Advanced vacuolation indicates propagation of various salmonid alphavirus type 2 isolates in Acholeplasma-infected BF-2 cells

During previous routine inspections of bluegill fry (BF-2) and rainbow trout gonad (RTG-2) cells incubated with organ samples from asymptomatic Arctic char Salvelinus alpinus, brook trout Salvelinus fontinalis, and rainbow trout Oncorhynchus mykiss, a distinctive, reproducible cytopathic effect (CPE) appeared. The striking CPE, involving progressive vacuolation turning into slowly proceeding pyknotic degeneration, was originally attributed exclusively to enhanced growth of Acholeplasma sp. However, at a recent re-examination of re-infected BF-2 cells using electron microscopy (EM), conventional PCR, and quantitative PCR (qPCR), a virus was also detected. Two days post inoculation (dpi), EM revealed characteristic virions inside cytoplasmic vacuoles and next to bacteria outside the cells. The nucleotide sequences of the viral nsP3 gene fragment obtained from supernatants of infected cells were 100% identical and representative for salmonid alphavirus type 2 (SAV 2). The 16S RNA gene (16S rDNA) fragment sequences of the Mollicutes-specific PCR product obtained from SAV-infected as well as virus-free BF-2 control cells were identical with Acholeplasma laidlawii. In addition, qPCR results indicated enhanced propagation of virus and bacteria increasing with vacuolation between 5 and 8 dpi. Advanced vacuolation can be regarded as a CPE of both SAV and A. laidlawii, suggesting a viral impact on the bacterial infection that turns a latent intracellular stage into an apparent degenerative condition.

Granular Cell Tumour in a California Kingsnake (Lampropeltis californiae)

A 21-year-old female California kingsnake (Lampropeltis californiae) was presented to the University of Veterinary Medicine, Vienna, Austria, with a space-occupying mass in the caudal abdomen. Following clinical, radiological and sonographical evaluation the mass was removed surgically. Histopathology and transmission electron microscopy confirmed the diagnosis of a granular cell tumour, but immunohistochemical labelling for a range of markers was negative. This lesion is rare in mammals and birds, but has not been reported previously in a reptile.

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.