Abstract
African swine fever (ASF) poses a significant threat to the global pig industry, with the disease having gradually expanded over the past decade worldwide. Once introduced to the wild boar population, the virus can establish itself, making it challenging to control it across extensive geographical areas. To facilitate the implementation of effective control measures, it is advantageous to classify administrative units based on the risk of ASF virus introduction and transmission. However, it should be noted that a key limitation in implementing control actions involving wildlife is the lack of detailed data on wild populations.
In this study, we classified the municipalities of Lombardy and Emilia-Romagna regions (Northern Italy) by evaluating the following parameters: i) the risk of ASF spread in the pig sector (low, medium, high), determined as a combination of pig density (number of holdings and heads) and pig movements (Tamba et al., 2020); ii) a habitat suitability index (HSI) for wild boar (ranging from 0 to 10), calculated as the geometric mean of suitability values assigned to land cover, elevation and slope (Qin et al., 2015); iii) the density of hunted wild boar per km2; iv) the presence of protected natural areas. The HSI and wild boar density were categorized into three classes, as the risk of ASF spread, so that the three parameters can be summed. The low risk class was assigned to HSI values ≤2 and to densities ≤1; the medium risk class to HSI values between 2 and 6, and densities between 1 and 4; the high risk class to HSI values >6 and densities ≥4. To the three classes were assigned increasing score of 0 (low), 0.5 (medium) and 1 (high). The sum of these scores at Municipality level was multiplied by 1.5, if a protected natural area is present.
The final score ranged between 0 and 4.5, and the corresponding risk classes were defined as follows: low (score ≤1), medium (score ≤2), and high (score is >2). The 1836 municipalities included in this study were classified as follows in terms of risk: 161 (9%) were classified as high risk, 248 (14%) as medium and 1427 (78%) as low. We noted that for Emilia-Romagna, the municipalities (330) were relatively evenly distributed across the three risk classes (about 33% in each class). Municipalities with higher or medium risk were concentrated in the hilly part of the region, with some exceptions in the lowlands due to a high presence of pig holdings.
This classification system appears to be useful for prioritizing intervention measures to control the wild boar population and/or improve biosecurity and surveillance in pig holdings.
References
Tamba M., Galletti G., Casadei G., Pezzi A., Santi A., Guberti V., Bellini S. (2020). A Method to Identify Areas at Risk of African Swine Fever Diffusion Where Planning a Preventive Wild Board Population Control Program. Proceedings of the Final international Conference of the COST Action ASF-STOP-Understanding and Combating African Swine Fever in Europe; 29–30 January 2020, Brescia, Italy. https://www.asf-stop.com/wp-content/uploads/2020/01/ASF-STOP-Final-Conference-Abstract-book.pdf (last access 4 May 2020)
Qin, Y., Nyhus, P. J., Larson, C. L., Carroll, C. J. W., Muntifering, J. R., Dahmer, T. D., Jun, L., & Tilson, R. (2015). An assessment of South China tiger reintroduction potential in Hupingshan and Houhe National Nature Reserves, China. Biological Conservation, 182, 72–86. https://doi.org/10.1016/j.biocon.2014.10.036