Prevalence of feline haemotropic mycoplasmas in convenience samples of cats in Germany.

The aim of this prospective study was to evaluate the prevalence of feline haemotropic mycoplasmas in Germany, to determine probable risk factors for these infections and to compare the diagnostic value of microscopic examination of blood smears to polymerase chain reaction (PCR). For the prevalence study, convenience samples (Ethylene diamine-tetraacetic acid (EDTA) blood) from 262 (64.5% male and 35.5% female) cats were included. A PCR for the detection of Mycoplasma haemofelis (MHF) and 'Candidatus Mycoplasma haemominutum' (CMH) as well as a feline leukaemia virus (FeLV)/feline immunodeficiency virus (FIV) enzyme-linked immunoassay was performed. Blood smears from 224 cats were examined and the sensitivity and specificity of the microscopic diagnosis were determined. The prevalence of CMH, MHF, and CMH/MHF co-infection was 22.5%, 4.5%, and 0.8%, respectively. CMH was significantly associated with male gender (P=0.047), older age (P=0.0015) and both FeLV (P=0.002) and FIV infections (P<0.0001). However, there was no association between the presence of anaemia and CMH/MHF infection. The respective sensitivity and specificity of the microscopic diagnosis were 10.3% and 87.1% for a CMH infection and 0.0% and 98.0% for MHF infection.

Effect of preexisting FeLV infection or FeLV and feline immunodeficiency virus coinfection on pathogenicity of the small variant of Haemobartonella felis in cats.

OBJECTIVE: To investigate the effects of preexisting FeLV infection or FeLV and feline immunodeficiency (FIV) coinfection on the pathogenicity of the small variant of Haemobartonella felis (Hfsm, California variant) in cats. ANIMALS: 20 FeLV infected, 5 FeLV-FIV coinfected, and 19 retrovirus-free cats. PROCEDURES: A client-owned cat, coinfected with FeLV and Hfsm, was the source for Hfsm. Inoculum 1 (FeLV free) was obtained by passage of source Hfsm through 4 FeLV-resistant cats. Inoculum 2 was obtained by further passage of Hfsm (inoculum 1) through 2 specific pathogen-free cats. RESULTS: A mild-to-moderate anemia started 21 days after inoculation, with its nadir occurring at 35 to 42 days after inoculation. Infection with Hfsm induced greater decrease in hemoglobin concentration in FeLV infected cats, compared with retrovirus free cats. Reticulocytosis, macrocytosis, and polychromasia of erythrocytes developed in anemic cats regardless of retrovirus infection status. Mean neutrophil counts decreased during the hemolytic episode. For most cats, the anemia was transient. Four FeLV infected cats, 1 of which was also FIV infected, developed fatal FeLV-associated myeloproliferative diseases. Of the surviving cats, 8 died over the next 24 months from other FeLV-related diseases. Hemolysis did not recur after the initial episode. Inoculum 1 induced more severe anemia than inoculum 2. CONCLUSIONS AND CLINICAL RELEVANCE: Our results support the clinical observation that cats coinfected with FeLV and H felis develop more severe anemia than cats infected with H felis alone. Infection with Hfsm may induce myeloproliferative disease in FeLV infected cats. The small variant of H felis may lose pathogenicity by passage through FeLV-free cats.

Fungal flora on cutaneous and mucosal surfaces of cats infected with feline immunodeficiency virus or feline leukemia virus.

OBJECTIVE: To compare cutaneous and mucosal mycoflora in cats infected with FIV or FeLV with that in noninfected cats. ANIMALS: 85 client-owned cats; 24 seropositive for FIV, 10 seropositive for FeLV, 1 seropositive for both viruses, and 50 seronegative for both viruses. PROCEDURE: Cutaneous specimens were obtained from the coat and external acoustic meatus (ear canal) and mucosal specimens from the oropharynx and rectum. Fungi were isolated from specimens, using Sabouraud dextrose agar incubated at 27 or 37 C for cutaneous and mucosal specimens, respectively. RESULTS: Fungal colonies were cultured from at least 1 specimen from 83 of 85 (97.6%) cats. The most common fungal isolates were Aspergillus spp (cultured from 59.3% of all specimens), Penicillium spp (50.0%), Cladosporium spp (44.2%), Scopulariopsis spp (41.8%), and lipophilic yeasts of the genus Malassezia (31.4%). A greater diversity of fungal genera was isolated from retrovirus-infected cats, and Malassezia spp were more commonly recovered from these cats, compared with noninfected cats. Candida albicans, Cryptococcus neoformans, and dermatophytes (eg, Microsporum canis) were rarely isolated from any cat. Significant differences in frequency of isolation of C. neoformans and dermatophytes were not found between infected and noninfected cats. CONCLUSIONS AND CLINICAL RELEVANCE: Cats infected with FIV or FeLV may have a greater diversity of cutaneous and mucosal mycoflora than noninfected cats. However, infected cats may be no more likely than noninfected cats to expose humans to zoonotic fungi such as C. albicans, C. neoformans, and M. canis.

