Malaria Ecotypes and Stratification

Schapira, Allan; Boutsika, Konstantina

doi:10.1016/b978-0-12-394303-3.00001-3

Cited by 27 publications

(29 citation statements)

References 114 publications

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“…It is unknown to what extent the varying degrees of population divergence identified here among nonurban locales has led to local adaptation (e.g., Wright, ), and how the now recent secondary contact among these locales, ushered in by urban gene flow across broad geographic distances, has altered these phenotypes. In fact, if selective pressures differ sufficiently among urban and nonurban, and even among nonurban environments, “urban ecotypes” may evolve and easily sweep across geographically distant urban areas as a result of human‐mediated transport (Krtinic, Ludoski, & Milankov, ; Schapira & Boutsika, ). As one example previously noted, our group has documented Western black widow spider behavioural differences between urban and nonurban habitats, where urban spiders are more densely aggregated, larger, and are more aggressive (Johnson, Gburek, & Stevens, ; Johnson et al., ; Trubl et al., ).…”

Section: Discussionmentioning

confidence: 99%

Urbanization as a facilitator of gene flow in a human health pest

et al. 2018

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Urban fragmentation can reduce gene flow that isolates populations, reduces genetic diversity and increases population differentiation, all of which have negative conservation implications. Alternatively, gene flow may actually be increased among urban areas consistent with an urban facilitation model. In fact, urban adapter pests are able to thrive in the urban environment and may be experiencing human-mediated transport. Here, we used social network theory with a population genetic approach to investigate the impact of urbanization on genetic connectivity in the Western black widow spider, as an urban pest model of human health concern. We collected genomewide single nucleotide polymorphism variation from mitochondrial and nuclear double-digest RAD (ddRAD) sequence data sets from 210 individuals sampled from 11 urban and 10 nonurban locales across its distribution of the Western United States. From urban and nonurban contrasts of population, phylogenetic, and network analyses, urban locales have higher within-population genetic diversity, lower between-population genetic differentiation and higher estimates of genetic connectivity. Social network analyses show that urban locales not only have more connections, but can act as hubs that drive connectivity among nonurban locales, which show signatures of historical isolation. These results are consistent with an urban facilitation model of gene flow and demonstrate the importance of sampling multiple cities and markers to identify the role that urbanization has had on larger spatial scales. As the urban landscape continues to grow, this approach will help determine what factors influence the spread and adaptation of pests, like the venomous black widow spider, in building policies for human and biodiversity health.

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Section: Discussionmentioning

confidence: 99%

Urbanization as a facilitator of gene flow in a human health pest

et al. 2018

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“…et al, 2015), and therefore, malaria is considered as a local and focal disease (Conn et al, 2015; Dash et al, 2008; Rath, 2004). Several studies involving different ecological and climatic settings have provided evidence that malaria epidemiology can be significantly variable across small eco-climatic scales (Jambulingam et al, 1991; Kaga and Ohta, 2012; Schapira and Boutsika, 2012). For example, malaria epidemiological outcomes including distributional prevalence of mosquito vectors and malaria transmission were correlated with different ecotypes in Nigeria (Okwa et al, 2009), Kenya (Ingasia et al, 2015), Brazil (Rosa-Freitas et al, 2007), Southeast Asia (Seng et al, 1999) and India (Jambulingam et al, 1991; Ramar et al, 2014; Shukla et al, 2007; Singh et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Comparative assessment on the prevalence of mutations in the Plasmodium falciparum drug-resistant genes in two different ecotypes of Odisha state, India

Kar

Chauhan

Nanda

et al. 2016

Infection, Genetics and Evolution

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Considering malaria as a local and focal disease, epidemiological understanding of different ecotypes of malaria can help in devising novel control measures. One of the major hurdles in malaria control lies on the evolution and dispersal of the drug-resistant malaria parasite, Plasmodium falciparum. We herewith present data on genetic variation at the Single Nucleotide Polymorphism (SNP) level in four different genes of P. falciparum (Pfcrt, Pfmdr1, Pfdhfr, and Pfdhps) that confer resistance to different antimalarials in two different eco-epidemiological settings, i.e. Hilly-Forest (HF) and Riverine-Plain (RP), in a high malaria endemic district of Odisha state, India. Greater frequency of antimalarial resistance conferring SNPs and haplotypes was observed in all four genes in P. falciparum, and Pfdhps was the most variable gene among the four. No significant genetic differentiation could be observed in isolates from HF and RP ecotypes. Twelve novel, hitherto unreported nucleotide mutations could be observed in the Pfmdr1 and Pfdhps genes. While the Pfdhps gene presented highest haplotype diversity, the Pfcrt gene displayed the highest nucleotide diversity. When the data on all the four genes were complied, the isolates from HF ecotype were found to harbour higher average nucleotide diversity than those from RP ecotype. High and positive Tajima’s D values were obtained for the Pfcrt and Pfdhfr genes in isolates from both the HF and RP ecotypes, with statistically significant deviation from neutrality in the RP ecotype. Different pattern of Linkage Disequilibrium (LD) among SNPs located in different drug-resistant genes was found in the isolates collected from HF and RP ecotypes. Whereas in the HF ecotype, SNPs in the Pfmdr1 and Pfdhfr were significantly associated, in the RP ecotype, SNPs located in Pfcrt were associated with Pfmdr1, Pfdhfr and Pfdhps. These findings provide a baseline understanding on how different micro eco-epidemiological settings influence evolution and spread of different drug resistance alleles. Our findings further suggest that drug resistance to chloroquine and sulfadoxine-pyrimethamine is approaching fixation level, which requires urgent attention of malaria control program in India.

