Diagnosis of Respiratory Diseases in Outsourced Beef Cattle Due to Mixed Infection of Bovine Adenovirus Type 7,Mycoplasma bovis and Bacteria

LI Yue;ZHU Lai-ping;TAO Song;ZHAN Jian-ju;YU Tao-ying;YAN Rui;ZHENG Bi-niu;GAO Lin;XIE Jia-rui;WANG Sheng-kui;YANG Shi-biao;YAO Jun;College of Veterinary Medicine, Yunnan Agricultural University;Gongshan Animal Disease Prevention and Control Center,Nujiang Prefecture, Yunnan Province;Bureau of Agriculture and Science and Technology in Menglian County;Center for Prevention and Control of Animal Disease in Lushui City,Nujiang Prefecture, Yunnan Province;Yunnan Tropical and Subtropical Animal Virus Diseases laboratory, Yunnan Animal Science and Veterinary Institute;

bovine adenovirus type 7;;Mycoplasma bovis;;bacteria;;mixed infection;;beef cattle;;respiratory disease

In August 2017,30 beef calves were purchased from Yuncheng,Shandong province,by a farmer in Xundian county,Kunming city. One week after arrival,respiratory diseases characterized by respiratory symptoms appeared one after another and began to die. To diagnose the possible causes of disease,nucleic acid detection and sequence analysis of common infectious diseases of beef cattle,as well as bacterial isolation and identification,were carried out. The results showed that nucleic acid tests for bovine adenovirus type 7 and Mycoplasma bovis were positive and one M. bovis strain( named XDJY-YN-2017) was isolated and identified from bovine lung tissues and trachea secretions. Two bacterial strains were also isolated and identified from bovine lung tissues. The sequence of protease gene of bovine adenovirus type 7 was 99% homologous to the reference strain( Accession: X53989) in NCBI Gen Bank. A phylogenetic tree based on 16 S r RNA sequences showed that XDJY-YN-2017 belonged to the same evolutionary clade as Israel 72242,UK 393 B08,268 B07,China Ningxia-1,HB0801,CQ-W70,08 M,Hubei-1 and NM2012 stains; formed another evolutionary clade with PG45 and 422 strains from Cuba; and was in a separate evolutionary clade from Donetta strain. The two bacterial strains were identified as Escherichia coli Ferguson strain( ID% = 99. 9%,T = 0. 8) and Kluyvera species( ID% = 76. 3%,T = 0. 61).Drug sensitivity test showed that E. coli Ferguson strain was sensitive to amoxicillin/clavulanic acid,polymyxin E,spectinomycin,gentamicin,ampulin,furantoin,while Kluyvera bacteria were sensitive to polymyxin E,ampomycin,furantoin,and spectinomycin.Thus,due to stress factors such as long distance transportation,forage feed replacement and environment change,the outsourced cattle developed mixed infections with bovine adenovirus 7,bovine mycoplasma and bacteria,leading to respiratory disease and death.