Skip to main content
NCBI home page
Veterinary Medicine and Science logoLink to Veterinary Medicine and Science
. 2025 Jun 26;11(4):e70394. doi: 10.1002/vms3.70394

Diagnosis and Treatment of Dirofilaria immitis in Two Cats From Italy

Mariaelisa Carbonara 1, Luigi Venco 2, Elena Bossolini 3, Giulia Roncetti 4, Vanessa R Barrs 5, Domenico Otranto 1,6,✉
PMCID: PMC12199810  PMID: 40569920

ABSTRACT

Dirofilaria immitis is a mosquito‐borne filarioid that primarily infects dogs. Infection of cats is infrequent, and diagnosis of feline cardiopulmonary dirofilariosis may be overlooked. Here we describe D. immitis infections in two cats from Central‐Northern Italy, where heartworm disease is endemic in dogs. Both cats tested positive on a rapid heartworm point of care (POC) antigen test. Case 1, a 13‐year‐old male castrated domestic shorthair (DSH) cat was investigated for progressive respiratory signs, including cough, nasal discharge, dyspnea and reverse sneezing. By contrast, Case 2, a 7‐year‐old male entire free‐roaming colony cat with a fractured right tibia, tested positive during pre‐surgical screening tests. Both cases were seropositive for Dirofilaria species anti‐IgG. A duplex real‐time PCR (dqPCR) for D. immitis and D. repens was positive for D. immitis DNA in Case 1 and negative in Case 2. Conventional PCR and sequencing of partial cox1 and 12S rRNA genes confirmed D. immitis infection in Case 1. Echocardiography displayed the presence of adult heartworms in the right heart and main pulmonary artery in both cases. These clinical cases highlight the importance of using a combination of antigenic, serological and diagnostic imaging tests to confirm dirofilariosis in cats. Dirofilariosis should be included in the differential diagnoses for cats living in Dirofilaria spp. endemic areas.

Keywords: cats, diagnosis, feline dirofilariosis, heartworm disease

Feline dirofilariosis is infrequent, and diagnosis may be overlooked. This study reports two cases of Dirofilaria immitis infections in cats from Central‐Northern Italy, diagnosed by both direct (antigenic test, molecular analyses) and indirect detection methods (indirect ELISA), as well as by imaging investigations (i.e., thoracic radiography and echocardiography).

graphic file with name VMS3-11-e70394-g002.jpg

1. Introduction

Among zoonotic mosquito‐transmitted filarioids, Dirofilaria immitis is the causative agent of heartworm disease (HWD), infecting primarily dogs but also cats (Perles et al. 2024). Compared to dogs, domestic felids are less suitable hosts, likely due to their protective immunological response (Morchón et al. 2004). Nematode development in the feline host is usually interrupted at immature adult stages (McTier et al. 2000). However, when adult nematodes develop in cats, parasitic burdens are typically low or characterized by occult infection, with no or transient microfilaremia. In addition, cats often harbour male‐only infections and/or aberrant parasite localization (McCall et al. 1992). Consequently, the prevalence of D. immitis infection in cats may be underreported in comparison with dogs (Venco et al. 2011; Carbonara et al.2025). Although from an epidemiological view, infected cats are unimportant reservoir hosts, from a clinical perspective, they may develop severe disease (Venco et al. 2015). The migration of immature adults to the pulmonary arteries and the subsequent death of many of them causes acute vascular and pulmonary inflammation known as heartworm‐associated respiratory disease (HARD), which may be subclinical or associated with acute or chronic clinical signs (Pennisi et al. 2020).

Chronic, mild to moderate respiratory signs, including dyspnoea, tachypnoea and coughing, are the most common clinical manifestations of D. immitis infection in cats. Vomiting unrelated to eating is also common, and some cats may present with hyporexia and low body condition score (Venco et al. 2015; Alberigi et al. 2022). Immune system downregulation ceases upon nematode death, and their fragmentation is associated with severe inflammatory and thromboembolic disease resulting in sudden or acute death in approximately 20% of cats (Dillon et al. 2017; Nelson and Johnson 2024). Clinical signs may subside when L5 larvae mature into adult nematodes, which downregulate pulmonary intravascular macrophages (Venco et al. 2015). In cats with D. immitis infection, there is typically a low burden of 1–3 adult heartworms with a lifespan of 2–4 years (Dillon et al. 2007).

