Abstract
            Background: Dirofilaria immitis is one of the most important parasites of the circulatory system of dogs that causes severe  cardiovascular events in the animal and it is reported to be the most common nematode in humans and dogs from many parts  of Iran.
    Methods: In order to investigate the presence of Dirofilaria immitis infection in Tabriz, Iran, a cross-sectional study was performed  on 200 owned and stray dogs. The blood samples were analyzed using Knott method. The prevalence of D. immitis infection was  reported to be 15% in owned dogs.  
  Results: The highest levels of infection were reported in dogs less than one year of age and the lowest in dogs aged over 9 years.  In a statistical survey, there was a significant relationship between infection and gender.  
  Conclusion: According to the findings of this study, due to the presence of D. immitis infection in this region, the need for a more  comprehensive examination and control of the infection in this region is emphasized.