Vectors, host range, and spatial distribution of Dirofilaria immitis and D. repens in Europe: a systematic review
Open accessPublished version of a preprint
Abstract
Background: Dirofilaria immitis and D. repens are mosquito-borne nematodes with dogs as primary hosts, but other mammalian species including humans can be also infected. In the last century, circulation of both pathogens was predominantly restricted to Southern Europe. However, different studies indicated a potential establishment in Central, Eastern and Western parts of Europe as an increasing threat to animal and human health. Therefore, we conducted a systematic literature review of Dirofilaria data in Europe to give a comprehensive overview of potential mosquito vectors and vertebrate hosts, including the collection of different metadata (e.g. sampling year and site), allowing to analyse the spread pattern of the parasites in Europe. Methods: On 24 January 2022, we conducted a systematic literature review of all available publications in the PubMed database reporting D. immitis and D. repens screening in mosquitoes and mammalian vertebrates in Europe. We only included acute infection of Dirofilaria spp., i.e. excluding studies only screening antibodies, and in addition noted the travel history and the accuracy of the sampling locations. These data were used to analyse the range of potential vectors and hosts and for a comparison of the spatial distribution between the twentieth and twenty-first century. Results: Both nematodes appear to have a high overlap of Aedes , Anopheles and Culex as potential vector species, which are abundant in Europe. Most published D. immitis infections were reported in dogs, while D. repens predominantly were reported in humans. Dirofilaria immitis infections were detected in a wider range of wild and zoo animals. Compared to the last century, many more countries especially in Central Europe were affected by Dirofilaria spp. circulation, illustrating a significant spread over the last 20 years. Conclusions: Our findings suggest that D. immitis and D. repens are a growing health concern for animals and humans in Europe. Continuous globalisation and climate warming will probably lead to a further spread and increased circulation in the future. All data are made available open access, which will enable further analysis. Graphical Abstract:
AI snapshot
Written from the paper’s full text.
TL;DR
This systematic review of European *Dirofilaria immitis* and *D. repens* found broad overlap in *Aedes*, *Anopheles*, and *Culex* potential vectors and a marked geographic expansion from Southern Europe into Central, Eastern, and Western Europe. Dogs were predominantly infected with *D. immitis*, while human cases were overwhelmingly *D. repens*.
Key findings
- From 3847 PubMed records, 473 (12.3%) met inclusion criteria. Mosquito screening included 38 publications (8.0%), 1,658,041 specimens, 62 mosquito taxa, and 14 European countries; *D. immitis* was detected in 17 taxa from 12 countries, *D. repens* in 31 species from 13 countries, and 15 taxa were positive for both.
- Dog infections were reported in 198 publications (41.9%), totaling 11,713 cases: 7757 (66.2%) *D. immitis*, 3948 (33.7%) *D. repens*, and 8 (0.1%) unspecified *Dirofilaria*. Human infections were reported in 199 publications (42.1%), totaling 2555 cases: 2438 (95.4%) *D. repens*, 95 (3.7%) unspecified, and 22 (0.9%) *D. immitis*.
- Cat infections were reported in 33 publications (7.0%), totaling 278 cases: 252 (90.1%) *D. immitis*, 24 (8.6%) *D. repens*, and 2 (0.7%) unspecified. Other mammals were reported in 59 publications (12.5%), mostly *D. immitis*, including wild carnivores and zoo animals.
- Until 2001, most *D. immitis* cases in dogs and other mammals were recorded in Southern Europe, especially Spain, Italy, and Portugal; no human cases were reported before 2001. In the twenty-first century, affected countries increased across South, Central, and Eastern Europe, with the most northern human infection reported in Finland.
Methods
- Systematic literature review of PubMed conducted on 24 January 2022 using the keyword “dirofilaria”; inclusion required English or German language, acute *Dirofilaria* infection (excluding antibody-only screening), and sampling in Europe.
- Data extracted included country, diagnosis/sampling date, sampling location, host species, travel history, screening method, and number tested/positive per *Dirofilaria* species; mosquito studies also recorded trap and pooling information.
- Spatial analysis classified sampling-location accuracy using NUTS levels and excluded reports with known travel history; visualizations and analyses were performed in R version 4.2.2.
Limitations
- The paper states that *D. repens* is probably underreported, particularly in dogs, because rapid diagnostic tests are available only for *D. immitis*; it also notes that factors making *D. repens* more successful in humans need further research, that other drivers such as landscape changes were not explored, and that mosquito/vertebrate studies show spatial bias toward Mediterranean and Southeast Europe, requiring more Central and Northern European studies.
- The text also makes evident a possible publication bias favoring novel wildlife-host findings, a diagnostic artefact from more routine testing of imported/travelling dogs, and the 2022 search date, which the authors describe as a starting point for future updates.
Model-written summary. Check it against the paper before relying on it.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
0 of 47 cited sources checked · 0 supported · 0 flagged
- Findingown data
Dirofilaria repens infections were reported for 31 different mosquito species from 13 European countries.
“Dirofilaria repens infections were reported for 31 different mosquito species from 13 countries with Aedes vexans (8 countries), Cx. pipiens s.l. (6 countries) and Anopheles maculipennis s.l. (6 countries) most frequently found positive.”
