| After unfruitful attempts in the 1960s to develop a live attenuated PPR vaccine, the decision was made to use the existing rinderpest vaccine. The close antigenic and immunogenic properties of these two morbilliviruses were expected to give small ruminants vaccinated against rinderpest a broad immunity against the PPR virus. This rinderpest heterologous vaccine also had the advantage of being inexpensive due to the large scale production of the rinderpest vaccine for cattle. In 1989, CIRAD (Diallo et al.) and The Pirbright Institute announced that they had obtained a homologous live PPR vaccine. The pathogenicity of this virus strain, isolated in 1975 in Nigeria, was attenuated through successive passages in cell cultures (Vero cells or green monkey kidney cells). The complete sequence of its genome was deposited in the GenBank under the reference X74443. Without risk for pregnant females, it provides immunity for at least three years, which covers the usual economic life of a goat or sheep. Protection becomes effective 14 days after a single injection. At the time, its adoption presented the advantage of not interfering in the epidemiological cycle and serological surveillance of rinderpest while providing small ruminants cross protection against this disease. In 1998, the OIE approved its adoption in PPR vaccination campaigns. In parallel, the continued use of the heterologous vaccine was prohibited to avoid introducing a bias into epidemiological studies of rinderpest. Although other vaccines used in India were developed from lineage IV PPRV strains (Sungri 96, Arasur 87 and Coimbatore 97), it is today the most widely used vaccine worldwide, recommended by the OIE for the vaccination of small ruminants.
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