TDK conference 2014

The host animals of the Dirofilaria species are primarily the wild and domesticated predators (Carnivora), however the zoonotic importance of the parasite is also elevating all over the world. The immediate hosts of Dirofilaria immitis (Onchocercidae family, Filarioidea superfamily) are species belonging to the Culicidae family. Mosquitos take the microfilariae by sucking blood from the infected animal and transfer them to the final host in L3 stage. For some days the larvae can be found in the surrounding connective tissues but from the 21st day depending on the location of the bite they can reach the abdominal and thoracic tissues. The parasite transforms from L3 into L4 stage within 3-12 days, during this period it stays between muscle fibers and proceeds towards the thoracic veins. The subcutaneously inoculated juvenile worms get to the thorax 120 days after infection and they reach the right side of the heart and its bigger vessels with the blood flow where they settle. This is the place where they reach their final size (25-30cm) and become mature. The mature females start to give birth to live larva (L1) after 6-9 months prepatens time. The microscopic worms start to circulate in the blood stream and wait for being picked up by a moquito to travel to their new host.

Dirofilaria immitis has a growing significance in Hungary. Several studies reported the harmful effects of the parasite in lung vessels and the heart. Lung lesions are followed by direct vascular effect of the worms in the pulmonary arteries. The death of the worms can lead to inflammatory reactions or thromboembolism. The bigger amount of afterload on the right ventricle developing ’cor pulmonale’. In our research we investigated dogs with antigen rapid tests, PCR, radiography and ultrasonography. We studied the early appearance of cardiac lesions caused by nematodes. According to the international studies, for sever clinical symptoms at least 30 worms should be present in the heart or major vessels. In our study syptoms already occured even in the presence of 2-3 parasites. In these cases cardiac morphological abnormalities have not been detected via ultrasonographyc examintations.

Since Oktober, 2012 we examined 85 dogs by microscopic and ELISA blood tests followed by PCR examinations in case of positive modified Knott tests. As part of the scanning we performed bilateral chest X-rays and echocardiographic examintations. 63 subjects were confirmed as microfilariae positive by thick blood-drop test and with one exception all of them proved to be Knott positive as well. Some of the thick blood-drop test negative cases were also examined by modified Knott test. In this group there were 7 Knott negative and one positive result. 12 microfilaria negative cases turned out to be ELISA positive and 8 other tests showed inconclusive results. On the other hand the serological rapid test showed the antigen of Dirofilaria immitis in the microfilariae infected blood in 40 out of 64 cases and 6 results were inconclusive. 18 of the positive cases also came out positive with the PCR tests. Among the inconclusive results 5 PCR tests were negative and one was positive. In the ELISA positive group we found 17 dogs where ultransonographic double-walled hyperechoic formula signs of the adult worms could be detected in the arteria pulmonalis. In further 11 positive cases the known formula could not be seen. In our study we performed pathological examintation in 3 cases where we previously found adult worms in the arteria pulmonalis via ultraechocardiographic examination.