Study On The Dynamics Of African Swine Fever With Direct And Indirect Transmission

African swine fever（ASF）is an acute hemorrhagic severe infectious disease caused by African swine fever virus（ASFV）,which exists in pigs for a long time.At present,its transmission among domestic pigs and wild pigs in most parts of the world,with a mortality rate of 100%.The outbreak of African swine fever（ASF）has seriously restricted the pig industry in China and even the world,bring incalculable economic losses to pig farmers,and pose a serious threat to food security.Although it has been a long time since the outbreak,little is known about the key mechanism of its infection and transmission and the reasons for the persistence of the disease.So,it is a key task at present to clearly understand the mechanism of ASFV infection and transmission and the reasons for its persistence,and to formulate measures to control the ASF outbreak.Firstly,ASFV may be transmitted in China through exposure to contaminated swill and the widespread use of pig products,but its impact on the spread of ASF is unclear.On this basis,we build the ASFV transmission model with the virus in the environment and swill.We compute the basic reproduction number₀,and prove that the disease-free equilibrium is globally asymptotically stable when₀<1 and the unique endemic equilibrium is globally asymptotically stable when₀>1.Using the actual information,parameter values are evaluated.The partial rank correlation coefficient（PRCCs）and extened fourier amplitude sensitivity test（e FAST）sensitivity analysis reveal that the release rate of ASFV from asymptomatic and symptomatic infectious pigs and the proportion of pig products from infectious pigs to swill have a significant impact on the ASFV transmission.Our findings suggest that the virus in the environment and contaminated swill contribute to the ASFV transmission.Our results may help animal health to prevent and control the ASFV transmission.Secondly,in order to explore the influence factors of ASF transmission and the reasons for the persistence of the disease,we establish a time-delay transmission model of domestic pig and wild boar based on direct contact and indirect contact.We calculate the threshold₀of the model and prove that the disease-free equilibrium is globally asymptotically stable when₀<1.In addition,there is an endemic equilibrium in the model.PRCCs and e FAST sensitivity analyses indicate that the frequency of contact between infectious boars and susceptible boars and transmission through environmental exposure are key factors in determining the severity of an ASF outbreak.The effects of relevant parameters on the transmission of ASF are simulated to observe the changes of the peak number of infectious cases and the peak arrival time during the outbreak of ASF.Our results suggest that direct contact transmission and surviving pigs from the initial ASF infection are key factors in the persistence of the virus.Our results may contribute to the assessment of disease control measures.