Incidence and Hematological Changes in Dogs Infected with Dirofilaria immitis in Thailand

Dirofilaria immitis is responsible for heartworm disease in dogs. Clinical signs are non-specific, ranging from asymptomatic to severe symptoms. The most common symptoms include coughing, emaciation, dyspnoea, and sudden loss of consciousness. Therefore, diagnosing heartworm infection in dogs requires a combination of methods, such as hematology and serology. This study was conducted on dogs with clinical signs, including anorexia, coughing, panting, and hind legs weakness, that was referred accidentally to a pet clinic in Thonburi district, Bangkok Province, Thailand, during 2020-2022. The examination was performed using a rapid enzyme immunoassay test and a thin blood smear. The total number of dogs admitted to a pet clinic during that period was 980. The result indicated infection of 21 (12 male and 9 female) dogs with heartworm (2.14%). The mean age of dogs was 5.62 ± 2.48 years. All infected dogs were classified under an open husbandry system that did not consistently use heartworm prevention products such as the macrocyclic lactone group. In the groups that received topical ectoparasites products, 10 dogs were detected with heartworm infection. The hematological changes in the infected dogs consisted of leucocytosis and increased levels of ALT, BUN, and creatinine. The study results can guide owners in choosing products that can prevent heartworm. Anti-mosquito nets should be deployed in areas where pets live, and always keep the environment clean.