Specific diagnosis of parvovirus enteritis in dogs and cats by in situ hybridization.

In a retrospective study, the fixed intestines of 10 dogs and 10 cats with intestinal lesions characteristic of parvovirus infection were assayed for the presence of parvovirus by in situ hybridization and immunohistochemistry. Parvoviral nucleic acid was localized by in situ hybridization in intestinal tissue in all 10 dogs and in nine of the 10 cats, whereas antigen was detected only in seven of 10 canine and eight of 10 feline intestines by immunohistochemistry. We conclude that an aetiological diagnosis can be established with a high degree of certainty by routine histology. Demonstration of the infectious agent by in situ hybridization, however, proves to be a valuable specific tool which allows an exact cellular localization of parvovirus in formalin-fixed, paraffin wax-embedded tissue sections.

Feline parvovirus propagates in cat bone marrow cultures and inhibits hematopoietic colony formation in vitro.

Feline parvovirus (FPV) causes leukopenia in naturally infected cats. We investigated the mechanism of hematopoietic depression by this virus in feline bone marrow cultured in vitro. In suspension cultures we demonstrated FPV propagation and replication using DNA molecular hybridization. Viral RNA and DNA were observed by in situ hybridization in about 10% of marrow cells at day 3. Granulocytes and their precursors were virtually absent from infected cultures after six days. Infected cells showed viral capsid protein predominantly in nuclei by immunofluorescence. In clonal assays, FPV most efficiently inhibited hematopoietic colony formation by myeloid progenitor cells (CFU-GM), but erythroid colony formation (BFU-E and CFU-E-derived) was also depressed in the presence of virus. Inhibition of colony formation could be abrogated by physical inactivation of the virus or preincubation with specific neutralizing antibodies. Recombinant human colony stimulating factors GM-CSF and G-CSF supported feline myelopoiesis in progenitor assays, and FPV completely inhibited factor dependent colony formation.

Comparison of feline parvovirus subspecific strains using monoclonal antibodies against a feline panleukopenia virus.

Four monoclonal antibodies (mAb) against a feline panleukopenia virus (FPLV) TU 1 strain, one of the host range variants of feline parvovirus (FPV), were produced and applied for antigenic analysis of FPLV, canine parvovirus (CPV) and mink enteritis virus (MEV). All mAbs were considered to be directed at epitopes on the virus capsid surface because they neutralized the infectivity and inhibited the hemagglutination (HA) of the homologous virus as well as other FPV strains. They were of the mouse IgG1 type. High antigenic homogeneity among FPLV strains was confirmed by HA-inhibition (HI) test with the mAbs and polyclonal immune sera against FPLV or CPV. But the TU 11 strain of FPLV was antigenically distinguished from the remaining 14 FPLV strains by both the HI test and the micro-neutralization test with one of the mAbs produced. MEV Abashiri strain was found to be antigenically indistinguishable from FPLV. Most of the CPV strains isolated after 1981 were considered to be antigenically different from earlier CPV isolates when some mAbs were applied in the serological tests, confirming the replacement of CPV by an antigenic variant in Japan. However, antigenically different CPVs were detected at the end of 1984 from unrelated epizootics occurred a month apart in the same area.

[Electron microscopy in the diagnosis of enteritis in cats]. / Electronenmicroscopie bij de diagnose van enteritis bij katten.

Over a five-year period (1981-1985) 346 faecal and intestinal samples of cats affected with diarrhoea were studied by electron microscopy. This method revealed the presence of virus in 144 out of 346 (41.6 per cent) samples studied. 117 (81.3 per cent) of these samples contained parvoviruses which were identified by using a specific immune serum (immuno electron microscopy). In addition, rotaviruses (two samples), coronaviruses (thirteen samples), coronavirus-like (ten samples) and picornavirus-like particles (two samples) were detected in the other specimens. The present study shows that electron microscopy is a useful and rapid procedure in the diagnosis of enteritis in cats as well as in other domestic animals.

Feline panleucopenia--in vivo infectivity studies.

Feline panleucopenia virus was separated into "full" and "empty" particles by banding in caesium chloride ultracentrifugation. Field cats free of serum neutralising antibodies were separately infected with "full", "empty" and "mixed" particles of the virus. No clinical disease was produced. However, cats infected with "full" particles developed antibody more rapidly than cats infected with the other particles.

Feline leukemia virus-associated enteritis--a condition with features of feline panleukopenia.

