Preliminary Epidemic Investigation On Major Viral Infectious Disease Of Farming Poultry In Hunan Province

Hunan Province is a large farming province,which produces a large amount of poultry meat for in and out of the province.However,some viral infectious diseases,such as Avian Influenza(AI),will bring tremendous destroy to poultry industry.For example,acute infectious diseases such as AI and Infectious Bronchitis(IB)can infected birds and caused a high mortality,while chronic infectious diseases such as Avian Leukosis and Marek's Disease mainly undermine the immune system of birds and cause the occurrence of various types of tumors.The control for t most of poultry vira l diseases is mainly based on prevention.Up to date,no epidemic investigation on the viral infectious diseases was carried out in the poultry farms in Hunan province.In this study,from January 2018 to February 2019,a total of 225 sera or tissue samples from 22 farms in 16 counties or cities of Hunan Province were collected.Six major avian viral pathogens(Avian Influenza Virus(AIV),Avian Leukosis Virus(ALV),Marek's Disease Virus(MDV),Infectious Bronchitis Virus(IBV),Chicken Astrovirus(CAstV),Avian Nephritis Virus(ANV))were investigated by PCR or reverse transcription PCR and T-A cloning.AIVs were detected in the samples from 5 farms,with positive rate of 23.81%(5/22)among the farms,and positive rate of 8.44% among all samples(19/225).E subgroup of ALV(ALV-E)was detected in 19 farms,ALV-J was detected in 1 farm and ALV-F was detected in 1 farm.The opositive rate of ALVE/F/J was 90.47%/4.76%/4.76% among the farms,respectively,and among them two ALVs that were likely to be new subgroups were found.Virulent MDV was detected in 3 farms,with the positive rate of 14.29%(3/21)among the farms,and the positive rate of 12.18%(19/156)among all samples.The nephropathogenic IBV was detected in 2 farms,with the positive rate of 9.52%(2/21)among farms,and the positive rate of 3.21%(5/156)among samples.CAstV was detected in 2 farms,with the positive rate of 9.52%(2/21)among farms,and the overall sample positive rate of 6.41%(10/156).Moreover,the two strains of CAstV might be new subtypes.ANV-2 was detected in one farm with the farm positive rate of 4.76%(1/21),and the overall sample positive rate of 0.64%(1/156).Generally,in this study,we found that ALV-E is common in poultry farms across Hunan Province,while its actual harm may be limited,and it may be gradually eliminated by the screening of breeders.Five strains of AIV identified in the present study were H5 and H7 subtypes,indicating that the prevention and control of H5 and H7 subtypes is still a challenge.The detection of nephropathogenici IBV indicates that prevention of IBV may focus on this pathotype.The finding of virulent MDV in the field suggested that the traditional MDV vaccine may not provide efficient protection against the epidemic strains.and it is necessary to develop a new effective MDV vaccine.Furthermore,the clinical significance of the new ALV genotypes,new CAstV and ANV-2 detected in the present study require further experiments to verify,but their potential hazards to the poultry industry need to be taken attention seriously.Overall,this study conducted a preliminary investigation on the prevalence of six major poultry viral pathogens in poultry farms in Hunan Province,and provided some basic epidemiological data for future prevention and treatment of these poultry diseases.