Veterinary session

Heartworm disease caused by D. immitis is a serious, life-threatening, mosquito-borne cardiopulmonary disease in dogs, which is becoming increasingly common both overseas and in European countries including Hungary. Contrary to the name of the disease, the adult worm colonises and causes damage primarily in the pulmonary arteries, rather than in the heart. In advanced cases, this results in right heart failure, as the worms’ size allows them to reach through the pulmonary arteries into the right heart, and in more severe cases into the vena cava, causing caval syndrome.

Identifying the current local prevalence is important in preventing the disease, so that information about the exposure of dogs to infection can be obtained and timely control measures can be taken. Therefore, the aim of our study was to determine the Hungarian prevalence of D. immitis infection in dogs in 2023 and to perform a statistical comparison of the reliability of the diagnostic tests (Knott, ELISA). We have calculated the positive and negative predictive values of these tests and determined their sensitivity and specificity. We also examined whether the prevalence of infection differs between areas of the country and whether it depends on the sex and the age of the animals. The study lasted from March 2023 to February 2024, during which time 1071 blood samples were collected from dogs in all counties that met the eligibility criteria of having been born in Hungary, never having been abroad, being at least 12 months old or older and not having received any preventive treatment with macrocyclic lactones in the last year. Knott and ELISA tests were performed on the samples and PCR analysis was used to separate positivity caused by D. immitis or D. repens, which is also capable of forming microfilariae. Based on our results, we found that the prevalence of D. immitis in Hungary is 12.0%, while the prevalence of mixed infection with D. repens is 3.92%. Regarding our results, the Knott’s test has a specificity of 93.0%, a sensitivity of 80.0%, a positive predictive value of 60.0% and a negative predictive value of 97.0%. ELISA shows a specificity of 94.0%, a sensitivity of 87.0%, a positive predictive value of 67.0% and a negative predictive value of 98.0%. The occurrence of heartworm disease is influenced by the type of area the animal lives in, the age of the dog and whether it has been castrated. In consideration of the above, heartworm disease remains endemic throughout Hungary, and the risk of infection increases with age if no preventive measures are taken. For this reason, it is essential that practising veterinarians provide adequate protection to reduce the risk of infection and thus the development of disease.