidence: 87%

Section: Predictions About Population Dynamics According To Habitat Amentioning

confidence: 95%

A Spatial and Temporal Approach to Microevolutionary Forces Affecting Population Biology in the Freshwater SnailBiomphalaria pfeifferi

Charbonnel

Quesnoit

Razatavonjizay³

et al. 2002

The American Naturalist

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“…As these lines (Table 2 and Supplementary Table S4) were inbred for three generations, they are likely fixed for genes that mediate resistance/susceptibility. In general, susceptibility has been found to be recessive to resistance (Webster et al, 2001a, b). Because the founding population for this work was predominantly resistant, susceptibility alleles (or combinations of alleles that lead to susceptibility) were expected to exist at low or intermediate frequencies.…”

Section: Discussionmentioning

confidence: 99%

Resistance of Biomphalaria glabrata 13-16-R1 snails to Schistosoma mansoni PR1 is a function of haemocyte abundance and constitutive levels of specific transcripts in haemocytes

Larson

Bender

Bayne

2014

International Journal for Parasitology

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Continuing transmission of human intestinal schistosomiasis depends on the parasite’s access to susceptible snail intermediate hosts (often Biomphalaria glabrata). Transmission fails when parasite larvae enter resistant individuals in wild snail populations. The genetic basis for differences in snail susceptibility/resistance is being intensively investigated as a means to devise novel control strategies based on resistance genes. Reactive oxygen species produced by the snail’s defence cells (haemocytes) are effectors of resistance. We hypothesised that genes relevant to production and consumption of reactive oxygen species would be expressed differentially in the haemocytes of snail hosts with different susceptibility/resistance phenotypes. By restricting the genetic diversity of snails, we sought to facilitate identification of resistance genes. By inbreeding, we procured from a 13–16-R1 snail population with both susceptible and resistant individuals 52 lines of B. glabrata (expected homozygosity ~87.5%), and determined the phenotype of each in regard to susceptibility/resistance to Schistosoma mansoni. The inbred lines were found to have line-specific differences in numbers of spreading haemocytes; these were enumerated in both juvenile and adult snails. Lines with high cell numbers were invariably resistant to S. mansoni, whereas lines with lower cell numbers could be resistant or susceptible. Transcript levels in haemocytes were quantified for 18 potentially defence-related genes. Among snails with low cell numbers, the different susceptibility/resistance phenotypes correlated with differences in transcript levels for two redox-relevant genes: an inferred phagocyte oxidase component and a peroxiredoxin. Allograft inflammatory factor (potentially a regulator of leucocyte activation) was expressed at higher levels in resistant snails regardless of spread cell number. Having abundant spreading haemocytes is inferred to enable a snail to kill parasite sporocysts. In contrast, snails with fewer spreading haemocytes seem to achieve resistance only if specific genes are expressed constitutively at levels that are high for the species.

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“…Species of Biomphalaria (B. pfeifferi [31, 32] and B. glabrata [33]) and their trematode parasites [34, 35] are surprisingly genetically diverse. Furthermore, in natural populations only some schistosome individuals are compatible with any snail individual [1, 7, 30, 60-61].…”

Section: Introductionmentioning

confidence: 99%

Successful parasitism of vector snail Biomphalaria glabrata by the human blood fluke (trematode) Schistosoma mansoni: A 2009 assessment

Bayne

2009

Molecular and Biochemical Parasitology

121

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Schistosomiasis, caused by infections by human blood flukes (Trematoda), continues to disrupt the lives of over 200,000,000 people in over 70 countries, inflicting misery and precluding the individuals’ otherwise reasonable expectations of productive lives. Infection requires contact with freshwater in which infected snails (the intermediate hosts of schistosomes) have released cercariae larvae. Habitats suitable for the host snails continue to expand as a consequence of water resource development. No vaccine is available, and the emergence and spread of resistance to the single licensed schistosomicide drug would be devastating. Since human infections would cease if parasite infections in snails were prevented, efforts are being made to discover requirements of intra-molluscan development of these parasites. Wherever blood flukes occur, naturally resistant conspecific snails are present. To understand the mechanisms used by parasites to ensure their survival in immunocompetent hosts, one must comprehend the internal defense mechanisms that are available to the host. For one intermediate host snail (Biomphalaria glabrata) and trematodes for which it serves as vector, molecular genetic and proteomic surveys for genes and proteins influencing the outcomes on infections are yielding lists of candidates. A comparative approach drawing on data from studies in divergent species provides a robust basis for hypothesis generation to drive decisions as to which candidates merit detailed further investigation. For example, reactive oxygen and nitrogen species are known mediators or effectors in battles between infectious agents and their hosts. An approach targeting genes involved in relevant pathways has been fruitful in the Schistosoma mansoni-B. glabrata parasitism, leading to discovery of a functionally relevant gene set (encoding enzymes responsible for the leukocyte respiratory burst) that associates significantly with host resistance phenotype. This review summarizes advances in the understanding of strategies used by both this trematode parasite and its molluscan host to ensure their survival.

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Spatio-temporal genetic variability in the schistosome intermediate host Biomphalaria pfeifferi

Cited by 15 publications

References 32 publications

A Spatial and Temporal Approach to Microevolutionary Forces Affecting Population Biology in the Freshwater SnailBiomphalaria pfeifferi

A Spatial and Temporal Approach to Microevolutionary Forces Affecting Population Biology in the Freshwater SnailBiomphalaria pfeifferi

Resistance of Biomphalaria glabrata 13-16-R1 snails to Schistosoma mansoni PR1 is a function of haemocyte abundance and constitutive levels of specific transcripts in haemocytes

Successful parasitism of vector snail Biomphalaria glabrata by the human blood fluke (trematode) Schistosoma mansoni: A 2009 assessment

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