An unexpected case of a dog from Poland co-infected with Dirofilaria repens and Dirofilaria immitis

Background: Dirofilariasis is a vector-borne disease caused by parasitic nematodes of the genus Dirofilaria spp. , considered an emerging problem of both veterinary and human medicine. Due to the climate changes and human activities, like traveling with pets, diseases spread to new non-endemic regions. Poland is dominated by subcutaneous dirofilariasis caused by D. repens infections. Cardiopulmonary dirofilariasis, also known as a heartworm disease is much more rare with only single autochthonous cases reported so far. Also, imported infections are observed sporadically in dogs traveling to endemic countries. In the present study, we report a first case of a dog from Poland, that has never traveled abroad, co-infected with Dirofilaria repens and Dirofilaria immitis. Case presentation: A 14-year-old mixed breed, an intact male dog with fever, lightly pale mucosal membranes, moderate abdominal pain, and mild cough was presented in a veterinary clinic in Warsaw, Poland. The examination of the blood sample collected for complete morphology and biochemistry revealed alive microfilariae. Presence of the DNA of both microfilariae species was detected using Real-Time PCR with species-specific primers. Conclusions Since the remaining diagnostic methods like Knott's test, antigen test or echocardiography did not reveal the presence of D. immitis , we discussed the impact of microfilariae periodicity and low worm burden infections on the limited efficiency of these techniques. We strongly recommend using a mixed diagnostic approach for the most sensitive and specific diagnosis as the ideal diagnostic method does not exist and several factors may easily lead to misdiagnosis. Furthermore, we considered factors that contribute to the uncontrolled spread of dirofilariasis like climate changes, introduction of new species of mosquitoes competent for the transmission of the disease, and wildlife animals as an important reservoir of this parasitosis. Since Poland borders countries considered endemic and pre-endemic for D. immitis , like Slovakia or Ukraine, we could expect an increase in autochthonous heartworm infection and changes in the epidemiological pattern of dirofilariasis in the near future.