鸡源B亚型禽偏肺病毒对火鸡的致病性研究OA

[Objective]This study aimed to investigate the pathogenicity of Avian metapneuovirus subtype B(aMPV/B)from chickens to turkeys.[Method]The previously isolated aMPV/B LN16 strain of chicken origin was used for a single nasal drip infection of 7-week-old turkeys(with 200 μL containing a dose of 5×104 TCID50 per bird.Turkeys in control group were inoculated with the same volume of PBS in the same way.13 in each group,and the trial period was 21 days.From 1 to 7 days after challenge,the clinical symptoms of turkeys were observed,and the palatal cleft swabs were collected.Real-time quantitative PCR was used to detect the viral copy numbers in the palatal cleft swabs.On the 7th day after challenge,three turkeys from each group were euthanized and necropsied.The lungs,trachea,larynx,and nasal turbinates were collected to examine the viral tissue distribution.The pathological changes of tissues and organs were observed by hematoxylin-eosin(HE)staining.Additionally,blood samples were collected from the brachial vein at 7,14,and 21 days after challenge.The antibody levels in turkey serum were determined by ELISA method.[Result]Clinical observation revealed that turkeys in infection group developed nasal discharge starting at 3 days after challenge.After continuous observation for 7 days,the incidence rate was 84.6%(11/13).No clinical symptoms were observed of turkeys in control group.Real-time quantitative PCR demonstrated turkeys in infection group excreted the virus 1 to 7 days after challenge,reaching the peak on the 3rd day,with an average virus copy number of 3.7×105 copies/200 μL.All the turkeys in control group were negative.Viral tissue distribution analysis showed that on the 7th day after challenge,the detection rate of virus in nasal conchae bone and trachea of the infected turkeys was 33.3%(1/3),while no virus was detected in lung and laryngeal tissues.Histopathological results showed that the nasal conchae,lungs,and trachea of turkeys in infection group all exhibited pathological damage of varying degrees,mainly manifested as inflammatory cell infiltration.No obvious pathological changes were observed in control group.ELISA results indicated that all serum samples were positive on the 7th day after challenge,and the average antibody reached peak levels at 8 934 at 14 days after challenge.[Conclusion]This study indicated that chicken aMPV/B was pathogenic to turkeys.The test results provided an important reference for the subsequent clinical diagnosis and prevention and control of avian metapneumovirus disease in turkeys.