Feline Leukemia Virus-infected Cats Research Articles

Comparative meta-analysis of feline leukemia virus and feline immunodeficiency virus seroprevalence correlated with GDP per capita around the globe

Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV) are two prevalent transmittable diseases for domestic cats. This paper reports the frequency of these two diseases compared globally across Gross Domestic Product (GDP) at purchasing power parity per capita (PPP). Information around FeLV and FIV rates of infection in specific locations around the world was analyzed from 47 published articles. Results show that based on the data available, the statistical model indicates that the highest percentage of FeLV or FIV infected cats live in areas of lower PPP (p ≤.001) with a decreasing rate of infection of FeLV and FIV with increasing income. Two theories for this could be that the lower PPP locations in this study were also in areas of greater feral cat and cat colony populations, as well as were areas with less emphasis on animal welfare and animal control programs. Additional research should be conducted to strengthen the study size in South America and Africa before further conclusions can be drawn.

Clinical and Haematological Disorders in Cats with Natural and Progressive Infection by Feline Leukemia Virus (FeLV)

Background: Feline leukemia virus (FeLV) is an important infectious agent in cats, responsible for great health damages and a large death amount. Among the most common clinical disorders caused by FeLV, severe hematological changes are related at the progressive infection, ordinarily presented as cytopenias. Regarding its oncogenic potential, lymphoma and leukemia are the most observed illness originated by the agent. Therefore, this study has the goal of describing and comparing clinical and hematological disorders in FeLV positive cats from a selected population.Materials, Methods & Results: Data of clinical evaluations of felines from a previously performed cross-sectional epidemiological study were compiled. This study obtained the prevalence of FeLV infected cats in Santa Catarina Plateau. Three groups were established from the original sample of 274 cats; Group 1 (control), FeLV negative and none clinical alterations (n = 80); Group 2, FeLV positive and none clinical changes (n = 9); Group 3, FeLV positive cats with clinical disorders (n = 29). Physical and hematological examination data were obtained from the medical records. The clinical changes at Group 3 were mucosal pallor (65.51% [19/29]), neurological disorders (20.69% [6/29]), lymphoma (20.69% [6/29]), coinfections (10.34% [3/29]) and leukemia (6.9% [2/29]). The most observed hematological disorders of Group 3 were anemia (65.51% [19/29]) and thrombocytopenia (62.7% [18/20]). At the complete blood count, the medium erythrocyte and eosinophil count, hemoglobin concentration and hematocrit were lower for Group 3 than the other two groups. The mean number of platelets count were higher for Group 1 than Group 2 and 3. The mean of the other variables remained between reference numbers. However, a descriptive analysis within the groups demonstrated that lymphopenia was observed in 34.48% (10/29) and neutropenia in 17.24% (5/29) at the Group 3. Discussion: The greater FeLV positive cats with clinical alterations number is a result of a sample obtained from a hospital population. In this scenario, cats are submitted to medical appointment in order to solve their clinical signs, not for purpose of infection screening. The frequency of non-neoplasic disease in FeLV positive cats was higher than neoplastic diseases. The mucosal pallor is the most important clinical change and it is an anemia consequence. A large number of clinical signs related in this study was non-specific. All the clinical changes are associated to FeLV infection, regardless the clinical syndrome observed. Neurological disorders frequency at this study was higher than other articles, being related to neoplastic lymphocytes in central nervous system at the resolved cases. Lymphoma and leukemia were the only neoplasms found in this FeLV study. Non-regenerative anemia was the main FeLV associated hematologic change. This disorder is originated by several mechanisms, such as the virus influence on bone marrow precursors and leukemic infiltration. Thrombocytopenia showed lower frequency than anemia and leukopenia, however, it was the second most common alteration in this study, which was observed in Group 2 and 3. The severe cytopenias related in Group 3 are probably due to the destruction or decrease of the production of these cells by the virus replication process. The clinical and hematological disorders found in this study, reveal the serious presentation and usually irreversible situation of this viral infection, originating important health harm to the affected cats.

