Selvey Linda A, Johansen Cheryl A, Broom Annette K, Antão Catarina, Lindsay Michael D, Mackenzie John S, Smith David W
School of Public Health, Curtin University, GPO Box U1987, Perth, WA, 6845, Australia.
The Arbovirus Surveillance and Research Laboratory, M504 School of Pathology and Laboratory Medicine, QEII Medical Centre, The University of Western Australia, Nedlands, WA, 6009, Australia.
BMC Infect Dis. 2014 Dec 10;14:672. doi: 10.1186/s12879-014-0672-3.
Murray Valley encephalitis virus (MVEV) is a flavivirus that occurs in Australia and New Guinea. While clinical cases are uncommon, MVEV can cause severe encephalitis with high mortality. Sentinel chicken surveillance is used at many sites around Australia to provide an early warning system for risk of human infection in areas that have low population density and geographical remoteness. MVEV in Western Australia occurs in areas of low population density and geographical remoteness, resulting in logistical challenges with surveillance systems and few human cases. While epidemiological data has suggested an association between rainfall and MVEV activity in outbreak years, it has not been quantified, and the association between rainfall and sporadic cases is less clear. In this study we analysed 22 years of sentinel chicken and human case data from Western Australia in order to evaluate the effectiveness of sentinel chicken surveillance for MVEV and assess the association between rainfall and MVEV activity.
Sentinel chicken seroconversion, human case and rainfall data from the Kimberley and Pilbara regions of Western Australia from 1990 to 2011 were analysed using negative binomial regression. Sentinel chicken seroconversion and human cases were used as dependent variables in the model. The model was then tested against sentinel chicken and rainfall data from 2012 and 2013.
Sentinel chicken seroconversion preceded all human cases except two in March 1993. Rainfall in the prior three months was significantly associated with both sentinel chicken seroconversion and human cases across the regions of interest. Sentinel chicken seroconversion was also predictive of human cases in the models. The model predicted sentinel chicken seroconversion in the Kimberley but not in the Pilbara, where seroconversions early in 2012 were not predicted. The latter may be due to localised MVEV activity in isolated foci at dams, which do not reflect broader virus activity in the region.
We showed that rainfall and sentinel chickens provide a useful early warning of MVEV risk to humans across endemic and epidemic areas, and that a combination of the two indicators improves the ability to assess MVEV risk and inform risk management measures.
墨累谷脑炎病毒（MVEV）是一种黄病毒，在澳大利亚和新几内亚出现。虽然临床病例并不常见，但MVEV可导致严重脑炎，死亡率很高。澳大利亚各地的许多地点都采用哨兵鸡监测，为人口密度低和地理位置偏远地区的人类感染风险提供早期预警系统。西澳大利亚的MVEV发生在人口密度低和地理位置偏远的地区，给监测系统带来后勤挑战，且人类病例很少。虽然流行病学数据表明在疫情爆发年份降雨量与MVEV活动之间存在关联，但尚未进行量化，而且降雨量与散发病例之间的关联不太明确。在本研究中，我们分析了西澳大利亚22年的哨兵鸡和人类病例数据，以评估哨兵鸡监测对MVEV的有效性，并评估降雨量与MVEV活动之间的关联。
使用负二项回归分析了1990年至2011年西澳大利亚金伯利和皮尔巴拉地区的哨兵鸡血清转化、人类病例和降雨量数据。哨兵鸡血清转化和人类病例用作模型中的因变量。然后根据2012年和2013年的哨兵鸡和降雨量数据对该模型进行测试。
除1993年3月的两例人类病例外，所有人类病例之前均出现了哨兵鸡血清转化。在前三个月的降雨量与所有感兴趣地区的哨兵鸡血清转化和人类病例均显著相关。在模型中，哨兵鸡血清转化也可预测人类病例。该模型预测了金伯利地区的哨兵鸡血清转化，但未预测皮尔巴拉地区的，2012年初该地区的血清转化未被预测到。后者可能是由于水坝孤立疫点的局部MVEV活动，这并未反映该地区更广泛的病毒活动。
我们表明，降雨量和哨兵鸡为流行和疫区的人类提供了有用的MVEV风险早期预警，并且这两个指标的结合提高了评估MVEV风险和为风险管理措施提供信息的能力。
