Research On H5N1 HPAI Epidemiology In Mainland,China

H5N1 HPAI virus infection was first encountered in China in 1996 with the discovery of a virus(GS/GD/96)that killed geese in Guangdong province.In January 2004,the first outbreak of H5N1 subtype Highly Pathogenic Avian Influenza(H5N1 HPAI)occurred in Mainland China,where a large-scale mandatory immunization policy has been being implemented since January 2006.In 2007,Alexander DJ proposed the concept that "epidemiology of avian influenza has been a revolutionary change." In 2008,China was listed in H5N1 HPAI entrenched country by the Food and Agriculture Organization(FAO).So far there have still been H5N1 HPAI occurred in domestic poultry and people in China.During the past 10 years,whether has the epidemiology of H5N1 HPAI of mainland China changed?What has changed?How have these changes influenced the prevention and control strategies of H5NI HPAI?The results of literature search on CNKI and PUBMED shows that in the past 10 years,the articles on the epidemiology of H5N1 HPAI in mainland China accounted for less than 2%,focusing on the environment,wild birds,as well as the risk factors of human infection,which have not successfully answered the questions proposed above.Therefore,the following series of studied have been carried out in order to obtain more in-depth understanding of the current characteristics of H5N1 HPAI distribution and risk factors,and to explore the key points of diseases prevention and control for small-scale poultry farms,thus for affording basic data foundation and technical support for the more efficient and cost-effective system of H5N1 HPAI prevention and treatment.1.The Study Base on GIS Technology on H5N1 HPAI Epidemiology Characteristic and Risk Factors in Mainland China.Systematically collecting and compiling the H5N1 HPAI outbreaks and surveillances datum from January 2004 to June 2013 in Mainland China,by comprehensive statistics method and GIS technology,the study researched on H5N1 HPAI epidemiology characteristics in Mainland China in the past 10 years,for locating the potential risk factors impacting on the H5N1 HPAI outbreaks and searching for the research direction of next phase.Study found the integrated measures of compulsory vaccination combined with culling had achieved good results in reducing HPAI prevalence and incidence;Chickens are the main target of invasion of H5N1 HPAI;There is no statistical association between the H5N1 epidemics and Water Distribution in Mainland China;Three-dimensional Curve Motions of y=79.2-33.869-4.833x2-0.222x3(R2=0.975)indicates the best reliability of goodness of fit,two-dimensional Curve Motions of y=60.117-16.943x+1.163x2(R2=0.91)second,both these can be used to predict the H5N1 HPAI epidemics trend based on time distribution;The correlation of the farming scale and the epidemiology distribution of H5N1 HPAI could exist;Study results indicated the focus on strengthening the surveillance for the domestic-wild poultry interface and poultry-market interface.2.The Research on the Genetic Evolution of Hemagglutinin(HA)of H5N1 HPAI Vs during 2006-2012.The HA genes of a total of 454 H5N1 HPAI strains isolated in the national HPAI epidemiology survey between Year 2006-2012 have been amplified,sequenced and analyzed for the research of the genetic evolution of H5N1 HPAI viruses,in order to further understand the recent region-specific distribution and evolution of H5N1 HPAI viruses in the Mainland China.Research results suggested three major characteristics of the epidemiology of H5N1 HPAI in domestic poultry as followed:H5N1 clade2.3.4 and 7 viruses had been the dominant strains during the 2006-2009 epidemic of poultry in Mainland China,however,since 2010,the H5N1 clade2.3.2 strains has been played a dominant role in the H5N1 HPAI epidemic;H5N1 clade2.3.4,clade7 and cladeO viruses have different host species orientation,represented by that close relation between clade2.3.2 and duck,and that almost all clade7 viruses have been isolated from chickens;The spatial distributions of H5N1 clade2.3.4,clade7 and cladeO between neighboring provinces were relative similar in part,but the general space orientation was not obvious.Clade2.3.2 branch distributed more widely in China;Clade7 virus in the northern region distributed more extensive than that in the south region.Cleavage site of HA from representative H5N1 virus analysis indicated that the amino acids of cleavage site from different clade virus after 2009 showed obvious regularity.P1-P5 sites of most isolates were RRRKR.P6 site of most of clade 2.3.2 and 2.3.4 virus was deletion;however,clade 7 virus was G.Moreover,a proportion of clade 2.3.2 and 7 virus owned the mutation of R-I at P8 site.Glycosylation site analysis showed the glycosylation sites of No.23,193 and 286 were conserved.The glycosylation sites of No.72,140,154,163,236,273 showed obvious differentiation between different clades.Receptor binding sites analysis showed,the key sites of 226 and 228 was avian-origin.Studies suggest that the move of migratory wildfowl and the trade of poultry and related products have played an important role in the H5N1 HPAI epidemic.3.The Study on Animal Health Situation in H5N1 HPAI Major Susceptible Poultry of Mainland China and Potential Infection Risk Factors for H5N1 HPAI.The study 1 and study2 above result showed the possible correlation between the epidemiology distribution of H5N1 HPAI and the scale of poultry farms and their products move.To further understanding the distribution characteristic of H5N1 susceptible poultry farming,analyze its potential impact on H5N1 HPAI outbreak and spread,using descriptive analysis method,the study has systematically analyzed from 2000 B.C.to the present the dynamic change of rearing volume and scaled degree of domestic poultry in Mainland China,the features of regional distribution on farm systems,the bio-security abilities of domestic poultry farms,the health situation in live poultry trades and markets,by collecting,compiling and analyzing datum of different sources