Discover how ecological niche modeling predicts heartworm disease transmission in the Canary Islands and its future under climate change scenarios.
Imagine a parasite so adaptable it can thrive in one of the world's most diverse ecosystems—the Canary Islands. This isn't the plot of a science fiction novel but the reality of Dirofilaria immitis, commonly known as heartworm. This mosquito-borne nematode represents a growing threat to both animal and human health in this Spanish archipelago, which has become a natural laboratory for studying disease transmission in a warming world.
For decades, the Canary Islands have been known as a hyperendemic zone for heartworm, meaning infection rates here are among the highest in Europe. But what makes these islands so susceptible? And how is climate change altering the disease landscape? Scientists are now combining ecology, climatology, and veterinary medicine to answer these questions through an innovative approach called ecological niche modeling—creating "invisible maps" that predict where disease will strike next.
Heartworm (Dirofilaria immitis) is a parasitic nematode that infects the pulmonary arteries and hearts of mammals. While dogs are the primary host, the parasite can also infect cats, ferrets, and even humans, making it a significant zoonotic concern. The parasite can grow up to 30 centimeters in length and survive in dogs for up to seven years, causing severe cardiovascular and respiratory damage 8 .
Temperature plays a critical role in this process. The development of heartworm larvae within mosquitoes stops below 14°C, making climate a fundamental factor in determining where the disease can thrive 8 .
The Canary Islands' unique combination of climatic conditions makes them exceptionally suitable for heartworm transmission. Located off the coast of Western Sahara, the archipelago enjoys mild temperatures year-round, moderated by oceanic influences. However, significant microclimates exist across the islands, creating patches of high and low transmission risk.
The western islands—including Tenerife, La Palma, La Gomera, and Gran Canaria—feature higher altitudes and more varied topography, which influences both temperature and mosquito habitat availability. The eastern islands—Lanzarote and Fuerteventura—are drier and less elevated, resulting in lower transmission rates 2 5 .
Interactive visualization of transmission risk across the archipelago
| Island | Prevalence in Dogs | Classification | Risk Level |
|---|---|---|---|
| Tenerife | 17.32% | Hyperendemic | |
| Gran Canaria | 16.03% | Hyperendemic | |
| La Palma | 15.65% | Hyperendemic | |
| La Gomera | 11.54% | Hyperendemic | |
| Fuerteventura | 1.74% | Low endemic | |
| Lanzarote | 0.99% | Low endemic | |
| El Hierro | 0% | Disease-free |
The heterogeneous distribution of heartworm across the islands has puzzled scientists for decades. While some areas report infection rates exceeding 30% in dogs, others remain virtually disease-free. This patchwork pattern prompted researchers to investigate the environmental factors driving transmission 2 .
Ecological niche modeling (ENM) is a sophisticated scientific approach that predicts the geographic distribution of species based on environmental conditions they need to survive. In the case of heartworm, researchers don't just model the parasite itself, but also its mosquito vectors—primarily Culex theileri and Culex pipiens in the Canary Islands 2 5 .
The fundamental premise is simple but powerful: by understanding the environmental preferences of both the parasite and its vectors, scientists can map where transmission is most likely to occur. This approach has transformed our ability to predict disease outbreaks before they happen.
Ecological niche modeling integrates environmental data, vector distribution, and parasite biology
Determined by environmental conditions that support mosquito breeding and survival
The number of heartworm generations possible given local temperatures
Primarily infected dogs that maintain the parasite in the environment
By combining these factors, researchers have created the first comprehensive risk model specifically designed for the Canary Islands' unique environment.
