Seasonal Drivers of the Epidemiology of Arthropod-Borne Viruses in Australia

Abstract

Arthropod-borne viruses are a major cause of emerging disease with significant public health and economic impacts. However, the factors that determine their activity and seasonality are not well understood. In Australia, a network of sentinel cattle herds is used to monitor the distribution of several such viruses and to define virus-free regions. Herein, we utilize these serological data to describe the seasonality, and its drivers, of three economically important animal arboviruses: bluetongue virus, Akabane virus and bovine ephemeral fever virus. Through epidemiological time-series analyses of sero-surveillance data of 180 sentinel herds between 2004–2012, we compared seasonal parameters across latitudes, ranging from the tropical north (−10°S) to the more temperate south (−40°S). This analysis revealed marked differences in seasonality between distinct geographic regions and climates: seasonality was most pronounced in southern regions and gradually decreased as latitude decreased toward the Equator. Further, we show that both the timing of epidemics and the average number of seroconversions have a strong geographical component, which likely reflect patterns of vector abundance through co-varying climatic factors, especially temperature and rainfall. Notably, despite their differences in biology, including insect vector species, all three viruses exhibited very similar seasonality. By revealing the factors that shape spatial and temporal distributions, our study provides a more complete understanding of arbovirus seasonality that will enable better risk predictions.

Identification and genomic characterization of the first isolate of bluetongue virus serotype 5 detected in Australia

“…; Melville ; Geoghegan et al . ). Indeed, the combined retrospective serological testing and subsequent virus genome characterization data from Kalumburu sentinel herd samples, further implicated the northern tip of Western Australia as a ‘hotspot’ for BTV emergence on the Australian mainland (Eagles et al .…”

Time-dependent selection pressure on two arthropod-borne RNA viruses in the same serogroup

“…The present study reports that despite similar etiological features between SBV and AKV, both viruses have distinct selection profiles and the strength of selection is likely to be time-dependent. The estimated mutation rate and the overall x of the recently emerged SBV are considerably higher than those estimates of AKV, which has been causing sporadic outbreaks in ruminant populations across the temperate and tropical regions since 1970s (Geoghegan et al, 2014;Jun et al, 2012;Kessell et al, 2011;Kono et al, 2008;Lee et al, 2007;Oem et al, 2014Oem et al, , 2012Yamakawa et al, 2006). Such discrepancies could possibly be attributed to the differences in the timing of emergence of these two infectious viral pathogens.…”

“…Although both viruses have similar etiological features and host range, they exhibit distinct geographical distributions and emerge at different time points. While AKV is relatively older and has been causing sporadic outbreaks in the cattle industries across Asia, Australia, and Africa since 1970s (Geoghegan et al, 2014;Jun et al, 2012;Kessell et al, 2011;Kono et al, 2008;Lee et al, 2007;Oem et al, 2014Oem et al, , 2012Yamakawa et al, 2006), SBV was first reported in autumn 2011 in Germany (Hoffmann et al, 2012) and subsequently, spread across most of the European countries Chaintoutis et al, 2014;Doceul et al, 2013;Dominguez et al, 2014;Herder et al, 2012;van den Brom et al, 2012;Yilmaz et al, 2014). The two viruses have similar genomic features with three genomic segments, small (S), medium (M) and large (L) (Fischer et al, 2013).…”

Bovine ephemeral fever epidemics in Kingdom Saudi Arabia: clinical, epidemiological and molecular investigation

“…In 2011 there were three different strains of the virus isolated. In addition, the average number of seroconversions had a strong geographical component that reflects patterns of vector biology responsible for BEF virus transmission [23]. Furthermore, the lower neutralizing antibody titers in 2007 suggesting reduced immunity reflects the importance of population immunity for the control of BEFV [24].…”