Abstract
The epidemiology of orf virus infection in Saudi Arabia (SA) has been researched since 1990. The results obtained during this period indicate that the disease is widespread, has great economic impact and that no vaccine has been used against it. The present study compares the immunogenicity and protective efficacy of three locally developed live orf virus vaccines. Two of them differ in their passage history in Vero cell culture and the third was used as a virulent virus in glycerine buffer. To the best of the authors' knowledge, no similar comparative study has been conducted in the Middle East utilising three types of vaccines prepared from the same virus strain. Selection of the candidate seed orf virus and performance of the quality control tests were as laid out by the OIE for veterinary vaccine production. The vaccine seed virus was a field orf virus isolated from a previous orf outbreak in Saudi Arabia. A simple novel formula was developed to calculate the rate of reduction in the healing time (RHT %) in the challenged sheep. This allowed direct comparison of the efficacy of the three types of vaccines employed in the present study. The efficacy of each vaccine was tested on a cohort of local Noemi sheep.
Highlights
Orf is a contagious zoonotic disease of sheep and goats
This paper describes a comparative study on three locally developed live vaccines prepared from a local field orf virus with the intention of finding one suitable to be recommended as a candidate vaccine to be used in the Kingdom
Following the 12 months’ challenge, the highest mean reduction time (MRT) % value was scored for the sheep that received the passage 20 vaccine (P20V) (30%), followed by those that received the live scab vaccine (LSV) (26.7%) and the lowest was scored by the passage 75 vaccine (P75V) (16.7%) group
Summary
Orf is a contagious zoonotic disease of sheep and goats. The causative agent is a Parapoxvirus of the family Poxviridae. The main lesions are usually found on the lips and around the mouth. Lesions can spread to the eyes, nostrils and teats (Abuelzein & Housawi 2009). The disease can take a generalised form throughout the body (Abuelzein & Housawi 1997). Orf is distributed worldwide and can cause great economic losses to sheep production (Robinson & Balassu 1981)
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