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A quantitative risk assessment approach for mosquito-borne diseases: malaria re-emergence in southern France.

Ponçon N, Tran A, Toty C, Luty AJ, Fontenille D - Malar. J. (2008)

Bottom Line: The result was mapped in the Camargue area.The sensitivity analysis showed that susceptibility, survival rate and human biting rate were the three most influential parameters for entomological risk.Assessment of vulnerability showed that among the imported cases in the region, only very few were imported in at-risk areas.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Recherche pour le Développement, UR016, Montpellier cedex 5, France. nicolas.poncon@agriculture.gouv.fr

ABSTRACT

Background: The Camargue region is a former malaria endemic area, where potential Anopheles vectors are still abundant. Considering the importation of Plasmodium due to the high number of imported malaria cases in France, the aim of this article was to make some predictions regarding the risk of malaria re-emergence in the Camargue.

Methods: Receptivity (vectorial capacity) and infectivity (vector susceptibility) were inferred using an innovative probabilistic approach and considering both Plasmodium falciparum and Plasmodium vivax. Each parameter of receptivity (human biting rate, anthropophily, length of trophogonic cycle, survival rate, length of sporogonic cycle) and infectivity were estimated based on field survey, bibliographic data and expert knowledge and fitted with probability distributions taking into account the variability and the uncertainty of the estimation. Spatial and temporal variations of the parameters were determined using environmental factors derived from satellite imagery, meteorological data and entomological field data. The entomological risk (receptivity/infectivity) was calculated using 10,000 different randomly selected sets of values extracted from the probability distributions. The result was mapped in the Camargue area. Finally, vulnerability (number of malaria imported cases) was inferred using data collected in regional hospitals.

Results: The entomological risk presented large spatial, temporal and Plasmodium species-dependent variations. The sensitivity analysis showed that susceptibility, survival rate and human biting rate were the three most influential parameters for entomological risk. Assessment of vulnerability showed that among the imported cases in the region, only very few were imported in at-risk areas.

Conclusion: The current risk of malaria re-emergence seems negligible due to the very low number of imported Plasmodium. This model demonstrated its efficiency for mosquito-borne diseases risk assessment.

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Distribution of An. hyrcanus susceptibility to P. vivax.
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Figure 9: Distribution of An. hyrcanus susceptibility to P. vivax.

Mentions: Anopheles hyrcanus susceptibility to P. vivax has not yet been tested, but this species has been considered a vector of P. vivax in Afghanistan for more than 30 years [30,31]. Genetic comparison based on ITS2 sequences between French, Afghan, Turkish and Iranian specimens concluded that they were identical. Hence, it was considered that An. hyrcanus was susceptible to tropical P. vivax strains, and estimation of its susceptibility, based on expert knowledge, was fitted as follows: Pert distribution (0.05; 0.20; 0.70) (Figure 9).


A quantitative risk assessment approach for mosquito-borne diseases: malaria re-emergence in southern France.

Ponçon N, Tran A, Toty C, Luty AJ, Fontenille D - Malar. J. (2008)

Distribution of An. hyrcanus susceptibility to P. vivax.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2527012&req=5

Figure 9: Distribution of An. hyrcanus susceptibility to P. vivax.
Mentions: Anopheles hyrcanus susceptibility to P. vivax has not yet been tested, but this species has been considered a vector of P. vivax in Afghanistan for more than 30 years [30,31]. Genetic comparison based on ITS2 sequences between French, Afghan, Turkish and Iranian specimens concluded that they were identical. Hence, it was considered that An. hyrcanus was susceptible to tropical P. vivax strains, and estimation of its susceptibility, based on expert knowledge, was fitted as follows: Pert distribution (0.05; 0.20; 0.70) (Figure 9).

Bottom Line: The result was mapped in the Camargue area.The sensitivity analysis showed that susceptibility, survival rate and human biting rate were the three most influential parameters for entomological risk.Assessment of vulnerability showed that among the imported cases in the region, only very few were imported in at-risk areas.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Recherche pour le Développement, UR016, Montpellier cedex 5, France. nicolas.poncon@agriculture.gouv.fr

ABSTRACT

Background: The Camargue region is a former malaria endemic area, where potential Anopheles vectors are still abundant. Considering the importation of Plasmodium due to the high number of imported malaria cases in France, the aim of this article was to make some predictions regarding the risk of malaria re-emergence in the Camargue.

Methods: Receptivity (vectorial capacity) and infectivity (vector susceptibility) were inferred using an innovative probabilistic approach and considering both Plasmodium falciparum and Plasmodium vivax. Each parameter of receptivity (human biting rate, anthropophily, length of trophogonic cycle, survival rate, length of sporogonic cycle) and infectivity were estimated based on field survey, bibliographic data and expert knowledge and fitted with probability distributions taking into account the variability and the uncertainty of the estimation. Spatial and temporal variations of the parameters were determined using environmental factors derived from satellite imagery, meteorological data and entomological field data. The entomological risk (receptivity/infectivity) was calculated using 10,000 different randomly selected sets of values extracted from the probability distributions. The result was mapped in the Camargue area. Finally, vulnerability (number of malaria imported cases) was inferred using data collected in regional hospitals.

Results: The entomological risk presented large spatial, temporal and Plasmodium species-dependent variations. The sensitivity analysis showed that susceptibility, survival rate and human biting rate were the three most influential parameters for entomological risk. Assessment of vulnerability showed that among the imported cases in the region, only very few were imported in at-risk areas.

Conclusion: The current risk of malaria re-emergence seems negligible due to the very low number of imported Plasmodium. This model demonstrated its efficiency for mosquito-borne diseases risk assessment.

Show MeSH
Related in: MedlinePlus