How does Dirofilaria immitis infection impact the health of dogs referred to cardiology care

Dirofilaria immitis is a nematode that can cause a disease that may present clinical signs from severe to absent. When dogs are symptomatic, the clinical signs are cardiorespiratory and nonspecific, which may be misleading. This study aimed to demonstrate the clinical presentations to cardiac care by evaluating 26 dogs subjected to clinical examination, complete blood count (CBC), specific tests for D. immitis infection, chest radiography, and echocardiography. Among them, 11 (42.3%) dogs were infected and 15 (57.7%) were non-infected. Most dogs presented with coughing (65.4%) and abnormal lung sounds (81%) independent of infection. Murmur at the tricuspid focus was present in 26.9% of the dogs, of which 57.1% were infected. Echocardiography revealed tricuspid regurgitation in 30.8% of the dogs and pulmonary regurgitation in 46.1%, of which 37.5% and 50% were infected, respectively. Worms were detected by echocardiography in 45.5% of the infected dogs. The x-rays showed that the bronchial pattern was present in 45.5% of the infected dogs and in 46.7% of the non-infected dogs. The interstitial pattern was present in 18.2% of the infected animals, in contrast to 6.7% of the non-infected dogs. The CBC results for all dogs were within the reference range, except for platelets. Although similar, the percentage of dogs with thrombocytopenia was higher among infected dogs (36.4%) than among the non-infected (6.7%). These results reinforce that due to the non-specific signs of infection, it is mandatory to perform parasitological assays when evaluating dogs presenting with cardiopulmonary signs.