Current state of canine heartworm in Portugal
Open accessAbstract
The favourable geo-climatic conditions in Portugal have made it highly conducive to the development of Dirofilaria immitis in dogs, leading to its identification as an endemic region. This nematode is rapidly spreading across Europe, particularly in northeastern countries. The objective of this study was to provide an updated assessment of the prevalence of this disease in Portuguese dogs, analysing the results in relation to epidemiological and geo-environmental factors, and to identify potential risk factors. A total of 1367 dogs from all continental and insular districts were included in the study and tested for D. immitis antigens. The overall prevalence was found to be 5.9%. It was observed that the disease is spreading northward, with previously unaffected districts now reporting cases, and that the prevalence in coastal districts exceeded that of inland ones. Notably, the Aveiro district exhibited a significant increase in D. immitis prevalence, while in certain districts such as Setúbal, Santarém, Madeira, or Faro, a stabilisation or decrease in prevalence was noted. Furthermore, outdoor and older dogs were found to be at a higher risk of infection. No positive cases were detected in the Azores. Most of the infected dogs were located in areas of high and medium risk of infection. This study underscores the importance of implementing pharmacological prophylaxis, vector control strategies, and public awareness programs to control the spread of this zoonotic disease.
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The general epidemiological profile identified in this study was characterized by middle-aged, mixed-breed, outdoor dogs from Mediterranean climate zones, consistent with previous descriptions in the veterinary literature.
“The general epidemiological profile identified in this study, characterized by middle-aged, mixed-breed, outdoor dogs from Mediterranean climate zones, is consistent with previous descriptions in the veterinary literature (4, 5, 12, 23).”
From Deciphering the socio-environmental factors associated with realized heartworm transmission risk in dogs from Portugal and Spain (2026) · cites this paper as [4]
The Results report higher prevalence among dogs aged 5–10 years and identify older age and outdoor lifestyle as risk factors. Our copy does not identify mixed breed as part of the profile, and the Results report no significant differences between climates. It therefore supports only part of the profile attributed to this paper. (LLM, conf=0.88)
Experimental — accuracy not yet measuredAge is not necessarily associated with a greater risk of infection per unit of time, but prevalence tends to increase with host age, most likely reflecting cumulative exposure over time in endemic areas.
“Likewise, although age is not necessarily associated with a greater risk of infection per unit of time, prevalence tends to increase with host age, most likely reflecting cumulative exposure over time in endemic areas (4, 5, 8–13).”
From Deciphering the socio-environmental factors associated with realized heartworm transmission risk in dogs from Portugal and Spain (2026) · cites this paper as [4]
The Results report that dogs older than five were more likely to test positive, and the Discussion suggests this may reflect more time in contact with infected vectors. The source does not assess infection risk per unit of time, and prevalence was lower in dogs over ten than in those aged five to ten, so it does not show a steady increase with age. (LLM, conf=0.84)
Experimental — accuracy not yet measuredIn Portugal, the national prevalence of D. immitis is approximately 5.9%, with higher values in the south reaching 9.4% and peaks up to 27.3% in central coastal areas.
“In Portugal, the national prevalence is approximately 5.9%, with higher values in the south reaching 9.4% and peaks of up to 27.3% in central coastal areas (4).”
From Deciphering the socio-environmental factors associated with realized heartworm transmission risk in dogs from Portugal and Spain (2026) · cites this paper as [4]
The Results report 5.9% prevalence among sampled Portuguese dogs, and the Discussion reports 27.3% in the central coastal area of Figueira da Foz. But the Discussion identifies the Algarve’s 9.4% as a 2015 figure and says its current prevalence is 8.8%; presenting 9.4% alongside the current national estimate without that distinction is misleading. Our copy provides section labels but no page numbers. (LLM, conf=0.90)
Experimental — accuracy not yet measuredEndophilic mosquito behavior may facilitate exposure inside dwellings, particularly in urban settings, and a lower perceived risk may reduce the use of chemoprophylaxis or repellents by owners.
“Endophilic mosquito behavior may facilitate exposure inside dwellings, particularly in urban settings, and a lower perceived risk may reduce the use of chemoprophylaxis or repellents by owners (4, 5).”
