Monthly analysis of the current risk of heartworm transmission in Portugal and Spain through ecological niche modeling as a control measure

Abstract

Heartworm disease (cardiopulmonary dirofilariosis) is a vector-borne parasitic disease caused by the parasitic nematode Dirofilaria immitis. It is transmitted by different species of culicid mosquitoes, with Culex pipiens being the most important species in the Iberian Peninsula, and Culex theileri in the Canary Islands and Madeira. The development of risk maps using ecological niche models (ENMs) has established itself as a useful tool in the prevention and control of various parasitic infections in different territories. The aim of this study was to produce monthly infection risk maps for all territories in Spain and Portugal, based on ecological modelling of Cx. pipiens in the Iberian Peninsula, the Islands and Madeira, and of Cx. pipiens together with Cx. theileri in the Canary Islands. These models were weighted with the number of generations of D. immitis calculated each month, thus obtaining infection risk maps for each month of the year. Models indicate that the risk of transmission is highest in summer, gradually decreasing in autumn until reaching zero levels in winter in most territories. In the Iberian Peninsula, the most affected areas are the south, the Mediterranean coast and the Balearic Islands. In the Canary Islands, the risk remains moderate during winter due to its thermal stability, especially in densely populated coastal areas. A similar pattern is observed in the Azores Islands and Madeira, where the risk, although lower, persists in winter and is concentrated in low-lying, inhabited areas. This approach allows the dynamics of heartworm infection to be studied throughout the year and constitutes the first time that monthly risk models have been developed in these territories, as well as the first risk maps for D. immitis transmission in the Azores Islands and Madeira.