Evaluation of in vivo and in vitro interactions of feline immunodeficiency virus and feline leukemia virus.

OBJECTIVE: To determine the potential mechanisms for disease potentiation where feline immunodeficiency virus (FIV) infection of persistently feline leukemia virus (FeLV)-infected cats results in more severe FIV disease and increased mortality than FIV infection of specific pathogen-free cats. DESIGN AND METHODS: To determine whether pseudotype formation resulting in expanded cell tropism may be an important mechanism, cellular targets and tissue distribution of FIV and FeLV were determined by in situ hybridization and/or immunohistochemistry. To determine whether FeLV can transactivate the FIV long terminal repeat (LTR) resulting in increased FIV expression, in vitro transient expression assays were performed. To examine whether persistent FeLV infection can cause the deletion of a suppressive T-lymphocyte population, peripheral blood mononuclear cell (PBMC) cultures from persistently FeLV-infected cats were infected with FIV and monitored for FIV antigen levels. RESULTS: Macrophages were the predominant target of FIV infection and were disseminated in a similar pattern in lymphoid and nonlymphoid tissues of both FIV-infected and FeLV/FIV-coinfected cats. FeLV-infected cells expressing FIV RNA were not present. Significant transactivation of the FIV LTR in FeLV-infected cells was not demonstrated. FIV antigen production was similar upon in vitro infection of PBMC from FeLV-infected and uninfected cats. CONCLUSIONS: Neither direct virus/virus interactions, such as FeLV/FIV pseudotype formation or transactivation of the FIV LTR in FeLV-infected cells, nor deletion of a regulatory cell subset from the blood of FeLV-infected cats, was found to be the mechanism of disease potentiation.

Retroviral transmission by the transplantation of connective-tissue allografts. An experimental study.

The transmission of a retrovirus by the transplantation of allografts of connective tissues was studied in a feline model with use of the feline leukemia virus, a retrovirus with a replication cycle and pathological characteristics similar to those of the human immunodeficiency virus. The retrovirus was used to infect four specific-pathogen-free cats that were subsequently used as tissue donors. Fresh allografts of menisci, patellar ligaments, and patellar ligament and bone composites were harvested from infected donors and were transplanted into the knee joints of twelve specific-pathogen-free cats. A fresh cancellous-bone allograft was transplanted into the proximal part of the tibia of four additional specific-pathogen-free cats, which served as positive control animals. Additional grafts from infected donors were harvested and were stored at -80 degrees Celsius for ten weeks. A fresh-frozen graft was then transplanted into the knee of twelve other specific-pathogen-free cats. Samples of plasma were obtained weekly from all twenty-eight cats and were tested with both an enzyme-linked immunosorbent assay to detect the presence of viral antigen and an immunofluorescent antibody assay to determine exposure to the virus. All types of fresh and fresh-frozen connective-tissue allografts from the infected donors resulted in transmission of the retrovirus to the recipient cats. The recipients had evidence of viral antigen or rising antibody titers as early as two weeks after the transplantation. Histological examination of specimens of the allografts revealed normal incorporation of the transplanted tissues, with no sign of rejection of the graft.

Chromosome abnormalities and oncogenesis in cat leukemias.

