Virulence of bluetongue virus for British sheep.

A South African isolate of bluetongue virus type 3 was inoculated intradermally into three different breeds of British sheep under conditions designed to test its virulence in animals under stress. All animals inoculated developed a pyrexia and viraemia followed by clinical evidence of bluetongue disease. Marked alterations in serum enzyme levels, in particular of creatine phosphokinase, lactate dehydrogenase and aldolase occurred in the more severely affected animals. Nine out of the 12 inoculated animals subsequently died. No major differences in response could be detected in the different breeds of sheep nor in the stressed compared with the unstressed groups. The virulence of this bluetongue virus isolate was thereby confirmed and its potential risk to the British sheep industry. Consequently, stringent import regulations must be maintained to prevent its entry into Britain.

An antigenic determinant which is variant in a population of Plasmodium falciparum is present in isolates of Plasmodium malariae.

A monoclonal antibody that is directed against an antigenic determinant which is variant in a population of Plasmodium falciparum also reacts with Plasmodium malariae.

Antigenic diversity found in isolates of Plasmodium falciparum from Papua New Guinea by using monoclonal antibodies.

Monoclonal antibodies were used to demonstrate antigenic diversity in over 100 primary isolates of Plasmodium falciparum collected from one area of Papua New Guinea. The frequencies of several parasite antigens in our sample is calculated. One particular antigen which had previously been shown to be absent in one-third of established isolates collected from several countries appeared ubiquitous in our sample from Papua New Guinea. A method is presented that can be used to test for associations between antigens; the analysis also reveals whether other variables affect these associations. Several associations between antigens were revealed. In one instance, the association between two particular parasite antigens was affected by the donor's age. The importance of characterizing the antigenic structure of P. falciparum populations, and its relevance to the introduction of an antimalarial vaccine are discussed.

The relationship between the in vitro response of Plasmodium falciparum to chloroquine, quinine and mefloquine.

We have measured the in vitro response of several isolates of Plasmodium falciparum to chloroquine, quinine and mefloquine. We show that parasites which are resistant to chloroquine also have a reduced sensitivity to quinine. However, there appears to be no correlation between chloroquine resistance and reduced sensitivity to mefloquine. We conclude that the emergence and spread of chloroquine resistance could also be establishing a population of parasites with a reduced sensitivity to quinine which may provide the basis for the eventual emergence of quinine resistance.

Comparison of bluetongue type 20 with certain viruses of the bluetongue and Eubenangee serological groups of orbiviruses.

The genome of bluetongue virus type 20 consists of 10 segments of double-stranded RNA each of which contains unique sequences as determined by oligonucleotide mapping. The 10 polypeptide products of the virus genome were detected in virus-infected cells, and in pulse--chase experiments there was no secondary cleavage of the primary gene products. Using stringent conditions for RNA--RNA reassociation, no significant homology could be detected between the genomes of bluetongue type 20 isolated in Australia and representative serotypes isolated in other geographic regions. The results suggest sequence divergence between geographically isolated viruses and not the recent introduction of a bluetongue virus into Australia.