Development And Preliminary Application Of Bivalent Tetravalent Inactivated Vaccine Against Pseudomonas Aeruginosa And Escherichia Coli In Mink

With the development of China economy,mink farming industry has developed,and the number of mink farmers has increased year by year.However,the incidence of some infectious diseases,especially bacterial respiratory diseases,has brought huge economic losses to mink farming industry and seriously affected the healthy development of fur animal industry.Mink hemorrhagic pneumonia(MHP)is an acute,febrile and highly lethal bacterial respiratory infectious disease causing mink death in recent years.It was first identified as a single infection casued by Pseudomonas aeruginosa.However,in recent years,clinical case studies have found that the pathogen of mink hemorrhagic pneumonia is not only Pseudomonas aeruginosa,but also Escherichia coli,as well as mixed infection of Escherichia coli and Pseudomonas aeruginosa.Mink haemorrhagic pneumonia caused by various pathogens can cause acute death of mink which brings more challenges in drug control and increases the economic losses of farmers,thus seriously hampers the development of mink farming industry in China.Mink hemorrhagic pneumonia cases occured in all regions of China,mainly in Hebei,Shandong,Liaoning,Heilongjiang and other provinces.There is no clinical symptom in mink at the early stage of infection.The main symptoms in the middle and late stages are loss of appetite and mental retardation,death immediately after screaming,nose and mouth bleeding,massive hemorrhage of lungs,spleen,kidney and other organs by autopsy.The therapeutic effect of antibiotics is not ideal.Especially in cases of single infection of Escherichia coli,it is very easy to produce resistance to antibiotics,and there are few kinds of antibiotics available.The disease is currently seriously plagued mink farmers in China.Mink hemorrhagic pneumonia cases were collected from Hebei,Shandong,Liaoning and Heilongjiang provinces.Pathogen isolation and identification,serotype and genotype identification,drug susceptibility test,mice and mink challenge test were carried out to isolate and identify the pathogen of mink hemorrhagic pneumonia.Pathogenicity of experimental animals was tested.At the same time,the bivalent inactivated vaccines of Pseudomonas aeruginosa and Escherichia coli from mink haemorrhagic pneumonia were developed,and the immunogenicity and immune protection of the vaccines were tested,and some clinical trials were carried out.The research results are as follows:(1)The results of isolation and identification of pathogenic bacteria showed that the main pathogens causing mink hemorrhagic pneumonia were Pseudomonas aeruginosa and Escherichia coli.There are isolated infections and mixed infections.The serotypes of Pseudomonas aeruginosa causing mink haemorrhagic pneumonia include D,E and M,among which G,D and E are the most common and highly pathogenic.The genotype of Escherichia coli causing mink hemorrhagic pneumonia is H and has strong pathogenicity.(2)The virulence tests on mice and minks showed that the isolated strains could cause the death of minks and mice,and cause the typical clinical symptoms of hemorrhagic pneumonia in minks.(3)Drug susceptibility test showed that Pseudomonas aeruginosa and Escherichia coli were highly resistant.Pseudomonas aeruginosa was highly resistant to cefotaxime and ceftazidime,sensitive to seven antibiotics such as ciprofloxacin,tobramycin and amikacin.Escherichia coli was highly resistant to 10 antibiotics.(4)A Bivalent Tetravalent Inactivated Vaccine against mink hemorrhagic pneumonia was developed by using Escherichia coli H genotype strains and Pseudomonas aeruginosa G,D and E serotypes strains,and its preliminary clinical application showed that the vaccine had good protection against hemorrhagic pneumonia caused by Escherichia coli and Pseudomonas aeruginosa in prewatered minks.After 21 days of vaccination,5 minks were all protected,Meanwhile,7 000 minks were immunized.The results showed that the vaccine had no adverse reactions and no hemorrhagic pneumonia.Through the above research,we have identified the main pathogens causing mink hemorrhagic pneumonia in China and their infection and epidemic situation,identified the serotypes and genotypes of these pathogens,pathogenicity and drug resistance,and developed a Multivalent Inactivated Vaccine suitable for the prevention and control of mink hemorrhagic pneumonia in China,which provides a technical guarantee for the prevention and control of mink hemorrhagic pneumonia in China.