Definitive ante mortem diagnosis of D. immitis infection can be difficult in cats due to non‐specific clinical signs, the lack of detectable microfilaremia (by Knott's modified test or PCR), the absence of detectable female antigens (by rapid antigen point of care [POC] tests) and antibody cross‐reactivity between D. immitis and Dirofilaria repens on indirect serological assays (in‐house enzyme‐linked immunosorbent assay, ELISA) (Venco et al. 2015; Pękacz et al. 2024). Thoracic radiography and echocardiography should be utilised routinely in clinical investigations for feline cardiopulmonary dirofilariosis (Litster and Atwel 2008).

In addition, lungworm parasites, such as Aelurostrongylus abstrusus and Troglostrongylus brevior, may cause similar clinical presentations (Giannelli et al. 2017). Although the latter nematodes are frequently considered causative agents of feline respiratory disease, dirofilariosis by D. immitis is often neglected and may not be tested for during initial diagnostic investigations (Nelson and Johnson 2024). Therefore, it is important to describe clinical cases of confirmed feline dirofilariosis to raise awareness of this disease, especially in endemic areas. This study reports two cases of D. immitis infections in cats from Central‐Northern Italy, diagnosed by both direct (antigenic test, molecular analyses) and indirect detection methods (indirect ELISA), as well as by imaging investigations (i.e., thoracic radiography and echocardiography).

2. Case Presentations

2.1. Case 1

In February 2024, a 13‐year‐old male neutered domestic shorthair cat (DSH) was presented to a private clinic in Grosseto Province (Toscana region, Central‐Northern Italy) with a 1‐month history of respiratory signs, including sporadic cough, nasal discharge, dyspnea and reverse sneezing, as well as intermittent vomiting. The cat had a mixed outdoor/indoor lifestyle and was not treated with antiparasiticides. Physical examination was unremarkable, and results of a complete blood count and serum biochemistry profile were within reference ranges. A complete blood count and blood smear evaluation were unremarkable, in particular with no microfilariae observed. Results of a POC immunochromatographic test for feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) were negative. Symptomatic therapy for vomiting was prescribed (maropitant, 1 mg/kg subcutaneous injection once a day; esomeprazole 1 mg/kg q 24 h PO and sucralfate, 250 mg q 7 h PO).

Five months later, in July 2024, the cat was represented for worsening respiratory signs with more severe and frequent coughing. The cat was now wheezing and displayed accentuated and frequent swallowing. Mild tachycardia (heart rate 190 bpm) and tachypnoea (respiratory rate 30 bpm) were noted, and a gallop rhythm was detected on cardiopulmonary auscultation. The remainder of routine physical examination was unremarkable. The animal weighed 4.5 kg and had normal body condition score of 4.5/9.

Thoracic radiographs showed a diffuse bronchointerstitial pattern and enlargement of the right pulmonary artery (Figure 1A,B). An antigen test for D. immitis, targeting female antigens, was positive (SNAP Heartworm RT Test, IDEXX Veterinary Diagnostics, Maines, USA). Echocardiography was performed under sedation with butorphanol (0.2 mg/kg IM), and the presence of adult nematodes in the right heart and pulmonary arteries was demonstrated, along with tricuspid valve regurgitation (Videos SA and SB). The cat was treated with methylprednisolone acetate (20 mg SC) on 15 September 2024 and again 1 month later. One week after the first injection, although it was not possible to physically reassess the cat, the owner reported resolution of all respiratory signs and resumption of the cat's normal behaviour and activity levels.

FIGURE 1.

FIGURE 1

Open in a new tab

Thoracic radiographs (A: right lateral view; B: dorsal ventral view) of Cat 1 with diffuse interstitial‐alveolar pattern and enlargement of the right pulmonary artery.

