0.05) difference in the frequency of infection with BLV between the two breeds.]]> 0.05). The highest heartworm prevalence by modified Knott test was observed in older than 6-year-old dogs (8.3%) followed by 3–6 years (2.7%) and the 6-month to 3 years (3.5%) age groups. The infection was more prevalent in males and short haired breeds. Our results suggest that heartworm treatment and preventive care should be considered in urban dogs of Ahvaz, Iran.]]>