A geospatial model of entry pathways of lumpy skin disease virus introduction into Australia

Abstract

Lumpy skin disease (LSD) is a disease of bovines resulting from the mechanical transmission of lumpy skin disease virus (LSDV) by arthropod vectors. While LSD has never been reported in Australia, the disease has spread through Asia and recently expanded to neighbouring countries such as Indonesia. The detection of LSD in Australian cattle would likely lead to trade restrictions, resulting in Australian cattle industries experiencing severe economic losses. There is a need for geospatial decision support tools to support border and post border surveillance efforts through the identification of areas which would be more vulnerable to a LSDV introduction. Previous risk assessments have calculated that overall risk of introduction into Australia is negligible to very low after evaluating four entry pathways, including windborne dispersal of arthropod vectors, commercial vessels carrying hitchhiker arthropod vectors (excluding live export vessels), returning live export vessels carrying hitchhiker arthropod vectors, and movements in Torres Strait Treaty area leading to the transport of hitchhiker arthropod vectors. However, the studies also reported very high uncertainty given a lack of robust empirical data for many of the model parameters and only described risk in terms of each pathway as a whole rather than describing spatial variation in risk. This study aimed to develop a novel integrated geospatial model for simulating the likelihood of LSDV-carrying vectors entering Australia via two different entry pathways: transport of vectors through shipping channels and vectors being carried long distances by strong wind currents. This model was used to explore the spatial variation in suitability for LSDV-carrying vectors entering Australia for each pathway independently and combined to identify geographical areas with the highest suitability. Furthermore, the study incorporated species distribution modelling and current bovine LSD case data in neighbouring countries to better model the current suitability of LSD in livestock, which were not included in the previous risk assessments. Pathway one showed the ports at Port Hedland and Dampier as having the highest suitability for LSDV-carrying vectors entering Australia compared to the rest of the country. Pathway two showed highest comparative suitability in Far North Queensland, with suitability extending as far as 25 degrees south. Furthermore, likelihood of vectors being carried by wind currents into Australia was highest in the summer months. A model combining both pathways highlighted areas along the northern tip of Far North Queensland and around Port Hedland in Western Australia as having the highest suitability for LSDV-carrying vectors entering Australia compared to the rest of the country. These findings may assist future modelling of exposure and spread of LSDV in the Australian bovine population following a successful incursion event, which may help guide local authorities with planning and prioritisation of integrated surveillance activities.