Quote in the paperNot a substantial claim - Findingnone given
The exotic Ae. albopictus was much more often reported to be infected with D. immitis than D. repens.
“Interestingly, the exotic Ae. albopictus was much more often reported to be infected with D. immitis than D. repens.”
Quote in the paperNot a substantial claim - Findingown data
Dirofilaria immitis was detected in 17 different mosquito taxa from 12 European countries.
“Dirofilaria immitis was detected in 17 different mosquito taxa from 12 countries, most frequently in Culex pipiens s.l. (11 countries) and Aedes caspius (7 countries).”
Quote in the paperNot a substantial claim - Findingcitation
Most published D. immitis infections in Europe were reported in dogs.
“Most published D. immitis infections were reported in dogs, while D. repens predominantly were reported in humans.”
- Also stated in: § Dirofilaria infections of animals · plain
“Most infections were reported from dogs as the primary host of Dirofilaria [1].”
Quote in the paperNot a substantial claim - Also stated in: § Dirofilaria infections of animals · plain
- Findingcitation
The number of publications reporting Dirofilaria spp. infections has increased in the last two decades compared to the previous century.
“The number of publications reporting Dirofilaria spp. infections have increased in the last two decades compared to the previous century [18, 22].”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [18] Genchi C, Kramer L. Subcutaneous dirofilariosis (Dirofilaria repens): an infection spreading throughout the old world. Parasit Vectors. 2017. https://doi.org/10.1186/s13071-017-2434-8. source
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- cites [22] Genchi C, Kramer LH. The prevalence of Dirofilaria immitis and D. repens in the Old World. Vet Parasitol. 2020;280:108995. https://doi.org/10.1016/j.vetpar.2019.108995. source
Not checked in the free run.
- Findingown data
Dirofilaria repens was exclusively found in 16 different mosquito taxa of the Aedes, Anopheles, Culiseta and Uranotaenia genus.
“Dirofilaria immitis was exclusively detected in Ae. behningi, while D. repens was exclusively found in 16 different taxa of the Aedes, Anopheles, Culiseta and the Uranotaenia genus, e.g. Ae. cantans, An. claviger, Cs. annulata or Ur. unguiculata.”
Quote in the paperNot a substantial claim - Findingown data
Dirofilaria were detected in a wide variety of wild carnivores and zoo animals in Europe.
“In addition, Dirofilaria were detected in a wide variety of wild carnivores [e.g. golden jackal (Canis aureus), grey wolf or Eurasian otter (Lutra lutra)] and zoo animals [e.g. lion (Panthera leo) or California sea lion (Zalophus californianus)].”
Quote in the paperNot a substantial claim - Findingreasoning
D. immitis infections were detected in a wider range of wild and zoo animals than D. repens.
“Dirofilaria immitis infections were detected in a wider range of wild and zoo animals.”
- Also stated in: § Dirofilaria infections of animals · hedged
“Zoo and wild animals were almost always infected by D. immitis, which again might be because D. immitis in comparison to D. repens infections more often leads to severe symptoms, corresponding test kits are available or because D. immitis has a broader host range.”
Quote in the paperNot a substantial claim - Also stated in: § Dirofilaria infections of animals · hedged
- Findingnone given
D. repens infections were predominantly reported in humans.
“Most published D. immitis infections were reported in dogs, while D. repens predominantly were reported in humans.”
- Also stated in: § Dirofilaria infections of humans · boosted
“In contrast to dogs, the overwhelming majority of cases in humans were caused by D. repens, confirming previous observations that most human Dirofilaria infections in Europe are caused by this species [67, 68].”
Quote in the paperSubstantial claim - Also stated in: § Dirofilaria infections of humans · boosted
- Findingown data
Dirofilaria immitis was exclusively detected in Ae. behningi among the mosquito taxa studied.
“Dirofilaria immitis was exclusively detected in Ae. behningi, while D. repens was exclusively found in 16 different taxa of the Aedes, Anopheles, Culiseta and the Uranotaenia genus, e.g. Ae. cantans, An. claviger, Cs. annulata or Ur. unguiculata.”
Quote in the paperNot a substantial claim - Findingown data
The majority of human Dirofilaria infections in Europe are caused by D. repens.
“In contrast to dogs, the overwhelming majority of cases in humans were caused by D. repens, confirming previous observations that most human Dirofilaria infections in Europe are caused by this species [67, 68].”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [67] Pampiglione S, Canestri Trotti G, Rivasi F. Human dirofilariasis due to Dirofilaria (Nochtiella) repens: a review of world literature. Parassitologia. 1995;37:149–93.
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- cites [68] Pampiglione S, Rivasi F. Human dirofilariasis due to Dirofilaria (Nochtiella) repens: an update of world literature from 1995 to 2000. Parassitologia. 2000;42:231–54.
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- Findingown data
A total of 15 mosquito taxa were found positive for both Dirofilaria species.
“A total of 15 mosquito taxa were found positive for both Dirofilaria species.”
Quote in the paperNot a substantial claim - Findingcitation
Both Dirofilaria immitis and D. repens have a high overlap of Aedes, Anopheles and Culex as potential vector species in Europe.
