Introduction
Orf virus (ORFV) is a member of parapoxvirus genus which belongs to the family Poxviridae . Ithas a linear double-stranded DNA which is about 135 kbp in size. Orfis (also known as contagious ecthyma) is an infectious pustular dermatitis which primarily affects sheep, goats and wild ruminants1 . It is characterized by proliferative skin lesions on the lips, muzzle, ears, eyelids, and found around the mouth and nostrils of lambs2 . Transmission within the herd is by direct contact between animals. The morbidity may reach 100%, but mortality is usually less than 1%. It is zoonotic and humans can become infected through direct contact with sick animals. In humans, it has predilection for the hands where it appears as rash-shaped papule and can progressively extend to form pustules3 . Sheeppox and goatpox are important trans-boundary diseases that are notifiable to the Office Internationale des Epizooties4 . Mortality and morbidity in young animals can be high5,6 . Exotic breeds of sheep and goats are more susceptible than indigenous breeds that exhibit some level of natural immunity7 while in naïve animals, mortality can reach100%8 .The disease is endemic in North African countries of Morocco, Tunisia, Algeria and Libya because of porous land borders coupled with legal and illegal trade of animals. It is widespread in Central Africa9 . It has been reported in Southern Europe, the Middle East, Central Asia, India and China10 . In West Africa, pastoral farming is widely practiced because of unrestricted trans-border movement leading to importation of ORFV which infects sheep and goats. Nigeria has the largest small ruminant population in Africa with about 73.8 million goats and 42.1 million sheep located mainly in the Northern part of the country11 . Clinical and serological evidence of Orf has been reported in Nigeria12 , with few reports of molecular identification. Since there is increased livestock trade and cross border activities between Nigeria and neighboring countries, it is important to determine the evolutionary diversity of ORFV in Nigeria. Also, the zoonotic nature of ORFV underpins the public health importance of this study. We determined the prevalence, and molecular epidemiology of ORFV in sheep and goats imported into Nigeria’s capital Abuja from neighboring countries, the temporal dynamics and evolution of ORFV across Africa.