Polymerase chain reaction-based detection of myc transduction in feline leukemia virus-infected cats.

Feline lymphomas are associated with the transduction and activation of cellular proto-oncogenes, such as c-myc, by feline leukemia virus (FeLV). We describe a polymerase chain reaction assay for detection of myc transduction usable in clinical diagnosis. The assay targets c-myc exons 2 and 3, which together result in a FeLV-specific fusion gene following c-myc transduction. When this assay was conducted on FeLV-infected feline tissues submitted for clinical diagnosis of tumors, myc transduction was detected in 14% of T-cell lymphoma/leukemias. This newly established system could become a useful diagnostic tool in veterinary medicine.

Diagnostic performances of two rapid tests for detection of feline leukemia virus antigen in sera of experimentally feline leukemia virus-infected cats.

ObjectivesThe objective of this study was to compare the diagnostic sensitivities and specificities of WITNESS FeLV-FIV (Zoetis) and SNAP FIV/FeLV Combo Test (IDEXX) for the detection of FeLV p27 antigen in the sera of experimentally feline leukemia virus (FeLV)-infected cats.MethodsDiagnostic sensitivities of WITNESS and SNAP were determined through testing of 47 serum samples collected from cats day 56 post-experimental infection with a virulent FeLV Rickard strain. Successful experimental infection was confirmed based on observation of FeLV antigen and proviral DNA in anti-coagulated (EDTA) whole-blood samples by immunofluorescent antibody (IFA) test and PCR, respectively. Diagnostic specificities of both tests were determined through testing of sera of 92 laboratory-housed, non-FeLV-exposed specific pathogen-free (SPF) cats.ResultsForty-one of 47 blood samples were IFA positive, whereas all 47 samples were PCR positive. All 92 non-FeLV-infected SPF cats were IFA and PCR negative. In comparison to IFA as the reference method, both WITNESS and SNAP tests yielded equivalent sensitivities and specificities of 100% and 97.8%, respectively. In comparison to PCR as the reference method, both WITNESS and SNAP tests likewise performed equivalently, with sensitivities and specificities of 91.5% and 100%, respectively.Conclusions and relevanceSensitivity and specificity of WITNESS FeLV-FIV for identifying FeLV p27 antigen in the sera of these experimentally FeLV-infected and non-FeLV-exposed SPF cats equaled those of the SNAP FIV/FeLV Combo Test. However, all positive results, regardless of the point-of-care test used, should be confirmed before making clinical decisions such as segregation from other cats or euthanasia.

Efficacy of treatment for FeLV: Hartman K, Block A, et al ( 1998) Treatment of feline leukemia virus-infected cats with paramunity inducer. Veterinary Immunology and Immunopathology65(2–4): 267–275

Efficacy of treatment for FeLV: Hartman K, Block A, et al ( 1998) Treatment of feline leukemia virus-infected cats with paramunity inducer. Veterinary Immunology and Immunopathology65(2–4): 267–275

Treatment of feline leukemia virus-infected cats with paramunity inducer

Two placebo-controlled double-blind trials were performed to determine the therapeutic efficacy of the paramunity inducer, Baypamun ® in feline leukemia virus (FeLV) -infected cats under controlled conditions. In the first study, 120 cats were involved; 60 cats were treated with Baypamun ® and 60 with a placebo preparation of virus-free cell culture medium. Dosage and administration of the drug over a 7-week period were performed according to the instructions given by the company. Remission of viremia occurred in 12% and 7% of the cats treated with Baypamun ® and placebo, respectively. This difference was not statistically significant. In the second study, 30 naturally infected cats were treated in a placebo-controlled double-blind trial. In total, 20 immunological, clinical, laboratory, and virological parameters were examined. No statistically significant differences could be demonstrated between Baypamun ® and placebo application. Therefore, FeLV infection was not influenced by Baypamun ® treatment.