“Both nematodes appear to have a high overlap of Aedes, Anopheles and Culex as potential vector species, which are abundant in Europe.”
- Also stated in: § Dirofilaria infections of mosquitoes · boosted
“There is a huge overlap between the potential vector species for D. immitis and D. repens, which are widespread in Europe and show host-feeding patterns with a substantial proportion of mammals, e.g. Cx. pipiens s.l. or An. maculipennis s.l. [42–44].”
Quote in the paperSubstantial claim - Also stated in: § Dirofilaria infections of mosquitoes · boosted
- Findingnone given
No human cases were reported before 2001.
“No human cases were reported before 2001.”
Quote in the paperNot a substantial claim- Rests on an assumption: The absence of reported human cases before 2001 reflects a true absence of human cases rather than lack of reporting or diagnosis.
- Findingown data
The studies on Dirofilaria in mosquitoes and vertebrates indicate a spatial bias toward countries in the Mediterranean and Southeast Europe.
“Finally, the studies on Dirofilaria in mosquitoes and vertebrates (Figs. 3, 4) indicate a spatial bias toward countries in the Mediterranean and Southeast Europe, while additional studies in Central and Northern Europe are necessary to accurately assess the local risk of Dirofilaria transmission.”
Quote in the paperSubstantial claim - Findingown data
A total of 1,658,041 mosquito specimens were tested over 62 mosquito taxa collected in 14 different European countries.
“Thirty-eight publications (8.0%) included screenings of mosquitoes for Dirofilaria with a total of 1,658,041 specimens tested over 62 mosquito taxa collected in 14 different European countries (Fig. 3).”
Quote in the paperNot a substantial claim - Findingnone given
The most Northern infection was reported in humans from Finland.
“The most Northern infection was reported in humans from Finland.”
Quote in the paperNot a substantial claim - Findingown data
The majority of the few D. immitis cases in dogs and other mammals until 2001 were recorded in Southern Europe, particularly in Spain, Italy and Portugal.
“Only focusing on the studies with unremarkable travel history, the majority of the few D. immitis cases in dogs and other mammals until 2001 were recorded in Southern Europe, particularly in Spain, Italy and Portugal (Fig. 5; see supplementary file 1 and supplementary file 2 for visualisation of all cases with unremarkable and unknown travel history).”
Quote in the paperNot a substantial claim- Rests on an assumption: Unremarkable travel history in a report indicates that the infection was autochthonous (locally acquired) rather than imported.
- Findingown data
A wide distribution of D. immitis was confirmed in dogs and other mammals for wide parts of Eastern Europe and Italy.
“A wide distribution in particular was confirmed in dogs and other mammals for wide parts of Eastern Europe and Italy.”
Quote in the paperNot a substantial claim - Findingreasoning
There is a significant increase in areas at risk, especially in more Northern countries.
“There is a significant increase in areas at risk, especially in more Northern countries.”
Quote in the paperSubstantial claim - Findingown data
Thirty-eight publications (8.0%) included screenings of mosquitoes for Dirofilaria.
“Thirty-eight publications (8.0%) included screenings of mosquitoes for Dirofilaria with a total of 1,658,041 specimens tested over 62 mosquito taxa collected in 14 different European countries (Fig. 3).”
Quote in the paperNot a substantial claim - Findingcitation
Wild animals in which Dirofilaria infections were identified were predominantly canids like red foxes, golden jackals, and grey wolves.
“Furthermore, there are some wild animals in which Dirofilaria infections were identified, predominantly in canids like red foxes [4, 5, 51–62], golden jackals [52–55, 63, 64], and grey wolves [2, 3, 51, 52, 55, 65, 66].”
Quote in the paperNot a substantial claim0 of 10 sources checked- cites [4] Medkour H, Laidoudi Y, Marié J-L, Fenollar F, Davoust B, Mediannikov O. Molecular investigation of vector-borne pathogens in red foxes (Vulpes vulpes) from southern France. J Wildl Dis. 2020;56:837–50. https://doi.org/10.7589/2019-09-234. source
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- cites [52] Penezić A, Selaković S, Pavlović I, Ćirović D. First findings and prevalence of adult heartworms (Dirofilaria immitis) in wild carnivores from Serbia. Parasitol Res. 2014;113:3281–5. https://doi.org/10.1007/s00436-014-3991-9. source
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- cites [55] Cirović D, Penezić A, Pavlović I, Kulišić Z, Cosić N, Burazerović J, et al. First records of Dirofilaria repens in wild canids from the region of Central Balkan. Acta Vet Hung. 2014;62:481–8. https://doi.org/10.1556/AVet.2014.021. source
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- cites [56] Marconcini A, Magi M, Macchioni G, Sassetti M. Filariosis in foxes in Italy. Vet Res Commun. 1996;20:316–9. https://doi.org/10.1007/bf00366537. source
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- Interpretationreasoning
Dirofilaria immitis and D. repens are a growing health concern for animals and humans in Europe.
“Our findings suggest that D. immitis and D. repens are a growing health concern for animals and humans in Europe.”
