Clinicopathologic features of a systemic coronavirus-associated disease resembling feline infectious peritonitis in the domestic ferret (Mustela putorius)

From 2002 to 2007, 23 ferrets from Europe and the United States were diagnosed with systemic pyogranulomatous inflammation resembling feline infectious peritonitis (FIP). The average age at the time of diagnosis was 11 months. The disease was progressive in all cases, and average duration of clinical illness was 67 days. Common clinical findings were anorexia, weight loss, diarrhea, and large, palpable intra-abdominal masses; less frequent findings included hind limb paresis, central nervous system signs, vomiting, and dyspnea. Frequent hematologic findings were mild anemia, thrombocytopenia, and hypergammaglobulinemia. Grossly, whitish nodules were found in numerous tissues, most frequently the mesenteric adipose tissue and lymph nodes, visceral peritoneum, liver, kidneys, spleen, and lungs. One ferret had a serous abdominal effusion. Microscopically, pyogranulomatous inflammation involved especially the visceral peritoneum, mesenteric adipose tissue, liver, lungs, kidneys, lymph nodes, spleen, pancreas, adrenal glands, and/or blood vessels. Immunohistochemically, all cases were positive for coronavirus antigen using monoclonal antibody FIPV3-70. Electron microscopic examination of inflammatory lesions identified particles with coronavirus morphology in the cytoplasm of macrophages. Partial sequencing of the coronavirus spike gene obtained from frozen tissue indicates that the virus is related to ferret enteric coronavirus.

Neurotropism of highly pathogenic avian influenza virus A/chicken/Indonesia/2003 (H5N1) in experimentally infected pigeons (Columbia livia f. domestica)

This investigation assessed the susceptibility of experimentally infected pigeons to the highly pathogenic avian influenza virus (HPAIV) H5N1 that caused recent outbreaks of avian influenza in birds and humans in several countries of Asia. For this purpose 14 pigeons were infected ocularly and nasally with 10(8) EID50 and clinical signs were recorded and compared with five chickens infected simultaneously as positive controls. The chickens demonstrated anorexia, depression, and 100% mortality within 2 days postinoculation. Three of the pigeons died after a history of depression and severe neurological signs consisting of paresis to paralysis, mild enteric hemorrhage, resulting in a mortality of 21%. Gross lesions in these pigeons were mild and inconsistent. Occasionally subcutaneous hyperemia and hemorrhage and cerebral malacia were observed. Microscopic lesions and detection of viral antigen were confined to the central nervous system of these pigeons. In the cerebrum and to a minor extent in the brain stem a lymphohistiocytic meningoencephalitis with disseminated neuronal and glial cell necrosis, perivascular cuffing, glial nodules, and in one bird focally extensive liquefactive necrosis could be observed. The remaining nine pigeons showed neither clinical signs nor gross or histological lesions associated with avian influenza, although seroconversion against H5 indicated that they had been infected. These results confirm that pigeons are susceptible to HPAIV A/chicken/Indonesia/2003 (H5N1) and that the disease is associated with the neurotropism of this virus. Although sentinel chickens and most pigeons did not develop disease, further experiments have to elucidate whether or not Columbiformes are involved in transmission and spread of highly pathogenic avian influenza.

Pathology of natural infections by H5N1 highly pathogenic avian influenza virus in mute (Cygnus olor) and whooper (Cygnus cygnus) swans