In September 2024, echocardiography was repeated and was unchanged compared with the previous examination in July 2024. Blood and serum samples were shipped to the Department of Veterinary Medicine, University of Bari (Italy), to perform indirect detection of Dirofilaria spp. antibodies (ELISA) and molecular confirmation (PCR). An in‐house ELISA to detect antibodies, based on somatic antigens of adult D. immitis nematodes, was positive (Perles et al. 2025). Deoxyribonucleic acid (DNA) was extracted from 200 µL of whole blood using a commercial kit (QIAamp DNA Blood Tissue, Qiagen, Hilden, Germany) and was analysed by a duplex real‐time PCR (dqPCR) assay for the detection of D. immitis (cox1 gene) and D. repens (second internal transcribed spacer) DNA (both microfilaria and adult nematode circulating genomic DNA) as described previously (Latrofa et al. 2012). D. immitis DNA was detected with a threshold cycle value of 29. Finally, two conventional PCRs targeting cox1 (∼350 bp, Pradeep et al. 2019) and 12S rDNA genes (∼330 bp, Otranto et al. 2011), respectively, were run to obtain sequences. The purified amplicon was sequenced and compared with those available in GenBank by Basic Local Alignment Search Tool (BLAST‐http://blast.ncbi.nlm.nih.gov/Blast.cgi). The BLAST analysis revealed 100% nucleotide identity with sequences of D. immitis in GenBank database (i.e., MW138020 for cox1 and KP760330 for 12S).

2.2. Case 2

In August 2024, a 7‐year‐old, entire male, DSH cat living in a cat colony from Arezzo (Toscana region, Central‐Northern Italy) with a history of nasal discharge and rhinitis was taken to a private veterinary hospital for surgical repair of a tibial fracture following car accident. On physical examination the cat had mild pallor of the oral mucous membranes, dandruff and nasal discharge. Heart rate was 220 bpm, and the cat was markedly tachypneic. Body condition score was normal, and with exception of the tibial fracture, the remainder of the physical examination was unremarkable. A heartworm antigen test (SNAP Heartworm RT Test, IDEXX Veterinary Laboratories, Maines, USA) was performed during pre‐surgical screening and was positive. In addition, complete blood cell count, serum biochemistry and tests for FIV and FeLV were performed. The cat tested positive for FIV and negative for FeLV. Abnormalities on serum biochemistry included hypoalbuminaemia (2.2; range: 2.8–3.7 g/dL), hyperglobulinaemia (6.8; range: 2.9–4.3 g/dL), increased total protein (8.9; range: 5.8–7.7 g/dL), reduced albumin/globulin ratio (0.3; range: 0.6–1.3) and increased alanine aminotransferase (ALT) activity [86; range: 33–70 UI/L]). The complete blood count identified non regenerative anaemia (20% haematocrit [range: 28%–43%]; 3.5 × 106/µL red blood cell count [range: 6–9.5 × 106/µL]; no reticulocytosis) and leukocytosis (25 × 1000/L leukocytes [range: 5.5–12 × 1000/L] with left‐shifted neutrophilia (16 × 1000/L segmented neutrophils [range: 2.3–10.3 × 1000/L]). No microfilariae were observed on blood smear evaluation. Echocardiography revealed adult worms in the right heart and main pulmonary artery, along with mild tricuspid valve regurgitation. Thoracic radiology showed mild hyperinflation of the lung fields with flattening of the diaphragm.

Due to the concurrent HWD, orthopaedic surgery was not performed, and antiplatelet treatment was started (clopidogrel, 18.75 mg q 24 h PO) to reduce the risk of thromboembolism. After 1‐month of cage rest, the tibial fracture was considered to have healed, and the cat was released back into the cat colony. The cat was reportedly in good health several months later.

In September 2024, blood and serum samples were shipped to the Department of Veterinary Medicine, University of Bari (Italy), as above described. The animal was seropositive for IgG anti‐Dirofilaria spp. but PCR negative for D. immitis (dqPCR and conventional PCRs).

3. Discussion

These two cases of feline HWD, in which the presence of adult nematodes in the right heart and main pulmonary artery was confirmed on echocardiography, highlight the importance of considering D. immitis infection in the differential diagnosis of respiratory signs and/or vomiting in cats that live in endemic areas. They also highlight the importance of screening for HWD, as recommended by the American Heartworm Society (AHS), in cats that are not receiving heartworm prophylaxis and are at high risk of infection (American Heartworm Society Feline Guidelines for the Prevention 2024).

Case 1 presented with clinical signs that although non‐specific, are typical of HARD in cats, namely, chronic respiratory signs and intermittent vomiting. This case was unusual in that it tested positive on each of the serological, antigen and molecular tests used. In this context, considering the low sensitivity of detection of microfilariae in cats (Venco et al. 2015), the serum antigenic heartworm test was preferred rather than the modified Knott's test to confirm the D. immitis infection. However, due to low worm burdens, negative results on both antigen and molecular tests are common in D. immitis infected cats (Venco et al. 2015).

