Martin Gerardo, Webb Rebecca J, Chen Carla, Plowright Raina K, Skerratt Lee F
College of Public Health, Medical and Veterinary Sciences, One Health Research Group, James Cook University, DB41-106, 1 James Cook Dr, Townsville City, QLD, 4811, Australia.
Australian Institute of Marine Sciences, Townsville, QLD, Australia.
Microb Ecol. 2017 Jul;74(1):106-115. doi: 10.1007/s00248-017-0934-x. Epub 2017 Jan 14.
Infectious diseases are transmitted when susceptible hosts are exposed to pathogen particles that can replicate within them. Among factors that limit transmission, the environment is particularly important for indirectly transmitted parasites. To try and assess a pathogens' ability to be transmitted through the environment and mitigate risk, we need to quantify its decay where transmission occurs in space such as the microclimate harbouring the pathogen. Hendra virus, a Henipavirus from Australian Pteropid bats, spills-over to horses and humans, causing high mortality. While a vaccine is available, its limited uptake has reduced opportunities for adequate risk management to humans, hence the need to develop synergistic preventive measures, like disrupting its transmission pathways. Transmission likely occurs shortly after virus excretion in paddocks; however, no survival estimates to date have used real environmental conditions. Here, we recorded microclimate conditions and fitted models that predict temperatures and potential evaporation, which we used to simulate virus survival with a temperature-survival model and modification based on evaporation. Predicted survival was lower than previously estimated and likely to be even lower according to potential evaporation. Our results indicate that transmission should occur shortly after the virus is excreted, in a relatively direct way. When potential evaporation is low, and survival is more similar to temperature dependent estimates, transmission might be indirect because the virus can wait several hours until contact is made. We recommend restricting horses' access to trees during night time and reducing grass under trees to reduce virus survival.
当易感宿主接触到能够在其体内复制的病原体颗粒时，传染病就会传播。在限制传播的因素中，环境对于间接传播的寄生虫尤为重要。为了评估病原体通过环境传播的能力并降低风险，我们需要量化其在病原体所处微气候等空间中发生传播的环境下的衰减情况。亨德拉病毒是一种源自澳大利亚翼手目蝙蝠的亨尼帕病毒，会传播给马和人类，导致高死亡率。虽然有疫苗可用，但其有限的接种率减少了对人类进行充分风险管理的机会，因此需要制定协同预防措施，比如破坏其传播途径。传播可能在病毒排泄到牧场后不久发生；然而，迄今为止尚无使用真实环境条件的存活估计。在此，我们记录了微气候条件并拟合了预测温度和潜在蒸发量的模型，我们用这些模型通过温度 - 存活模型并基于蒸发量进行修正来模拟病毒存活情况。预测的存活率低于先前估计，并且根据潜在蒸发量来看可能更低。我们的结果表明，传播应该在病毒排泄后不久以相对直接的方式发生。当潜在蒸发量较低且存活情况更类似于温度依赖性估计时，传播可能是间接的，因为病毒可以等待数小时直到发生接触。我们建议在夜间限制马匹接近树木，并减少树下的草丛以降低病毒存活几率。
