Infectivity of Parapoxvirus Orf after 35 Years of Refrigeration

The aim of this study was to evaluate the persistence and infectivity of a Parapoxvirus orf sample that was kept under refrigeration for 35 years, originating from an animal with a presumptive diagnosis of contagious ecthyma. The sample, identified as CIZIP/1989, was collected from a goat with clinical suspicion of contagious ecthyma in 1989, originating from a flock of sheep and goats in São Paulo, Brazil. After 35 years of refrigeration under the stress of temperature variations, viral isolation was performed in cell culture using MDBK cells. In addition, a Polymerase Chain Reaction (PCR) was carried out to confirm the presence of the virus in the sample. Through the viral isolation in cell culture, cytopathic effect (CPE) was observed after 24 h of plate incubation. The presence of the contagious ecthyma virus in the sample was confirmed by PCR. Furthermore, phylogenetic analysis revealed a high identity with other reference sequences, some of which had already been identified in Brazil. Sequencing analysis of the CIZIP/1989 sample showed nucleotide identity ranging from 38% to 98% and amino acid identity from 19% to 100%. This study represents an important report of detection and isolation of viable Parapoxvirus orf from a sample maintained under refrigeration for 35 years. In addition, the study demonstrated a high infective capacity of the inoculum in cells, which highlights the epidemiological relevance of the results, especially due to the persistence of the virus in the environment under certain climatic conditions.