Characteristics of feline panleucopaenia virus strains enabling definitive classification as parvoviruses

[Parvovirus infections in cats in animal shelters]

Due to widespread vaccination programs against feline panleukopenia virus (FPV), the disease associated with this virus infection, feline panleukopenia, is rarely seen in privately owned cats in Germany. In contrast, the situation in animal shelters differs due to the constant intake of new cats that are often unprotected. In such facilities, panleukopenia outbreaks are common and often accompanied by a high number of fatalities. Due to the high contagiosity of the virus, some shelters do not accept cats with clinical signs suspicious for panleukopenia, since these animals can pose a risk to the shelter population. However, not only cats with panleukopenia shed parvovirus, but also healthy, asymptomatic cats can and thus contribute to risk of infection. Nevertheless, the risk for panleukopenia outbreaks in animal shelters can be reduced by rigorous outbreak management. This includes hygiene measures using correctly applied cleaning and disinfection protocols, quarantine measures, separate isolation units, as well as specific prophylactic measures, such as identification of infected animals and immunization of susceptible groups.

Isolation and Genetic Characterization of Parvoviruses From Dogs, Cats, Minks, and Raccoon Dogs in the Eastern Region of Shandong Province, China

The eastern region of Shandong province, China, is an intensive economic mink and raccoon dog breeding area. To investigate the molecular variations of parvovirus in cats, dogs, minks, and raccoon dogs from this region, feline panleukopenia virus (FPV), canine parvovirus 2 (CPV-2), mink enteritis virus (MEV), and raccoon dog parvovirus (RDPV) were separately isolated and characterized from the respective animals with gastroenteritis. PCR amplification showed that there were 15/18 (83.3%), 9/13 (69.2%), 8/11 (72.7%), and 3/7 (42.9%) samples from the diseased animals separately positive for FPV, CPV-2, MEV, and RDPV. Of these, a total of six FPV, six MEV, four CPV-2, and three RDPV strains were successfully isolated using F81 cells. Next, the near-complete genomes of 19 parvovirus isolates were amplified and analyzed. The viral particle 2 (VP2) sequence alignment showed that they shared 97.2–100% nucleotide similarity. Phylogenetic analysis showed that the five FPV isolates were in the same branch, and an FPV isolate was closely related with MEV and RDPV isolates obtained in this study. These suggested that cross-species infection occurred in the Shandong region between the FPV, MEV, and RDPV. For the four CPV-2 isolates, three were antigenic variant strains CPV-2a, and the other was antigenic variant strain CPV-2c. Additionally, the mutations that had emerged in the VP2 amino acids of CPV-2 also occurred in the VP2 from the FPV, MEV, and RDPV isolates. This study suggested that the continuous evolution of the parvovirus may be accelerated in areas with a high density of economic animal trading/breeding, and controlling parvovirus infection in these animals remains a challenge.

Analysis of the vp2 gene sequence of a new mutated mink enteritis parvovirus strain in PR China

BACKGROUND

Mink enteritis virus (MEV) causes a highly contagious viral disease of mink with a worldwide distribution. MEV has a linear, single-stranded, negative-sense DNA with a genome length of approximately 5,000 bp. The VP2 protein is the major structural protein of the parvovirus encoded by the vp2 gene. VP2 is highly antigenic and plays important roles in determining viral host ranges and tissue tropisms. This study describes the bionomics and vp2 gene analysis of a mutated strain, MEV-DL, which was isolated recently in China and outlines its homologous relationships with other selected strains registered in Genbank.