- Also stated in: § Conclusions · plain
“Dirofilaria immitis and D. repens are an increasing threat to veterinary and public health in Europe.”
Quote in the paperSubstantial claim - Also stated in: § Conclusions · plain
- Interpretationcitation
Dirofilaria immitis and D. repens have to be considered endemic in countries that were considered Dirofilaria-free in the twentieth century, e.g. Czech Republic.
“Dirofilaria immitis and D. repens have to be considered endemic in countries that were considered to be Dirofilaria-free in the twentieth century, e.g. Czech Republic [40, 41].”
- Also stated in: § Conclusions · plain
“Both parasites have dramatically expanded their circulation area and are now endemic in areas that were considered Dirofilaria-free only one or two decades ago [23].”
Quote in the paperSubstantial claim0 of 3 sources checked- cites [40] Morchón R, Montoya-Alonso JA, Rodríguez-Escolar I, Carretón E. What has happened to heartworm disease in Europe in the last 10 years? Pathogens. 2022;11:1042. https://doi.org/10.3390/pathogens11091042. source
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- cites [41] Morchón R, Carretón E, González-Miguel J, Mellado-Hernández I. Heartworm disease (Dirofilaria immitis) and their vectors in Europe - new distribution trends. Front Physiol. 2012;3:196. https://doi.org/10.3389/fphys.2012.00196. source
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- cites [23] Masny A, Gołąb E, Cielecka D, Sałamatin R. Vector-borne helminths of dogs and humans - focus on central and eastern parts of Europe. Parasit Vectors. 2013;6:38. https://doi.org/10.1186/1756-3305-6-38. source
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- Also stated in: § Conclusions · plain
- Interpretationreasoning
Climate warming is probably one of the most important factors for the spread of Dirofilaria.
“However, probably one of the most important factors for the spread of Dirofilaria is climate warming.”
Quote in the paperSubstantial claim - Interpretationcitation
The spread of Dirofilaria in Europe is in part a diagnostic artefact, i.e. imported and travelling dogs are more routinely tested, leading to more detection.
“In part this might be also a diagnostic artefact, i.e. imported and travelling dogs are more routinely tested, which leads to more detection [39].”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [39] Genchi C, Bowman D, Drake J. Canine heartworm disease (Dirofilaria immitis) in Western Europe: survey of veterinary awareness and perceptions. Parasit Vectors. 2014;7:206. https://doi.org/10.1186/1756-3305-7-206. source
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- Premisecitation
Increasing temperatures in Europe have allowed the widespread establishment of exotic, daybiting mosquito species such as Ae. albopictus.
“Finally, increasing temperatures in Europe also allowed the widespread establishment of exotic, daybiting mosquito species such as Ae. albopictus [79–81], which is an important potential vector for D. immitis and D. repens and the establishment of the species in numerous European regions has been linked to increased Dirofilaria circulation [22].”
Quote in the paperSubstantial claim0 of 3 sources checked- cites [79] Miranda MÁ, Barceló C, Arnoldi D, Augsten X, Bakran-Lebl K, Balatsos G, et al. AIMSurv: first pan-European harmonized surveillance of Aedes invasive mosquito species of relevance for human vector-borne diseases. GigaByte. 2022. https://doi.org/10.46471/gigabyte.57. source
Not checked in the free run.
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- Interpretationreasoning
The warming climate and the abundant presence of potential competent vectors allows the establishment of the parasites in Central Europe, e.g. Germany and Poland.
“The warming climate and the abundant presence of potential competent vectors allows the establishment of the parasites in Central Europe, e.g. Germany and Poland.”
Quote in the paperSubstantial claim - Premisecitation
High numbers of stray dogs in some countries act as reservoirs for Dirofilaria parasites.
“Another reason is the continuously high number of stray dogs in some countries, which are not subject to regular treatment and act as reservoirs for the parasites, e.g. countries with many stray dogs, such as Romania or Bulgaria continue to regularly report Dirofilaria spp. cases [74–76].”
Quote in the paperSubstantial claim0 of 3 sources checked- cites [74] Hamel D, Silaghi C, Lescai D, Pfister K. Epidemiological aspects on vector-borne infections in stray and pet dogs from Romania and Hungary with focus on Babesia spp. Parasitol Res. 2012;110:1537–45. https://doi.org/10.1007/s00436-011-2659-y. source
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- cites [75] Ciucă L, Musella V, Miron LD, Maurelli MP, Cringoli G, Bosco A, et al. Geographic distribution of canine heartworm (Dirofilaria immitis) infection in stray dogs of eastern Romania. Geospat Health. 2016;11:499. https://doi.org/10.4081/gh.2016.499. source
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- Premisecitation
Outdoor keeping of dogs is considered a crucial factor leading to a higher risk for mosquito bites compared to dogs kept inside.
“Besides climate warming and stray dogs, outdoor keeping of dogs is considered a crucial factor, leading to a higher risk for mosquito bites compared to dogs kept inside [45].”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [45] Fuehrer H-P, Morelli S, Unterköfler MS, Bajer A, Bakran-Lebl K, Dwużnik-Szarek D, et al. Dirofilaria spp. and Angiostrongylus vasorum: current risk of spreading in Central and Northern Europe. Pathogens. 2021;10:1268. https://doi.org/10.3390/pathogens10101268. source
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- Premisecitation
Prolonged warm periods extend the transmission season.
