Leucemia viral felina em gatos domésticos de Caxias do Sul, Brasil

Abstract

The feline leukemia virus (FeLV) represents a significant challenge in veterinary clinics worldwide. Several studies have demonstrated a high prevalence of FeLV in various locations in Brazil. Transmission occurs through close contact between infected and susceptible cats. Detection can be performed through immunological (rapid) tests and molecular techniques such as quantitative polymerase chain reaction (qPCR or qRT-PCR), which also allows for viral load assessment. This dissertation aimed to (1) study the frequency of FeLV infections in domestic cats in the municipality of Caxias do Sul and (2) evaluate the viral load data of infected animals. The initial sampling consisted of 598 sequentially attended cats in 7 clinics and 2 veterinary hospitals from January 2022 to March 2023. General information was collected (reason for consultation, residence, age, sex, reproductive status, outdoor access, vaccination), general clinical condition was evaluated, and samples of total blood were collected. From this population, 366 animals with rapid test results for p27 antigen detection using commercial kits at the time of consultation and properly collected blood samples were selected. These samples underwent DNA/RNA extraction and detection/quantification of proviral DNA using qPCR. Samples positive for FeLV proviral DNA were also tested for viral RNA detection/quantification using RT-qPCR. The results showed a total of 112 (30.6%) positive cases in the rapid test and/or qPCR, including males (n=64/112, 57.1%) and females (n=48/112, 42.9%), neutered (n=80/112, 71.3%) and sexually intact cats (n=32/112, 28.6%), with outdoor access (n=76/112, 67.9%) or not (n=34/112, 30.4%), vaccinated (n=36/112, 32.1%) or not (n=74/112, 66.1%). Comparative evaluation of different categories demonstrated that unvaccinated cats (OR 2.52, p < 0.001), clinically ill cats (OR 2.88, p < 0.001), cats with outdoor access (OR 2.70, p < 0.001), and cats with apathetic behavior (OR 3.06, p < 0.001) had higher odds of being infected with FeLV. Among clinical manifestations, lethargy (OR 3.09, p < 0.001), anemia (OR 13, p < 0.001), and neoplasms (OR 5.9, p < 0.001) were more frequent in FeLV-positive animals. Multivariate analysis was performed to verify the correlation of risk factors with FeLV infection, showing statistical significance for unvaccinated cats (OR 9.67; 95% CI: 1.85-23.69) and cats vaccinated with triple (OR 9.67, 95% CI: 3.37-27.76) and quadruple (OR 2.74, 95% CI: 1.53-4.89) vaccines, as well as cats with outdoor access (OR 2.52, 95% CI: 1.49-4.23). Anemia and neoplasia were associated with FeLV infection (OR 9.11, 95% CI: 2.41-29.49 and OR 4.14, 95% CI: 1.42-12.11, respectively). Samples from 103 cats underwent proviral and viral load analysis. Viral and proviral load analyses allowed for preliminary classification of infections as high progressive (n=12/109, 11%), low progressive (n=35/109, 32.1%), and regressive (n=11/109, 10.1%). The high FeLV prevalence demonstrated in this study emphasizes the need to establish effective control and prevention strategies in the region to reduce transmission risk factors. [resumo fornecido pelo autor]