Feline leukemia virus (FeLV) is a retrovirus distributed worldwide in domestic cats and with different outcomes (progressive, regressive, abortive, focal). The present study reports an epidemiological survey of FeLV frequency and the evaluation of some risk factors and the two main disease outcomes (progressive and regressive) in an urban cat population from Brazil. A total of 366 cats with sociodemographic information and p27 FeLV antigen test performed were included in the study. FeLV DNA (provirus) in the blood samples of all cats was detected via real-time polymerase chain reaction (qPCR). Plasma samples from 109 FeLV-positive and FeLV-negative cats were also submitted to reverse transcription (RT-qPCR) to determine the FeLV viral load. The results demonstrated that 112 (30.6%) cats were positive through the p27 antigen and/or qPCR. A risk factor analysis demonstrated that cats without vaccination against FeLV (OR 9.9, p < 0.001), clinically ill (OR 2.9, p < 0.001), with outdoors access (OR 2.7, p < 0.001), and exhibiting apathetic behavior (OR 3.1, p < 0.001) were more likely to be infected with FeLV. FeLV-infected cats were also more likely to present with anemia (OR 13, p < 0.001) and lymphoma (OR 13.7, p = 0.001). A comparative analysis of the different detection methods in a subset of 109 animals confirmed FeLV infection in 58 cats, including 38 (65.5%) with progressive, 16 (27.6%) with regressive, and 4 (6.9%) with probably focal outcome diseases. In conclusion, this study demonstrates a high prevalence of FeLV in this urban cat population from Brazil and highlights the need to establish more effective prevention strategies (such as viral testing, vaccination programs, specific care for FeLV-positive cats) to reduce diseases associated with this virus in Brazil.

Com o aumento da população de felinos domésticos, o vírus da Leucemia Viral Felina (FeLV) se tornou um problema significativo na saúde desses animais. O FeLV é um retrovírus que compromete o sistema imunológico dos gatos, levando a alta morbidade e mortalidade. O vírus pode causar anemia arregenerativa, imunossupressão, linfoma e leucemia. A infecção pode ter diferentes desfechos, como regressiva, abortiva, focal ou progressiva, dependendo da resposta imunológica do animal e das características do vírus. O FeLV é transmitido principalmente por meio de mordidas e contato com secreções, mas também pode ser transmitido por compartilhamento de alimentos, durante a gestação e lactação, ou através de transfusões sanguíneas. Os felinos infectados podem apresentar uma variedade de sinais clínicos, muitas vezes acompanhados de sinais inespecíficos como perda de peso e anorexia. O diagnóstico da FeLV pode ser feito por testes diretos como Enzyme Linked ImmunonoSorbent Assay (ELISA), Ensaio de Imunofluorescência (IFA) e Reação em Cadeia da Polimerase (PCR), com cada método oferecendo diferentes níveis de sensibilidade e especificidade. Não há cura para a FeLV, mas o tratamento visa manter a qualidade de vida dos gatos infectados por meio de manejo adequado, nutrição, e controle de parasitas. A prevenção é essencial e inclui a vacinação, especialmente com vacinas quíntuplas, e medidas profiláticas como evitar o contato com gatos infectados e realizar testes regulares. O aumento da conscientização dos tutores e o acesso a diagnósticos e vacinas são fundamentais para controlar a disseminação da FeLV. A pesquisa e a educação contínua são cruciais para melhorar a gestão e a prevenção dessa doença. Desta forma, é fundamental aprofundar o conhecimento sobre o FeLV. Portanto, o objetivo deste trabalho é realizar uma revisão abrangente da literatura relacionada a este vírus e apresentar um panfleto online explicativo, ressaltando a importância do risco de infecção de felinos não vacinados contra a FeLV.

Feline panleukopenia is a viral disease of domestic cats caused by Protoparvovirus carnivoran 1. This virus species is generally classified into feline parvovirus (FPV) and canine parvovirus type 2 (CPV-2) according to phylogenetic characteristics and association with diseases in the animal hosts. Despite the availability of vaccines, feline panleukopenia has been reported in cats from Brazil. This study aimed to detect and characterize Protoparvovirus carnivoran 1 in blood samples from 368 domestic cats in southern Brazil. Total DNA was extracted from these samples, and FPV/CPV-2 detection was performed using a specific real-time polymerase chain reaction (qPCR) assay. The viral protein 2 (VP2) gene was further sequenced to identify the FPV/CPV-2 genotype. The results showed nine blood samples (2.45%) testing positive for Protoparvovirus carnivoran 1. Partial VP2 gene was successfully sequenced in six of these positive samples. A phylogenetic analysis with a large dataset classified all protoparvoviruses into three main clades: A, B, and CPV. Four of the viruses sequenced in this study (IDs 9917, 9919, 9927, and 9936) were classified in clade A, one (ID 9944) in clade B, and one (ID 9930) in clade CPV. Furthermore, three FPVs from clade A showed total nucleotide identity among themselves and also with field FPV sequences, while two of them (IDs 9936 and 9944) showed high nucleotide identity with two different modified live virus vaccines (from Clades A and B, respectively). These findings suggest that domestic cats are infected by field-like and/or vaccine-related FPV strains, as well as CPV-2 in southern Brazil.