Clinicopathological, epizootological, and morphological characterization of canine transmissible venereal tumor in dogs in Astana, Kazakhstan: A one-year Veterinary Diagnostic Center study.

Background and Aim: Canine transmissible venereal tumor (CTVT), also known as transmissible venereal sarcoma, is a naturally occurring, contagious neoplasm primarily transmitted by the transfer of viable tumor cells during mating. Although the disease is widely distributed worldwide, epidemiological and clinicopathological data from Central Asia remain scarce. This study aimed to characterize the epizootological distribution, clinical manifestations, hematological and biochemical alterations, microbiological findings, and morphological features of CTVT in dogs presented to a Veterinary Diagnostic Center in Astana, Kazakhstan. Materials and Methods: A prospective observational study was conducted from February 2024 to February 2025. A total of 2,500 dogs were screened, and 425 dogs with tumor-like lesions underwent clinical, laboratory, cytological, histopathological, and microbiological investigations. Twenty-three dogs with confirmed CTVT were included in the final analysis. Animals were categorized according to the presence (n = 13) or absence (n = 10) of purulent complications. Clinical examination, complete blood count, serum biochemical analysis, cytological evaluation using smear-imprint and fine-needle aspiration techniques, histopathological assessment, and microbiological testing were performed. Statistical analyses included Student's t-test, Mann-Whitney U test, Fisher's exact test, and odds ratio estimation, with significance set at p < 0.05. Results: CTVT accounted for 23 of 425 tumor-bearing dogs (5.4%). The disease was more frequently observed in males (73.9%) and in dogs aged 1.5-5 years (65.2%). Mixed-breed dogs represented the largest affected group (47.8%). Clinically, all dogs exhibited friable genital masses accompanied by hemorrhagic discharge, while purulent exudation occurred in 56.5% of cases. Extragenital involvement was identified in 8.7% of dogs. Animals with purulent complications showed significantly elevated heart rate and respiratory rate (p < 0.001), leukocytosis, reduced hemoglobin concentration, and lower hematocrit values. Biochemical analysis revealed increased concentrations of urea, creatinine, alanine aminotransferase, aspartate aminotransferase, bilirubin, and alkaline phosphatase in dogs with purulent lesions. Cytological examination demonstrated round tumor cells with eccentrically positioned nuclei, coarse chromatin, prominent nucleoli, abundant cytoplasmic vacuoles forming a characteristic "string-of-pearls" pattern, and marked mitotic activity. Histopathological findings confirmed the diagnosis and supported the observed cytomorphological features. Conclusion: This study provides the first comprehensive clinicopathological, epizootological, microbiological, and morphological characterization of CTVT in dogs from Kazakhstan. Male sex, reproductive age, and inadequate reproductive control were associated with disease occurrence. Cytoplasmic vacuolization and high mitotic activity were reliable morphological indicators of CTVT. The findings provide valuable baseline data to improve diagnosis, surveillance, and disease management strategies in Central Asia.