RESULTS

The MEV-DL strain can infect F81 cells with cytopathic effects. Pig erythrocytes were agglutinated by the MEV-DL strain. The generation of MEV-DL in F81 cells could infect mink within three months and cause a disease that was similar to that caused by wild-type MEV. A comparative analysis of the vp2 gene nucleotide (nt) sequence of MEV-DL showed that this was more than 99% homologous with other mink enteritis parvoviruses in Genbank. However, the nucleotide residues at positions 1,065 and 1,238 in the MEV-DL strain of the vp2 gene differed from those of all the other MEV strains described previously. It is noteworthy that the mutation at the nucleotide residues position 1,238 led to Asp/Gly replacement. This may lead to structural changes. A phylogenetic tree and sequence distance table were obtained, which showed that the MEV-DL and ZYL-1 strains had the closest inheritance distance.

CONCLUSIONS

A new variation of the vp2 gene exists in the MEV-DL strain, which may lead to structural changes of the VP2 protein. Phylogenetic analysis showed that MEV-DL may originate from the ZYL-1 strain in DaLian.

Immuno-chromatographic assay for diagnosis of feline leukemia virus infection

Feline leukemia virus (FeLV) infectious disease is one of feline infection diseases spreading broadly all over the world. For bedside diagnosis of FeLV infectious disease, an immuno-chromatographic assay was investigated. Five different monoclonal antibodies were developed against the major core protein FeLV-p27. Among them, the combination of FL6 and FL12, which had little epitopic overlap each other, showed the highest sensitivity with no cross-reaction to the other feline virus antigens when they were employed to the immuno-chromatographic assay. The system had a practical detection limit of 0.5 ng of FeLV-p27 per 0.1 ml of feline sera within 15 min. In comparison with clinical standard methods, the system gave rapidly and accurately the same diagnosis with neither false negative nor false positive. Moreover, it did not need any pretreatment of blood specimen.

Growth characteristics of canine pathogenic viruses in MDCK cells cultured in RPMI 1640 medium without animal protein

Madin Darby canine kidney (MDCK) cells were adapted to serum-free RPMI 1640 medium and used for cultivation of canine viruses. RPMI 1640 medium was supplemented with a soybean peptone, L-glutamine and antibiotics, so that the protein concentration was less than 5 microg/ml (RPMI/SP medium). The resulting adapted MDCK-SP cells showed steady growth after the twenty-eighth passage in RPMI/SP medium (MDCK-SP cell culture). Canine distemper virus, canine parvovirus, canine adenoviruses and canine parainfluenza virus, which are the principal components of canine combined virus vaccines, grew in the MDCK-SP cell culture as efficiently as the parental MDCK cells cultured in the conventional Eagle's MEM containing fetal bovine serum. Consequently, the use of MDCK-SP cell culture can make current canine vaccine products much safer, of higher quality and at lower cost.

Antigenic and genomic comparisons of some feline parvovirus subspecies strains

Fourteen feline parvovirus (FPV) strains isolated from cats, mink and dogs were comparatively examined on their antigenic and genetic diversities by using monoclonal antibodies against feline panleukopenia virus (FPLV) and restriction enzyme analysis of viral DNA. Mink enteritis virus (MEV) strains recently isolated in the northeastern area of the People's Republic of China were found to possess more similar antigenic and genetic properties to the antigenic variant virus of canine parvovirus (CPV) ("new" antigenic type CPV), than to FPLV strains and MEV Abashiri strain of Japan. A feline isolate detected in normal cat feces was considered to be rather CPV because of its antigenic and genetic characteristics. An early isolate of "new" antigenic type CPV strains showed a similar cleavage pattern to those of "old" antigenic type CPV strains when digested with HinfI. The results including some features above-mentioned suggest the presence of antigenic heterogeneities and genomic polymorphisms among FPV subspecies viruses.