including,Livestock Yearbook from 2000 to 2012,national target epidemiology investigations from 2007 to 2011,and the poultry health survey on two provinces of Anhui and Liaoning.Study found that H5N1 HPAI outbreaks significantly influenced on the poultry volume and structure.From 2004 to 2010,the poultry structure changed slowly,while it changed quickly since 2010.Raising management and disease prevention capabilities for breeding farms was positively correlated with the raising scales;living poultry moving has mainly involved chicken transporting,about 80%live poultry inflows have been from the other areas of the same province,the live poultry markets with high level of standardized management only accounting for 4%,the markets with moderate level only for 28%.Studies suggest that implementing category management for poultry farms basing on its' scales,promoting farming structure adjustment,improving market regulation and circulation,are the focuses of the adjustment for H5N1 HPAI prevention and control measures.4.A Meta-analysis of The Risk Factors for Avian Influenza in Poultry FarmsPoultry farms are the interesting unit of control and prevention of H5N1 HPAI,but there is no systematic review performed to find and evaluate the risk factors of Avian Influenza infection.The objective of this meta-analysis was to better understand epidemiology of AI and further research on AI prevention through identifying the risk factors associated with AI infection among poultry farms.Methods:The results from 15 selected studies on risk factors for AI infections among poultry farms were analyzed quantitatively and synthetically by Meta-analysis.Results:Opening water source(OR=2.89),near farm infection(OR=7.39)and other livestock(OR=1.90)had significant association with AI infections in poultry farms.The stratified results indicated that the risk factors between different types of farms were certain difference.Conclusions:The main risk factors influencing the AI infections among poultry farms were farms ambient condition(opening water source,near farm infection)and other livestock.5.A Case-Control Study on HPAI Risk Factors at Farm Level in Six ProvincesThe study 1 and study 3 above result shows small and medium scale poultry farms running a higher risk of H5N1 HPAI.The study4 result shows that there are differences existing in H5N1 HPAI risk factors between different regions and different scale poultry farm.To further understand current situation of small and medium scale farms and their risk level of H5N1 HPAI,based on geographical distribution,selecting a total of 96 backyard farms and small&medium scale farms of six provinces including Yunnan,Anhui et al,using the method of questionnaires combined with laboratory sampling and testing,the study investigated animal health situation of small and medium scale farms,carried out a retrospective case-control study,and thus located and analyzed H5NI HPAI risk factors in these farms.Survey showed that the farms of more than 500 birds are mainly for the purpose of making profits more for-profit farms,small and medium scale poultry farms transport their products more frequently at least once per week,whose feeding and managing system has not changed compared with 2006,and no significant differences in the system between different regions.These farms themselves' purchasing vaccines and drugs is a common phenomenon;Univariate and multivariate logistic regression analyses' results showed that risk factors of farms with H5N1 HPAI at farm-level included near poultry farm(OR=11.980,95%CI:1.177-121.920),opening water source like lake(OR=14.036,95%CI:1.664-118.397);protective factors include prohibiting the entrance of external vehicle(OR=0.090,95%CI:0.010-0.808),supervisor(OR=0.076,95%CI:0.009-0.647)and frequency of disinfection(OR=0.187,95%CI:0.045-0.781).Liner model Logit[P(Y=1)]=-0.069+2.483X1+2.642X7-2.412X18-2.578X27-1.678X31 has the best reliability of goodness of fit and can be used to predict the H5N1 HPAI epidemics trend at farm level.Study result indicated the importance of enhancement of auditing conditions of disease control and prevention,of strengthening the education of small and medium farms,of prompting capabilities for feeding and management system of small and medium farms,aiming at reducing the risks of small and medium farms with H5N1 HPAI and promoting the national overall capabilities for disease prevention and control.6.Research of Assessing and Improving Current Prevention and Control Measures of H5N1 HPAIIn order to understand that current strategies for HPAI H5N1 prevention and control,"YES or No" matched current disease situation,latest technology and executive capacities of relative institutions,consulting the strategies recommended by FAO/WHO,the research designed the evaluating indicator system and scoring methods for H5N1 HPAI control strategies and measures.The system include a total of 38 indicators of 11 major items including control and prevention programs,technical storage,information exchange ability,epidemiology study capacity,laboratory capacity and et al.Each indicator is a four-tier grading system,and the semi-quantitative evaluation is launched according to cumulative value.The results showed that emergency preparedness and prevention system scored 63.9 points,emergency response scored 66.7 points,recovery and promotion of poultry production scored 80 points,indicating that the current system of H5N1 HPAI prevention and control is effective,but still waits to be improved.Integrating the results of six studies above,aiming at adjusting and improving the route&measures of H5N1 HPAI control and prevention,the proposals of a series of strategies and measures are brought forward,including regionalization management strategies of H5N1 HPAI control and prevention using compartmentalization,the mandatory immunization policy should gradually withdraw from H5N1 HPAI control and prevention,the best scientific surveillance program with higher sensitivity and specificity,the adjustment of the range and compensation mechanism of culling instead.