Assessment of the monthly risk of dirofilariosis infection in Europe and its projection to 2100 under climate change from a One Health perspective

Abstract

Background: Dirofilariosis is a vector-borne zoonotic disease primarily caused by the parasitic nematodes Dirofilaria immitis and D. repens. In Europe, the disease has expanded from traditionally endemic southern countries to central and northeastern regions, many of which are now also considered endemic. This study aimed to generate infection risk maps for dirofilariosis in Europe using ecoinformatic tools, at both annual and monthly scales, to serve as a prevention tool and contribute to more effective control of the disease, as well as helping to stop its spread.

Methods: A habitat suitability map was generated for the two most important and widely distributed culicid vectors in Europe (Culex pipiens and Aedes albopictus). This map was weighted with the number of D. immitis generations in the vectors, both annually and monthly. The resulting annual risk map was validated with georeferenced records of D. immitis- and D. repens-infected dogs and cats. In addition, a future habitat suitability projection for both vector species was performed for the year 2100 under the Representative Concentration Pathway (RCP) 8.5 climate change scenario.

Results: Dirofilariosis infection risk in Europe is highest in southern countries, where favorable climatic conditions and increased vector activity coincide. Central Europe showed medium- to high-risk values, while northern latitudes exhibited low or very low risk, correlating with lower average temperatures. Of the geolocated infected animals, 35.9%, 51% and 13% were located in high-, medium-, or low-risk areas, respectively. Infection risk appears to be very limited during winter, restricted mainly to Mediterranean coastal areas, the Canary Islands (Spain), and Madeira (Portugal); while in spring/summer it becomes high in these places and moderate across other parts of the range such us central and northeastern Europe. The 2100 projection predicts a 161.6% increase in habitat suitability for the vectors, particularly in northeastern regions, high-altitude areas, and northernmost countries.

Conclusions: The combined use of habitat suitability for Culex pipiens and Aedes albopictus and the number of Dirofilaria spp. generations allowed the development of a more comprehensive color-coded dirofilariosis infection risk map than previously available. Monthly infection risk maps across Europe could help guide targeted prevention and control measures, disrupt disease establishment in specific areas and seasons, and raise awareness about infection risks in both animals and humans.