Analysis of experimental mink enteritis virus infection in mink: in situ hybridization, serology, and histopathology

Strand-specific hybridization probes were used in in situ hybridization studies to localize cells containing mink enteritis virus (MEV) virion DNA or MEV replicative-form DNA and mRNA. Following the experimental MEV infection of 3-month-old unvaccinated mink, a significant increase in serum antibodies to MEV was detected at postinfection day (PID) 6, 2 days after the onset of fecal shedding of virus. Prior to the appearance of virus in feces, viral DNA could be detected in the mesenteric lymph node and intestine. The largest percentage of cells positive for virion DNA was 10% and was detected in the intestine on PID 6. However, replication of the virus apparently peaked at PID 4. The number of MEV replicative-form DNA and mRNA molecules was found to be approximately 250,000 copies per infected lymph node cell or crypt epithelial cell. The localization, levels, and time course of viral replication have important implications for the pathogenesis of MEV-induced disease. The data presented on MEV are correlated with earlier results on the other mink parvovirus, Aleutian mink disease parvovirus, and a possible explanation for the remarkable differences in pathogenesis of disease caused by these two parvoviruses is discussed.

Emergence, natural history, and variation of canine, mink, and feline parvoviruses

This chapter discusses the emergence of canine parvovirus (CPV), the evidence concerning the previous emergence of mink enteritis virus (MEV) as the cause of a new disease in minks in the 1940s, and the mechanisms that determine the host ranges and other specific properties of the viruses of cats, minks, and dogs. The viruses are classified as the feline parvovirus subgroup of the genus Parvovirus, within the family Parvoviridae. Feline panleukopenia virus (FPV), MEV, and CPV are classified as “host range variants.” In addition to the viruses of cats, minks, and dogs, similar viruses naturally infect many species within the families Felidae, Canidae, Procyonidae, Mustelidae, and possibly the Viverridae. The differences in virulence for minks observed after inoculation of MEV or FPV suggests that there are subtle differences between FPV and MEV that have yet to be defined. Genetic mapping studies indicate that only three or four sequence differences between the FPV and CPV-2 isolates within the VP-1 lVP-2 gene determine all of the specific properties of CPV that have been defined: the pH dependence of hemagglutination, the CPV-specific epitope, and the host range for canine cells and dogs.

Analysis of parvovirus infections using strand-specific hybridization probes

The autonomous parvoviruses cause a broad spectrum of acute and chronic infections of animals and man. The discrimination of sites of viral replication from sites of viral sequestration is an important goal in elucidating the pathogenesis of these diseases. It is possible to employ strand-specific RNA hybridization probes in such analyses because a 'plus' sense probe will react with single stranded virion DNA and duplex replicative form DNA, but a 'minus' sense probe will react preferentially with obligate replicative intermediates (duplex replicative form DNA and mRNA). Strand-specific RNA hybridization probes were developed for the Aleutian mink disease parvovirus (ADV) and were used to study acute and chronic infections of mink. Such probes were capable of differentiating replicative intermediates (duplex replicative form DNA and mRNA) from single-stranded virion DNA in Southern blot analysis and in strand-specific in situ hybridization. ADV infection of seronegative newborn mink kits causes an acute, cytopathic infection of type II alveolar cells. Replication in these cells is highly permissive and is characterized by high levels of replicative intermediates and virion DNA. A fatal respiratory distress syndrome and hyaline membrane formation result from impaired surfactant production by the infected type II cells. On the other hand, ADV infection of adult mink is associated with a persistent infection and a disorder of the immune regulation. The target cells for viral replication in adult mink are confined to the lymphoid system and the bone marrow. Replication in these cells, which are probably lymphocytes, is restricted, and characterized by greatly reduced levels of replicative intermediates and virion DNA. It, therefore, seems that disease in the infected adult mink results from a restricted infection by ADV. Large amounts of virion DNA can also be demonstrated in locations where replication cannot be detected and apparently represents sequestration of virion particles by elements of the reticuloendothelial system. Thus, replication and sequestration can, in fact, be distinguished by the strand-specific in situ hybridization. These studies indicate that strand-specific in situ hybridization is a potentially valuable method for studying the pathogenesis of parvovirus infections.

