Efficacy of ultrasound in diagnosis of dirofilariasis in dogs caused by Dirofilaria immitis

Abstract

Ultrasonic diagnostics is a modern and effective method of laboratory testing of both animals and humans, used for estimation of overall state, and for detection of different pathologies in organs and systems. The aim of the present study was to establish the efficacy of ultrasonic diagnostics of dog dirofilariasis caused by Dirofilaria immitis parasitism, based on several indexes of invasion intensity. It was established that the number of D. immitis helminths found depended on the intensity indexes of microdirafilariasis invasion: using echocardiography, there were no helminths found under the index lower than 40 larvae/cm3. Under the index higher than that, we visualized 1–10 parasite individuals in the cavity of the right ventricle and right atrium, and at the tricuspid valve leaflets. It was established by the results of echocardiography of dogs invaded by D. immitis that the level of invasion intensity impacts significantly on the animals’ heart structure and function, and on their intracardiac hemodynamics. It was proved that under increase of microfilaria number in the blood, heart function deteriorates. Under the invasion intensity lower than 40 larvae/cm3, the changes were characterized by a slight increase in thickness of the posterior wall of the left ventricle in diastole, aorta diameter, left atrium and pulmonary artery (by 6.2%). Under the invasion intensity of 40–60 larvae/cm3, the deterioration in heart structure and function was followed by thickening of the interventricular septum in diastole, posterior wall of the left ventricle in diastole (by 5.6%), increase in ejection fraction index (by 7.0%), widening of aorta root, pulmonary artery, diameter of the left ventricle (by 21.4%), and with increase in indexes of ratio between diameters of the left ventricle and pulmonary artery, and aorta (by 15.6%). Signs of hemodynamic deterioration were established in sick animals, which was characterized by increase of blood speed in the tricuspid valve (by 33.7%), and its decrease in the pulmonary artery (14.1%). Under the invasion intensity higher than 60 larvae/cm3, the aforementioned indexes changed even more significantly. We observed thickening of the posterior wall of the right ventricle in diastole, decrease of the end-systolic size of the left ventricle (by 13.0%), blood speed increase in the aorta and mitral valve (by 12.2%). The obtained results show the necessity of echocardiographic testing of dogs with cardiac dirofilariasis, which allows effective proof of the diagnosis and also helps to understand the overall state of the animal more deeply and to provide it with the appropriate symptomatic cure.