Infection with feline leukemia virus (FeLV) was demonstrated immunohistologically in 218 necropsied cats suffering from enteritis. The animals were divided into three groups according to histopathological criteria. The first group exhibited the signs of feline panleukopenia in intestine, lymphoid tissues, and bone marrow. Only 1.6% of these animals were FeLV-infected. The animals of the second group had histopathological alterations as seen in cats suffering from feline panleukopenia, but these were found only in the intestine and not in lymphoid tissues or bone marrow. Of these 71.9% were infected with FeLV. The third group consisted of all other cats suffering from enteritis of which 6.3% were FeLV-positive. The association between FeLV infection and the lesions seen in the animals of group 1 (feline panleukopenia) and group 3 (other types of enteritis) is statistically not significant whereas the alterations exhibited by the cats of group 2 are significantly FeLV-associated. Cats with FeLV-associated enteritis (group 2) are of a mean age of about 2.5 years and are significantly older than animals with feline panleukopenia which are of a mean age of about half a year. Thus a FeLV-associated enteritis exists as a histopathologically recognizable condition which sometimes might be mistaken for feline panleukopenia in routine post-mortem investigations.

Characterization of antigenic variation among mink enteritis virus isolates.

Three antigenic forms of natural field isolates of mink enteritis virus were revealed with a panel of monoclonal antibodies generated against the closely studied feline panleukopenia virus and canine parvovirus-2 virus. Two types (types 2 and 3) were shown to be closely related by agar-gel precipitin tests and by restriction enzyme mapping. However, types 2 and 3 differed from the type 1 isolates in the same tests. In cross-protection studies, inactivated viral vaccines made from any one of the 3 variant types of mink enteritis virus protected mink against challenge exposure by the homologous, as well as the heterologous, antigenic types.

Comparison of the viral proteins of canine parvovirus-2, mink enteritis virus and feline panleukopenia virus.

Canine parvovirus-2 (CPV-2), Mink enteritis virus (MEV) and feline panleukopenia virus (FPV) were produced using identical cell culture and purification techniques. The distributions of the haemagglutinating activity of the three different parvoviruses in a CsCl gradient were similar with haemagglutinating peaks identified at 1.48-1.49, 1.42, 1.36 and 1.30-1.31 g cm-3. The number and distribution of the viral proteins and the equivalent protein molecular weights are similar for all three viruses in SDS-polyacrylamide gels (10%). Four viral proteins were identified and their molecular weights were determined: protein A (77 500-79 500), protein B (63 000-63 500), protein C (61 500-63 000) and protein D (50 000-55 000). The viral protein D although reported for some other parvoviruses has not previously been demonstrated in CPV-2, MEV or FPV.

Feline panleukopenia. II. The relationship of intestinal mucosal cell proliferation rates to viral infection and development of lesions.

Proliferation rates of small intestinal mucosal cells of noninfected germfree and specific pathogen-free kittens were compared to the incidence of infected cells and microscopic lesions in kittens experimentally infected with panleukopenia virus. Mucosal crypt length, cells per crypt, mitotic index and villous length were greater in specific pathogen-free kittens than in germfree kittens. Crypt cells per unit length and villous length per crypt length ratio were greater in germfree kittens. The cryptal cell proliferation rate of specific pathogen-free kittens was 2.24 times that of germfree kittens. Mucosal crypt length, cell per crypt and villous length were greater in the proximal jejunum than in the midjejunum of kittens within groups. Cell proliferation rates per crypt did not differ between areas of the intestine in kittens within groups. There were more virus-infected cells and lesions in specific pathogen-free kittens than in germfree kittens. The incidence of virus-infected cells and lesions was greater in the proximal jejumum and decreased along the small intestine.

[Isolation of reoviruses from mink]. / Der Nachweis von REO-Viren bei Nerzen

In this first report of the isolation of reovirus from mink, isolates were obtained from 18 to 26 young mink with viral enteritis, by using cultures of cat kidney cells. The isolated also produced cytopathic changes in cell cultures of mink kidney, dog kidney, piglet kidney, calf kidney, bovine embryonic kidney and calf testis. A characteristic feature was the formation of eosinophilic inclusion bodies in the cytoplasma of culture cells. Haemagglutination tests were negative with erythrocytes from cat, rabbit, pig, horse and cattle. Attempts to infect old and young mink, kittens and ferrets with tissue culture material failed. It was not known to what extent this second infection with reovirus influenced the course of mink viral enteritis.