Chromosome abnormalities are found in feline leukemia virus (FeLV)-infected tumor cells as well as in tumor cells free of the virus. Three cell lines derived from tumors in the domestic cat (Felis catus), two of thymic origin and one of multicentric lymphoma origin, were analyzed cytogenetically to determine whether the FeLV virus was associated with chromosomal abnormalities in these tumor cell lines. One thymic tumor and the multicentric lymphoma were FeLV infected. The other thymic tumor cell line was FeLV-free. The normal diploid number in the domestic cat is 38. All three cell lines had numerical chromosome abnormalities with modal numbers of 37, 38 (pseudodiploid), and 39, respectively and had consistent structural chromosome abnormalities. Three markers in the virus-free cell line (S markers) were shared with one or the other of the virus-positive cell lines. The two FeLV-positive cell lines did not have S markers in common. The finding of chromosome abnormalities in both the virus-infected and the virus-free cell lines suggests that these abnormalities may be important in oncogenesis. The FeLV virus could not be considered the only causative agent of the abnormalities observed.

Detection of feline immunodeficiency virus infection in bone marrow of cats.

Natural or experimental feline immunodeficiency virus (FIV) infection in cats is often associated with hematologic abnormalities which are similar to those observed in human immunodeficiency virus (HIV) infected patients. To determine if cells in bone marrow are infected with FIV and whether severity of hematopoietic disorder is correlated with the level of viral infection, bone marrow tissues from ten experimentally and two naturally FIV infected cats were examined by in situ hybridization for presence of FIV RNA. Seven of the 12 FIV infected cats were also naturally or experimentally coinfected with feline leukemia virus (FeLV). FIV RNA was detected mainly in megakaryocytes and unidentified mononuclear cells in the bone marrow of cats that were sick and had marrow hypercellularity and immaturity. These included all cats in the acute phase of FIV infection and two of seven long term FIV infected cats. One long term FIV infected cat with lymphosarcoma was also positive for FIV RNA in bone marrow cells. The other four long term FIV infected cats were relatively healthy, with normal bone marrow morphology, and were negative for FIV infected cells. Bone marrow from three non-infected and two cats infected with FeLV alone were also negative for FIV RNA by in situ hybridization. We concluded that megakaryocytes and mononuclear cells were targets of the viral infection and that the presence of FIV RNA in cells of the bone marrow correlated with marrow hypercellularity and immaturity, and severity of illness.

Hematopoietic target cells of anemogenic subgroup C versus nonanemogenic subgroup A feline leukemia virus.

Feline leukemia viruses (FeLVs) belonging to interference subgroup C induce fatal anemia resembling human pure red cell aplasia (PRCA). Subgroup A FeLVs, although closely related genetically to FeLVs of subgroup C, do not induce PRCA. The determinants for PRCA induction by a molecularly cloned prototype subgroup C virus (FeLV-Sarma-C [FSC]) have been localized to the N-terminal 241 amino acids of the surface glycoprotein (SU) gp70. To investigate whether the anemogenic activity of FSC reflects a unique capacity to infect erythroid progenitor cells, we used correlative immunogold, immunofluorescence, and cytological staining to study prospectively the hemopoietic cell populations infected by either FSC or FeLV-FAIDS-61E-A (F6A), a prototype of subgroup A virus. The results demonstrated that although only FSC-infected animals developed erythrocyte aplasia, the env SU and the major core protein (p27) were expressed in a surprisingly large fraction of the lymphoid, erythroid, and myeloid lineage marrow cells in both FSC- and F6A-infected cats. Between days 8 and 17 postinoculation, gp70 and p27 were detected in 43 to 73% of erythroid, 25 to 75% of lymphoid, and 35 to 50% of myeloid lineage cells, regardless of whether the cats were infected with FSC or F6A. Thus, anemogenic subgroup C and nonanemogenic subgroup A FeLVs have similar hemopoietic cell tropism and infection kinetics, despite their divergent effects on erythroid progenitor cell function. Acute anemia induction by subgroup C FeLV, therefore, does not reflect a unique tropism for marrow erythroid cells but rather indicates a unique cytopathic effect of the SU on erythroid progenitor cells.

Pathogenicity of feline leukemia virus is commonly associated with variant viruses.

Many of the serious diseases resulting from feline leukemia virus (FeLV) infection are associated with the generation of novel variant viruses. The prototype FeLV-A virus is highly stable and circulates in the cat population without apparent antigenic change. However, recombination with cellular oncogenes produces viruses which cause leukemia or other malignant diseases. Other recombinants within the env genes of FeLV-A and endogenous FeLV are recognized as belonging to a second subgroup, FeLV-B, the presence of which is correlated with an increased risk of infection with FeLV and a higher incidence of leukemia. Mutants of FeLV which affect the env gene are phenotypically of a third subgroup, FeLV-C, and have a close association with erythroid aplasia. None of these viruses, apart from FeLV-B, is transmitted further in nature. Therefore the generation of these novel viruses and the production of disease is an inadvertent consequence of FeLV infection.

