Clinical and blood count findings in dogs naturally infected with Dirofilaria immitis


heartworm, clinical signs, complete blood count, lung inflammation.

How to Cite

Bendas, A. J. R., Alberigi, B., Galardo, S., Labarthe, N., & Mendes-de-Almeida, F. (2022). Clinical and blood count findings in dogs naturally infected with Dirofilaria immitis . Brazilian Journal of Veterinary Medicine, 44, e001922.


Dirofilaria immitis is a nematode that infects canids worldwide as well as other mammalian species, including humans. Worms and dogs are well adapted to one another, making dogs the best urban host for the parasite. Nevertheless, 30% of dogs do not sufficiently present microfilaremia, that is, the low larval load impairs transmission by mosquitoes and diagnosis by its detection in the blood samples. Therefore, the canine diagnosis must always include a microfilaria test and serological tests to detect adult worm antigens. To describe the clinical findings in naturally infected dogs in Rio de Janeiro, 34 dogs were included in the study. All dogs were evaluated for history, anamnesis, physical examination, complete blood count (CBC), D. immitis testing for antigens (ELISA test SNAP 4Dx Plus®), and microfilarial burden. The most frequent complaint from the owners was coughing (14.7%, 5/34). The most common CBC finding was eosinophilia (29.4%), followed by thrombocytopenia (26.5%) and neutrophilia (14.7%). Of the 34 animals, 91.2% were microfilaremic, with a mean count of 11.939 microfilaria/mL. Veterinarians working in areas endemic to D. immitis should always undergo screening tests and pulmonary auscultation, and increased expiratory sounds, even in the absence of coughing, can be considered a sign of the disease, along with eosinophilia, thrombocytopenia, and neutrophilia.


Abraham, D. (1988). Biology of Dirofilaria immitis. In P. F. Boreham & R. B. Atwell (Eds.), Dirofilariasis (pp. 29-46). Florida: CRC Press.

Atwell, R. B., Sutton, R. H., & Moodie, E. W. (1988). Pulmonary changes associated with dead filariae (Dirofilaria immitis) and concurrent antigenic exposure in dogs. Journal of Comparative Pathology, 98(3), 349-361. PMid:3392249.

Bendas, A. J. R., Paiva, J. P., Rossi, M. I. D., Knackfuss, F. B., Silvano, D. R. B., Mendes-de-Almeida, F., Guerrero, J., & Labarthe, N. (2008). The use of doxycycline in microfilaremic Dirofilaria immitis (Leidy, 1856) naturally infected dogs. International Journal of Applied Research in Veterinary Medicine, 6(1), 55-59.

Bezerra, L. S., Lima, G. R. F., Araújo, V. M. J., Teixeira, G. G., Coelho, J. M. A., Farzat, F. A., Oliveira, E. S., Pinheiro, V. C., Mendes, A. L. S., Ramires, P., Silva, I. N. G. S., Pinheiro, B. Q., & Rodrigues, V. H. V. (2021). Perfil epidemiológico, hematológico e bioquímico em cães com Dirofilaria sp. no Ceará. Research Social Development, 10(8).

Dillon, R. (2007). Feline heartworm disease: Cats get heartworms too! Auburn: College of Veterinary Medicine, Auburn University.

Feitosa, F. L. F. (2014). Semiologia veterinária: A arte do diagnóstico (3a ed.). São Paulo: Roca.

Genchi, C., Kramer, L. H., Sassera, D., & Bandi, C. (2012). Wolbachia and its implications for the immunopathology of filariasis. Endocrine, Metabolic & Immune Disorders Drug Targets, 12(1), 53-56. PMid:22214329.

Jain, N. C. (1986). Schalm’s veterinary haematology (4th ed., 1221 p.). Philadelphia: Lea & Febiger.

Knight, D. H. (2004). Heartworm infection. In L. G. King (Ed.), Textbook of respiratory diseases of dogs and cats (pp. 517-525). St. Louis: Saunders.

Knott, J. A. (1939). Method for making microfilarial surveys on day blood. Transactions of the Royal Society of Tropical Medicine and Hygiene, 33(2), 191-196.

Lilliehöök, I., Gunnarsson, L., Zakrisson, G., & Tvedten, H. (2000). Diseases associated with pronounced eosinophilia: A study of 105 dogs in Sweden. The Journal of Small Animal Practice, 41(6), 248-253. http:// PMid:10879402.