Apparent lack of effect of vaccination against mink enteritis virus (MEV). A challenge study

The mink enteritis virus part of a triple vaccine was tested in mink. No raise in antibody response was measured after vaccination. Subsequent challenge of groups of vaccinated or not-vaccinated animals revealed no differences in virus excretion or antibody response in the different animals.

A solid-phase fluorescent immunoassay for detecting canine or mink enteritis parvoviruses in faecal samples

Mink enteritis virus (MEV) and canine parvovirus (CPV) were detected in faecal samples from experimentally or naturally infected minks and dogs, respectively, using antibody-coated polyacrylamide beads (immunobeads, IB) as the solid phase for immunofluorescence (IF) tests. The specificity and sensitivity of the immunobead assay (IBA) were studied by comparing it with an enzyme-linked immunoassay (ELISA), a haemagglutination (HA) test and an IF test using tissue cultures. The IBA was as sensitive as ELISA, but more sensitive than the HA test and the IF test. Furthermore, the use of IB as the matrix for the immunological reactions allows FITC- or enzyme-conjugated antibodies to be used as indicators of the reactions and a simultaneous investigation of several pathogenic agents.

The propagation of feline panleukopenia virus in micro-carrier cell culture and use of the inactivated virus in the protection of mink against viral enteritis

Using microcarrier cell culture for the production of virus antigen, a formalin-inactivated feline panleukopenia virus vaccine was evaluated for protection of mink against specific mink enteritis virus infection. The vaccine showed a good immunogenic effect in mink when used either alone or in combination with Clostridium botulinum type C-toxoid and/or Pseudomonas aeruginosa vaccine. A single vaccination induced persistent immune responses for periods of at least 1 year, as evaluated by ELISA and challenge tests. Neither immunological interference between vaccine constituents nor adverse reactions were observed.

Properties of an Australian isolate of bovine parvovirus type 1

An Australian bovine parvovirus isolate (BPV 267) was found to haemagglutinate human, guinea-pig, rat and dog erythrocytes, out of a range of 16 species of erythrocyte tested. The haemagglutinating activity was generally found to be both pH and temperature dependent. The virus was found to replicate best in intestinal epithelium, macrophage and lung cells, out of 9 bovine cell types tested. Highest yields of virus were obtained by the use of selected cell strains at low-passage levels which were maintained near neutral pH under conditions of high rates of cell growth. Studies of the rates of thermal inactivation with time showed the virus to be relatively stable at 37 degrees C, 56 degrees C and 70 degrees C, the incorporation of serum proteins, 1 M MgCl2 and 2 M NaCl in the medium having no influence on stability at 56 degrees C. The virus was resistant to the action of CHCl3, ether and 1% trypsin, and its replication was inhibited by BUDR, this effect being reversed by thymidine. Actinomycin D was found to inhibit virus replication, but only when applied during the first 8 h post-infection. Density gradient studies showed infective virus to have a density of 1.41 g cm-3; haemagglutinating non-infective virus with defective morphology having a density of 1.31 g cm-3. In addition, a proportion of morphologically-complete haemagglutinating, but non-infective virus particles was found at a density of 1.36 g cm-3. The virus proved to have a mean diameter of 22 nm.

A non-haemagglutinating isolate of mink enteritis virus

A virus was isolated from mink showing clinical and pathological signs of mink enteritis. This virus was identified as mink enteritis virus (MEV) from results of serological tests, determination of its density in CsCl (1.415 g cm-3), and morphology, including size (20 nm in diameter). The isolate was designated MEV-S. In contrast to other known MEV strains, the MEV-S isolate has no haemagglutinating (HA) activity with swine red blood cells (RBCs) at 4 degrees C and pH 6.8. Neither was there any HA at other pH values and temperatures, or when horse, bovine and rhesus monkey RBC's were used.