Mortality in wild aquatic birds due to infection with highly pathogenic avian influenza viruses (HPAIV) is a rare event. During the recent outbreak of highly pathogenic avian influenza in Germany, mortality due to H5N1 HPAIV was observed among mute and whooper swans as part of a rapid spread of this virus. In contrast to earlier reports, swans appeared to be highly susceptible and represented the mainly affected species. We report gross and histopathology and distribution of influenza virus antigen in mute and whooper swans that died after natural infection with H5N1 HPAIV. At necropsy, the most reliable lesions were multifocal hemorrhagic necrosis in the pancreas, pulmonary congestion and edema, and subepicardial hemorrhages. Major histologic lesions were acute pancreatic necrosis, multifocal necrotizing hepatitis, and lymphoplasmacytic encephalitis with neuronal necrosis. Adrenals displayed consistently scattered cortical and medullary necrosis. In spleen and Peyer's patches, mild lymphocyte necrosis was present. Immunohistochemical demonstration of HPAIV nucleoprotein in pancreas, adrenals, liver, and brain was strongly consistent with histologic lesions. In the brain, a large number of neurons and glial cells, especially Purkinje cells, showed immunostaining. Occasionally, ependymal cells of the spinal cord were also positive. In the lungs, influenza virus antigen was identified in a few endothelial cells but not within pneumocytes. The infection of the central nervous system supports the view that the neurotropism of H5N1 HPAIV leads to nervous disturbances with loss of orientation. More investigations are necessary to clarify the mechanisms of the final circulatory failure, lung edema, and rapid death of the swans.

Detection of canine oral papillomavirus-DNA in canine oral squamous cell carcinomas and p53 overexpressing skin papillomas of the dog using the polymerase chain reaction and non-radioactive in situ hybridization

Nineteen cutaneous and mucocutaneous papillomas, as well as 29 oral and 25 non-oral squamous cell carcinomas of dogs were analyzed immunohistologically for the presence of papillomavirus (PV)-antigens. Canine oral papillomavirus (COPV)-DNA was detected in formalin-fixed, paraffin-embedded tissues by polymerase chain reaction (PCR) and non-radioactive in situ hybridization (ISH). Furthermore, the expression of the tumor suppressor protein p53 was investigated. PV-antigens were detectable in more than 50% of the oral and cutaneous papillomas, while no PV-antigens could be demonstrated in venereal papillomas. One squamous cell carcinoma was PV-antigen positive. Only two cutaneous papillomas of the head showed a strong p53-specific immunostaining, while overexpressed p53 was detectable in approximately 35% of all squamous cell carcinomas. It was possible to amplify fragments of the E6, E7 and L1 gene by polymerase chain reaction (PCR) from five of eight oral and from five of eight cutaneous papillomas as well as from three oral squamous cell carcinomas. Nine of 10 papillomas showed a strong nucleus-associated hybridization signal typical for COPV-DNA. In three squamous cell carcinomas COPV-DNA was located in nests of the epithelial tumor cells surrounding 'horn pearls' or disseminated in the carcinoma tissue. These observations support the view that COPV may also induce non-oral papillomas in the dog and confirm the opinion that a progression of viral papillomas into carcinomas in dogs may occur.

Influenza A(H5N8) Virus Similar to Strain in Korea Causing Highly Pathogenic Avian Influenza in Germany

Highly pathogenic avian influenza (H5N8) virus, like the recently described H5N8 strain from Korea, was detected in November 2014 in farmed turkeys and in a healthy common teal (Anas crecca) in northeastern Germany. Infected wild birds possibly introduced this virus.

Characterization of the proliferation state in canine mammary tumors by the standardized AgNOR method with postfixation and immunohistologic detection of Ki-67 and PCNA

Paraffin-embedded tissue sections of 96 surgically removed mammary tumors from female dogs were analyzed for their proliferation state using three different methods. The AgNOR method, originally developed by Ploton and coworkers in 1986, modified and standardized by the AgNOR committee, is an easy, inexpensive silver-staining procedure used to determine cell proliferation and prognosis of various tumors. Due to the standardized staining protocol of the AgNOR method and a postfixation step, results obtained were of excellent quality for image-analysis processing. The growth fraction was evaluated by counting of immunohistologically positive-stained cells for Ki-67 or proliferating-cell nuclear antigen (PCNA). The values determined were, in general, lower with Ki-67 (MIB1) than with PCNA (PC10). Nevertheless, the labeling indices of these antigens correlated significantly (P < 0.001). Though the differences of the means between the tumor groups according to the classification system of the World Health Organization were significant for all three investigated methods (P < 0.001), there was a considerable overlap between the tumor groups concerning all investigated parameters. An exploratory data analysis (multivariate analysis) as performed to evaluate the prognostic relevance of the three methods including further anamnestic, clinical, gross, and histopathologic variables. Besides the histopathologic diagnosis (survival P < 0.001; survival time P < 0.05; reappearance of tumor growth P < 0.05), only the PCNA-labeling index (time until reappearance of tumor growth P < 0.001) was of prognostic significance.

