Detection of feline leukaemia virus in blood and bone marrow of cats with varying suspicion of latent infection

The purpose of this study was to determine if polymerase chain reaction (PCR) could be used to detect FeLV proviral DNA in bone marrow samples of cats with varying suspicion of latent infection. Blood and bone marrow samples from 50 cats and bone marrow from one fetus were collected, including 16 cats with diseases suspected to be FeLV-associated. Serum enzyme-linked immunosorbent assay (ELISA), blood and bone marrow immunofluorescent antibody test (IFA), and blood and bone marrow PCR were performed on each cat, and IFA and PCR on bone marrow of the fetus. Forty-one cats were FeLV negative. Five cats and one fetus were persistently infected with FeLV. Four cats had discordant test results. No cats were positive on bone marrow PCR only. It appears persistent or latent FeLV infection is not always present in conditions classically associated with FeLV.     

The prevalence of feline immunodeficiency virus infection in hyperthyroid cats

One hundred and thirty-four male and female hyperthyroid cats (mean age 11.9 years) were tested for the presence of feline immunodeficiency virus antibodies. Thirty-two (23.9%) were positive. The prevalence of feline immunodeficiency virus antibodies was greater in male cats (30.5%) than in female cats (17.2%). The prevalence of feline immunodeficiency virus infection in hyperthyroid cats is similar to the prevalence of feline immunodeficiency virus in the sick cat population and less than that of sick aged cats at the Massey University Clinic and Hospital. The findings of this survey do not support involvement of feline immunodeficiency virus in the pathogenesis of hyperthyroidism in the cat.     

Neoplasia associated with feline immunodeficiency virus infection in cats of southern California.

Between 1988 and 1991, feline immunodeficiency virus (FIV) infection status was evaluated in 1,160 cats examined at an oncology referral and general practice in Los Angeles, California. Twenty-nine (2.5%) cats were FIV positive. Neoplasia was present in 18 of the 29 (62%) cats. Sampling for neoplasia was intentionally biased in the oncology referral group. However, 33% (6/18) of FIV-infected cats with neoplasia originated from the general practice. Three neoplastic processes were observed; myeloproliferative disease (MPD; 5/18), lymphoma (LSA; 5/18), and squamous cell carcinoma (SCC; 7/18). One cat had LSA and SCC. Extranodal sites of LSA were common (66%) in FIV-infected cats. Sites of LSA were submandibular and mesenteric lymph nodes, liver, kidneys, periorbital area, and diffuse (heart, pancreas, bladder). Sites of SCC were sublingual (n = 2), nasal planum (n = 3), nasal planum and eyelids (n = 1), and mandible (n = 2). Feline leukemia virus co-infection was observed in 17% (5/29) of FIV-infected cats. The FIV-infected cats with MPD were young (range, 8 months to 13 years; median, 4 years) and had short survival duration (2, 6, 21, 134, 249 days) even in response to aggressive treatment. The FIV-infected cats with LSA were older (median age, 8 years; range, 4 to 14 years) and survived 60 days if untreated. Cats administered chemotherapy survived 39, 45, 217, and 243 days; the latter 2 cats had partial remission of 2 months' duration. Older FIV-infected cats had SCC (median age, 12 years; remission range, 7 to 16 years) because of more frequent association of both diseases in older cats with outdoor environment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence of feline leukemia virus infection and serum antibodies against feline immunodeficiency virus in unowned free-roaming cats

OBJECTIVE: To determine prevalence of FeLV infection and serum antibodies against feline immunodeficiency virus (FIV) in unowned free-roaming cats. DESIGN: Cross-sectional serologic survey. ANIMALS: 733 unowned free-roaming cats in Raleigh, NC, and 1,143 unowned free-roaming cats in Gainesville, Fla. RESULTS: In Raleigh, overall prevalence of FeLV infection was 5.3%, and overall seroprevalence for FIV was 2.3%. In Gainesville, overall prevalence of FeLV infection was 3.7%, and overall seroprevalence for FIV was 4.3%. Overall, FeLV prevalence was 4.3%, and seroprevalence for FIV was 3.5%. Prevalence of FeLV infection was not significantly different between males (4.9%) and females (3.8%), although seroprevalence for FIV was significantly higher in male cats (6.3%) than in female cats (1.5%). CONCLUSIONS AND CLINICAL RELEVANCE: Prevalence of FeLV infection and seroprevalence for FIV in unowned free-roaming cats in Raleigh and Gainesville are similar to prevalence rates reported for owned cats in the United States. Male cats are at increased risk for exposure to FIV, compared with female cats.     

