New insights into the phylogeographic history of Dirofilaria immitis in the Canary Islands

Abstract

Dirofilaria immitis, a nematode that causes heartworm disease, is transmitted by mosquito vectors such as Culex spp., Aedes spp., and Anopheles spp.. It is prevalent worldwide, with increasing cases in Europe, particularly due to factors like globalization, pet movement, and climate change. In Spain and Portugal, the disease has high incidence variability, with islands like Gran Canaria showing particularly high prevalence rates. Although control measures have reduced the impact, reservoirs of the disease persist, necessitating ongoing monitoring. Diagnostic techniques, including serology and molecular methods, are crucial for identifying infections in hosts and vectors. Despite advancements in molecular diagnostics, genetic markers need further optimization to improve the understanding of the disease’s impact and predict future transmission patterns. Previous studies on the genetic diversity of D. immitis have shown low variability, but more research is needed in hyperendemic areas like Gran Canaria to better understand the disease’s evolution [1]. This study aims to analyze the genetic diversity in D. immitis from infected dogs in Gran Canaria, using mitochondrial and nuclear markers. Following primer optimization, we generated >100 new sequences and >40,000 bp from 21 worms present in different dogs across veterinary clinics. The genetic diversity and structure are low at the global level if we compare it with the results obtained for its sister species D. repens [2]. On the island of Gran Canaria, new minor haplotypes appear in the mitochondrial marker COI that seem to indicate that the disease originates there or comes from an introduction from the continent in historical times. Comparative studies with data from massive sequencing of endemic areas are needed to obtain a more robust view of their evolutionary history, structure and diversity at the genomic level. The data obtained here can help in the implementation of surveillance and control measures for this region.