Persistence of viral RNA in rabbits which overcome an experimental RHDV infection detected by a highly sensitive multiplex real-time RT-PCR

An internally controlled multiplex real-time RT-PCR using TaqMan probes and external standards for absolute RNA quantification was developed as a new diagnostic tool for the detection of rabbit haemorrhagic disease virus (RHDV). The test revealed a specificity of 100%, an analytical sensitivity of 10 copies/well and a linearity over a range from 10(1) to 10(10) copies. The viral loads in organs, leukocytes, sera and excretions of seropositive, convalescent rabbits which were overcoming an experimental infection with RHDV were determined using the validated assay. As a result, viral RNA was demonstrated and quantified for at least 15 weeks. Thus, a persistence of viral RNA after experimental infection of rabbits could be shown for the first time. In contrast, neither antigen nor infectious virus could be detected by antigen-ELISA, immunohistochemistry or experimental transmission. Therefore, further experiments are necessary to prove that the persistence of RNA is linked with the persistence of infectious virus particles.

Encephalitis in a stone marten (Martes foina) after natural infection with highly pathogenic avian influenza virus subtype H5N1

Recent outbreaks of disease in different avian species, caused by the highly pathogenic avian influenza virus (HPAIV), have involved infection by subtype H5N1 of the virus. This virus has also crossed species barriers and infected felines and humans. Here, we report the natural infection of a stone marten (Martes foina) from an area with numerous confirmed cases of H5N1 HPAIV infection in wild birds. Histopathological examination of tissues from this animal revealed a diffuse nonsuppurative panencephalitis with perivascular cuffing, multifocal gliosis and neuronal necrosis. Additionally, focal necrosis of pancreatic acinar cells was observed. Immunohistochemically, lesions in these organs were associated with avian influenza virus antigen in neurons, glial cells and pancreatic acinar cells. Thus, the microscopical lesions and viral antigen distribution in this stone marten differs from that recently described for cats naturally and experimentally infected with the same virus subtype. This is the first report of natural infection of a mustelid with HPAIV H5N1.

Immunohistochemical detection of P53 overexpression in paraffin wax-embedded squamous cell carcinomas of cattle, horses, cats and dogs

One hundred and six squamous cell carcinomas (SCCs) of cattle, horses, cats and dogs were analysed immunohistochemically for overexpression of p53 protein. The monoclonal antibody pAb 240, which recognizes only mutant p53, was used. Of 41 bovine ocular SCCs, 26 (63.4%) showed p53 nuclear reactivity. All of six (100%) equine ocular SCCs and seven of nine (77.7%) SCCs of the equine penis or vulva gave positive reactions. In nine of 11 (81.8%) feline SCCs of the ear and in seven of 14 (50%) feline SCCs of other locations, p53 immunoreactivity was detected. Only seven of 25 (29.5%) canine cutaneous SCCs gave a positive reaction. Thus p53 antigen could be detected immunohistochemically in formalin-fixed and paraffin wax-embedded tissues of SCCs of domestic animals. The results support the view that, as in man, p53 overexpression plays an important role in the development of most SCCs of the animal species studied. This was in particular true for feline SCCs of the ear and for bovine and equine ocular SCCs, which are assumed to be related to ultraviolet radiation.

Distribution of lesions and antigen of highly pathogenic avian influenza virus A/Swan/Germany/R65/06 (H5N1) in domestic cats after presumptive infection by wild birds