IgG from acutely infected cats blocks mucosal feline immunodeficiency virus infection

We have previously shown an absence of detectable systemic or local infection in cats exposed to an infectious (100 TCID(50)) feline immunodeficiency virus (FIV) plasma inoculum via either the rectal or vaginal mucosa. In contrast, this same plasma inoculum was infectious via parenteral inoculation. Moreover an equivalent dose of cell-free tissue culture-origin virus inoculum infected 100% of cats by either the rectal or vaginal exposure route. To evaluate this phenomena, we used a tissue culture system to identify a heat-stable factor in the plasma of cats acutely (3 weeks) infected with FIV that blocked infection of naive peripheral blood mononuclear cells (PBMC) by either cell-free or cell-associated FIV in vitro. A single application of as little as a 1:200 dilution of either heparinized or Alsevier's anticoagulated plasma effectively inhibited production of FIV p26 in culture over a 21-day co-culture period. Depletion of antibody using a protein A column abrogated the inhibitory effect of FIV plasma against in vitro FIV infection. Co-inoculation of heat-inactivated plasma with 400 TCID(50) FIV-B-2542 cell-free supernatant virus onto the vaginal mucosa of two cats resulted in complete inhibition of infection in one cat and increased time to infection in the second. Thus, antibody found in the plasma of cats acutely infected with FIV blocks cell-associated and cell-free infection, inhibits virus production in previously infected cells, and reduces mucosal transmission efficiency in vivo. Extrapolation may help explain the relatively inefficient mucosal transmission of human immunodeficiency virus-1 (HIV) and other lentiviruses.     

Effect of primary phase feline immunodeficiency virus infection on cats with chronic toxoplasmosis.

The effect of primary phase feline immunodeficiency virus (FIV) infection on clinical signs, hematological values, Toxoplasma gondii oocyst shedding, T. gondii-specific serology, T. gondii-specific cell-mediated immune responses, non-specific cell-mediated immune responses, and lymphocyte subpopulations from cats with experimentally induced chronic toxoplasmosis was studied. No significant clinical or hematologic abnormalities were noted following inoculation with FIV. T. gondii-specific IgM was significantly increased, concanavalin A, T. gondii tachyzoite antigen and T. gondii secretory antigen induction of lymphocyte transformation were significantly suppressed, and CD4+ cell numbers were significantly decreased following inoculation with FIV. The changes were attributed to FIV effects on the immune system and resultant activated toxoplasmosis.     

Husbandry practices for cats infected with feline leukemia virus or feline immunodeficiency virus.

Cats that are persistently infected with FeLV or feline immunodeficiency virus but are not manifesting clinical signs of disease are at risk for developing a wide variety of immunosuppressive, degenerative, or neoplastic diseases. Infected cats should be isolated to prevent transmission of virus to healthy cats, and to protect infected cats from exposure to pathogens that can cause life-threatening secondary infections. Iatrogenic transmission of virus from infected cats in isolation to healthy cats may be reduced by strict adherence to handling, sanitation, and disinfection procedures. Husbandry practices that may delay the complications of infection include regular vaccination, provision of high-quality diets, reduction of stress, control of endoparasites and ectoparasites, and early and aggressive treatment of clinical signs of disease.     

Shedding of feline immunodeficiency virus in semen of domestic cats during acute infection

OBJECTIVE: To examine shedding of cell-free and cell-associated feline immunodeficiency virus (FIV) in semen of domestic cats during acute infection. ANIMALS: 7 specific-pathogen-free sexually intact male cats. PROCEDURE: 6 cats were inoculated IV with 5 x 10(6) 50% tissue culture infective doses of FIV-NCSU1, and 1 cat served as an uninfected (control) cat. Infection was confirmed in the 6 cats. Periodically for up to 16 weeks after inoculation, cats were anesthetized and ejaculates obtained by use of electroejaculation. Virus was isolated from filtered seminal plasma and washed seminal cells by co-cultivation with a feline CD4+ T-cell line. Seminal cell lysates were also examined for a 582-base pair segment of FIV gag provirus DNA, using a nested polymerase chain reaction amplification. RESULTS: During the acute phase of FIV infection, virus was evident in semen of 5 inoculated cats. Five cats had virus-positive seminal plasma and 3 had virus-positive cellular constituents during the study. Virus was isolated from 8/22 (36%) seminal plasma samples and 2/17 (18%) seminal cell specimens. Provirus DNA was detected in 5/24 (21%) seminal cell lysates. Cell-free virus was isolated as early as 6 weeks after inoculation, whereas cell-associated virus was isolated as early as 12 weeks after inoculation. Provirus DNA was detected in seminal cells from one cat as early as 1 week after inoculation. CONCLUSIONS AND CLINICAL RELEVANCE: Cell-free and cell-associated FIV are shed in semen of cats early during the course of infection. Samples obtained before seroconversion may contain virus. Virus shedding in ejaculates varies between and within cats during acute infection.     