Molecular cloning of the Aleutian disease virus genome: expression of Aleutian disease virus antigens by a recombinant plasmid

Three nonoverlapping segments representing approximately 80% of the 4.8-kilobase pair Aleutian disease virus (ADV-G) duplex genome were molecularly cloned into either bacteriophage M13mp9 (M13bm2 = 0.07 to 0.15 map unit; M13bm1 = 0.15 to 0.54 map unit) or plasmid pUC8 (pBM1 = 0.54 to 0.88 map units). In addition the 0.54- to 0.88-map unit segment of a Danish isolate of ADV (DK ADV) was also cloned into pUC8 (pBM2). The recombinant plasmids pBM1 and pBM2 induced expression of several polypeptides in Escherichia coli JM103 that were specifically recognized by sera from mink infected with ADV. The same three proteins with approximate molecular weights of 55,000, 34,000, and 27,000 were detected both by immune blotting and by immunoprecipitation of [35S]methionine-labeled JM103 (pBM1). None of these proteins were recognized in JM103 or JM103 (pUC8), nor were they detected by sera from normal mink. Purified pBM1 and pBM2 DNA appeared identical in size by gel analysis and contour length measurement, and electron microscopic heteroduplex mapping revealed no visible areas of heterology. However, restriction endonuclease mapping showed that pBM2 was different from pBM1, indicating that this segment of the ADV genome was similar but not identical for two strains of ADV (ADV-G and DK ADV). Furthermore, when cloned DNA from ADV-G was labeled with [32P]dCTP by nick translation, DNA relatedness to several field strains of ADV (Utah I, Pullman, and DK), but not to mink enteritis virus or cellular DNA, was shown by Southern blot hybridization.

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.

Antigenic structure and variation of canine parvovirus type-2, feline panleukopenia virus, and mink enteritis virus

The antigenic structure and variation of canine parvovirus type-2 (CPV), feline panleukopenia virus (FPV), mink enteritis virus (MEV), and a closely related virus of raccoons (RPV) was investigated using a panel of 13 monoclonal antibodies (mAb) formed against CPV and 8 mAb formed against FPV. Each mAb both neutralized and inhibited the hemagglutination of the homologous virus. All mAb tested immunoprecipitated the two capsid proteins. Five mAb were specific for the CPV isolates and one reacted with the FPV, MEV, and RV isolates, but not the CPV. Another mAb reacted only with certain FPV and MEV isolates. The remaining 14 mAb reacted with most parvoviral isolates from the four animal species. Antigenic variation was observed both within and between the parvovirus isolates from each species. The 12 MEV isolates could be grouped into three antigenic types based on their reactivity with the panel of mAb. Antigenic variants of either CPV or FPV were readily selected with several mAb. Analysis of these variant viruses by direct serological tests and competition radioimmune assays between different mAb revealed that the capsid surface contained at least two determinants, each being comprised of many different but overlapping epitopes.

Antigenic relationships between canine parvovirus type 2, feline panleukopenia virus and mink enteritis virus using conventional antisera and monoclonal antibodies

The antigenic relationships between three similar parvoviruses, canine parvovirus type 2 (CPV), feline panleukopenia virus (FPV) and mink enteritis virus (MEV) were investigated. Antisera against all 3 viruses and monoclonal antibodies (mAb) to CPV were prepared and the viruses compared using several serological methods. When conventional sera were used in the hemagglutination-inhibition and agar gel precipitin (AGP) tests there were no differences between the CPV viral isolates studied, but antigenic differences were revealed between the CPV isolates and the FPV or MEV. Of 16 mAb produced against CPV, six reacted only with the CPV. The other 10 mAb reacted with all three parvoviruses. Additionally, an antigenic difference was detected by AGP tests between one FPV isolate and the other FPV and MEV isolates. Including both conventional sera and mAb to CPV in a single AGP test with the CPV, MEV and FPV antigens permitted the comparison of results obtained with the different antibodies. The results reported revealed antigenic differences between CPV and FPV or MEV that were most clearly defined using mAb.