In early 2006, the highly pathogenic avian influenza virus (HPAIV) H5N1 of the Asian lineage caused the death of wild aquatic birds in Northern Germany. In the mainly affected areas, a trans-species transmission of HPAIV H5N1 to mammals occurred between birds and domestic cats and 1 Stone Marten (Martes foina), respectively. Here, we report lesions and distribution of influenza virus antigen in 3 cats infected naturally with HPAIV H5N1 A/swan/Germany/R65/06. The hemagglutinin partial nucleotide sequences of the viruses were genetically closely related to a H5N1 HPAIV obtained from a dead Whooper Swan (Cygnus cygnus) of the same area. At necropsy, within the patchy dark-red and consolidated lungs, there was granulomatous pneumonia caused by Aelurostrongylus sp. Histologically, the main findings associated with influenza in all cats were bronchointerstitial pneumonia and marked random hepatic necrosis. In addition, all animals displayed lymphoid necrosis in the spleen and Peyer's patches and necrosis of the adrenal cortex. Immunohistochemically, nucleoprotein of HPAIV was present intralesionally in the lungs, liver, adrenal glands, and lymphoid tissues. Oropharyngeal swabs were shown to be suited to detect HPAIV by quantitative real-time polymerase chain reaction (RT-PCR) in these cats, despite the paucity of influenza virus antigen in the upper respiratory tract by means of immunohistochemistry. The results show that outdoor cats in areas affected by HPAIV in wild birds are at risk for lethal infection. In conclusion, hepatic necrosis was, besides bronchointerstitial pneumonia, the primary lesion, suggesting that in naturally infected cats, damage to the liver plays an important role in the pathogenesis of H5N1 influenza.

Detection of chelonid herpesvirus DNA by nonradioactive in situ hybridization in tissues from tortoises suffering from stomatitis-rhinitis complex in Europe and North America

Chelonid herpesvirus (ChHV) infection in tortoises associated with stomatitis-rhinitis complex is a severe, mostly epizootic disease characterized by proliferative and diphtheroid-necrotizing glossitis, pharyngitis, rhinitis, and tracheitis, often occurring with pneumonia and encephalitis. The UL5 gene from a German ChHV isolate was used to generate a digoxigenin-labeled 307-base-pair DNA probe by polymerase chain reaction (PCR). ChHV DNA was detected in paraffin-embedded tissues of five naturally infected tortoises (two Afghan tortoises [Testudo horsfieldii], USA; two Hermann's tortoises [Testudo hermanni], Switzerland; one T. hermanni, Germany) by means of in situ hybridization (ISH) and PCR. Distribution of ChHV DNA exhibits many characteristics of alphaherpesvirus but also some characteristics of betaherpesvirus infections. The amino acid sequence of a portion of the ChHV UL5 homolog exhibited more than 50% similarity to alphaherpesvirus UL5 proteins. Nuclear hybridization signals were detected in epithelial cells of the lingual mucosa and glands. Furthermore, ChHV DNA was observed in tracheal epithelium, pneumocytes, hepatocytes, the renal tubular epithelium, cerebral glia cells and neurons, and intramural intestinal ganglia. ChHV DNA in endothelial cells of many organs underlines the systemic character of the disease. Importantly, ChHV DNA was detected by ISH in multiple tissues of tortoises originating from different geographic provenances. This indicates a high degree of conservation of the UL5 gene fragment among viruses prevalent in tortoises on different continents. With the described ISH, a molecular biological tool is available for rapid and specific diagnosis of ChHV infections and, more importantly, comparative pathogenetic studies of ChHV isolates from geographically unrelated regions.

The non-essential UL50 gene of avian infectious laryngotracheitis virus encodes a functional dUTPase which is not a virulence factor

The DNA sequence of the infectious laryngotracheitis virus (ILTV) UL50, UL51 and UL52 gene homologues was determined. Although the deduced UL50 protein lacks the first of five conserved domains of the corresponding proteins of mammalian alphaherpesviruses, the ILTV gene product was also shown to possess dUTPase activity. The generation of UL50-negative ILTV mutants was facilitated by recombination plasmids encoding green fluorescent protein (GFP), and expression constructs of predicted transactivator proteins of ILTV (alphaTIF, ICP4) were successfully used to increase the infectivity of viral genomic DNA. A GFP-expressing UL50-deletion mutant of ILTV showed reduced cell-to-cell spread in vitro, and was attenuated in vivo. A similar deletion mutant without the foreign gene, however, propagated like wild-type ILTV in cell culture and was pathogenic in chickens. We conclude that the viral dUTPase is not required for efficient replication of ILTV in the respiratory tract of infected animals. The replication defect of the GFP-expressing ILTV recombinant is most likely caused by toxic effects of the reporter gene product, since spontaneously occurring inactivation mutants exhibited wild-type-like growth.