Prevalence of feline leukemia virus and antibodies to feline immunodeficiency virus in cats in Norway.

Serum samples from 224 Norwegian cats were analyzed for the presence of feline leukemia virus (FeLV) p27 common core antigen, and for antibodies to feline immunodeficiency virus (FIV). Ninety specimens originated from the serum bank at the central referral clinic at the Norwegian College of Veterinary Medicine, which had been collected during the years 1983-1989; 67 sera were submitted from veterinarian practitioners; while 67 sera originated from cats presented for euthanasia. The cats were classified into one "healthy" and one "sick" group. Only 2.2% of sick cats and 1.2% of healthy cats showed FeLV antigenemia, a finding which is lower than which has been reported from many other countries. The prevalence of FIV antibodies was 10.1% in sick cats and 5.9% in healthy cats. Antibodies to FIV was most prevalent in male cats (14.7%) than in female cats (2.1%), and more prevalent among domestic cats (12.0%) compared to pedigree cats (2.4%). Antibodies to FIV in the cats demonstrated increasing prevalence with increasing age. It may be concluded that FeLV causes minor problems in Norwegian cats, while FIV is present in a similar prevalence to what is reported from other countries.     

Dose response studies of acute feline immunodeficiency virus PPR strain infection in cats

The effects of virus dose on host response were evaluated for the PPR strain of feline immunodeficiency virus (FIV-PPR). Specific pathogen-free cats were inoculated intravenously with 50, 250 or 1250 TCID(50) of FIV-PPR. Two weeks after inoculation, virus was detected in 10(6) peripheral blood mononuclear cells (PBMCs) of all infected animals, and the CD4(+):CD8(+) T lymphocyte ratios fell from greater than 2 to approximately 1 in all infected animals within the first 8 weeks after infection. Provirus detected in all groups using PCR and 10(3) PBMC was biphasic. Nine of 15 animals were positive between weeks 2 and 4 p.i. and 14 of 15 were positive by week 8 p.i. Transient lymphadenopathy was detected in most cats receiving 1250 TCID(50) and the 250 TCID(50) of virus, whereas no lymphadenopathy was detected in the 50 TCID(50) group or the five uninfected cats. Animals that had received the largest dose seroconverted earliest (on average at week 4.0) and those receiving the least seroconverted last (on average at week 5.6). Neither neutropenia nor lymphopenia were detected. FIV-specific CTL responses of memory effector cells could be detected in animals receiving all three doses but was highly variable among individual animals. Neurological manifestations determined after 15 weeks p.i. were observed in most infected cats, including two of the three that had received 50 TCID(50) of virus. However, the observed neurologic abnormalities were markedly less severe in the animals receiving the least amount of virus. Therefore, lymphadenopathy and neurologic signs of illness were less severe and seroconversion was slower in the animals that received the lowest dose compared with those receiving the 250 and 1250 TCID(50) doses of the FIV-PPR strain.     

Differentiation of feline immunodeficiency virus vaccination, infection, or vaccination and infection in cats

BACKGROUND: Serodiagnosis of feline immunodeficiency virus (FIV) is complicated by the use of a formalin-inactivated whole-virus FIV vaccine. Cats respond to immunization with antibodies indistinguishable from those produced during natural infection by currently available diagnostic tests, which are unable to distinguish cats that are vaccinated against FIV, infected with FIV, or both. HYPOTHESIS: An enzyme-linked immunosorbent assay (ELISA) detecting antibodies against formalin-treated FIV whole virus and untreated transmembrane peptide will distinguish uninfected from infected cats, regardless of vaccination status. ANIMALS: Blood samples were evaluated from uninfected unvaccinated cats (n = 73 samples), uninfected FIV-vaccinated cats (n = 89), and FIV-infected cats (n = 102, including 3 from cats that were also vaccinated). METHODS: The true status of each sample was determined by virus isolation. Plasma samples were tested for FIV antibodies by a commercial FIV diagnostic assay and an experimental discriminant ELISA. RESULTS: All samples from uninfected cats were correctly identified by the discriminant ELISA (specificity 100%). Of the samples collected from FIV-infected cats, 99 were correctly identified as FIV-infected (sensitivity 97.1%). CONCLUSIONS AND CLINICAL IMPORTANCE: With the exception of viral isolation, the discriminant ELISA is the most reliable assay for diagnosis of FIV. A practical strategy for the diagnosis of FIV infection would be to use existing commercial FIV antibody assays as screening tests. Negative results with commercial assays are highly reliable predictors for lack of infection. Positive results can be confirmed with the discriminant ELISA. If the discriminant ELISA is negative, the cat is probably vaccinated against FIV but not infected. Positive results are likely to represent infection.     

