Arthropod‐borne Viruses in Australia, 1973‐1976

Abstract

Summary The period 1973‐76 saw additions to knowledge of Australian arboviruses in several directions. A large epidemic of Murray Valley encephalitis (MVE) allowed evaluation of serological diagnostic techniques not available in previous major outbreaks, and also added to knowledge of clinical features and epidemiology. Its wide geographical distribution, with cases recognized for the first time in central Australia, suburhan Adelaide and east central Queensland, possibly associated with what has been described as “the most extraordinary set of weather conditions to affect Australia in this century”, triggered new consideration of epidemic prediction and vector control. The recognition of regular summer‐autumn occurrence of epidemic polyarthritis in southern Australia suggested the possibility of year‐round survival of Ross River virus, and perhaps of other togaviruses, in that area. Further evidence was obtained for previous suggestions that Kunjin virus might cause febrile disease of man. Bovine ephemeral fever was repeatedly epizootic and its epidemiology became a major focus of investigation, with accent on possibilities of control by vaccination. Important progress was made in Japan and then in Australia in linking Akabane virus with a disease of domestic animals. The continuation of field programmes in Queensland and Western Australia, and the commencement of new ones in Northern Territory, the Murray Valley of Victoria and elsewhere, led to the discovery of “new” viruses and extended the known host and geographic range of other viruses, adding complexity to the Australian arbovirus pattern. An ambitious programme of serological surveillance of virus infection in sentinel cattle herds covered a wide area of Australia and New Guinea and produced important results which could well be supplemented in other hosts. Progress in this period does not contradict the previous suggestion that complete elucidation of the epidemiology of arboviruses in Australia is a distant goal within the limits of current techniques, but it does suggest that collaboration between units and between disciplines can provide steady and useful progress.

Human Arbovirus Infections Along the South Coast of New South Wales

“…Mosquitoes collected from widely separated areas of Australia distant from the south coast of New South Wales have yielded both BF virus (Marshall, Woodroofe and Hirsch, 1982;Standfast et ai, 1984) and GG virus (Doherty, 1977;Marshall et ai, 1980;Marshall, 1980;Marshall, 1984), strongly supporting the view that further studies of the pathogenic potential of these two viruses are warranted.…”

Isolation of Murray Valley Encephalitis Virus and Other Arboviruses in the Ord River Valley 1972–1976

“…One hundred and fifty three of the isolates were from pools of Culex annuUrostris, confirming its role as a major arbovirus vector in Australia (Doherty, 1972(Doherty, , 1977. The remaining viruses were isolated from four relatively minor species: Aedeomyia catasticta yielded thirty seven virus strains of which thirty two were of the Corriparta serological group, and Culex fatigans, Aedes tremulus and Aedes normanensis yielded the remaining five strains.…”

“…Most of these virus types have been repeatedly isolated. Seven (MVE, Kunjin, Kokobera, Sindbis, Koongol, Wongal, Wongorr) have previously been isolated elsewhere in Australia (Doherty, 1972(Doherty, , 1977 and seven appear to be 'new'. These 'new' viruses include the three rhabdovirusesKimberley, Kununurra and Parry's Creek.…”

GENETIC ANALYSIS OF KUNJIN VIRUS ISOLATES USING HAEIII AND TAQI RESTRICTION DIGESTS OF SINGLE‐STRANDED cDNA TO VIRION RNA

“…This may permit divergent genetic types to emerge over extended time periods. For flaviviruses such as KUN, birds, particularly waterbirds, are the major host (Doherty, 1977). Such birds may act to distribute viruses rapidly over extensive areas so that a single KUN genetic type is maintained.…”

“…It is widely accepted that both viruses are enzootically maintained in tropical northern Australia. Serological surveys suggest that birds, particularly waterbirds, and feral pigs are important natural hosts (Gard et al, 1976;Doherty, 1977;. The major arthropod vector is Cx.…”