A DNA vaccine containing an infectious Marek's disease virus genome can confer protection against tumorigenic Marek's disease in chickens

A DNA vaccine containing the infectious BAC20 clone of serotype 1 Marek's disease virus (MDV) was tested for its potential to protect against Marek's disease (MD). Chickens were immunized at 1 day old with BAC20 DNA suspended either in PBS, as calcium phosphate precipitates, incorporated into chitosan nanoparticles, in Escherichia coli DH10B cells, or bound to gold particles for gene-gun delivery. Challenge infection with MDV strain EU1 was performed at 12 days old, and four out of seven birds immunized with BAC20 DNA in saline by the intramuscular route remained free of MD until day 77 after challenge infection. A delay in the development of the disease could be observed in some animals vaccinated with other BAC20 DNA formulations, but clinical MD and tumour formation were evident in all but one bird. Five out of seven animals immunized with the vaccine virus CVI988 were protected against MD, but none out of seven birds survived EU1 challenge infection after injection of negative-control plasmid DNA. In a second animal experiment, five out of 12 chickens immunized with BAC20 DNA and six out of eight birds immunized with virus reconstituted from BAC20 DNA remained free of MD after challenge infection. In contrast, none out of 12 chickens survived challenge infection after immunization with BAC20 DNA lacking the essential gE gene or with gE-negative BAC20 virus. The results suggested that an MDV BAC DNA vaccine has potential to protect chickens against MD, but that in vivo reconstitution of vaccine virus is a prerequisite for protection.

Detection of European porcine reproductive and respiratory syndrome virus in porcine alveolar macrophages by two-colour immunofluorescence and in-situ hybridization-immunohistochemistry double labelling

Two groups of five pigs aged 6 weeks were each infected oronasally with one of two different European isolates of porcine reproductive and respiratory syndrome virus (PRRSV). The animals were killed sequentially at 4, 7, 14 or 21 days post-inoculation for examination. The methods used consisted of histopathology, and mono- and double-labelling techniques based on in-situ hybridization, immunofluorescence and immunohistochemistry. Porcine alveolar macrophages (PAMs) contained large amounts of PRRSV antigen and PRRSV RNA, as shown by double labelling with (1) either PRRSV immunofluorescence or PRRSV-specific in-situ hybridization with digoxigenin-labelled riboprobes, and (2) immunolabelling with Mac 387 antibody for calprotectin. Expression of PRRSV-RNA was not detectable in cytokeratin-positive hypertrophic and proliferating pneumocytes or in cells of alveolar ducts or bronchiolar epithelium. The use of two-colour immunofluorescence with confocal laser scanning microscopy and double labelling with in-situ hybridization-immunohistochemistry showed that PAMs were the only pulmonary target cells. This contradicts earlier reports that epithelial pulmonary cells may also be infected by PRRSV.

Studies on the Virulence of Two Field Isolates of the Classical Swine Fever Virus Genotype 2.3 Rostock in Wild Boars of Different Age Groups

The virulence of two isolates of the classical swine fever virus (CSFV) was studied in experimentally infected wild boars of different ages. The isolates, originating from wild boars shot in Mecklenburg-Western Pomerania (isolate '1829-NVP') and in Rhineland-Palatinate (isolate '11722-WIL'), belong to the genetic subgroup 2.3 Rostock. Clinical picture, transient viraemia, virus excretion and gross lesions at necropsy as well as a failure of virus detection at the end of the experiment revealed that this virus subtype was only moderately virulent. Whereas one subadult wild boar and both 7-week-old wild boar piglets infected intranasally became sick and died, only one of three 8-week-old animals which survived after contact infection remained CSFV positive until the end of the experiment [34 days post infection (dpi)], although neutralizing antibodies were present. This underlines the role of young boars in CSF epidemics. The isolate '11722-WIL' was shed by an infected adult wild boar and was transmitted to susceptible piglets. Interestingly, all animals which became sick and died also were found to be infected with a secondary pathogen. Therefore, we assume that after infection with moderately virulent CSFV simultaneous infections with other pathogens may be important for the clinical course and the outcome of the disease as well as for a spread of the virus in field.

