Studies on Cultural Characteristics of Contagious Ecthyma (orf) Virus

Ecthyma contagiosum is a viral disease of sheep and goats, which is caused by Parapoxvirus. Primary cell cultures of lamb testis, lamb kidney, rabbit kidney and permanent cell lines: foetal sheep kidney (FSK), sheep foetal thymus (SFT), sheep foetal muscle (SFM), sheep plexus choroideus (SPC), bovine trachea (BTR), embryonic bovine trachea (EBTR), Madin Darby bovine kidney (MDBK) and baby hamster kidney (BHK 21) were used. For inoculation of the cell cultures, 10% suspensions of scabs in PBS or nasal swabs from Orf infected sheep and goats were used. The vaccinal strain Phylaxia was used as reference. Reproduction of isolates was controlled daily by assessment of the cytopathic effect and dynamics was monitored on 5 types of cell cultures after 10 consecutive passages. Intracellular, extracellular and total virus titres were determined. The viral replication in cell cultures was confirmed by PCR. Most sensitive to the virus were the primary and permanent cell cultures of sheep and rabbit origin, the least sensitive were the permanent cell cultures. Over the permanent cell cultures monolayer changes appeared on 3–4 day, then increased, and between the 5 and 7 days covered most space until the 7–12 day when complete lost of monolayer was observed. Viral yield of EBTR and MDBK varied from log10 to log 10 TCID50/mL. Cytopathic effect after stationary culturing was found by hour 12–24: later then the roller cultivation and the viral titres were by 0.5 to 1.0 log10 lower. DNA from 045 gene, 392 bp of size, was amplified successfully by PCR. The primary and permanent cell cultures of sheep origin were the most suitable for cultivation of Orf viruses, because the viruses were multiplied in highest quantity. Upon use of primary and permanent cell cultures of sheep origin, the cytophatic effect was the strongest and depended on the type of cultivation: roller or stationary. The used PCR variant was able to confirm the Orf virus in samples as well as in cell cultures.