Molecular characterization of contagious ecthyma virus (CEV) isolated from goat and cross-protection studies

Abstract

Contagious ecthyma (CE) is a zoonotic viral infection caused by the Parapoxvirus in sheep and goats which is classified in the family of Poxviridae. In this study, the Penorf CE vaccine strain that originated from lambs (PKCE1 strain) and three CE strains (O-CEV1, O-CEV2, O-CEV3) originated from kids were used for molecular characterization and cross-protection studies. A phylogenetic similarity has been investigated by comparing the B2L gene of CE viruses originated from kids and lambs. It was observed that the isolates O-CEV1 and O-CEV2 had a similar DNA sequence (100%) whereas the other isolate, O-CEV3 had a different DNA sequence from the others, and the proportion of the difference between them was 2.6% as stated in the similarity index. The phylogenic evaluation revealed that CE viruses were not species specific and have different genotypes in lambs and kids in Turkey. Penorf vaccine strain which is still known as lamb origin was found to be also kid origin. In the pathogenity studies in kids and lambs, there was no rise in the body temperatures of lambs and kids and hyperemia, vesicles and pustules occurred in the scarified skin regions from the second day of the epruvation. In addition to these findings, it was determined that the healing in lesions occurred after the scabs fell off beginning from the 38th to 55th days of the study. At the end of the this study, the presence of CE strains with different pathogenicity properties was revealed. In goats vaccinated with Penorf vaccine, protection to O-CEV3 field isolate has been observed, but not obtained protection to PK-CK1 strain. As a result, the phylogenic evaluation revealed that CE viruses were not species specific and have different genotypes in lambs and kids in Turkey. The Penorf vaccine strain, which is still known to be of lamb origin, was found to be of kid origin and it was not seen to protect lambs against CE disease due to the genomic differences. Therefore, it was concluded from this data that at least a bivalent CE vaccine containing lamb and kid isolates should be prepared and used for effective immunity against CE infection, especially in lambs and kids.