Estimating the Postmortem Interval of Wild Boar Carcasses

Knowledge on the postmortem interval (PMI) of wild boar (Sus scrofa) carcasses is crucial in the event of an outbreak of African swine fever in a wild boar population. Therefore, a thorough understanding of the decomposition process of this species in different microhabitats is necessary. We describe the decomposition process of carcasses exposed in cages. Trial 1 compared a wild boar and a domestic pig (Sus scrofa domesticus) under similar conditions; Trial 2 was performed with three wild boar piglets in the sunlight, shade, or in a wallow, and Trial 3 with two adult wild boar in the sun or shade. The wild boar decomposed more slowly than the domestic pig, which shows that standards derived from forensic studies on domestic pigs are not directly applicable to wild boar. The carcasses exposed to the sun decomposed faster than those in the shade did, and the decomposition of the carcass in the wallow took longest. To assess the state of decomposition, we adapted an existing total body scoring system originally developed for humans. Based on our studies, we propose a checklist tailored to wild boar carcasses found in the field that includes the most important information for a reliable PMI estimation.

Evaluation of formalin-fixed paraffin-embedded tissues from vaccine site-associated sarcomas of cats for papillomavirus DNA and antigen

OBJECTIVE

To determine whether vaccine site-associated sarcomas (VSS) from cats contain papillomavirus antigen or DNA.

SAMPLE POPULATION

50 formalin-fixed paraffin-embedded tissue blocks of VSS from cats.

PROCEDURE

Sections from each tissue block were evaluated for papillomavirus antigen by use of an avidin-biotin-complex immunohistochemical staining method, using rabbit anti-bovine papillomavirus type-1 antibody. The DNA was extracted from sections of each tissue block, and polymerase chain reaction assays were performed, using primers designed to amplify regions of the E5 gene of bovine papillomavirus and consensus primers designed to amplify a region of the L1 gene of animal papillomaviruses. Sections from 20 of the tissue blocks were evaluated by use of nonradioactive in situ hybridization for bovine papillomavirus DNA.

RESULTS

Papillomavirus antigen and DNA were not detected in any of the VSS.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that papillomaviruses likely do not have any direct involvement in the pathogenesis of VSS in cats.

Minute excretion of highly pathogenic avian influenza virus A/chicken/Indonesia/2003 (H5N1) from experimentally infected domestic pigeons (Columbia livia) and lack of transmission to sentinel chickens

Five out of sixteen domestic pigeons, inoculated oculo-nasally with a high dose of highly pathogenic avian influenza virus A/chicken/Indonesia/2003 (H5N1), developed clinical signs and neurological lesions leading to death of three pigeons 5-7 days after inoculation [Klopfleisch, R., Werner, O., Mundt, E., Harder, T. & Teifke, J. P. (2006). Vet Pathol 43, 463-470]. H5N1 virus was recovered from all organs sampled from two apparently healthy pigeons at 3 days post-infection and from the three pigeons which died spontaneously. All surviving birds shed virus via the oropharynx and the cloaca at minimal titres and seroconverted. Sentinel chickens reared in direct contact to the pigeons neither developed clinical signs nor seroconverted to the H5N1 virus.

Neurotropism in blackcaps (Sylvia atricapilla) and red-billed queleas (Quelea quelea) after highly pathogenic avian influenza virus H5N1 infection

