No abstract

Sheep and goat pox (SGP) with peste des petits ruminants (PPR) are transboundary viral diseases of small ruminants that cause huge economic losses. Recombinant vaccines that can protect from both infections have been reported as a promising solution for the future. SGP was used as a vector to express two structural proteins hemagglutinin or the fusion protein of PPRV. We compared immunity conferred by recombinant capripoxvirus vaccines expressing H or F or both HF. Safety and efficacy were evaluated in goats and sheep. Two vaccine doses were tested in sheep, 10TCDI50 in 1ml dose was retained for the further experiment. Results showed that the recombinant HF confers an earlier and stronger immunity against both SGP and PPR. This recombinant vaccine protect also against the disease in exposed and unexposed sheep. The potential Differentiating Infected from Vaccinated Animals of recombinant vaccines is of great advantage in any eradication program.

BackgroundRift Valley fever is an emerging zoonotic viral disease, enzootic and endemic in Africa and the Arabian Peninsula, which poses a significant threat to both human and animal health. The disease is most severe in ruminants causing abortions in pregnant animals, especially sheep animals and high mortality in young populations. High mortality rates and severe clinical manifestation have also been reported among camel populations in Africa, to attend however none of the currently available live vaccines against RVF have been tested for safety and efficacy in this species. In this study, the safety and efficacy (through a neutralizing antibody response) of the thermostable live attenuated RVF CL13T vaccine were evaluated in camels in two different preliminary experiments involving 16 camels, (that 12 camels and 4 pregnant camels).ResultsThe study revealed that the CL13T vaccine was safe to use in camels and no abortions or teratogenic effects were observed. The single dose of the vaccine stimulated a strong and long-lasting neutralizing antibody response for up to 12 months.ConclusionThe presence of neutralization antibodies is likely to correlate with protection; however protection would need to be confirmed by challenge experiments using the virulent RVF virus.

Rift valley fever (RVF) is a highly significant vector-borne disease causing huge economic loses in livestock (ruminants and camels) and also human fatalities. The disease is endemic in most Sub-Saharan African countries, including West Africa, and has been present in the Middle East since 2010. Vaccination is considered to be the most effective way to prevent and control the expansion of the disease. Currently available attenuated live vaccines for RVF have significant limitations in that they are either thermolabile (CL13 strain vaccine) or causes abortion and teratogenic effects (Smithburn strain vaccine). This study therefore set out to develop a safe and effective thermostable live attenuated RVF vaccine. The existing CL13 vaccine, which is a naturally attenuated strain, was made thermostable through three cycles of heating (56°C) and selection. The resulting candidate vaccine (CL13T) was stable at 4°C for 20 months and shows significantly improved levels of thermostability over the existing CL13 vaccine. A pilot batch of the CL13T vaccine was produced and tested for safety and efficacy in cattle, sheep and goats. The vaccine was found to be safe, with no clinical signs or side effects observed in vaccinated animals, and there was no evidence for circulation of the virus in the blood of animals post-vaccination. On testing for efficacy in cattle, sheep and goats, through the detection of neutralizing antibodies post-vaccination, good levels of neutralizing antibodies were detected for a minimum of one year in sheep and goats, and neutralizing antibodies were detected for least 4 months in cattle. This new thermostable vaccine could represent an efficient tool for the control of rift valley fever in endemic countries. The vaccine also has the potential to be used, along with an appropriate diagnostic test, to differentiate vaccinated from infected animals (DIVA).

A combined vaccine against peste des petits ruminants (PPR) and sheep/goat pox (SGP), based on Nigeria 75 PPR strain and sheep pox Romania strain, was developed and applied in the field. Safety and efficacy were evaluated on goats and sheep in comparison with monovalent PPR and SGP vaccines. Goats were challenged by PPR virulent strain and sheep by SP virulent strain. The result showsthat the combined PPR/SGP vaccine confers a good protection against both PPR and SGP infection with no significant difference with monovalent vaccines. The combined vaccine was used in Morocco and other African countries on small ruminant flocks with good safety and satisfactory sero-conversion detected against both PPR and SGP viruses, as soon as 14 days post vaccination. It's the first time where a combined vaccine was applied in large vaccination campaigns to prevent in one shot the two diseases.