In a groundbreaking 2023 study, researchers set out to develop a more accurate transmission risk model for heartworm in the Canary Islands. Their approach was meticulous and multi-faceted 2 5 :
| Tool/Technique | Function | Application |
|---|---|---|
| Geographic Information Systems (ArcMap 10) | Spatial analysis and mapping | Processed environmental variables and created risk maps |
| MaxEnt 3.4 Software | Ecological niche modeling | Predicted suitable habitats for mosquito vectors |
| Climate Projection Models (IPCC RCPs) | Future climate scenarios | Projected how risk would change by 2080 |
| Enzyme-linked Immunosorbent Assay (ELISA) | Detecting heartworm infections | Validated model predictions with actual infection data |
| Global Positioning System (GPS) | Precise location mapping | Georeferenced mosquito collection and infection sites |
The ecological niche model revealed clear patterns of transmission risk across the Canary Islands:
Perhaps most importantly, the model demonstrated remarkable accuracy—the vast majority of infected dogs were located in areas predicted to be high-risk, validating the ecological niche modeling approach.
Looking toward the future, the researchers made a surprising discovery. While many assume climate change will dramatically expand heartworm territory, the projections for 2080 tell a more nuanced story:
| Aspect of Change | Projected Impact | Implications |
|---|---|---|
| Overall area suitable for transmission | Increase of only 5.02% | Rather than dramatic expansion, distribution shifts |
| Optimal transmission zones | Movement from coastal to midland areas | Changing risk patterns require updated prevention strategies |
| Transmission season | Lengthening in midland and highland areas | Year-round prevention becomes more important |
| Geographic distribution | Altitudinal shift rather than simple expansion | New areas become at risk while some current areas may see reduced risk |
The research indicates that the most significant impact of climate change won't be a simple expansion of heartworm territory, but rather a redistribution of risk zones. As temperatures warm, optimal transmission conditions will shift from coastal areas toward the midlands, creating new at-risk regions that were previously protected by cooler temperatures.
Visualization of projected changes in transmission risk under different climate scenarios
Heartworm exemplifies the "One Health" concept—the understanding that human, animal, and environmental health are inextricably linked. While humans are "dead-end hosts" for heartworm (the parasite rarely completes its life cycle), infection can still cause significant health issues, primarily pulmonary nodules that are often mistaken for tumors in diagnostic imaging 3 9 .
Recent research in Gran Canaria has revealed an even more surprising connection between heartworm and human health. A 2025 study found that owners of infected dogs showed a significantly higher prevalence of allergic diseases compared to owners of uninfected dogs. This suggests that exposure to the parasite—even without full infection—may trigger immune responses that increase susceptibility to allergies 6 .
Comparative prevalence of allergic diseases in owners of infected vs. uninfected dogs
Owners of infected dogs show higher allergy rates
Cats are also vulnerable to heartworm, though their infections differ from those in dogs. Feline heartworm disease often presents as Heartworm Associated Respiratory Disease (HARD), with symptoms easily mistaken for asthma. A 2023 study found that cats seropositive for heartworm were six times more likely to show hypersensitivity to environmental allergens, further supporting the parasite-allergy connection .
The ecological niche modeling research in the Canary Islands represents a paradigm shift in how we approach heartworm prevention. By moving from reactive treatment to proactive prediction, veterinarians and public health officials can target prevention efforts more effectively than ever before.
The findings offer both warnings and reasons for hope. While climate change is shifting transmission patterns, the research demonstrates that strategic prevention can reduce heartworm prevalence even in hyperendemic areas. In Gran Canaria, concerted prevention efforts have already driven a remarkable decline in canine heartworm prevalence—from 67.02% in 1994 to 15.81% in 2020 3 9 .
As the climate continues to change, the "invisible maps" created through ecological niche modeling will become increasingly vital tools in protecting both animal and human health. The story of heartworm in the Canary Islands serves as a powerful reminder that in our interconnected world, understanding disease means understanding the complex relationships between parasites, hosts, vectors, and environment.
The future of disease prevention lies not just in treating the sick, but in understanding the ecological patterns that determine why some places become hotspots while others remain safe havens. Through this knowledge, we can work toward a world where heartworm—and other climate-sensitive diseases—lose their foothold, even as the planet changes around us.