Isolation and Phylogenetic Analysis of Parapoxvirus orf From Outbreaks in Sheep in the Brazilian Midwest

This study aimed to isolate Parapoxvirus orf and characterize its genetic diversity through phylogenetic analysis in small ruminants from the state of Mato Grosso, Brazil.

A total of 103 scab samples were collected from sheep affected by nine contagious ecthyma outbreaks across three different mesoregions of Mato Grosso (Southeast, Northeast, and North) between 2023 and 2024. Viral DNA was amplified using conventional polymerase chain reaction (PCR) with primers PPP3 and PPP4 targeting the B2L gene to confirm the presence of Parapoxvirus orf. Following confirmation, 21 samples were selected for sequencing and phylogenetic analysis. Additionally, fifteen viable scab samples were selected for viral isolation using Madin-Darby bovine kidney cells cultured in RPMI medium in 24-well plates at approximately 70% confluence 24 h after passage.

All scab samples (103/103) tested positive for Parapoxvirus orf by PCR. Phylogenetic analyses revealed genetic similarities between the obtained isolates and previously reported circulating isolates from Brazil, including a close genetic relationship with circulating isolates from Mato Grosso. Furthermore, a cytopathic effect was observed in 80% of the samples. PCR also detected Parapoxvirus orf in the culture supernatants from all isolation assays.

This study confirms the circulation of Parapoxvirus orf in the state of Mato Grosso, Brazil. The genetic similarity of the identified isolates with those previously reported in Brazil and other countries highlights the need to strengthen biosecurity, prevention, and control policies for this zoonotic disease.