Cardiopulmonary radiographic changes in dogs naturally infected with Dirofilaria immitis

Abstract

ABSTRACT: Heartworm disease is a zoonosis caused by Dirofilaria immitis, a nematode parasite of worldwide distribution and considered one of the most virulent of dogs, which are definitive and infected hosts during the blood meal of vector mosquitoes (Aedes sp., Anopheles sp. and Culex sp.). The disease has a worldwide prevalence, with a higher incidence in tropical and subtropical climate areas, and affects animals of any breed, sex, and age group. Most animals are asymptomatic, but the disease can cause various cardiovascular and respiratory symptoms. The pathophysiology is related to vessel obstruction and an intense inflammatory reaction in the lung parenchyma, with cardiovascular and respiratory symptoms leading to signs that can be severe and lead to the death of the host. It can be diagnosed through blood tests, and chest X-rays are used to assess the severity of clinical signs and help establish a prognosis. Cardiovascular alterations appear as an increase in vascular caliber, an increase in the right heart silhouette, and pulmonary patterns compatible with infection. This study aimed to describe the conditional radiographic changes caused by the parasite in the lungs, intrathoracic vessels and heart in 30 dogs, independent of breed and sex, with an average age of 9.9 years and an average weight of 10.25kg, originating from routine care at a veterinary hospital in the city of Rio de Janeiro, from January 2022 to December 2022. All animals were diagnosed with a positive heartworm infection and cardiorespiratory symptoms as essential conditions for participation in the study. The animals were x-rayed and had their lung patterns evaluated, in addition to measuring their vascular caliber and cardiac indices using vertebral-heart size (VHS), manubrium-heart size (MHS) and sphericity index (CSI). Most animals presented pulmonary patterns such as bronchoalveolar and bronchial and increased VHS and MHS indices. Increased and borderline values of CSI measurements were found in half of the patients, demonstrating that the parasite can trigger significant radiographic changes or present potential further worsening.