Feline Leukemia Virus p27 Antigen Concentration and Proviral DNA Load Are Associated with Survival in Naturally Infected Cats.

Longitudinal studies of cats naturally infected with feline leukemia virus (FeLV) are important for understanding disease outcomes. Levels of p27 antigen and copy numbers of proviral DNA have been associated with FeLV-infection courses. The purpose of this prospective study was to establish cutoff values for p27 antigen concentration and proviral DNA load that distinguished high positive from low positive groups of cats and to evaluate an association with survival. At enrollment, 254 cats were tested by point-of-care and microtiter plate enzyme-linked immunosorbent assays (ELISAs) for p27 antigen and real-time polymerase chain reaction (PCR) for proviral DNA. The 127 positive cats were retested monthly for six months and monitored for survival over the four-year study. A receiver operating characteristic-based analysis of samples with concordant or discordant qualitative results for p27 antigen and proviral DNA was used to establish cutoff values, and when applied to test results at enrollment for classifying cats as high positive or low positive, a significant difference in survival was observed. High positive cats had a median survival of 1.37 years (95% CI 0.83-2.02) from time of enrollment, while most low positive cats were still alive (93.1% survival). Quantitative results for p27 antigen concentration and proviral DNA load were highly correlated with survival times in FeLV-infected cats.

Causes of death and euthanasia in domestic cats in the Santa Catarina plateau (1995-2015) / Causas de morte e eutanásia em felinos domésticos no Planalto de Santa Catarina (1995-2015)

Knowledge about the causes of death in felines constitutes important information to owners, veterinarians, and researchers, aiming at reducing the number of deaths in this species. In order to determine the main causes of death or euthanasia in cats in the Santa Catarina plateau, data from 1995 to 2015 available in necropsy files of the Laboratory of Animal Pathology (LAPA) of the State University of Santa Catarina (UDESC) were collected and evaluated. In that period, 1,728 cats were necropsied, mainly males (46.12%) and adults (50.11%). The mean ages at death for kittens, adults, and elderly were 5.07 months, 3.9 years, and 13.9 years, respectively. Of the 1,728 necropsy reports assessed, the cause of death was identified in 1,184 (68.52%) cases. The main cause of death was associated with infectious diseases (15.8%), with prevalence of feline infectious peritonitis (29.76%), followed by neoplasms (11.98%) with lymphoma (44.93%) and leukemia (16.91%) as the most common, and traumas (11.81%) mainly caused by motor vehicle accidents. These results show the need for owner awareness, as well as establishment of prophylaxis and vaccination programs, aimed at reducing the number of deaths and thus increasing life expectancy in the feline population.(AU)

O conhecimento a respeito da causa mortis em felinos é importante para que se construa um informativo para proprietários, médicos veterinários e pesquisadores, objetivando a redução no número de mortes na espécie. Com o intuito de determinar as principais causas de morte ou eutanásia em felinos domésticos no planalto catarinense foram avaliados os arquivos de registro das necropsias do período de 1995 a 2015 do Laboratório de Patologia Animal da Universidade do Estado de Santa Catarina. No período, foram necropsiados 1.728 felinos, principalmente machos (46,12%), adultos (50,11%). A idade média para filhotes foi de 5,07 meses, enquanto para adultos foi 3,9 anos e para idosos 13,9 anos. Das 1.728 necropsias de felinos, a enfermidade que levou o animal a morte foi determinada em 1.184 (68,52%). As doenças infecciosas foram a principal causa de morte (15,8%), dentre as quais a peritonite infecciosa felina (29,76%) foi a mais frequente; seguida das neoplasias (11,98%), sendo o linfoma (44,93%) e a leucemia (16,91%), as mais comuns; e dos traumatismos (11,81%), principalmente atropelamentos por veículos automotivos. Estes resultados refletem a necessidade da conscientização dos proprietários, bem como da instituição de programas de profilaxia e vacinação, visando a redução de mortes e o aumento na expectativa de vida para a população felina.(AU)

Retroviral DNA--the silent winner: blood transfusion containing latent feline leukemia provirus causes infection and disease in naïve recipient cats.