Comparison of canine parvovirus with mink enteritis virus by restriction site mapping

The genomes of canine parvovirus and mink enteritis virus were compared by restriction enzyme analysis of their replicative-form DNAs. Of 79 mapped sites, 68, or 86%, were found to be common for both types of DNA, indicating that canine parvovirus and mink enteritis virus are closely related viruses. Whether they evolved from a common precursor or whether canine parvovirus is derived from mink enteritis virus, however, cannot be deduced from our present data.

A simple procedure to obtain continuous cell lines from bovine peripheral blood leucocytes

A method is described by which cell lines can be readily developed from bovine peripheral leucocytes. Fifteen cell lines have been developed from 25 attempts, passage levels up to 60 being reached. The cell lines are aneuploid and predominantly epithelial, show split ratio capabilities of 1:4 to give monolayers with 5 days of routine passage, and have high resistance to laboratory contamination with bacterial and fungal agents. Data are given concerning establishment, morphology, viral susceptibility and chromosomal counts of established cell lines.

Diagnostic experience from an epidemic of canine parvoviral enteritis

Summary

Hemagglutination (HA) test and electron microscopy (EM) were used to diagnose canine parvoviral enteritis on fecal samples from 58 hospitalized dogs of a huge epidemic. By HA‐tests the presence of the canine parvovirus (CPV) involved was shown in samples from 15 dogs (∼ 26%). A reference antiserum was used to identify the virus of each sample by hemagglutination inhibition (HI). By EM parvovirus‐like particles were seen in samples from 28 dogs (∼ 48%). Particles in six samples were identified as CPV by immunoaggregation. Sera from 17 out of 19 dogs examined showed specific HI titers during the acute stage of illness. A high incidence of concomitant infection with Campylobacter spp was found by the bacteriologists.

Zusammenfassung

Diagnostische Erfahrungen während einer Epidemie von Parvovirus‐Enteritis der Hunde

Während einer grossen Epidemie von Parvovirus‐Enteritis der Hunde (in Schweden) wurde der Nachweis von Virus in Kotproben mit Hilfe der Hëmagglutination (HA) und Elektronenmikroskopie (EM) versucht; die Kotproben stammten von 58 hospitalisierten Hunden. Mit dem HA‐Test ließ sich das ursächliche Parvovirus in den Proben von 15 Hunden nachweisen (= ∼ 26%). In jeder von diesen Proben wurde das Virus durch Hämagglutination‐Hemmung (HAH) mit einem Referenzserum identifiziert. Mit der EM waren Parvovirus‐ähnliche Partikel in den Proben von 28 Hunden zu finden (= ∼ 48%). In 6 von diesen Proben wurden die Partikel mittels der Immunaggregation als das ursächlichen Parvovirus identifiziert. In 17 Serumproben von 19 untersuchten Hunden wurden spezifische HAH‐Titer während der akuten Krankheitsphase festgestellt. Die Bakteriologen wiesen ein gehäuftes Vorkommen von gleichzeitiger Infektion mit Campylobacter spp nach.

Résumé

Expériences de diagnostic durant une épidémie d'entérite à Parvovirus chez des chiens

On a recherché la mise en évidence du virus dans des matières fécales à l'aide de l'hémagglutination (HA) et de la microscopie électronique (EM) durant une forte épidémie d'entérite à Parvovirus chez des chiens en Suède. Les échantillons d'excréments provenaient de 58 chiens hospitalisés. Le Parvovirus a été mis en évidence par test HA dans les échantillons de 15 chiens (∼ 26%). Le virus a été identifié dans chacun de ces échantillons au moyen de l'inhibition de l'hémagglutination (HAH) avec un sérum de référence. On a trouvé des particules identiques au microscope électronique dans les échantillons de 28 chiens (∼ 48%). Les particules dans 6 de ces prélèvements furent identifiées comme Parvovirus au moyen de l'immunoaggrégation. Un titre HAH spécifique a été établi durant la phase aiguë de la maladie dans 17 échantillons sérologiques sur 19 chiens examinés. La bactériologie a montré la présence fréquente d'une infection simultanée à Campylobacter spp.

