The isolation and importance of Simbu group viruses in South Africa

Abstract

The five viruses used in this study were isolated from cattle. An additional virus was recovered from a pool of biting midges, (Culicaides spp). The six viruses shared common group specific antigens in the cross-complement fixation test but in the cross-serum-virus neutralization test, they were shown to be three distinct viruses. In the cross-serum-virus microneutralization test utilizing reference sera and viruses of the Simbu serogroup it was demonstrated that they represented local strains of Shamonda, Shuni and Saba virus. Using suckling mice and the chicken embryo as a model it was shown that the South African strains of Shuni and Sabo virus also exhibited variable peripheral infectivity for suckling mice, a characteristic which was distinct from their teratogenic properties as determined in chicken embryos. Although mortality was higher the local strains of Shuni, Sabo and Shamonda virus also induced dramatic deformities in the chicken embryo. Additional mouse-brain passage of a local strain of Shuni virus, markedly reduced the peripheral infectivity of the virus, without apparently affecting its teratogenic potential at for the chicken embryo.

Die 5 virusse wat in hierdie studie gebruik is, oorspronklik uit beeste geisoleer. 'n Bykomstige virus is uit 'n poel van bytende muggies (Culicaides spp.) herwin. Die 6 virusse deel gemeenskaplike groepspesifieke antigene in die kruis-komplementbindingstoets, maar in die kruis-serum-virus neutralisasietoets is hulle as drie aparte virusse opgewys. In die kruis-serum-virus mikroneutralisasietoets met verwysings sera en virusse van die Simbu serogroep is gedemonstreer dat hulle lokale stamme van die Shamonda, Shuni en Sabo virusse verteenwoordig. Deur die gebruik van die baba-muis en kuiken embrio model, is daar getoon dat die Suid-Afrikaanse stamme van Shuni en Sabo virus, ook 'n wissellende perifere besmetlikheid vir baba-muise toon, 'n kenmerk wat skynbaar apart is van hul teratogene kenmerke soos bepaal in kuiken embrios. Alhoewel mortaliteit hoer was, het die lokale stamme van Shuni, Sabo en Shamonda virusse ook dramatiese misvormings in die kuiken-embrio geinduseer. Verdere muisbrein passasie van 'n lokale stam van Shuni virus, het die perifere besmetlikheid van die virus verminder, skynbaar sonder om sy teratogene potensiaal vir die kuiken-embrio in elk geval, te affekteer.