Prevalence, Recombination Events, and Risk Factors of FeLV Infection in Domestic Cats from Colombia.

Feline leukemia virus (FeLV) is one of the primary pathogens in domestic felines, causing significant immunosuppression, lymphomas, and even death. Various subtypes of this virus have been described, with FeLV-A being the least pathogenic and the most widely distributed subtype. Conversely, the recombination of FeLV-A with endogenous retroviral sequences has resulted in variant B, which is associated with the development of leukemias and lymphomas. FeLV transmission occurs primarily through grooming between individuals, facilitating its distribution and circulation. The aim of this study was to characterize subtype B and analyze risk factors associated with viral infection in a sample of felines from Colombia. To achieve this, blood samples were taken from the cephalic or jugular veins of 151 felines in four municipalities of Antioquia, and data on age, sex, and area of origin were collected. PCR was performed on a region of the pol gene (306 bp), and only FeLV-positive feline samples underwent a second PCR for the env gene (1400 bp). Only env-positive PCR products were sequenced, and phylogenetic and recombination analyses were performed. Logistic regression was used to calculate the odds ratios (OR) for each variable (age, sex, and area of origin). The overall FeLV positivity rate was 33.77%, with an association found between male sex and FeLV infection (OR = 2.23, p = 0.038), as well as between the area of origin and FeLV infection (OR = 0.22, p = 0.035). Of the total samples, only 11 (7.3%) amplified for FeLV-B, with seven samples from Buriticá and four from Medellín. The recombination analyses confirmed that all sequences belonged to the FeLV-B subtype and were unique recombinants. The molecular presence of the virus in the study area demonstrates that the circulation of this retrovirus remains active. Additionally, the area of origin and male sex are risk factors for FeLV infection. Finally, an increase in FeLV positivity was observed, and while the B variants are generated de novo in each feline, it is crucial to continue health monitoring, especially in regions distant from major urban centers.