Potential risk factors of swine erysipelas outbreak in Northeast Mainland China

Swine erysipelas is a common infectious disease that affects the pig-breeding industry. The purpose of this study was to elucidate the risk factors and their role in the prevalence of swine erysipelas so that one may be able to better prevent and control the swine erysipelas outbreaks in Northeast China. Using spatial clusters, the study area was divided into two parts: South Central Mainland China (hot spots) and Northeast Mainland China (potential outbreak areas). We investigated a total of 31 environmental factors and used the lasso regression and k-fold cross-validation methods to determine the main factors involved. Seven risk factors were determined to have a major impact on swine erysipelas. Multiple logistic regression was used to examine the contribution of these seven risk factors to the outbreak from 2008 to 2018, in the two research regions. In South Central Mainland China, where swine erysipelas was most prevalent, the extreme maximum temperature [OR = 1.143 (95%CI: 1.032-1.342)], total precipitation [OR = 2.298 (95%CI: 1.410-5.112)] and precipitation ≥0.1 mm [OR = 2.396 (95%CI: 1.329-5.941)] exhibited positive effects. The maximum wind speed [OR = 0.550 (95%CI: 0.303-0.775)] and concentration of O3-8H-90 per [OR = 0.876 (95%CI: 0.747-0.980)] exhibited negative effects. Summer was the main season for the erysipelas epidemic in South Central Mainland China. In Northeast China, only the total precipitation [OR = 1.048 (95%CI: 0.900-0.989)] was positively correlated with the prevalence of swine erysipelas, whereas the other factors were not significant. There was no obvious seasonal feature for the epidemic. Through the comparison and analysis of risk factors between the two research regions, more attention should be given to the impacts of high temperature and precipitation on the swine erysipelas epidemic in Northeast China.