Romero João F, Gardner Ian, Price Derek, Halasa Tariq, Thakur Krishna
Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada.
Aquaculture Environmental Operations, Aquaculture Management Division, Fisheries and Oceans Canada, Ottawa, Ontario, Canada.
Transbound Emerg Dis. 2022 Jul;69(4):2029-2044. doi: 10.1111/tbed.14195. Epub 2021 Jul 3.
Simulation models are useful tools to predict and elucidate the effects of factors influencing the occurrence and spread of epidemics in animal populations, evaluate the effectiveness of different control strategies and ultimately inform decision-makers about mitigations to reduce risk. There is a paucity of simulation models to study waterborne transmission of viral and bacterial pathogens in marine environments. We developed a stochastic, spatiotemporal hybrid simulation model (DTU-DADS-Aqua) that incorporates a compartmental model for infection spread within net-pens, an agent-based model for infection spread between net-pens within and between sites and uses seaway distance to inform farm-site hydroconnectivity. The model includes processes to simulate infection transmission and control over surveillance, detection and depopulation measures. Different what-if scenarios can be explored according to the input data provided and user-defined parameter values, such as daily surveillance and depopulation capacities or increased animal mortality that triggers diagnostic testing to detect infection. The latter can be easily defined in a software application, in which results are summarized after each simulation. To demonstrate capabilities of the model, we simulated the spread of infectious salmon anaemia virus (ISAv) for realistic scenarios in a transboundary population of farmed Atlantic salmon (Salmo salar L.) in New Brunswick, Canada and Maine, United States. We assessed the progression of infection in the different simulated outbreak scenarios, allowing for variation in the control strategies adopted for ISAv. Model results showed that improved disease detection, coupled with increasing surveillance visits to farm-sites and increased culling capacity for depopulation of infected net-pens reduced the number of infected net-pens and outbreak duration but the number of ISA-infected farm sites was minimally affected. DTU-DADS-Aqua is a flexible modelling framework, which can be applied to study different infectious diseases in the aquatic environment, allowing the incorporation of alternative transmission and control dynamics. The framework is open-source and available at https://github.com/upei-aqua/DTU-DADS-Aqua.
模拟模型是预测和阐明影响动物群体中流行病发生和传播的因素的影响、评估不同控制策略的有效性并最终为决策者提供降低风险缓解措施信息的有用工具。用于研究海洋环境中病毒和细菌病原体水传播的模拟模型很少。我们开发了一种随机时空混合模拟模型（DTU-DADS-Aqua），该模型包含一个用于网箱内感染传播的分区模型、一个用于站点内和站点间网箱之间感染传播的基于主体的模型，并使用航道距离来确定养殖场之间的水文连通性。该模型包括模拟感染传播以及对监测、检测和扑杀措施进行控制的过程。根据提供的输入数据和用户定义的参数值，可以探索不同的假设情景，例如每日监测和扑杀能力，或因动物死亡率增加而触发诊断检测以发现感染。后者可以在软件应用程序中轻松定义，每次模拟后都会汇总结果。为了展示该模型的能力，我们针对加拿大新不伦瑞克省和美国缅因州养殖的大西洋鲑（Salmo salar L.）跨界种群中的实际情景模拟了传染性鲑鱼贫血病毒（ISAv）的传播。我们评估了不同模拟疫情情景下的感染进展情况，考虑了针对ISAv采取的控制策略的变化。模型结果表明，改进疾病检测，同时增加对养殖场的监测访问次数以及提高感染网箱的扑杀能力，可减少感染网箱的数量和疫情持续时间，但感染ISAv的养殖场数量受影响最小。DTU-DADS-Aqua是一个灵活的建模框架，可用于研究水生环境中的不同传染病，允许纳入替代的传播和控制动态。该框架是开源的，可在https://github.com/upei-aqua/DTU-DADS-Aqua上获取。
