An Analysis Of A Natural Spreading Of African Swine Fever Along Sino-Russia Boundary

African swine fever(ASF)remains a severe threat to the swine industry globally due to its' tremendous socio-economy impact,international and local trade restriction.The rapid spread of ASF has been a great menace to Asia,particularly China.The existence of similar habitat and wild boar population along the Sino-Russian and Korea border and the possibilities that infected wild boar cross the border raised a big concern.The eastward spread of ASF affecting both domestic and wild pig in the Russian Federation and the outbreak in Irkutsk near the China border farther increased the risk along the NE China border.Our current research in ASF is mainly essential to provide scientific evidence on the pattern of transmission,spatial distribution,the driving factors and the role of wild boar for the natural cross continent transmission of the virus.Accordingly,prediction of habitat suitability,surveillance and risk assessment along the border was vital.To investigate ASF in the wild boar population,we collected blood samples from hybrid wild boar farms.Both validated molecular and serological tests were employed for laboratory examination.We preprocessed the spatial modelling data through spatial rarefication and pairwise geographic distance comparison to reduce spatial autocorrelation of presence points.Principal component analysis(PCA)applied to reduce multi-collinearity among predictor variables.We selected the maximum entropy algorithm for spatial modelling of ASF,wild boar and vector separately.The accuracy of the models were assessed by the AUC.We utilized the Global Positioning System(GPS)collar and marked baits for wild boar movement monitoring;a semi-quantitative method for risk assessment.The Least Cost Paths(LCP)between Eastern Europe and NE China was plotted using Spatial Data Modeller toolbox in ArcGIS.Actual transmission distance and time intervals calculated and the arrival dates of ASF-infected wild boar was predicted by cumulative maximum transmission distances per season and cover with their associated minimum time intervals along the LCPs.The main results described as followings:1 Surveillance of African swine fever in Wild boars,HeilongjiangThe ASFV genomic sequence asserted that blood sample collected from one dead and three-health hybrid wild boar after ASF occurrence in NE China were positive for ASFV with the PCR.The epidemiological surveillance showed that all samples collected from hybrid wild boar before the first incidence of ASF in NE China was negative for ASFV.A phylogenetic analysis of the sequences clustered China/HLJ/2018/boar ASFV within p72 genotype ? and serotype 8.This virus contained additional TRS between the I173R and the I329L protein genes and was different from previously reported Jilin wild boar strains but 100%sequence identity with Estonia 2014 and Georgia 2007/1.No antibodies against ASFV was detected in the entire tested serum with ELSIA indicating no previously circulating ASFV in hybrid wild boar.2 A Prediction of African swine fever in China along the Russian and Korean BordersA high probability for both virus and host was predicted in the central parts of the three-province.The largest patch about 80%was located in the Liaoning,Jilin and Heilongjiang bordering Korea and the RF.It consists of the Changbai Mountains along the Korean border,the Liao River plain and the Songnen intermountain plain in the center of the NE China.The eastern patch was situated in the Sanjiang plain along the river Ussuri and through the Khanka Lake.About a third of the southeastern border between China and Korea(420 km),mainly in the Liaoning province along the river Yalu and Tumen were situated in the high probability zone for virus and host.In the central section of the Sino-Korean border in the Changbai Mountains,about(224 km)in the Jilin province was also crossing a high probability area.Further,a southern section of the Sino-Russian border in Heilongjiang province along the river Ussuri(437 km)was also highly suitable for both disease and host.A contiguous low probability for both virus and host was predicted about(20%)in the Xingan Mountains to the north of about 51.5° N and in the Liao river plain in the extreme west of the NE China.3 Monitoring of Wild boar Movement along the Sino-Russian and Korean BorderThe GPS satellite track recorded that the maximum daily movement of 4.02±0.8 km for female and 4.6±0.9 km for the male wild boar.Both wild boar spent most of their activities at a low elevation closer to the capturing site.The marked bait technique indicated that all the bait consumed successfully and the average dispersal distance of the wild boar away from the baiting site was 6.4±0.3 km.4 Risk Assessment for the ASF Introduction into NE China by Wild boar MovementOur model showed that the presence of suitable habitat and ASF outbreak density in both domestic pig wild boar revealed by a high-risk score.The overall risk of ASF transmission by infected wild boar movement was low.The risk score was low for the distance from China to the nearest ASF outbreak in wild boar and domestic pig in RF.Therefore,while the transmission of ASF by infected wild boar movement seems unlikely because of the long distance between NE China and the nearest ASF in wild boar at RF,the presence of suitable habitat increased the risk,which necessitate regular monitoring and surveillance to control the spread the disease.5 The Reality of the Natural Eastward Spreading of ASF from Europe to ChinaOur result indicated that the prevalence of ASF-infected wild boar was high in forest cover and cropland at low elevation.ASF-infected wild boar generally occurred within a short distance and at a short time interval,except for a few long jumps.The Least Cost Path showed high costs for wild boar to cross Xinjiang,NW China and Mongolia to reach NE China.Instead,the Paths lead almost straight eastward along the 59.5° Northern latitude through Siberia and would have taken a minimum of 219 or 260 days and would have arrived at 12 March or 22 April 2019.Conclusions1 Before the first outbreak of ASF in China in August 2018,the wild boar in Heilongjiang was free of ASFV.2 The majority of NE China predicted to be in a high-risk area for ASF occurrence that need an urgent action to strengthen control and prevention program.3 Although the overall risk of transmission of ASF from Russia to China was low,the risk was greatly high for the existence of large surface area of suitable habitat along the border4 The cause of the first ASF outbreak in China was not due to the natural cross border movement of wild boar from western Russian.Recommendations1 Regular surveillance and monitoring with a detailed follow-up study along the identified priority section of the Sino-Russian and Sino-Korean borders should be conducted.2 Personnel working in hybrid wild boar farms should be advised to follow strict biosecurity procedure.3 Follow-up study with targeted control measures,disinfecting procedures at the farm gate,should be practised.4 Extensive research should be done on wild boar movement along the border considering all season of the year,to know the seasonal variation of wild boar movement.