Epidemiology, clinical features, and molecular detection of orf virus in Haryana (India) and its adjoining areas

Orf is an acute, highly contagious, and economically important viral disease of small ruminants. In this study, six orf suspected outbreaks among goats and sheep were investigated from Haryana state and adjoining areas of Rajasthan state during the year 2021. The disease was diagnosed on the basis of clinical signs and molecular identification. The causative agent of the disease, orf virus (ORFV), was confirmed using polymerase chain reaction (PCR) targeting immunodominant envelope antigen (B2L) gene and confirmed by sequencing. The morbidity in goats ranged from 8.75 to 100%, whereas in sheep, it ranged from 0 to 8%. The higher mortality was observed among flocks with mixed infections of orf and peste des petits (PPR) or orf and haemonchosis as compared to other outbreaks. The phylogenetic analysis of sequenced PCR products clustered the current study strains in the same clad with Indian as well as strains from other countries with nucleotide identity more than 99%, signifying a close genetic relationship. The study highlighted the circulation of strains of a single cluster among sheep and goats in Haryana and adjoining areas. Prompt diagnosis of the disease is highly important for facilitating the implementation of control measures to minimize the losses suffered by small and marginal farmers in this region. Further detailed studies are required to delineate the molecular details of ORFV for better understanding the dynamics and molecular epidemiology of strains circulating in the country and for designing the effective vaccines against the disease which are currently lacking in the country.