BACKGROUND: The feline leukemia virus (FeLV) is a gamma-retrovirus of domestic cats that was discovered half a century ago. Cats that are infected with FeLV may develop a progressive infection resulting in persistent viremia, immunodeficiency, tumors, anemia and death. A significant number of cats mount a protective immune response that suppresses viremia; these cats develop a regressive infection characterized by the absence of viral replication and the presence of low levels of proviral DNA. The biological importance of these latter provirus carriers is largely unknown. RESULTS: Here, we demonstrate that ten cats that received a transfusion of blood from aviremic provirus carriers developed active FeLV infections, some with a progressive outcome and the development of fatal FeLV-associated disease. The infection outcome, disease spectrum and evolution into FeLV-C in one cat mirrored those of natural infection. Two cats developed persistent antigenemia; six cats were transiently antigenemic. Reactivation of infection occurred in some cats. One recipient developed non-regenerative anemia associated with FeLV-C, and four others developed a T-cell lymphoma, one with secondary lymphoblastic leukemia. Five of the ten recipient cats received provirus-positive aviremic blood, whereas the other five received provirus- and viral RNA-positive but aviremic blood. Notably, the cats that received blood containing only proviral DNA exhibited a later onset but graver outcome of FeLV infection than the cats that were transfused with blood containing proviral DNA and viral RNA. Leukocyte counts and cytokine analyses indicated that the immune system of the latter cats reacted quicker and more efficiently. CONCLUSIONS: Our results underline the biological and epidemiological relevance of FeLV provirus carriers and the risk of inadvertent FeLV transmission via blood transfusion and demonstrate the replication capacity of proviral DNA if uncontrolled by the immune system. Our results have implications not only for veterinary medicine, such as the requirement for testing blood donors and blood products for FeLV provirus by sensitive polymerase chain reaction, but are also of general interest by revealing the importance of latent retroviral DNA in infected hosts. When aiming to eliminate a retroviral infection from a population, provirus carriers must be considered.

Long-term impact on a closed household of pet cats of natural infection with feline coronavirus, feline leukaemia virus and feline immunodeficiency virus.

A closed household of 26 cats in which feline coronavirus (FCoV), feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) were endemic was observed for 10 years. Each cat was seropositive for FCoV on at least one occasion and the infection was maintained by reinfection. After 10 years, three of six surviving cats were still seropositive. Only one cat, which was also infected with FIV, developed feline infectious peritonitis (FIP). Rising anti-FCoV antibody titres did not indicate that the cat would develop FIP. The FeLV infection was self-limiting because all seven of the initially viraemic cats died within five years and the remainder were immune. However, FeLV had the greatest impact on mortality. Nine cats were initially FIV-positive and six more cats became infected during the course of the study, without evidence of having been bitten. The FIV infection did not adversely affect the cats' life expectancy.

Year two of follow-up evaluation of a randomized, blind field trial of a commercial feline leukemia virus vaccine.

A blind randomized field trial of a commercial FeLV vaccine was conducted. Cats on study were vaccinated with either a commercial FeLV vaccine or a placebo, then housed with FeLV-positive cats in a ratio of approximately 2 study cats to 1 infected cat (results of the first 12 months of the study have been reported). All surviving placebo-treated and FeLV-vaccinated cats were re-vaccinated 1 year after initial exposure to FeLV-infected cats. Exposure continued for an additional 12 months, and the viremia status of the cats was monitored by immunofluorescent antibody (IFA) and ELISA testing at 4-month intervals. During the second year of observation, 1 additional FeLV-vaccinated cat had positive results of 2 consecutive ELISA tests, but remained IFA negative. Classifying this cat as persistently viremic reduced the estimate of the preventable fraction, but did not alter the conclusions drawn earlier, viz, that vaccination appreciably reduces the number of cats that become persistently viremic after long-term natural exposure.