“Prolonged warm periods extend the transmission season [11].”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [11] Genchi C, Kramer LH, Rivasi F. Dirofilarial infections in Europe. Vector Borne Zoonotic Dis. 2011;11:1307–17. https://doi.org/10.1089/vbz.2010.0247. source
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- Premisecitation
The establishment of Ae. albopictus in numerous European regions has been linked to increased Dirofilaria circulation.
“Finally, increasing temperatures in Europe also allowed the widespread establishment of exotic, daybiting mosquito species such as Ae. albopictus [79–81], which is an important potential vector for D. immitis and D. repens and the establishment of the species in numerous European regions has been linked to increased Dirofilaria circulation [22].”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [22] Genchi C, Kramer LH. The prevalence of Dirofilaria immitis and D. repens in the Old World. Vet Parasitol. 2020;280:108995. https://doi.org/10.1016/j.vetpar.2019.108995. source
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- Premisecitation
Higher temperatures lead to faster development of Dirofilaria larvae inside the mosquito vector.
“Higher temperatures lead to faster development of Dirofilaria larvae inside the mosquito vector [77, 78].”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [77] Fortin JF, Slocombe J. Temperature requirements for the development of Dirofilaria immitis in Aedes triseriatus and Ae. vexans. Mosq News. 1981;41:625–33.
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- cites [78] Cancrini G, Pietrobelli M, Frangipane di Regalbono AF, Tampieri MP, della Torre A. Development of Dirofilaria and Setaria nematodes in Aedes albopictus. Parassitologia. 1995;37:141–5.
Not checked in the free run.
- Premisecitation
Ae. albopictus is an important potential vector for D. immitis and D. repens.
“Finally, increasing temperatures in Europe also allowed the widespread establishment of exotic, daybiting mosquito species such as Ae. albopictus [79–81], which is an important potential vector for D. immitis and D. repens and the establishment of the species in numerous European regions has been linked to increased Dirofilaria circulation [22].”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [22] Genchi C, Kramer LH. The prevalence of Dirofilaria immitis and D. repens in the Old World. Vet Parasitol. 2020;280:108995. https://doi.org/10.1016/j.vetpar.2019.108995. source
Not checked in the free run.
- Premisereasoning
There is a significant difference in the severity of disease in the animal host between D. repens and D. immitis.
“As discussed in detail above, there is a significant difference in the severity of disease in the animal host between D. repens and D. immitis.”
Quote in the paperSubstantial claim - Interpretationcitation
Several other mammalian species diagnosed with an infection were held in zoos or as pets, allowing diagnosis.
“Similarly, several other mammalian species diagnosed with an infection were held in zoos or as pets, allowing diagnosis [47–50].”
Quote in the paperNot a substantial claim0 of 4 sources checked- cites [47] Mazzariol S, Cassini R, Voltan L, Aresu L, Di Regalbono F, Heartworm A. Dirofilaria immitis infection in a leopard (Panthera pardus pardus) housed in a zoological park in north-eastern Italy. Parasit Vectors. 2010;3:25. https://doi.org/10.1186/1756-3305-3-25. source
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- cites [48] Alho AM, Marcelino I, Colella V, Flanagan C, Silva N, Correia JJ, et al. Dirofilaria immitis in pinnipeds and a new host record. Parasit Vectors. 2017;10:142. https://doi.org/10.1186/s13071-017-2073-0. source
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- cites [49] Molnár V, Pazár P, Rigó D, Máthé D, Fok E, Glávits R, et al. Autochthonous Dirofilaria immitis infection in a ferret with aberrant larval migration in Europe. J Small Anim Pract. 2010;51:393–6. https://doi.org/10.1111/j.1748-5827.2010.00950.x. source
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- cites [50] Ruiz de Ybáñez MR, Martínez-Carrasco C, Martínez JJ, Ortiz JM, Attout T, Bain O. Dirofilaria immitis in an African lion (Panthera leo). Vet Rec. 2006;158:240–2. https://doi.org/10.1136/vr.158.7.240. source
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- May combine two claims. 20
- Classified as probably not a substantial claim. 6
May combine two claims.
Findingown dataA total of 33 publications reported Dirofilaria infections in cats (278 cases): 252 (90.1%) D. immitis, 24 (8.6%) D. repens, and 2 (0.7%) not further specified.
“Only 33 publications (7.0%) reported Dirofilaria infections in cats (278 cases): 252 (90.1%) D. immitis, 24 (8.6%) D. repens and two (0.7%) not further specified Dirofilaria species.”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataCompared to the twentieth century, many more countries, especially in Central Europe, were affected by Dirofilaria spp. circulation, illustrating a significant spread over the last 20 years.
“Compared to the last century, many more countries especially in Central Europe were affected by Dirofilaria spp. circulation, illustrating a significant spread over the last 20 years.”
- Also stated in: § Dirofilaria infections of humans · boosted
“We observed a strong increase of affected countries for both humans and dogs, including countries in Eastern and Southern Europe (e.g. Ukraine, Slovakia, Greece), but also Central Europe including the Netherlands, Germany or Poland.”
