Evaluation of Protective Efficacy of Inactivated Thermostable Vaccine Against Nairobi Sheep Disease Virus

Abstract

Sheep and goats (n= 4/group) were inoculated with thermos-stabilized inactivated Nairobi sheep disease virus vaccine. Four unvaccinated animals for each group were kept as control. Vaccinated groups were given a booster vaccine dose 21 days later. Immune response was monitored by neutralizing antibody titers were determined by micro-plaque reduction neutralization test and confirmed by immunofluorescence assay. Two doses of the inactivated vaccine stimulated a strong immune response in the vaccinated animals. The vaccinated and mock group were challenged with virulent 1473 strain of the Nairobi sheep disease virus. All animals developed fever and viremia with varying degrees between sheep and goats post challenge. Mock vaccinated sheep developed high viremia levels relative to the vaccinated group and developed severe disease. In contrast, mock vaccinated goats showed a slight temperature compared to vaccinated goats. After challenge, two control sheep died from the disease whereas the vaccinated sheep survived. Vaccinated sheep suffered mild to moderate clinical reactions with pyrexia. Formalin inactivated vaccine fully protected the animals against the lethal 1473 challenge virus.