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“…vector ecology, socio-economic characteristics of the at-risk population) are taken into account when determining locally appropriate mixes of interventions or the appropriateness of implementing reactive case detection on the basis of passively detected cases [2, 26, 27]. In Cambodia the intention is that expert panels at national, province and OD level will screen village-level classifications based on the MIS estimates of incidence and upgrade or downgrade the risk category of specific villages where this is deemed to be appropriate.…”

Section: Discussionmentioning

confidence: 99%

“…Efforts to use malaria stratification to directly guide control and prevention activities date back to the 1940s [1]. Although a wide variety of stratification methodologies and typologies have been used since, most have involved supplementing existing malariometric data with information on the spatial distribution of key determinants of transmission risk including climate, ecology, geomorphology and the presence or abundance of key vector species [2, 3]. In essence this basic framework has not changed substantially over time, although developments in geographical information systems (GIS), remote sensing and geostatistical techniques have led to major advances in the sophistication and reproducibility of spatial risk estimates [4, 5].…”

Section: Introductionmentioning

confidence: 99%

Novel approaches to risk stratification to support malaria elimination: an example from Cambodia

Cox

Sovannaroth

Soley

et al. 2014

Malar J

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BackgroundAccurate malaria stratification is essential for effective targeting of interventions but represents a particular challenge in pre-elimination settings. In these settings transmission is typically sufficiently low and spatially heterogeneous to warrant a need for estimates of malaria risk at sub-district or village level but is also likely to be sufficiently high to render the type of decision support systems appropriate to the final stages of malaria elimination impractical. In such a scenario it is arguably more feasible to strengthen existing passive malaria surveillance systems so that routinely generated case data can provide an effective basis for stratifying malaria risk. This paper explores the utility of routine malaria surveillance data for the stratification of malaria risk in Cambodia, where the target is malaria elimination by 2025.MethodsA malaria information system (MIS) was developed to generate timely, routine data on temporal and spatial variations in malaria cases reported through public health facilities and village malaria workers (VMWs). The MIS was implemented across all malaria endemic districts in the country during 2010–11. In 2012 MIS data were extracted and assessed on the basis of coverage and completeness. Village-level incidence estimates for 2011 were generated using predefined data inclusion criteria.ResultsIn 2011, the MIS covered 681 health facilities and 1,489 VMW villages; the overall completeness of monthly reporting was 82& and 97& for health facilities and VMWs respectively. Using these data it was possible to estimate malaria incidence for 89& of villages covered by the MIS. The resulting stratification highlights the highly heterogeneous nature of malaria transmission in Cambodia and underlines the importance of village-level data for effective targeting of interventions, including VMWs. Challenges associated with implementing the MIS and the implications of these for developing viable and sustainable MIS in Cambodia and elsewhere are discussed.ConclusionsThis study demonstrates the operational feasibility of introducing a system to routinely generate village level malaria case data in Cambodia. Although resulting incidence estimates are subject to various limitations and biases the data provide an objective, repeatable basis for a dynamic system of stratification which is appropriate for guiding the transition between malaria pre-elimination and elimination phases.Electronic supplementary materialThe online version of this article (doi:10.1186/1475-2875-13-371) contains supplementary material, which is available to authorized users.

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Malaria Ecotypes and Stratification

Cited by 27 publications

References 114 publications

Urbanization as a facilitator of gene flow in a human health pest

Urbanization as a facilitator of gene flow in a human health pest

Comparative assessment on the prevalence of mutations in the Plasmodium falciparum drug-resistant genes in two different ecotypes of Odisha state, India

Novel approaches to risk stratification to support malaria elimination: an example from Cambodia

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