Quote in the paperSubstantial claim- Also stated in: § Dirofilaria infections of humans · boosted
May combine two claims.
Findingown dataA total of 198 publications reported dog infections, with 11,713 cases; 7757 (66.2%) were D. immitis, 3948 (33.7%) D. repens, and 8 (0.1%) were not further differentiated.
“A total of 198 publications (accounting for 41.9% of the included publications) reported dog infections, with a total of 11,713 cases. Of these, 7757 (66.2%) were identified as D. immitis, 3948 (33.7%) as D. repens, and eight (0.1%) were not further differentiated Dirofilaria species.”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataA total of 199 publications described human Dirofilaria spp. infections, summing to 2555 reported human cases; 2438 (95.4%) were D. repens, 95 (3.7%) not further specified, and 22 (0.9%) D. immitis.
“In 199 publications (42.1%), human Dirofilaria spp. infections were described, summing up to 2555 reported human cases, of which the majority of 2438 (95.4%) were D. repens, followed by 95 (3.7%) not further specified Dirofilaria spp. and 22 (0.9%) D. immitis.”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataA total of 59 publications described Dirofilaria infection in other mammals, the majority of which were caused by D. immitis.
“In addition, 59 publications (12.5%) described Dirofilaria infection in other mammals, the majority of which were caused by D. immitis (Fig. 4).”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataMost studies on Dirofilaria prevalence in mosquitoes focused on Southern and Eastern Europe, but some studies also confirmed autochthonous circulation in Central Europe, e.g. Austria or Germany.
“Most studies on Dirofilaria prevalence in mosquitoes focused on Southern and Eastern Europe, but some studies also confirmed autochthonous circulation in Central Europe, e.g. Austria or Germany.”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataIn the twenty-first century, D. immitis infections were found in most countries of South and Central Europe and even in Central Europe, such as Poland and France.
“In the twenty-first century, D. immitis infections were found in most countries of South and Central Europe and even in Central Europe, such as Poland and France.”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataDirofilaria repens infections, especially human cases, were reported much more widespread than D. immitis already during the twentieth century in various regions in Italy and France, while dogs were only tested positive in Italy and Spain.
“Dirofilaria repens infections, especially looking into human cases, were reported much more widespread than D. immitis already during the twentieth century in particular for various regions in Italy and France, while dogs were only tested positive in Italy and Spain (Fig. 6).”
Quote in the paperNot a substantial claimProbably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
Findingown dataA total of 3847 publications were extracted from PubMed, of which 473 (12.3%) matched inclusion criteria.
“A total of 3847 publications were extracted from PubMed. Of these, 473 (12.3%) matched our inclusion criteria (Fig. 1).”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataThe number of publications reporting Dirofilaria increased from the beginning of the 1990s and another increase in the mid-2000s.
“We observed an increase in publications reporting Dirofilaria from the beginning of the 1990s and another increase in the mid-2000s (Fig. 2).”
Quote in the paperNot a substantial claimMay combine two claims.
PremisecitationRapid tests are only available for D. immitis and not for D. repens.
“Additionally, rapid tests are only available for D. immitis and not D. repens.”
- Also stated in: § Dirofilaria infections of humans · plain
“as mentioned above, rapid tests are only available for D. immitis and current preventative and curative treatments are designed for D. immitis and are not as effective against D. repens [18].”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [18] Genchi C, Kramer L. Subcutaneous dirofilariosis (Dirofilaria repens): an infection spreading throughout the old world. Parasit Vectors. 2017. https://doi.org/10.1186/s13071-017-2434-8. source
Not checked in the free run.
- Also stated in: § Dirofilaria infections of humans · plain
May combine two claims.
InterpretationcitationThe increase in publications reporting Dirofilaria spp. infections is most likely driven by both increased research and awareness, but also the spread of the parasites.
“This is most likely driven by both increased research and awareness, but also the spread of the parasites [25, 39].”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [25] Genchi C, Rinaldi L, Cascone C, Mortarino M, Cringoli G. Is heartworm disease really spreading in Europe? Vet Parasitol. 2005;133:137–48. https://doi.org/10.1016/j.vetpar.2005.04.009. source
Not checked in the free run.
- cites [39] Genchi C, Bowman D, Drake J. Canine heartworm disease (Dirofilaria immitis) in Western Europe: survey of veterinary awareness and perceptions. Parasit Vectors. 2014;7:206. https://doi.org/10.1186/1756-3305-7-206. source
Not checked in the free run.
May combine two claims.
InterpretationreasoningDirofilaria repens might be underreported and its actual prevalence among dogs is probably higher due to lack of rapid diagnostic tests.
“Therefore, D. repens might be underreported and its actual prevalence among dogs is probably higher [11].”
- Also stated in: § Limitations of this study · hedged
“Therefore, D. repens infections are probably underreported, particularly in dogs, due to the lack of rapid diagnostic tests.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [11] Genchi C, Kramer LH, Rivasi F. Dirofilarial infections in Europe. Vector Borne Zoonotic Dis. 2011;11:1307–17. https://doi.org/10.1089/vbz.2010.0247. source
Not checked in the free run.