The clinical scenario in Case 2 was different since the cat did not show signs of HARD. The low A/G ratio, increased total protein, hyperglobulinaemia and leukocytosis were suggestive of chronic inflammation and could be associated with FIV infection, chronic rhinitis and/or possibly HWD, as similar findings can be found in canine HWD (Cavalera et al. 2022). In this case, as the diagnosis of D. immitis infection was already achieved by antigen test, the clinical relevance of performing modified Knott's test was scarce. Echocardiography confirmed the presence of adult nematodes in the right heart and pulmonary arteries, emphasizing the capability of cats to harbour these nematodes subclinically (Genchi et al. 2008). However, the findings of right heart abnormalities associated with the presence of adult heartworms on echocardiography underlines the importance to rule out D. immitis infection before anaesthesia to reduce the risks associated with impaired haemodynamics (Ohad and Dan 2014).

For initial diagnostics to rule in a possible diagnosis of HWD, an antibody test along with thoracic radiography is recommended by the European Advisory Board on Cat Diseases (Pennisi et al. 2020). If the antibody test is negative and thoracic radiographs are unremarkable, HWD is less likely. Importantly, if the antibody test scores negative, the D. immitis infection cannot be ruled out as the antibody test positivity depends on the larval stage developments (Berdoulay et al. 2004); on the other hand, radiographic abnormalities are often transitory (Selcer et al. 1996).

If the cat has detectable D. immitis antibodies and/or radiographic changes consistent with possible HWD, it is then recommended to perform a POC test for D. immitis serum antigen, a modified Knott's test or Millipore filtration for microfilariae detection and echocardiography for the visualization of adult worms. If any of these second‐round tests are positive, a diagnosis of HWD is confirmed (Pennisi et al. 2020). On the other hand, the American Heartworm Society Feline Guidelines for the Prevention (2024) state that initial screening tests should include both a POC antigen test and an antibody test and recommend that blood samples should be routinely heated to facilitate antigen recovery in the POC antigen test.

Patent infections with circulating microfilaria occur in only 20% of cats infected by mature adult male and female D. immitis nematodes, and the duration of microfilaremia is restricted to a few months (Pennisi et al. 2020). The most effective tests to detect microfilaria in peripheral blood are PCR and the modified Knott's test (Smith et al. 2024). However, as above mentioned, in both cases in this report, only blood smears were evaluated, which have a lower sensitivity for detection of circulating microfilariae than the modified Knott's test. In PCRs to detect D. immitis from blood samples of infected dogs, microfilaria contribute the major source of DNA that is amplified. PCR is also suggested to be able to detect, in canine blood, fragments of sloughed cuticles from adult nematodes and other developmental stages as well as dead nematode remnants, which would explain the PCR positivity in Case 1 (Murillo et al. 2024). However, the possibility that Case 1 had microfilaremia cannot be ruled out as modified Knott's test was not performed. Unlike Case 1, dqPCR was negative in Case 2 reflecting the poor suitability of molecular tools in detecting D. immitis infection in cats due to low parasitic loads (Hays et al. 2020). Nevertheless, PCR‐negative results could also be due to the presence of inhibitors in clinical samples such as PCR interferents (e.g., haemoglobin and anticoagulants), which occur in blood‐derived DNA samples (Sidstedt et al. 2020).

Overall, diagnosis of heartworm infection in cats may be hindered by the lack of detectable antigens (i.e., false negative results on blood PCR or rapid antigenic POC tests), antibody cross‐reactivity within the genus Dirofilaria (i.e., false positive results at ELISA) and/or the presence of dead worms (i.e., false positive results from direct detection methods). Thus, both thoracic radiography and echocardiography should also be used to confirm clinical diagnosis (Litster and Atwel 2008).

Considering that sudden death may occur in cats infected by D. immitis, timing of diagnosis and clinical management is fundamental to reduce the risk of negative outcomes (Garrity et al. 2019). As far as the therapeutic approach employed in Case 1, corticosteroid therapy provided significant clinical improvement, suggesting that inflammation plays a key role in the pathogenesis of feline cardiopulmonary dirofilariosis (Pennisi et al. 2020). Depot corticosteroids were used in Case 1 because of difficulties in administering oral medication. However, shorter acting preparations (oral prednisolone or IV/IM dexamethasone) are recommended by the AHS for the treatment of HARD (American Heartworm Society Feline Guidelines for the Prevention 2024). In contrast to the recommendation in canine dirofilariosis, adulticide‐based treatments (e.g., melarsomine) are not recommended in cats due to the risk of anaphylaxis after nematode death; in cats, the mainstay of treatment is corticosteroids and/or supportive therapy, according to the patient's clinical signs (TroCCAP 2019).

