Assessment of the risk of malaria re-introduction in the Maremma plain (Central Italy) using a multi-factorial approach

AbstractKeywords: Mosquito-borne diseases, Residual anophelism, Anopheles labranchiae, Vectorial capacity, Climatechange, Plasmodium falciparum, Experimental infectionBackgroundIn recent years, the increase in globalization [1], the risein the average temperature of the earth together with anincreasing frequency and intensity of extreme weatherevents, as storms, floods and droughts [2,3], and theenvironmental changes induced by human activities [4],have raised the concern about the possible introductionor reintroduction of Vector Borne Diseases in Countrieswhere these were absent or eradicated [5]. These con-siderations, coupled with the recent spread of somemosquito vector borne diseases in Europe [6,7] and theincreasing number of imported malaria cases recordedin the Continent [8] have renewed interest in the possi-ble reintroduction of malaria in Southern Europe [7-9],particularly in the countries facing the Western Medi-terranean Basin, where potential Anopheline vectors arestill present [10-13]. Moreover, in recent years auto-chthonous malaria cases have been sporadically reportedin Italy, France, Spain and Greece [14-20].In 2005, a five-year study was implemented in Italy, aswell as in other South European countries, with the aim toassess the status of the local potential malaria vectors andthe possible re-introduction of malaria transmission[21-25]. In Italy, the selected study area was the Maremmaplain, a region that was hyperendemic for malaria until60 years ago [26-28] and that more recently was recog-nized as the major “at risk” area for the malaria reintro-duction into Italy [14,29,30].In Maremma, after the malaria eradication campaign(1947-1951), Anopheles labranchiae, the main endophilicvector of the Anopheles maculipennis complex was dra-matically reduced in abundance. However, in subsequentyears, the species has progressively re-colonized most ofthe area coming back to substantial densities [31-33].This was mainly due to the introduction of intensive ricecultivation in the early 1970s. Since then, Maremma hasbeen subjected to continuous entomological surveillancethat was intensified after1997, when an autochthonousPlasmodium vivax malaria case, transmitted byAn. lab-ranchiae, occurred in the Province of Grosseto [14]. Thestudies carried out in the area since eradication, providesa database that allowed a follow-up the history of malariaand its vectors in Maremma over the past 60 years. Start-ing from the findings of the most recent entomologicaland environmental studies [23,34], the present study waschosen to evaluate the malariogenic potential of the areausing a multifactorial approach.Methods