- Also stated in: § Limitations of this study · hedged
May combine two claims.
InterpretationcitationContinuous globalisation and climate warming will probably lead to a further spread and increased circulation of D. immitis and D. repens in the future.
“Continuous globalisation and climate warming will probably lead to a further spread and increased circulation in the future.”
- Also stated in: § Spread of Dirofilaria in Europe · hedged
“This spread has been predicted since the early 2000s [25, 73] and with continuous climate warming will further increase in the future.”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [25] Genchi C, Rinaldi L, Cascone C, Mortarino M, Cringoli G. Is heartworm disease really spreading in Europe? Vet Parasitol. 2005;133:137–48. https://doi.org/10.1016/j.vetpar.2005.04.009. source
Not checked in the free run.
- cites [73] Genchi C, Mortarino M, Rinaldi L, Cringoli G, Traldi G, Genchi M. Changing climate and changing vector-borne disease distribution: the example of Dirofilaria in Europe. Vet Parasitol. 2011;176:295–9. https://doi.org/10.1016/j.vetpar.2011.01.012. source
Not checked in the free run.
- Also stated in: § Spread of Dirofilaria in Europe · hedged
Probably not a substantial claim: may not pass S3 (load-bearing).
PremisecitationDirofilaria repens impedes the spread of D. immitis in dogs in Southern Italy.
“Another explanation could be that D. repens influences the circulation of D. immitis, e.g. it has been shown for Southern Italy that D. repens impedes the spread of D. immitis in dogs [72].”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [72] Genchi C, Basano S, Bandi F, Sacco D, Venco B, Vezzoni L. Factors influencing the spread of heartworms in Italy Interaction between Dirofilaria immitis and Dirofilaria repens. Baravia: American Heartworm Society; 1995. p. 65–71.
Not checked in the free run.
May combine two claims.
InterpretationreasoningDirofilaria immitis and D. repens are spreading in Europe and more humans and animals are at risk of infection.
“It is undeniable that both, D. immitis and D. repens, are spreading in Europe and more humans and animals are at risk of infection.”
Quote in the paperSubstantial claimMay combine two claims.
PremisecitationDirofilaria repens infections are often asymptomatic in dogs, which might lead to a longer time period where a dog is infective.
“Additionally, D. repens infections are often asymptomatic in dogs which might lead to a longer time period where a dog is infective, and a mosquito can ingest and transmit the parasite to further hosts [6, 73].”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [6] Simón F, Siles-Lucas M, Morchón R, González-Miguel J, Mellado I, Carretón E, et al. Human and animal dirofilariasis: the emergence of a zoonotic mosaic. Clin Microbiol Rev. 2012;25:507–44. source
Not checked in the free run.
- cites [73] Genchi C, Mortarino M, Rinaldi L, Cringoli G, Traldi G, Genchi M. Changing climate and changing vector-borne disease distribution: the example of Dirofilaria in Europe. Vet Parasitol. 2011;176:295–9. https://doi.org/10.1016/j.vetpar.2011.01.012. source
Not checked in the free run.
May combine two claims.
PremisecitationTransport of pets has significantly increased during the twenty-first century as a consequence of the Pet Travel Scheme introduced by the European Union in 2000, leading to an increase in imported cases.
“Transport of pets has significantly increased during the twenty-first century as a consequence of the Pet Travel Scheme, which was introduced by the European Union in 2000 and made travel of companion animals significantly easier and led to an increase in imported cases [27].”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [27] Trotz-Williams LA, Trees AJ. Systematic review of the distribution of the major vector-borne parasitic infections in dogs and cats in Europe. Vet Rec. 2003;152:97–105. https://doi.org/10.1136/vr.152.4.97. source
Not checked in the free run.
Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing). May combine two claims.
InterpretationcitationDirofilaria repens is more difficult to control because rapid tests are only available for D. immitis and current preventative and curative treatments are designed for D. immitis and are not as effective against D. repens.
“Furthermore, it has been proposed that D. repens is more difficult to control, because, as mentioned above, rapid tests are only available for D. immitis and current preventative and curative treatments are designed for D. immitis and are not as effective against D. repens [18].”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [18] Genchi C, Kramer L. Subcutaneous dirofilariosis (Dirofilaria repens): an infection spreading throughout the old world. Parasit Vectors. 2017. https://doi.org/10.1186/s13071-017-2434-8. source
Not checked in the free run.
May combine two claims.
InterpretationcitationThe majority of dog cases were caused by D. immitis, which is well known to cause a more severe disease in dogs compared to D. repens, leading to a higher probability of diagnosis.
“The majority of these cases were caused by D. immitis, which is well known to cause a more severe disease in dogs compared to D. repens, leading to a higher probability of diagnosis [7].”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [7] Bowman DD, Atkins CE. Heartworm biology, treatment, and control. Vet Clin North Am Small Anim Pract. 2009;39:1127–58. https://doi.org/10.1016/j.cvsm.2009.06.003. source
Not checked in the free run.
Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).
Interpretationnone givenThe higher number of publications on wild or uncommon hosts compared to dogs is probably attributed to a publication bias favouring novel findings in wildlife species.
