A Preliminary Investigation of the Ecology of Arboviruses in the Derby Area of the Kimberley Region, Western Australia

Abstract

Summary A survey of mosquito populations in the Derby area of the Kimberley region, Western Australia, in March/April of 1977 yielded a total of 3,318 adult female mosquitoes. Fifteen taxa were represented, seven being new locality records for this area. Culex annulirostris was the dominant species, comprising 85·41% of the total catch. All mosquitoes collected were processed for virus isolation and thirteen strains of four (and possibly five) distinct arboviruses were obtained, all from pools of Culex annulirostris. These viruses include Murray Valley encephalitis, Ross River, Wongal, an untyped non‐haemagglutinating member of the Koongol group and a virus which reacts to polyvalent antisera against the Anopheles A and B groups. With the exception of Ross River, all these viruses had been previously isolated from the Ord River Valley, some 500 km to the north‐east. Comparison of virus isolations in the Ord Valley and Derby supports the suggestion that both sites share a common viral flora. Both also display an exceeedingly high overall isolation rate (approximately 20% for Cx. annulirostris pools). Such comparisons suggest that a number of arboviruses transmitted by Cx. annulirostris are active throughout the Kimberley region and have peak isolation rates at the end of the wet season. Further studies are needed to fully define these viral cycles.

Fine-temporal forecasting of outbreak probability and severity: Ross River virus in Western Australia

“…This research also supports previous studies on mosquito-host interactions, their role in RRV transmission and outbreaks, owing to maximum tidal heights in estuarine, flood plans, and wetland areas [42]. The tropical regions of Derby and Broome experience some of the highest tidal variation in Australia, and in the southern hemisphere [44,45]. In both Derby and Broome the weekly maximum tidal height was an important driver in the probability of an outbreak and also incidence, with the inundation of mangroves being known to force animal reservoirs closer to urban areas [16].…”

Genetic Variation of Murray Valley Encephalitis Virus

“…The similarity of the Kimberley isolates with the Charleville and Toolamba isolates of 1974 suggests a spread from the north-west of Australia to the south-east. This contention is strengthened by the fact that the Kimberley is the only proven enzootic area in Australia (Liehne et al, 1976b;Wright et al, 1981).…”

“…The principal vertebrate hosts are believed to be water-birds (Liehne et al, 1976a;Marshall et al, 1982). Culex annulirostris appears to be the major vector in the primary cycle (Kay, 1980Wright et al, 1981). The south-eastern distribution of MVE is marked by sporadic epidemics of encephalitis in humans (Anderson, 1954;Doherty, 1977), the last of which occurred in 1974.…”

Genome-Scale Phylogeny and Evolutionary Analysis of Ross River Virus Reveals Periodic Sweeps of Lineage Dominance in Western Australia, 1977–2014

“…The surveillance program was initiated in the southwest region, where the majority of the WA population resides, in 1987, and the earliest samples from the south in our data set date to this time. Prior to this, study isolates derived from northern WA regions in 1977-1986 were collected as part of an independent research project (39). Mosquito-based surveillance activities in the central, remote, and arid regions of WA are only usually conducted opportunistically in response to FIG 5 MAFFT alignment of the Ross River virus data set revealed a 12-amino-acid insertion within the hypervariable region of the nsP3 gene, which was unique and characteristic of G3 and G4 isolates.…”