Included studies were not critically appraised using an existing studyquality tool as data resulted from unintentional exposures to the alienspecies rather than as a result of intentional experimental manipulation.However, details relating to the study that could be used to infer quality(for example, study type, study design, spatial scale, comparators andtimescale as applicable) were coded as part of the systematic mappingprocess. Simple descriptive statistics relating to these details weregenerated in Excel to provide an overview of the quality of the availableevidence.
There is currently little evidence demonstrating a change in the occurrence,frequency or severity of human health impacts resulting from exposure toalien species in Europe. The evidence base predominantly constitutes data onarthropods, plants and algae taken from journal articles published since 2001(Table 3), and much of the available evidence represents first reports ofillness or injury resulting from exposure to alien species. Five studiesprovide the first reports of transmission of exotic diseases (two ofChikungunya virus and three of dengue fever) by non-native mosquito speciesof the Aedes genus (A. albopictus and A. aegypti) established within Europe [15-19]. Two adults were infected with dengue inFrance in 2010 , and around 17 in Croatia following identification ofdengue fever in a returning German tourist the same year . An outbreak ofdengue fever in Madeira, Portugal in 2012 (the first dengue epidemic reportedin Europe since 1928) affected at least 1800 people within a matter of months. In 2007 in Ravenna, Italy, an outbreak of Chikungunya virus perhapsintroduced by a visitor from India affected two villages, leaving over 200ill and one dead . Two cases were identified in France in 2010, in younggirls who were bitten during a sleepover near an imported case of Chikungunyavirus . Although these studies represent outbreaks occurring at arelatively local scale, the number of individuals affected ranged from 2 tomore than 2000. Another impact arising from contact with alien animal speciesis contact dermatitis. The first localised reports of dermatitis associatedwith contact with caterpillars of the oak processionary moth Thaumetopoea processionea follow the accidental introduction of the species to London (UK) fromcontinental Europe on imported trees . Local residents and managementworkers were affected.
Evidence also suggests that harmful blooms of alien unicellular algae such asOstreopsis species are causing significant health impacts along European coasts, withcases reported from Italy [21, 22], Spain and France [23, 24]. Numbersaffected ranged from only a handful of cases to over two hundred depending onthe outbreak. Those affected were beach users involved in a range ofrecreational activities including swimming and diving, and suffered from bothrespiratory problems and skin irritations following contact that regressedover time .
Most papers included in the systematic map present numbers of patientsaffected by an illness or outbreak resulting from environmental exposure toan alien species and so many of the features associated with a well-designedscientific experiment are lacking. For example, temporal and geographicalscales tend to reflect the extent of the outbreak and comparators are rarelyreported. Studies that assess longer term impacts (e.g. Ambrosia [25, 26]) tend to report longer time periods and larger geographic areas butare still reliant on recorded data of impacts. These data reflect only thoseindividuals contacting relevant agencies or reporting symptoms (e.g. toallergy centres), and so anyone affected that did not seek medical attention,or conversely, anyone exposed who did not experience symptoms, will not berepresented. Many studies were excluded because there was no attempt toinclude a temporal comparator.
This systematic map expands the existing evidence base demonstrating animpact of alien species on human health and complements recent reviews onthis topic (e.g. [1, 3]) by focusing on evidence for changing health impactsrelated to changes in distribution and abundance of alien species. Despiteclear risks to human health from a number of alien species (there aremultiple cases of skin burns following exposure to the sap of Heracleum mantegazzianum reported in the literature, for example ), there is little evidencedemonstrating changes in the occurrence, frequency or severity of humanhealth impacts resulting from exposure to these species in Europe. Much ofthe evidence contained within this map refers to cases of illness or injurythat demonstrates an impact where it has not been reported previously, ratherthan demonstrating any temporal change. The lack of evidence suitable forinclusion in this systematic map appear to be in part due to challenges inlinking ecological factors such as abundance or spread with actual humanhealth impacts (as opposed to potential health impacts as inferred by pollenloadings or vector competence). This indeed implies rather complex studydesigns, because at first temporal change in species distribution orabundance and temporal change in impact must be assessed, and additionally itis required that these two temporal changes are set into relation with eachother and evidence must be provided for the relation among them (Fig. 3).However, lacking evidence probably also reflects a lack of central recordingfor injuries caused by alien species, and reflects difficulties inattributing impacts to a specific species e.g. in the case of allergies,stings, or in identifying the specific vector where there are a range ofnative and introduced candidate species, and this may complicate attempts tomeasure changes. It is likely that many cases are attributed at a broad level(e.g. an allergy to pollen) and that assessment of causal species (of whichthere may be multiple affecting any given individual) is not worth pursuingby primary care practitioners as it would be unlikely to affect the course oftreatment required.
Given the limited evidence base available, it is difficult to currentlyassess the extent of the impacts of alien species on human health, let alonedetermine whether global change is driving changes in the occurrence,frequency or severity of human health impacts and, if so, in whichdirections. Better linking between data on spread/abundance and human healthimpacts over time (and ideally from the point of introduction onwards forspecies that are not yet established or still spreading) are required toexplore this issue further, and are likely to require collaborativeapproaches between the environmental and the health communities. Thetaxonomic and geographical biases in the available data make it difficult todraw broader conclusions about changes in health impacts as they may nottransfer across species or regions. For established alien species that arewidespread, studies correlating health impacts against abundance or comparingdifferent climatic conditions (such as annual rainfall) or management regimeson health outcomes may be valuable in helping to determine their impacts. Formore recently introduced species, studies mapping health impacts may help tomonitor spread, focus awareness raising activities aimed at minimisingexposure, and provide justification for action aimed at containing thespecies within a restricted area if eradication is not possible. However,this research suggests that these types of studies are still relatively rarein the scientific literature.
There is a clear need for better recording/reporting of impacts to determinewhether particular alien species present a human health issue or not, toidentify any trends (such as changes in impacts) and to inform policy andmanagement appropriately. We recommend that a precautionary approach isadopted towards species likely to pose a threat to human health, andparticularly for those species with demonstrable health impacts notedelsewhere. Prevention, detection and rapid response should be prioritised forspecies of highest concern and risk not yet present and preparations made toraise awareness among relevant professionals (e.g. doctors, environmentalmanagers) and publics most likely to encounter the species (e.g. swimmers,gardeners as appropriate) to facilitate identification and minimise impactsresulting from exposure. For species already present in an area, morethorough assessment of the scale of impacts to date would be valuable injustifying the case for management (or otherwise), and in helping to informother areas not yet affected by the potential impacts. Depending on thespecies of concern, alternative forms of data such as vector competence orpopulation sensitivity may be necessary to underpin prioritisation ormanagement decisions until suitable evidence regarding absolute trends inhealth impacts have been established. 2b1af7f3a8