In situ hybridisation for the detection of Leishmania species in paraffin wax-embedded canine tissues using a digoxigenin-labelled oligonucleotide probe.

The diagnosis of canine leishmaniosis (CanL) is currently predominantly achieved by cytological or histological identification of amastigotes in biopsy samples, demonstration of specific anti-Leishmania antibodies and PCR-based approaches. All these methods have the advantage of being sensitive and more or less specific; nevertheless, most of them also have disadvantages. A chromogenic in situ hybridisation (ISH) procedure with a digoxigenin-labelled probe, targeting a fragment of the 5.8S rRNA was developed for the detection of all species of Leishmania parasites in routinely paraffin wax-embedded canine tissues. This method was validated in comparison with traditional techniques (histology, PCR), on various tissues from three dogs with histological changes consistent with a florid leishmaniosis. Amastigote forms of Leishmania gave clear signals and were easily identified using ISH. Various tissues from 10 additional dogs with clinical suspicion or/and a positive serological test but without histological presence of amastigotes did not show any ISH signals. Potential cross-reactivity of the probe was ruled out by negative outcome of the ISH against selected protozoa (including the related Trypanosoma cruzi) and fungi. Thus, ISH proved to be a powerful tool for unambiguous detection of Leishmania parasites in paraffin wax-embedded tissues.

Generalized encephalitozoonosis in a young kitten with cerebellar hypoplasia.

In recent years opportunistic infections due to microsporidial organisms have become increasingly important in immunocompromised people. Infected animals could serve as reservoirs of such infections. A case of generalized encephalitozoonosis in a young kitten is reported. Diagnosis was established by histopathological, immunohistochemical and molecular biological investigations demonstrating characteristic lesions and DNA of Encephalitozoon cuniculi in formalin-fixed and paraffin wax-embedded tissue sections. Infections due to E. cuniculi are not common in cats, but a potential role of domestic cats in transmission of the infectious agent cannot be excluded.

Localization of avian bornavirus RNA by in situ hybridization in tissues of psittacine birds with proventricular dilatation disease.

Proventricular dilatation disease (PDD) of psittacine birds is caused by a number of different genotypes of a novel viral species, avian bornavirus (ABV). Here we present an in situ hybridization (ISH) procedure using digoxigenin-labeled RNA probes for localizing viral genomic and mRNA of ABV-2 and ABV-4 in tissues of affected birds. Out of eleven immunohistochemically positive birds ISH signals were only found in seven. Partial sequencing of the viral genome had shown that four of them were infected with ABV-2, two with ABV-4 and one had a mixed infection with ABV-2 and ABV-4. ISH signals were present in the brain, in the vegetative nerve system, glandular epithelia and smooth muscle cells of the intestinal tract and in cardiomyocytes. Hybridization signals for viral genome were more abundant than signals for mRNA. As the probes were not strictly genotype-specific, four of the birds had hybridization signals with both, the ABV-2 and ABV-4 probes. The signals achieved with the homologous probes were more intense and more abundant than those resulting from heterologous probes. Taken together, the results of this study show that ISH can be used as a tool for localizing ABV sequences in tissues of birds with PDD and confirm the causative role of ABVs by showing viral replication in affected tissues.

Infections with weakly haemolytic Brachyspira species in pigs with miscellaneous chronic diseases.

The prevalence of infections with different Brachyspira species was assessed in 202 pigs with various chronic herd problems using different methods. Twenty-seven pigs (13.4%) were positive for Brachyspira spp. with at least one of the methods used. The highest number of positives was identified with mucosal scraping-PCR (23), followed by PET-PCR (22) and bacteriological-biochemical analysis (15). With the exception of three cases of B. pilosicoli infections, only weakly pathogenic Brachyspira species were identified. The majority was B. murdochii, followed by B. innocens and B. intermedia. Concurrent infections with two or more Brachyspira species were common and accounted for 37.1% of the total. Presence of weakly haemolytic Brachyspira was associated with wasting and diarrhoea in a number of cases. This investigation shows that infections with weakly haemolytic Brachyspira spp. may contribute to colonic pathology in pigs with chronic herd problems and that mixed infections seem to occur more frequently than previously noticed.

[The use of in-situ hybridization for the detection of Brachyspira spp. in pigs]. / Einsatz der in situ Hybridisierung zum Nachweis von Brachyspira spp. beim Schwein.

Diagnosis of Brachyspira infections in swine and the differentiation of the involved bacteria is time-consuming and in most cases unsatisfactory. Detecting Brachyspira directly in the damaged Brachyspira of the large intestine could provide a direct correlation between histological lesionsa and bacterial growth. In this study we investigated whether in-situ hybridization (ISH) with a digoxigenin-labeled RNA-probe is a suitable method for detecting Brachyspira in the mucosa of the large intestine. Formalin-fixed and paraffin-embedded tissue sections of the large intestine from 78 pigs, which showed macroscopic and histological findings of Brachyspira-associated colitis, were stained with hematoxylin and eosin and Warthin-Starry silver impregnation and subjected to ISH. We used a RNA-probe with a length of 334bp, complementary to a part of the 23S rRNA of all members of the genus Brachyspira. All sections were treated with this anti-sense probe and with a sense control probe. 64 samples (82%) showed clearly positive ISH signals. Thus ISH is a suitable method for detecting Brachyspira directly within the lesions of the large intestine. The quantity of Brachyspira identified by ISH was always lower than by Warthin-Starry staining. Whether this reflects lower sensitivity of the ISH technique, or the fact that other bacteria with morphological similarities to Brachyspira were also stained by Warthin-Starry is unknown as yet. The present investigations provide a basis of further research developing specific probes to distinguish between pathogenic and non pathogenic Brachyspira species and probes detecting other bacteria with morphological similarity to Brachyspira.

Screening for West Nile virus infections of susceptible animal species in Austria.

Avian mortality and encephalomyelitis in equines are considered good indicators for West Nile virus (WNV) activity. We retrospectively tested 385 horse sera for WNV antibodies and looked for WNV nucleic acid and/or WNV antigen in paraffin embedded tissues from 12 horses with aetiologically unresolved encephalomyelitis and 102 free-living birds of different species which had been found dead. With the exception of four horses originating from eastern European countries investigated on the occasion of transit through Austria, all horse sera were negative. Nested RT-PCR of the horse tissues yielded no amplification of WNV-RNA. Also, all bird samples, examined by immunohistochemistry, in situ hybridization and nested RT-PCR were negative for WNV. These results indicate that currently WNV cannot be considered a significant pathogen in Austria.

Development of a multiple primer RAPD assay as a tool for phylogenetic analysis in Listeria spp. strains isolated from milkproduct associated epidemics, sporadic cases of listeriosis and dairy environments.

A total of 82 Listeria strains comprising four species were examined by amplification with a multiple primer random amplified polymorphic DNA (RAPD) assay. It was the objective of the study to set up a procedure suitable for analysis of the relationships among strains from milkproduct-associated epidemics, strains from sporadic cases of listeriosis and field strains from dairy products and dairy environments. In a preliminary study, 205 primers, each 10 bp long, were screened for suitability as primers and 44 primers showing reliable and reproducible RAPD patterns at a defined reaction condition were selected. The 82 strains were assigned to 54 RAPD groups positioned in 13 major clusters. Strains isolated during milk product-associated epidemics were found to belong to a single cluster I. Human isolates from sporadic cases of listeriosis predominantly were assigned to four separate clusters. It was found that strains of clinical origin were mainly assigned to other clusters than strains of non-clinical origin.