Estudo clínico da síndrome de imunodeficiência adquirida em gatos domésticos de São Paulo

Com a finalidade de estudar a magnitude da ocorrência do vírus da leucemia felina (VLF) e do vírus da imunodeficiência dos felinos (VIF) entre os felinos domésticos de São Paulo, 401 animais de ambos os sexos, idade e raças variadas, foram submetidos à pesquisa de anticorpos humorais (VIF) e de antígenos virais solúveis (VLF) através do teste imunoenzimático - ELISA (Feline Leukímia Virus Antígen / Feline Immunodeficiency Virus Antibory - CITE® - Agritech Systems Inc.). Desses, 123 eram felinos sadios e os demais 278 animais eram felinos doentes atendidos no Departamento de Clínica Médica/Hospital Veterinário da FMVZ/USP. Foram observados 8 (6,5%) reagentes ao VIF entre os felinos sadios e 39 (14%) entre os gatos doentes. Em relação ao VLF, 2 (1,6%) dos animais sadios e 30 (10,8%) entre os gatos doentes foram reagentes ao teste imunoenzimático e apenas um animal foi reagente a ambos os vírus. A infecção pelo VIF foi mais freqüente entre os machos, quando comparada às fêmeas, na proporção de 4:1, não tendo sido, no entretanto, observada diferença entre machos e fêmeas infectados em relação ao VLF. As infecções oportunistas, como a causada por Haemobartonella felis, foram as doenças associadas mais freqüentemente observadas tanto nos felinos VLF positivos quanto nos VIF positivos. Em relação aos tumores, a forma mediastinal do linfoma foi a mais freqüente entre os felinos VLF positivos. As demais condições mórbidas que se associaram à infecção pelos dois Retrovirus foram de natureza e freqüência variáveis. A idade média dos animais infectados pelo VIF foi de 4,4 + 3,0 anos e dos felinos infectados pelo VLF, de 2,4 + 1,7 anos. Todos os animais reagentes e sintomáticos não sobreviveram mais do que dois anos. Por outro lado, não houve nenhum óbito entre os animais assintomáticos infectados por qualquer um dos Retrovirus durante o mesmo período de observação, demonstrando que operíodo de pré-patência pós-infecção pode ser bastante longo.

Use of two virustatica (AZT, PMEA) in the treatment of FIV and of FeLV seropositive cats with clinical symptoms

In the present study the therapeutic efficacy and the side effects of two antiretroviral compounds used in human acquired immunodeficiency syndrome (AIDS) research, 3′-azido-2′,3′-dideoxythymidine (AZT, zidovudine, Retrovir) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA), were investigated in the treatment of cats naturally infected with feline immunodeficiency virus (FIV) and cats naturally infected with feline leukemia virus (FeLV). AZT was administered subcutaneously at a dose of 5 mg kg −1 body weight every 12 h and PMEA was administered subcutaneously at a dose of 2.5 mg kg −1 body weight every 12 h during a 3 week hospitalization. The therapeutic efficacy of both compounds was investigated. There was a stronger potency of PMEA than of AZT on the regression of stomatitis in FIV and in FeLV infected cats. In addition, in FIV infection PMEA had a stronger effect on the improvement of the general clinical status. Both antiretroviral compounds were potent agents to improve the immunologic status of FIV infected cats by raising the CD4/CD8 ratio. In FeLV infection PMEA and AZT appeared to reduce antigenemia. The hematological side effects caused by PMEA were severe and stronger than those of AZT. Therefore the advantage of PMEA in clinical and immunologic improvement was diminished by the hematologic disorders, which do not allow long term treatment with this drug in the dose used.

Use of immunomodulators as an aid to clinical management of feline leukemia virus-infected cats

Use of immunomodulators as an aid to clinical management of feline leukemia virus-infected cats

Antibody response of kittens after vaccination followed by exposure to feline leukemia virus-infected cats

Summary Protein (western) blot analysis and virus-neutralization assay were used to evaluate the antibody response of specific-pathogen-free kittens to FeLV vaccination and followed by natural exposure. Several kittens had barely detectable reactions to specific FeLV antigens prior to vaccination or exposure. Correlation was not found between protection against persistent viremia and antibody response after vaccination as measured by western blot analysis or virus neutralization assay. A statistically significant (P < 0.01) difference in the antibody response against p27 antigen after natural exposure to FeLV was observed between persistently viremic kittens and transiently viremic or aviremic kittens. Measurable (P < 0.05) virus neutralizing antibody titer after FeLV exposure was found only in a small number of kittens that were protected against persistent viremia. Lack of association between humoral response and vaccination-induced protection against persistent FeLV infection suggests an important role for cell-mediated immunity in such protection.

