This report presents the first detection of canine circovirus (CanineCV) in South Korea, which was identified in a dog with hemorrhagic diarrhea. A 5-year-old male Golden Retriever presented with acute, watery and bloody diarrhea that had persisted for three weeks. Pathologically, granulomatous inflammation, fibrinoid vasculitis, and hemorrhagic foci were observed in the small intestine and mesenteric lymph nodes. Characteristic intracytoplasmic amphophilic inclusion bodies were observed in histiocytic cells within the granulomatous lesions. CanineCV was amplified by polymerase chain reaction from the small intestine, mesenteric lymph nodes, and fecal samples. A genomic analysis of the complete capsid gene from the Korean strain of CanineCV revealed that it shares the highest nucleotide and amino acid sequence similarities, at 94.2% and 94.1% respectively, with the American UCD3-478 isolate. Phylogenetic analysis based on the nucleotide sequence of the capsid gene classified the Korean strain as type 4 CanineCV. This case highlights the importance of genomic surveillance for emerging pathogens in South Korea and lays the groundwork for further research into the epidemiology and pathogenicity of CanineCV in canine enteric diseases.

Doxorubicin is an effective chemotherapeutic agent widely used in veterinary oncology, particularly as part of the CHOP protocol for canine lymphoma. Despite its therapeutic benefit, cardiotoxicity remains a serious dose-limiting adverse effect. Although clinically significant cardiotoxicity is typically reported at cumulative doses of 150-240 mg/m 2 in dogs, functional cardiac deterioration has been observed at lower doses, with progression to congestive heart failure rarely reported. This case report describes doxorubicin-induced cardiotoxicity below the established cumulative threshold in a dog with multicentric lymphoma, which presented with overt clinical signs of congestive heart failure, including coughing, syncope, and pleural effusion. The dog also exhibited marked echocardiographic changes, including right atrial enlargement and a reduction in fractional shortening from 33% to 21% over 2 weeks, ultimately resulting in death 53 days after symptom onset. The clinical diagnosis was supported by the temporal relationship with doxorubicin administration and serial cardiac imaging findings. This case highlights that severe cardiotoxicity can occur even below traditionally accepted cumulative thresholds, reinforcing the importance of individualized, ongoing cardiac monitoring and early intervention, regardless of dose.

Small B-cell lymphoma typically has a more favorable prognosis compared to diffuse large B-cell lymphoma (DLBCL). Here, we present the first documented case of canine DSBCL characterized by extensive lymphocyte infiltration in the spleen, leading to splenic rupture and death. A 10-year-old neutered male Shih Tzu presented with lethargy, skin lesions, and generalized lymphadenopathy. On the day of admission, the dog experienced shock, accompanied by bradycardia and hypotension, and subsequently died. Necropsy confirmed splenic rupture, and cytology, histopathology, and immunophenotyping of the lymph nodes confirmed the diagnosis of diffuse small B cell lymphoma (DSBCL). Similar neoplastic cells were identified in the spleen and inguinal skin, establishing a diagnosis of stage V lymphoma with multi-organ infiltration. This case shows that while non-DLBCL B-cell lymphomas are often indolent, certain subtypes, such as DSBCL, may exhibit aggressive behavior, emphasizing the need to carefully evaluate the extent of infiltration in such cases.