Viral inactivation in blood and red cell concentrates with benzoporphyrin derivative.

Using both the vesicular stomatitis virus (VSV) and feline leukemia virus (FeLV) as models we have shown that the photosensitizer benzoporphyrin derivative ring A (BPD), when activated with red light (600-700 nm), is effective in eliminating both free virus and virally infected cells from spiked blood products and whole blood drawn from viremic cats experimentally infected with FeLV, under conditions which appear to share red blood cells. The effect of photodynamic therapy on infected lymphocytes, as visualized by scanning electron microscopy, initially appeared as a limited area of tiny holes in the membrane. These holes were subsequently seen to increase in size until the membrane appeared completely decomposed. The red cell membranes however, seem to be undamaged by such photodynamic treatment.

Feline leukemia virus infection and diseases.

Feline leukemia virus is a naturally occurring, contagiously transmitted and oncogenic immunosuppressive retrovirus of cats. The effects of FeLV are paradoxical, causing cytoproliferative and cytosuppressive disease (eg, lymphoma and myeloproliferative disorders vs immunodeficiency and myelosuppressive disorders). In the first few weeks after virus exposure, interactions between FeLV and hemolymphatic system cells determine whether the virus or the cat will dominate in the host/virus relationship--persistent viremia and progressive infection or self limiting, regressive infection will develop. The outcome of these early host/virus interactions is revealed in the diagnostic assays for FeLV antigenemia and viremia. The latter, in turn, predict the outcome of FeLV infection in cats. Known host resistance factors include age and immune system functional status. Known virus virulence factors are magnitude of exposure and virus genotype. Molecular analysis of FeLV strains indicated that natural virus isolates exist as mixtures of closely related virus genotypes and that minor genetic variations among FeLV strains can impart major differences in pathogenicity. The genetic coding regions responsible for cell targeting and specific disease inducing capacity (eg, thymic lymphoma, acute immunosuppression, or aplastic anemia) have been mapped to the virus surface glycoprotein and/or long terminal repeat regions for several FeLV strains. Infection by specific FeLV strains leads to either malignant transformation or cytopathic deletion of specific lymphocyte and hemopoietic cell population, changes that prefigure the onset of clinical illness. Another notable feature of the biology of FeLV is that many cats are able to effectively contain and terminate viral replication, an important example of host immunologic control of a retrovirus infection and a process that can be selectively enhanced by vaccination. Thus, FeLV infection serves as a natural model of the multifaceted pathogenesis of retroviruses and as a paradigm for immunoprophylaxis against an immunosuppressive leukemogenic retrovirus.

Chronic oral infections of cats and their relationship to persistent oral carriage of feline calici-, immunodeficiency, or leukemia viruses.

Two hundred and twenty-six cats from the Veterinary Medical Teaching Hospital (VMTH), a cat shelter, and a purebred cattery were tested for chronic feline calicivirus (FCV), feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) infections. Chronic oral carriage of FCV was present in about one-fifth of the cats in each of the groups. FIV infection was not present in the purebred cattery, was moderately prevalent (8%) in the pet population of cats examined at the VMTH for various complaints and was rampant in the cat shelter (21%). Unexpectedly high FeLV infection rates were found in the hospital cat population (28%) and in the purebred cattery (36%), but not in the cat shelter (1.4%). FCV and FeLV infections tended to occur early in life, whereas FIV infections tended to occur in older animals. From 43 to 100% of the cats in these environments had oral cavity disease ranging from mild gingivitis (23-46%), proliferative gingivitis (18-20%), periodontitis (3-32%) and periodontitis with involvement of extra-gingival tissues (7-27%). Cats infected solely with FCV did not have a greater likelihood of oral lesions, or more severe oral disease, than cats that were totally virus free. This was also true for cats infected solely with FeLV, or for cats dually infected with FeLV and FCV. Cats infected solely with FIV appeared to have a greater prevalence of oral cavity infections and their oral cavity disease tended to be more severe than cats without FIV infection. FIV-infected cats that were coinfected with either FCV, or with FCV and FeLV, had the highest prevalence of oral cavity infections and the most severe oral lesions.