The epidemiologic role of passerine birds in the spread of highly pathogenic avian influenza virus (HPAIV) remains controversial. However, confirmed natural infections with HPAIV in Passeriformes, their close contact to poultry and humans, and their role as a human food source indicate a need for increased research on passerines. To date, there are only a few studies on viral shedding and pathomorphologic changes in songbirds infected with HPAIV. To investigate susceptibility, clinical outcome, virus spread, and pathomorphology, the authors inoculated oculo-oronasally 22 red-billed queleas (Quelea quelea) and 11 blackcaps (Sylvia atricapilla) with A/Cygnus cygnus/Germany/R65/2006 (H5N1) using 2 different doses of either 10(4) EID50 (50% egg infective dose) or 10(6) EID50 per animal. They monitored all birds for clinical signs and oropharyngeal and cloacal virus shedding. They also performed immunohistochemistry and obtained molecular virologic data by real-time reverse transcription polymerase chain reaction in tissue samples. In contrast to blackcaps, where 100% of the infected individuals died, queleas were much less susceptible, with a mortality of 82% and 18%, depending on the doses applied. In both species, the virus was shed within 3 to 6 days postinfection, mainly via the respiratory tract. Viral antigen was detected in 100% of the succumbed birds, particularly in the central nervous system. In blackcaps, the heart, lungs, and pancreas were mainly infected. In contrast, the pancreas was predominantly affected in queleas, whereas the heart and the lower respiratory tract were of minor relevance. The authors hypothesize that neurotropism should be considered a main factor for the fatal course of disease in Passeriformes after infection with HPAIV.

Diagnosis of feline herpesvirus infection by immunohistochemistry, polymerase chain reaction, and in situ hybridization

An adult domestic shorthair cat had severe chemosis due to purulent and necrotizing blepharitis and conjunctivitis. Purulent rhinitis, necrotizing glossitis, and dermatitis were also diagnosed. The cat was positive for feline immunodeficiency virus and feline leukemia virus. Histologically, intranuclear Cowdry type A inclusions were found within numerous epithelial cells adjacent to the lesions in skin, conjunctiva, and tongue. Electron microscopic examination revealed herpesviral particles within the lesions. Paraffin-embedded skin and tongue tissues were processed in a polymerase chain reaction, using primers to amplify a 306-bp region of the thymidine kinase gene of feline herpesvirus type 1, resulting in a distinct amplification product of the predicted size. The distribution of feline herpesvirus was demonstrated by immunohistochemistry and nonradioactive in situ hybridization. Positive immunostaining was found in nuclei and cytoplasm of numerous epithelial cells within and next to the lesions, whereas in situ hybridization, performed with a digoxigenin-labeled double-stranded DNA probe, revealed hybridization signal only in nuclei of intact epithelial cells. Neither immunohistochemistry nor in situ hybridization showed feline herpesvirus type 1 in tissues of lungs, liver, spleen, intestine, or brain.

Subacute liver necrosis after experimental infection with rabbit haemorrhagic disease virus (RHDV)

Rabbit haemorrhagic disease (RHD) is usually peracute to acute, while subacute to chronic disease is rare. This paper describes gross and histopathological findings in four out of 20 rabbits aged 14 weeks, experimentally infected with one of two German field isolates of RHD virus. Eight rabbits survived the infection for 10 days and were killed after four of them, infected with 100 to 10 000 haemagglutination units, had started to develop progressive jaundice. Histopathologically, icteric livers showed severe subacute centrilobular bridging necrosis with calcification, and proliferation of periportal hepatocytes and bile ducts. Positive-strand RHDV RNA was detected by in-situ hybridization, mainly in periportal macrophages. Loss of the normal hepatic architecture, reparation (fibrosis) and hepatocellular regeneration, together with moderate inflammatory reaction, are signs of liver cirrhosis. These signs, observed in young rabbits given small doses of RHD virus, are interpreted as an unusual outcome of experimental inoculation.

Infected and apoptotic cells in the IBDV-infected bursa of Fabricius, studied by double-labelling techniques

Infections of young chickens with infectious bursal disease virus (IBDV) result in depletion of lymphoid cells of the bursa of Fabricius (BF) due to necrosis and apoptotic processes. Interactions between IBDV and lymphoid cells were investigated by labelling paraffin-embedded tissue sections of infected BF with combinations of either immunohistochemistry (IHC), in situ hybridization (ISH) or in situ TUNEL reaction (IST). With regard to specificity and sensitivity, results of ISH were comparable to those of IHC. By double-labelling it was shown, for the first time, that viral antigen was present in most of the apoptotic cells. This suggests that IBDV may be directly involved in the induction of the apoptotic process. However, some cells also showed either viral antigen or DNA fragmentation, especially at the early stages of infection. It should be taken into account, therefore, that the apoptotic processes might also be induced by IBDV through indirect interaction between cells. Remarkably, in some of the infected lymphoid cells ISH signals were observed in the nucleolus.