“However, it has to be kept in mind that the higher number of publications on wild or uncommon hosts compared to dogs probably are attributed to a publication bias favouring novel finding in wildlife species.”
Quote in the paperNot a substantial claimProbably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
InterpretationreasoningZoo and wild animals were almost always infected by D. immitis, which might be because D. immitis more often leads to severe symptoms, corresponding test kits are available, or because D. immitis has a broader host range.
“Zoo and wild animals were almost always infected by D. immitis, which again might be because D. immitis in comparison to D. repens infections more often leads to severe symptoms, corresponding test kits are available or because D. immitis has a broader host range.”
Quote in the paperNot a substantial claimProbably not a substantial claim: may not pass S3 (load-bearing).
PremisecitationCats are assumed not to play an important role for Dirofilaria transmission.
“Besides dogs and humans, there were also several reports of infections in cats, although it is assumed that cats do not play an important role for Dirofilaria transmission [46].”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [46] Lee ACY, Atkins CE. Understanding feline heartworm infection: disease, diagnosis, and treatment. Top Companion Anim Med. 2010;25:224–30. https://doi.org/10.1053/j.tcam.2010.09.003. source
Not checked in the free run.
The paper relies on this without support.
Unremarkable travel history in a report indicates that the infection was autochthonous (locally acquired) rather than imported.
“For the spatial analysis of the Dirofilaria distribution, we only included reports with unremarkable travel history.”
“Reports with a known travel history were excluded from analysis.”
The paper relies on this without support.
The absence of reported human cases before 2001 reflects a true absence of human cases rather than lack of reporting or diagnosis.
“No human cases were reported before 2001.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
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 [12]
In Results and discussion, “Spread of Dirofilaria in Europe” identifies outdoor keeping as a risk factor for dogs; “Dirofilaria infections of humans” reports dog infections in Southern Europe. The source does not describe a general profile of middle-aged, mixed-breed dogs from Mediterranean climate zones, so it supports only part of the attributed comparison. (LLM, conf=0.85)
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 [12]
The Results and discussion sections on animal infections and spread in Europe discuss hosts, geography, and transmission factors, but not whether prevalence rises with host age. Searches for age-related prevalence and cumulative exposure found no passage addressing the claim or distinguishing prevalence from infection risk per unit of time. (LLM, conf=0.76)
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 [12]
The Results and discussion section on animal infections reports cases by host species, but does not assess breed or sex predisposition in dogs. Searches for breed, hunting dogs, and management practices found no passage comparing hunting or working dogs with companion animals or attributing differences to their management. Page numbers were not available in our copy. (LLM, conf=0.75)
Experimental — accuracy not yet measured
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Mosquito-taxon counts imply two taxa exclusive to D. immitis
MinorIf D. immitis was found in 17 taxa and 15 taxa were positive for both species, two taxa-not just Ae. behningi-were positive exclusively for D. immitis.
“Dirofilaria immitis was detected in 17 different mosquito taxa from 12 countries”
“A total of 15 mosquito taxa were found positive for both Dirofilaria species. Dirofilaria immitis was exclusively detected in Ae. behningi”
The citation lists haven’t been fetched yet
References 76 · Cited by 22
Research works printed but not linked: 3
- Birago F. Trattato cinegetico, ovvero della caccia. Milan: Sfondrato V; 1626. p. 77.
- PubMed. National Library of Medicine. 2025. https://pubmed.ncbi.nlm.nih.gov/. Accessed 29 Mar 2025.
- Gavrilović P, Blitva-Robertson G, Özvegy J, Kiskároly F, Becskei Z. Case report of dirofilariasis in gray wolf in Serbia. Acta Parasitol. 2015;60:175–8.
- Authors
- Hattendorf, C., & Lühken, R.
- Affiliations
- Bernhard Nocht Institute for Tropical Medicine (DE)
- Corresponding author
- Lühken, Renke
- ORCID
- Lühken, Renke
- Venue
- Infectious Diseases of Poverty
- Published
- 2025-07-02
- Volume
- 14
- Issue
- 1
- Pages
- 58-58
- ISSN
- 2049-9957 (ISSN-L)
- PMC
- PMC12217203
- OpenAlex
- W4411919973
- Semantic Scholar
- fd358e026527de814b0c623fc5d23f945fea46e3
- Cited by
- 22
- References
- 76
- Citations by year
- 2026: 17 · 2025: 5
- FWCI
- 3.85
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Locations
- Infectious Diseases of Poverty (publishedVersion, cc-by)
- bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion, cc-by-nc)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Funders
- Bundesministerium für Bildung und Forschung (01Kl2022)
- Bernhard-Nocht-Institut für Tropenmedizin
- 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
- Dirofilaria immitis, Dirofilaria repens, canine heartworm disease, lymphatic filariasis, mosquito vectors, Aedes, Anopheles, Culex, host range, spatial distribution, disease spread, dogs, human, wildlife, Europe, global warming, globalization
- MeSH terms
- Mosquito Vectors, Animals, Dirofilaria immitis, Dirofilariasis, Dog Diseases, Dogs, Europe, Humans, Host Specificity, Dirofilaria repens
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