Evaluation of antiviral activity and toxicity of dextran sulfate in feline leukemia virus-infected cats.

The feline leukemia virus (FeLV) disease model was used to conduct a toxicity and antiretrovirus efficacy trial of dextran sulfate (DS; molecular mass, 7,000 to 8,000 Da). In vitro, FeLV infection of feline lymphoid cells was inhibited by 10 micrograms of DS per ml. DS was administered to cats by continuous intravenous infusion at doses of 600, 120, 24, or 4.8 mg/kg of body weight per day, beginning 24 h before FeLV challenge. Doses of 24 mg/kg/day and more were excessively toxic, causing intestinal lesions and death. Similar changes were observed in unchallenged animals receiving 24 mg/kg/day, indicating that toxicity was DS mediated. The dosage of 4.8 mg/kg/day was subtoxic but did not prevent the induction and persistence of FeLV viremia. The results demonstrate that DS by continuous intravenous infusion is excessively toxic at high doses and ineffective at preventing FeLV infection at a subtoxic dose in the FeLV cat model.

Hematologic effects of short-term oral diethylcarbamazine treatment given to chronically feline leukemia virus-infected cats

Diethylcarbamazine (N,N-diethyl-4-methyl-1-piperazine carboxamide [DEC]) is widely used, especially in tropical regions, to prevent and treat filariasis. The antifilarial effect of this drug has been attributed to immunomodulation. Evidence is accumulating to indicate that DEC may mitigate the course of feline leukemia virus infection (FeLV) in cats. Previous studies have suggested that continuous oral DEC treatment given shortly after evidence of FeLV infection prevents or delays lymphopenia and prolongs survival. The present study focuses on the hematologic effects of one month oral DEC treatment given to adult chronically FeLV-infected cats and uninfected cats as compared to untreated FeLV-infected cats. Such treatment frequently resulted in abruptly lowered peripheral lymphocyte counts in chronically FeLV-infected cats. Further studies are warranted to evaluate whether administration of DEC could eliminate circulating retroviral-infected cells.

IgG-Fc-receptor positive and negative T cells from feline leukemia virus-infected cats.

IgG-Fc-receptor positive and negative T cells from feline leukemia virus-infected cats.

The epidemiology of the feline leukemia virus (FeLV)

Clustering of cases of feline lymphosarcoma (LSA) has been observed by veterinarians for many years. In 1964 it was discovered that feline LSA was caused by an oncornavirus, the feline leukemia virus (FeLV). In 1970, a simple, indirect immunoflourescent antibody (IFA) test for FeLV was developed which enabled large numbers of cats, living in their natural (household) environments, to be tested for the virus. In one study, over 2,000 cats were tested and the results showed conclusively that FeLV is a contagious agent for cats. This finding was independently confirmed by several other investigators using different testing procedures. After discovering the contagious nature of FeLV a test and removal program was devised which successfully prevents the spread of FeLV and the development of FeLV diseases in the pet cat population. There is, at present, no evidence that FeLV infects humans living with FeLV infected cats.

Brief Communication: Detection of Complement-Dependent Lytic Antibodies in Sera From Feline Leukemia Virus-Infected Cats by the Chromium-51 Release Assay 2

Sera from feline leukemia virus-infected cats lysed FL74 cells in the presence of an appropriate complement source; lysis was detected with the use of the 51 Cr release method. Serum complement from both rabbits and guinea pigs mediated lysis. Partial correlation of results was obtained from preliminary comparisons of lysis and immunofluorescence tests with the use of FL74 cells as targets.