Abstract
Background:
Canine parvovirus (CPV) causes acute hemorrhagic gastroenteritis in dogs, whereas canine circovirus (CanineCV), an emerging virus, is associated with immunosuppression and gastrointestinal disease. However, data on CPV–CanineCV coinfections are limited in Vietnam.

Aim:
The aim of this study was to investigate the prevalence and clinical, hematological, biochemical, and pathological features of CPV–CanineCV coinfections in dogs with enteric disease in Hanoi, Vietnam.

Methods:
The fecal and blood samples from suspected CPV cases were tested using molecular diagnostics. Clinical and laboratory findings were compared between the CPV mono- and coinfected groups. Necropsies were performed on the deceased animals.

Results:
CPV infection was confirmed in 94.68% (89/94) of the cases, with 21.28% (19/89) showing CanineCV coinfection. Diarrhea, vomiting, and anorexia were observed in both groups, but coinfected dogs exhibited more severe symptoms, higher mortality, longer treatment, and worse recovery. The hematological findings included marked leukopenia, lymphopenia, and thrombocytopenia. Biochemical changes, such as hypoglycemia, hypoproteinemia, hypoalbuminemia, and mild liver enzyme elevations, along with notable hypokalemia and mild metabolic acidosis, were observed. Pathological findings showed a more extensive intestinal and systemic damage in patients with co-infections.

Conclusion:
CPV–CanineCV coinfection results in more severe disease than CPV alone. Routine Canine CV screening in CPV-positive dogs is recommended for better clinical management.

Key words: Circovirus; Coinfection; Dogs; Hanoi; Parvovirus.