VP5 and the N terminus of VP2 are not responsible for the different pathotype of serotype I and II infectious bursal disease virus

Two serotypes have been identified in infectious bursal disease virus (IBDV), a member of the family BIRNAVIRIDAE: A reverse genetics system was used for generation of chimeras in genome segment A of the two serotypes, in which the complete viral VP5 gene and 3' noncoding region (NCR), or parts thereof, were exchanged. The engineered viruses were characterized in vitro and in vivo in comparison to serotype I and II IBDV. Our results show that IBDV chimeras exhibit a different phenotype in cell culture compared to the wild-type viruses. In in vitro-cultivated bursal-derived cells, chimeric viruses infected B lymphocytes, as does serotype I IBDV. Surprisingly, serotype II virus was also able to infect in vitro-cultivated bursal cells, but these were neither B lymphocytes nor macrophages. After infection of susceptible chickens all chimeras replicated in the bursa of Fabricius (BF), and three chimeric viruses caused mild depletion of bursal cells. In contrast, after infection of chickens with a chimeric IBDV containing exchanged VP5 as well as 3'-NCR, no depletion was detectable. The serotype II strain did not replicate in the BF nor did it cause depletion of bursal cells. Thus, the origin of VP5 does not explain the different pathotype of IBDV serotype I and II.

Experimental Infection of Calves with Escherichia coli O104:H4 outbreak strain

In 2011, a severe outbreak of hemolytic-uremic syndrome was caused by an unusual, highly virulent enterohemorrhagic E. coli (EHEC) O104:H4 strain, which possessed EHEC virulence traits in the genetic background of human-adapted enteroaggregative E. coli. To determine magnitude of fecal shedding and site of colonization of EHEC O104:H4 in a livestock host, 30 (ten/strain) weaned calves were inoculated with 10¹⁰ CFU of EHEC O104:H4, EHEC O157:H7 (positive control) or E. coli strain 123 (negative control) and necropsied (4 or 28 d.p.i.). E. coli O157:H7 was recovered until 28 d.p.i. and O104:H4 until 24 d.p.i. At 4 d.p.i., EHEC O104:H4 was isolated from intestinal content and detected associated with the intestinal mucosa. These results are the first evidence that cattle, the most important EHEC reservoir, can also carry unusual EHEC strains at least transiently, questioning our current understanding of the molecular basis of host adaptation of this important E. coli pathovar.

Lyssavirus distribution in naturally infected bats from Germany

In Germany, to date three different lyssavirus species are responsible for bat rabies in indigenous bats: the European Bat Lyssaviruses type 1 and 2 (EBLV-1, EBLV-2) and the Bokeloh Bat Lyssavirus (BBLV) for which Eptesicus serotinus, Myotis daubentonii and Myotis nattereri, respectively, are primary hosts. Lyssavirus maintenance, evolution, and epidemiology are still insufficiently explored. Moreover, the small number of bats infected, the nocturnal habits of bats and the limited experimental data still hamper attempts to understand the distribution, prevalence, and in particular transmission of the virus. In an experimental study in E. serotinus a heterogeneous dissemination of EBLV-1 in tissues was detected. However, it is not clear whether the EBLV-1 distribution is similar in naturally infected animals. In an attempt to further analyze virus dissemination and viral loads within naturally infected hosts we investigated tissues of 57 EBLV-1 positive individuals of E. serotinus from Germany by RT-qPCR and compared the results with those obtained experimentally. Additionally, tissue samples were investigated with immunohistochemistry to detect lyssavirus antigen in defined structures. While in individual animals virus RNA was present only in the brain, in the majority of E. serotinus viral RNA was found in various tissues with highest relative viral loads detected in the brain. Interestingly, viral antigen was confirmed in various tissues in the tongue including deep intralingual glands, nerves, muscle cells and lingual papillae. So, the tongue appears to be a prominent site for virus replication and possibly shedding.