MSc. Dissertation 2018
Rift valley fever (RVF) is a zoonotic disease caused by Rift Valley fever virus (RVFV)
with impact on animal and human health. Vaccines developed against RVF have safety
and efficacy concerns and administered by needles posing risks of RVFV transmission.
This study reports the safety and immunogenicity of attenuated RVF MP-12 and its
recombinant arMP-12ΔNSm21/384 vaccines. A total of 32 sheep, 15 goats and 23 zebu
calves were vaccinated with 1x10 5 plaque forming units (PFU)/ml of MP-12 or arMP-
12ΔNSm21/384 RVF vaccine candidates intramuscularly or intradermally. Six animals
from each species were vaccinated with Eagle's Minimum Essential Medium (EMEM) as
negative controls. RVFV neutralizing antibody was tested in serum samples collected on
days 0, 3, 5, 7, 14, 21, 28, 35, 70, 84 and 87. Rectal temperatures were taken on days of
blood collection and signs of illness were observed daily post vaccination (PV). On day 87
PV, all intramuscularly vaccinated animals were re-vaccinated with 1 x 10 4 PFU/ml of the
MP-12 vaccine and blood samples were obtained on days 7, 14, and 21 PV. The vaccines
were found to be safe and all vaccinated animals produced neutralizing antibodies against
RVFV. Higher antibody response was observed in animals that were vaccinated
intradermally with arMP-12ΔNSm21/384 RVF vaccine with geometric mean antibody
titers (GMT) of 1113 in goats, 210 in sheep and 22 in zebu calves as compared to
intramuscularly vaccinated animals with GMT of 160 in goats, 51 in sheep and 63 in zebu calves. On re-vaccination, the antibody titers increased rapidly, reaching maximum titers of 470 in sheep, 640 cattle and 640 in goats. Overall, this study indicates that these RVFV vaccines are promising candidate for the prevention of RVF among domestic ruminants, however intradermal vaccination works better for sheep and goats while intramuscular vaccination works better for zebu calves.