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.