Using epidemiological methods for detection and control of zoonoses is an important factor in public health. There are zoonoses which are not regularly controlled and about which there is no accurate data on their prevalence; these zoonoses pose a threat to human health. These zoonoses are: anaplasmosis, borreliosis, ehrlichiosis and dirofilariasis. Blood samples were collected from 29 asymptomatic dogs in 2015 in Istria and testedwith SNAP® 4Dx® Plus screening test and modified Knott test. In 29 dogs examined with the modified Knott test, dirofiralia was found in 15 (52%) dogs, and by usingSNAP® 4Dx® Plus screening test heartworms are established in 6 (21%) dogs. D. immitis is present in 40% of positive dogs. Analysis ofrisk factors such as breed, sex, age, keeping dogs outside all the time or just during the daytime, purpose of the dog and dog´s environment indicates that there is no significant difference in the occurrence of Dirofilaria between breed, sex and age.However, statistically significant differences are found indogs kept outside and considering dog´s purpose. The statistically significant difference is found between truffle dogs and hunting dogs.The prevalence in truffle dogs is 2.75 (CI 95% from 1,78 %up to 6,41 %) times higher than the prevalence in hunting dogs.Also, exposure to dirofilarasis in truffle dogs was 12.7 (CI 95% from 1,8 % up to 83,77 %) times bigger than that in hunting dogs (P ˂ 0.05).It turned out that regardless of the purpose of dogs, exposure to dirofilariasis in western Istria is higher if the dogs are keptfor a long time outdoor. By comparing two groups of dogs we found out that the prevalence of D. immitis in dogs who stayed 24 hours outside of a housewas 4,17 (CI 95% from 1,02 %up to 17,08 %) times higher than in dogs who stayed only outside during the day (P ˂ 0.05), and the possibility of the invasion of these dogs withD. immitisis even 10.05 (CI 95 % from 1,03 % up to 107,08 %) times higher. Knowledge about prevalence, identifying risks, defining risk factors and quantification of risk is a postulate for the definition and implementation ofanimal health strategies and the implementation of prevention and control measures in order to protect the health of both dogs and humans.