These two cases demonstrate the range of clinical presentations in D. immitis infected cats, from subclinical infection to severe respiratory disease. Although rapid POC antigen tests for D. immitis have a specificity approaching 100% (American Heartworm Society Feline Guidelines for the Prevention 2024), the imaging tests provided a clinical diagnosis and staging of cardiac and pulmonary lesions. Investigations for feline dirofilariosis should be prioritized in cats not receiving heartworm prevention, living in regions where heartworm is endemic in dogs.

Overall, considering the severe clinical outcomes and the challenges in diagnosis and therapy for Dirofilaria infection in cats, monthly administration of drugs with proven chemoprophylactic effect (e.g., selamectin, moxidectin and eprinomectin) is recommended as a safe and effective option to prevent heartworm infection in the feline host (ESCAAP 2024); Otranto et al.2025.

Author Contributions

Mariaelisa Carbonara: conceptualization, data curation, investigation, formal analysis, methodology, writing – original draft, writing – review and editing. Luigi Venco: conceptualization, data curation, investigation, methodology, writing – review and editing. Elena Bossolini: data curation, methodology, writing – review and editing. Giulia Roncetti: data curation, methodology, writing – review and editing. Vanessa R. Barrs: data curation, investigation, writing – original draft, writing – review and editing. Domenico Otranto: conceptualization, data curation, investigation, supervision, writing – original draft, writing – review and editing.

Ethics Statement

Ethical approvals were not required because these are case reports of two clinical patients and not an experimental research study on animals.

Consent

Written informed consents were obtained from the owners.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Videos SA and SB: Echocardiographic video exam of Cat 1 showing few double‐lined echoes referable to adult D. immitis nematodes, which can be seen free and floating into the right cardiac chambers. A: Right parasternal long‐axis ‘4 chambers’ view; B: Right parasternal short‐axis view at the base of the heart.

Download video file (3.3MB, mp4)

Supporting information

Download video file (2.2MB, mp4)

Acknowledgements

The authors would like to thank the owners of the cats for consenting to publish this report. D.O. was partially supported by EU funding within the Next Generation EU‐MUR PNRR Extended Partnership initiative on Emerging Infectious Diseases (Project no. PE00000007, INF‐ACT).

Open access publishing facilitated by Universita degli Studi di Bari Aldo Moro, as part of the Wiley ‐ CRUI‐CARE agreement.

Funding: The authors received no specific funding for this work.

Data Availability Statement

All data supporting the main conclusions of this study are included in the manuscript. Raw data are available from the corresponding author upon reasonable request. No datasets were generated or analysed during the current study.

