Viruses recovered from mosquitoes and wildlife serum collected in the Murray Valley of South-eastern Australia, February 1974, during an epidemic of encephalitis.

Pools of mosquitoes collected in the Murray Valley in February, 1974, during an encephalitis epidemic yielded 239 isolates of 11 distinct viruses. These included 39 isolates of MVE virus, an incriminated causative agent of encephalitis in man, and 111 isolates of Kunjin virus, a probable causative agent. An additional isolate of MVE virus was recovered from the serum of a white-faced heron, Ardea novaehollandiae.

Arboviruses of coastal south-eastern Australia.

During investigations of epidemic polyarthritis at Nelson Bay, New South Wales, 12 strains of Ross River virus, the causative agent, were recovered from pools of mosquitoes. In addition, the mosquito pools yielded 9 strains of the flavivirus Edge Hill, 4 strains of a bunyavirus, Gan Gan, 1 strain of an orbivirus Tilligerry, and 1 strain of an ungrouped probable arbovirus, Yacaaba. The latter 3 viruses were found to be antigenically distinct from previously recorded arboviruses.

Antigenically distinct strains of Ross River virus from north Queensland and coastal New South Wales.

Ross River virus strains recovered from north Queensland and the central coast of New South Wales can be clearly discriminated by the use of a short incubation haemagglutination inhibition test. Antigenic homology of strains within these regions and heterology between the regions seem unaffected by time, passage history, adaptation to laboratory mice and the nature of the original source material yielding the strains. It is concluded that the two antigenic types are enzootic to their respective regions and that they have evolved in isolation from a common ancestral virus.

Serological evidence of inter-epidemic infection of feral pigs in New South Wales with Murray Valley encephalitis virus.

The sera of 617 feral pigs, collected from three widely separated areas of northern and central New South Wales, were examined for antibody to Murray Valley encephalitis (MVE) virus and to Ross River virus. Haemagglutination-inhibition (HI) antibody was detected to MVE in 58% of sera and to Ross River virus in 15% of sera. Neutralization tests suggested that the MVE HI antibody resulted from infection with MVE virus in the summers of 1971-1972 and 1972-1973 when the virus was not known to be active in New South Wales.