Prevalences of feline leukaemia virus and feline immunodeficiency virus infections in cats in Sydney

Objective To determine prevalences of feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) infections in ‘healthy’ cats that, through acute misadventure or other circumstance, were presented to veterinary practitioners. Prevalences of FeLV and FIV in this population were compared to those in a population of predominantly sick cats. Design and procedures Serum specimens were obtained over a 2-year period from 200 cats oldeer than 1 year of age presented to veterinary clinics for routine procedures, including cat fight injuries or abscesses, vehicular trauma, neutering, dental scaling, vaccination, grooming or boarding. An additional 894 sera were obtained over approximately the same period from specimens submitted by veterinarians to a private clinical pathology laboratory, mainly from sick cats suspected of having immune dysfunction, but including some sera from healthy cats being screened prior to FeLV vaccination. FIV antibody and FeLV antigen were detected in samples using commercial enzyme immunoassays. Results Amongst 200 ‘healthy’ cats, the prevalence of FeLV infection was 0 to 2%, and the prevalence of FIV was 6.5 to 7.5%, depending on the stringency of the criteria used to define positivity. FIV infection was significantly more prevalent in cats which resided in an inner city environment (P = 0.013). Of the 894 serum specimens submitted to the laboratory by practitioners, 11/761 (1.4%) were FeLV positive, while 148/711 (20.8%) were FIV positive. The prevalence of FIV was significantly higher in these predominantly ‘sick’ cats than in cats seen for routine veterinary procedures (P < 0.00001), while there was no difference in the prevalence of FeLV (P = 0.75) Conclusions The prevalence of FeLV and FIV in healthy cats may have been substantially overestimated in some previous Australian surveys. FeLV infection would appear to be a rare cause of disease in Australian cats. The higher prevalence of FIV positivity in sick as opposed to healthy cats infers that FIV infection contributes to the development of disease.     

Prevalence of feline immunodeficiency virus infection in domesticated and feral cats in eastern Australia

Serum samples from 340 pet cats presented to three inner city clinics in Sydney Australia, 68 feral cats from two separate colonies in Sydney, and 329 cattery-confined pedigree and domestic cats in eastern Australia, were collected over a 2-year period and tested for antibodies directed against feline immunodeficiency virus (FIV) using immunomigration (Agen FIV Rapid Immunomigration test) and enzyme-linked immunosorbent assay methods (Snap Combo feline leukaemia virus antigen/FIV antibody test kit, IDEXX Laboratories). Western blot analysis was performed on samples in which there was discrepancy between the results. Information regarding breed, age, gender, housing arrangement and health status were recorded for all pet and cattery-confined cats, while the estimated age and current physical condition were recorded for feral cats. The FIV prevalence in the two feral cat populations was 21% and 25%. The majority of FIV-positive cats were male (60-80%). The FIV prevalence in cattery-confined cats was nil. The prevalence of FIV in the pet cat sample population was 8% (27/340) with almost equal prevalence in 'healthy' (13/170) and 'systemically unwell' (14/170) cats. The age of FIV-positive pet cats ranged from 3 to 19 years; all FIV-positive cats were domestic shorthairs with outside access. The median age of FIV-positive pet cats (11 years) was significantly greater than the median age of FIV-negative pet cats (7.5 years: P<0.05). The prevalence of FIV infection in male pet cats (21/172; 12%) was three times that in female pet cats (6/168; 4%; P<0.05). With over 80% of this pet cat population given outside access and continued FIV infection present in the feral population, this study highlights the need to develop rapid, accurate and cost-effective diagnostic methods that are not subject to false positives created by concurrent vaccination against FIV. This is especially important in re-homing stray cats within animal shelters and monitoring the efficacy of the new vaccine, which has not been challenged against Australian strains. The absence of FIV within cattery-confined cats highlights the value in routine screening and indoor lifestyles. This study provides cogent baseline FIV prevalences in three cat subpopulations which can be used for appraising potential disease associations with FIV in Australia.