References

  1. Alberigi, B. , Campos D. R., Branco A. S., et al. 2022. “Feline Heartworm in Clinical Settings in a High Canine Prevalence Area.” Frontiers in Veterinary Science 9: 819082. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. American Heartworm Society Feline Guidelines for the Prevention . 2024. “Diagnosis, and Management of Heartworm (Dirofilaria immitis) Infection in Cats.” https://d3ft8sckhnqim2.cloudfront.net/images/AHS_Feline_Guidelines_WEB_08NOV202_FINAL.pdf?1731438572.
  3. Berdoulay, P. , Levy J. K., Snyder P. S., et al. 2004. “Comparison of Serological Tests for the Detection of Natural Heartworm Infection in Cats.” Journal of the American Animal Hospital Association 40: 376–384. [DOI] [PubMed] [Google Scholar]
  4. Carbonara, M. , Perles L., Venco L., et al. 2025. “ Dirofilaria Spp. Infection in Cats From the Mediterranean Basin: Diagnosis and Epidemiology.” International Journal for Parasitology 55: 317–325. [DOI] [PubMed] [Google Scholar]
  5. Cavalera, M. A. , Paltrinieri S., Giordano A., et al. 2022. “Serum Protein Electrophoresis in Dirofilaria immitis Naturally Infected Dogs: Latest News and a Systematic Literature Review.” Veterinary Parasitology 305: 109720. [DOI] [PubMed] [Google Scholar]
  6. Dillon, A. R. , Blagburn B., Tillson D. M., et al. 2007. “Immature Heartworm Infection Produces Pulmonary Parenchymal, Airway, and Vascular Disease in Cats.” Journal of the American Veterinary Medical Association 21: 608–609. [Google Scholar]
  7. Dillon, A. R. , Blagburn B. L., Tillson M., et al. 2017. “The Progression of Heartworm Associated Respiratory Disease (HARD) in SPF Cats 18 Months After Dirofilaria immitis Infection.” Parasites & Vectors 10: 533. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. ESCCAP Guideline 05 Fifth Edition December 2024. . Control of Vector‐Borne Diseases in Dogs and Cats. https://www.esccap.org/uploads/docs/32ir16g1_0775_ESCCAP_Guideline_GL5_20241203_1p.pdf.
  9. Garrity, S. , Lee‐Fowler T., and Reinero C.. 2019. “Feline Asthma and Heartworm Disease: Clinical Features, Diagnostics and Therapeutics.” Journal of Feline Medicine and Surgery 21: 825–834. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Genchi, C. , Venco L., Ferrari N., Mortarino M., and Genchi M. 2008. “Feline Heartworm (Dirofilaria immitis) Infection: A Statistical Elaboration of the Duration of the Infection and Life Expectancy in Asymptomatic Cats.” Veterinary Parasitology 158: 177–182. [DOI] [PubMed] [Google Scholar]
  11. Giannelli, A. , Capelli G., Joachim A., et al. 2017. “Lungworms and Gastrointestinal Parasites of Domestic Cats: A European Perspective.” International Journal for Parasitology 47: 517–528. [DOI] [PubMed] [Google Scholar]
  12. Hays, K. M. , Rodriguez J. Y., Little S. E., et al. 2020. “Heartworm Prevalence in Dogs Versus Cats: Multiple Diagnostic Modalities Provide New Insights.” Veterinary Parasitology 277S: 100027. [DOI] [PubMed] [Google Scholar]
  13. Latrofa, M. S. , Dantas‐Torres F., Annoscia G., Genchi M., Traversa D., and Otranto D. 2012. “A Duplex Real‐Time Polymerase Chain Reaction Assay for the Detection of and Differentiation Between Dirofilaria immitis and Dirofilaria repens in Dogs and Mosquitoes.” Veterinary Parasitology 185: 181–185. [DOI] [PubMed] [Google Scholar]
  14. Litster, A. L. , and Atwell R. B. 2008. “Feline Heartworm Disease: A Clinical Review.” Journal of Feline Medicine and Surgery 10: 137–144. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. McCall, J. W. , Dzimianski M. T., McTier T. L., et al. 1992. Biology of Experimental Heartworm Infections in Cats. American Heartworm Society. [Google Scholar]
  16. McTier, T. L. , Shanks D. J., Watson P., et al. 2000. “Prevention of Experimentally Induced Heartworm (Dirofilaria immitis) Infections in Dogs and Cats With a Single Topical Application of Selamectin.” Veterinary Parasitology 91: 259–268. [DOI] [PubMed] [Google Scholar]
  17. Morchón, R. , Ferreira A. C., Martín‐Pacho J. R., et al. 2004. “Specific IgG Antibody Response Against Antigens of Dirofilaria immitis and Its Wolbachia Endosymbiont Bacterium in Cats With Natural and Experimental Infections.” Veterinary Parasitology 125: 313–321. [DOI] [PubMed] [Google Scholar]
