A study on Dirofilaria immitis in healthy urban dogs from Ahvaz, Iran

Heartworm infection is one of the most important parasitic diseases in dogs and an increasing number of cases are reported each year by necropsy in Ahvaz. This study was conducted to determine the prevalence of Dirofilaria immitisinfection and to investigate the risk factors related to heartworm disease in urban dogs in this area. Blood samples were collected from 100 dogs from Feb 2007 to Feb 2008. All samples were examined by modified Knott test, direct smear and antigen detection (Immunochromatographic antigen rapid canine D. immitisAg Test Kit) technique to detect circulating microfilaria and adult antigen of D. immitis, respectively. Of the total 100 dogs, 1% were positive bydirect smear, 5% were positive by modified Knott test and 6% were positive by antigen detection. In addition, 1% of positive dogs were determined to have occult D. immitisinfections. Dirofilaria immitiswas the only canine filarial parasite present in this study. From these three methods, modified Knott test, due to microfilarial identification on concentrated blood had the highest validity. The difference between outdoor and indoor dogs was found significant (P = 0.033), whereas no statistically significant differences were observed between different age groups, sexes and breeds (P>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.