From Deciphering the socio-environmental factors associated with realized heartworm transmission risk in dogs from Portugal and Spain (2026) · cites this paper as [4]
The Discussion (page unavailable) reports infection in dogs kept mostly or strictly indoors and links low awareness among owners in northern Portugal to insufficient chemoprophylaxis. The Introduction (page unavailable) describes urban conditions favourable to mosquito vectors. Our copy does not attribute indoor exposure to endophilic mosquito behaviour or discuss reduced repellent use. (LLM, conf=0.86)
Experimental — accuracy not yet measuredThe results are consistent with previous studies reporting no clear breed or sex pre-disposition beyond differences attributable to management practices, such as those observed between hunting or working dogs and companion animals.
“Regarding intrinsic host factors, the results are consistent with previous studies reporting no clear breed or sex pre-disposition beyond differences attributable to management practices, such as those observed between hunting or working dogs and companion animals (4, 5, 10, 12, 26–29).”
From Deciphering the socio-environmental factors associated with realized heartworm transmission risk in dogs from Portugal and Spain (2026) · cites this paper as [4]
The Results report no statistically significant difference between male and female dogs, while the Results and Discussion identify outdoor lifestyle as a significant risk factor. The paper does not assess breed predisposition or compare hunting or working dogs with companion animals, so those parts of the attributed claim are unsupported (no page numbers provided). (LLM, conf=0.86)
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References 57 · Cited by 11
Research works printed but not linked: 1
- [35]Araujo A. Canine and human Dirofilaria immitis infections in Portugal. A review Parassitologia 1996 38 366
- Authors
- Esteves-Guimarães, J., Matos, J. I., Leal-Sousa, B., Oliveira, P., Lobo, L., Silvestre-Ferreira, A. C., Soares, C. S., Rodríguez-Escolar, I., Carretón, E., Morchón, R., Fontes-Sousa, A. P., & Montoya-Alonso, J. A.
- Affiliations
- Clínica Veterinária Aanifeira, 4520-409 Santa Maria da Feira, Portugal
- Universidad de Las Palmas de Gran Canaria (ES)
- Clínica dos Gatos (Portugal) (PT)
- Universidade do Porto (PT)
- Center for Animal and Veterinary Science (CECAV), Associate Laboratory for Animal and Veterinary Science (AL4AnimalS), Department of Veterinary Sciences, University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal
- University of Trás-os-Montes and Alto Douro (PT)
- Universidad de Salamanca (ES)
- Corresponding author
- Fontes-Sousa, Ana Patrícia
- ORCID
- Venue
- Animals
- Publisher
- MDPI AG
- Published
- 2024-04-25
- Volume
- 14
- Issue
- 9
- Pages
- 1300
- ISSN
- 2076-2615 (ISSN-L)
- PMC
- PMC11083104
- OpenAlex
- W4395672806
- Cited by
- 11
- References
- 57
- Citations by year
- 2026: 4 · 2025: 6 · 2024: 1
- FWCI
- 3.78
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Animals (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- Acceda (Universidad de Las Palmas de Gran Canaria) (submittedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT) (submittedVersion, cc-by)
- Funders
- ELANCO SPAIN S.L (CN-240/030/162, PIFULPGC-2017-CCSALUD-3, UIDB/04308/2020, UIDB/00772/2020)
- Grants for the financing of predoctoral contracts” programme of the Universidad de Las Palmas de Gran Canaria (CN-240/030/162, PIFULPGC-2017-CCSALUD-3, UIDB/04308/2020, UIDB/00772/2020)
- University of Salamanca-Banco Santander predoctoral scholarship (CN-240/030/162, PIFULPGC-2017-CCSALUD-3, UIDB/04308/2020, UIDB/00772/2020)
- Fundação para a Ciência e a Tecnologia (CN-240/030/162, PIFULPGC-2017-CCSALUD-3, UIDB/04308/2020, UIDB/00772/2020)
- Topics
- Health Sciences › Medicine › Infectious Diseases › Parasitic Diseases Research and Treatment
- Health Sciences › Veterinary › Small Animals › Helminth infection and control
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Research on Leishmaniasis Studies
- Keywords
- canine heartworm disease, Dirofilaria immitis, dogs, prevalence, Portugal, risk factors, geographic distribution, older dogs, zoonoses, vector control, prophylaxis, disease spread
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