  18. Murillo, D. F. B. , Campbell E. J., Moorhead A. R., and Wang C. 2024. “Evaluation of Diagnostic Techniques for Early Detection of Heartworm in Experimentally Infected Dogs: Identification of Dirofilaria immitis‐Derived microRNA in the Initial 28 Weeks Post‐Inoculation.” Parasites & Vectors 17: 258. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Nelson, C. T. , and Johnson C. M. 2024. “Evaluation of Feline Heartworm Disease Based on Gross Necropsy, Serology, Pulmonary Histopathology, and Radiographic Evidence in Adult Shelter Cats in Northeastern Alabama.” Parasites & Vectors 17: 161. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Ohad, D. G 2014. “Sedation and Anesthesia for Pets With Cardiac Disease.” In World Small Animal Veterinary Association World Congress. 166–169. https://www.vin.com/doc/?id=7054640.
  21. Otranto, D. , Brianti E., Dantas‐Torres F., et al. 2011. “Morphological and Molecular Data on the Dermal Microfilariae of a Species of Cercopithifilaria From a Dog in Sicily.” Veterinary Parasitology 182: 221–229. [DOI] [PubMed] [Google Scholar]
  22. Otranto, D. , Carbonara M., Baneth G., et al. 2025. “Feline Vector‐Borne Diseases: From Local Risks to Global Concerns.” Trends in Parasitology. 10.1016/j.pt.2025.04.009. [DOI] [PubMed] [Google Scholar]
  23. Pękacz, M. , Basałaj K., Młocicki D., et al. 2024. “Molecular Insights and Antibody Response to Dr20/22 in Dogs Naturally Infected With Dirofilaria repens .” Scientific Reports 14: 12979. Erratum in: Sci Rep. 2024;14: 14499. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Pennisi, M. G. , Tasker S., Hartmann K., et al. 2020. “Dirofilarioses in Cats: European Guidelines From the ABCD on Prevention and Management.” Journal of Feline Medicine and Surgery 22: 442–451. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Perles, L. , Dantas‐Torres F., Krücken J., Morchón R., Walochnik J., and Otranto D. 2024. “Zoonotic Dirofilariases: One, No One, or More Than One Parasite.” Trends in Parasitology 40: 257–270. [DOI] [PubMed] [Google Scholar]
  26. Perles, L. , Carbonara M., Mendoza‐Roldan J. A., Venco L., Gabrielli S., and Otranto D. 2025. “An Indirect ELISA for the Detection of Antibodies Against Dirofilaria Spp. in Cats.” Parasites & Vectors 18: 16. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Pradeep, R. K. , Nimisha M., Pakideery V., et al. 2019. “Whether Dirofilaria repens Parasites From South India Belong to Zoonotic Candidatus Dirofilaria hongkongensis (Dirofilaria sp. Hongkongensis)?.” Infection, Genetics and Evolution 67: 121–125. [DOI] [PubMed] [Google Scholar]
  28. Selcer, B. A. , Newell S. M., Mansour A. E., and McCall J. W. 1996. “Radiographic and 2‐D Echocardiographic Findings in Eighteen Cats Experimentally Exposed to D. ZMMZTZS via Mosquito Bites.” Veterinary Radiology & Ultrasound 37: 37–44. [Google Scholar]
  29. Sidstedt, M. , Rådström P., and Hedman J. 2020. “PCR Inhibition in qPCR, dPCR and MPS‐Mechanisms and Solutions.” Analytical and Bioanalytical Chemistry 412: 2009–2023. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Smith, R. C. , Tomlinson T. D., Bowles J. V., and Starkey L. A. 2024. “Comparative Performance Analysis of Different Microfilaria Testing Methods for Dirofilaria immitis in Canine Blood.” Parasites & Vectors 17: 460. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. TroCCAP . 2019. Guidelines for the Diagnosis, Treatment and Control of Feline Endoparasites in the Tropics. 2nd ed. TroCCAP. https://www.troccap.com/2017press/wp-content/uploads/2019/06/TroCCAP_Feline_Endo_Guidelines_English_Ver2.pdf. [Google Scholar]
  32. Venco, L. , Genchi M., Genchi C., Gatti D., and Kramer L. 2011. “Can Heartworm Prevalence in Dogs be Used as Provisional Data for Assessing the Prevalence of the Infection in Cats?” Veterinary Parasitology 176: 300–303. [DOI] [PubMed] [Google Scholar]
  33. Venco, L. , Marchesotti F., and Manzocchi S. 2015. “Feline Heartworm Disease: A 'Rubik's‐Cube‐Like' Diagnostic and Therapeutic Challenge.” Journal of Veterinary Cardiology 17: S190–S201. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Videos SA and SB: Echocardiographic video exam of Cat 1 showing few double‐lined echoes referable to adult D. immitis nematodes, which can be seen free and floating into the right cardiac chambers. A: Right parasternal long‐axis ‘4 chambers’ view; B: Right parasternal short‐axis view at the base of the heart.

Download video file (3.3MB, mp4)

Supporting information

Download video file (2.2MB, mp4)

Data Availability Statement

All data supporting the main conclusions of this study are included in the manuscript. Raw data are available from the corresponding author upon reasonable request. No datasets were generated or analysed during the current study.

Articles from Veterinary Medicine and Science are provided here courtesy of Wiley

RESOURCES