Lombard, C. W., & Ackerman, N. (1984). Right heart enlargement in heartworm-infected dogs: A radiographic, electrocardiographic, and echocardiographic correlation. Veterinary Radiology, 25(5), 210-217. http://dx.doi. org/10.1111/j.1740-8261.1984.tb01929.x.

Madril, A.B., Silva, E.G., Alves, C.C., Vasconcellos, A. L., Sousa, E. P., & Costa, P. P. C. (2020). Perfil hematológico de cães infectados por Dirofilaria immitis. In Anais do 12º Salão Internacional de Ensino, Pesquisa e Extensão (SIEPE). Bagé: UNIPAMPA.

Nelson, R. W., & Couto, C. G. (2015). Medicina interna de pequenos animais (5a ed.). Rio de Janeiro: Elsevier.

Nelson, T., McCall, J. W., Jones, S., & Moorhead, A. (2014). Current guidelines for the prevention, diagnosis and management of heartworm (Dirofilaria immitis) infection in dogs: 2014 revised 2018. Holly Springs, NC: American Heartworm Society.

Newton, W. L., & Wright, W. H. (1956). The occurrence of a dog filariid other than Dirofilaria immitis in the United States. The Journal of Parasitology, 42(3), 246-258. PMid:13332492.

Niwetpathomwat, A., Kaewthamasorn, M., Tiawsirisup, S., Techangamsuwan, S., & Suvarnvibhaja, S. A. (2007). A retrospective study of the clinical hematology and the serum biochemistry tests made on canine dirofilariasis cases in an animal hospital population in Bangkok, Thailand. Research in Veterinary Science, 82(3), 364-369. PMid:17095027.

Oliveira, I. N. V., Moreira, H. R., Fazio-Junior, P. I., Castro, L. R. S., Trindade, C. E. D., Bezerra, D. K. O., Madeira, E. A. O., Almeida, M. B., & Fernandes, J. I. (2013). Perfil hematológico e bioquímico de cães infectados por Dirofilaria immitis da localidade da Ilha de Algodoal, Pará. Brazilian Journal of Veterinary Medicine, 35(Suppl. 2), 74-80.

Polizopoulou, Z. S., Koutinas, A. F., Saridomichelakis, M. N., Patsikas, M. N., Desiris, A. K., Roubies, N. A., & Leontidis, L. S. (2000). Clinical and laboratory observations in 91 dogs infected with Dirofilaria immitis in northern Greece. The Veterinary Record, 146(16), 466-469. PMid:10819132.

Rocha, C. A. R. (2010). Dirofilaria immitis and canine dirofilariasis: A retrospective study [Dissertação de mestrado]. Universidade de Trás-os-Montes e Alto Douro, Portugal.

Romano, A. E., Saunders, A. B., Gordon, S. G., & Wesselowski, S. (2021). Intracardiac heartworms in dogs: Clinical and echocardiographic characteristics in 72 cases (2010-2019). Journal of Veterinary Internal Medicine, 35(1), 88-97. PMid:33617036.

Scott, M. A. (2008). Leukocytes. In S. L. Stockham & M. A. Scott (Eds.), Fundamentals of veterinary clinical pathology (pp. 53-106). Ames: Wiley-Blackwell.

Tudor, N., Ionita, L., Tapaloaga, D., Tudor, P., Ionita, C., & Vlagioiu, C. (2014). Radiographic cardiopulmonary changes in dogs with heartworm disease. Romanian Biotechnological Letters, 19(6), 9918-9924.

Venco, L., Kramer, L., & Genchi, C. (2005). Heartworm disease in dogs: Unusual clinical cases. Veterinary Parasitology, 133(2-3), 207-218. PMid:15890447.

Waner, T., Harrus, S., Weiss, D. J., Bark, H., & Keysary, A. (1995). Demonstration of serum antiplatelet antibodies in experimental acute canine ehrlichiosis. Veterinary Immunology and Immunopathology, 48(1-2), 177-182. PMid:8533312.

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Copyright (c) 2022 Alexandre José Rodrigues Bendas, Bruno Alberigi, Suzane Galardo, Norma Labarthe, Flavya Mendes-de-Almeida