Resumen

Experiencias en el diagnóstico de una epidemia de parvovirus‐enteritis en caninos

Mediante pruebas de hemaglutinación y microscopía electrónica se diagnosticó parvovirus‐enteritis en caninos en muestras fecales de 58 caninos hospitalizados a raiz de una extensa epidemia. Con la prueba de hemaglutinación se detectó la presencia de virus en muestras fecales de 15 caninos (∼ 26%). Un antisuero de referencia se utilizó para la identificación del virus (prueba de inhibición de la hemaglutinación). Con microscopía electrónica se identificó parvovirus en muestras fecales de 28 caninos (∼ 48%). El virus fué identificado en seis muestras fecales utilizando la prueba de inmunoagregación. Sueros de 17 de 19 caninos examinados demostraron títulos específicos de inhibición de la hemaglutinación durante la etapa aguda de la enfermedad. Se demostró también una alta incidencia de infección concomitante con Campylobacter spp.

Cytology of canine cutaneous round cell tumors. Mast cell tumor, histiocytoma, lymphosarcoma and transmissible venereal tumor

Sixty-four canine cutaneous round cell tumors were divided into 25 mast cell tumors, 15 histiocytomas, nine cutaneous lymphosarcomas and 15 transmissible venereal tumors. The final diagnosis was made from cytologic, clinical and histologic findings. Cytologic features were significantly distinctive in mast cell tumor, transmissible venereal tumor, and most cases of histiocytoma and lymphosarcoma to allow a diagnostic opinion. This opinion was supported by subsequent histologic examination. In some instances cytology was considered essential in rendering a diagnostic opinion even though histology was available.

Canine hemorrhagic enteritis: detection of viral particles by electron microscopy

At necropsy, several dogs which died showing symptoms of hemorrhagic diarrhea, had significant lesions of the mucosa that were found especially in the duodenum and upper part of the small bowel. Study of ultrathin sections from the diseased mucosa revealed particles resembling parvoviruses in altered nuclei of cells of the intestinal crypts. Electron microscopic examination of intestinal contents by negative staining has shown the presence of many viral particles which have a diameter of 24 nm and whose profile is consistent with an icosahedral shape. These virions float at a density of 1.43 g/cm3 in cesium chloride and agglutinate rhesus monkey and swine red blood cells at 4 degrees C. A possible etiological role is discussed. This virus is compared with the minute virus of canines and the Feline Panleukopenia virus.

Experimental feline panleucopenia in the conventional cat

Coventional kittens, 12-27 weeks old, were inoculated with cell-cultured feline panleucopenia virus and killed sequentially between day 3 and day 24 after inoculation. All developed a non-fatal mild disease between days 2 and 9, characterized by lymphopenia, neutropenia, listlessness, depression and the development of neutralizing antibodies to the virus. Small intestinal bacterial counts were reduced during the period of maximal clinical disease, presumably a result of decreased food intake. There was involution of the thymus with marked depletion of lymphocytes between days 3 and 12. Depletion of lymphocytes also characterized the lesions in the lymph nodes between days 3 and 8. At the same time crypt lesions with spotty distribution were in the small intestinal and colonic mucosa. The changes were loss of crypt epithelial cells with compensatory attenuation of the remaining epithelium. Electron microscopically, the number and size of microvilli and secretory granules were reduced but there was no change indicating lethal cell injury. There were no virus particles. The findings point to an early and transient cellular damage by the virus. Intestinal alkaline phosphatase activity disappeared from the luminal surface of the attenuated crypt epithelial cells. Otherwise, intestinal alkaline and acid phosphatase activity were not altered in inoculated cats.