Liu Xiufan: New Trends in Poultry Disease Epidemic
Release time:
Oct 11,2018
Avian influenza and Newcastle disease are the main infectious diseases that endanger the poultry industry in China. How to effectively prevent and control them has always been a major problem perplexing the industry. Recently, at the Seventh Veterinary Drug Conference held in Wuhan, Hubei Province, Liu Xiufan, academician of the Chinese Academy of Engineering, interpreted the epidemic trends of the above-mentioned poultry diseases.
Newcastle disease has been perplexing the development of poultry industry in China. Since the 1990 s, atypical Newcastle disease has occurred frequently in immune chickens in China, and clinical symptoms of Newcastle disease have also occurred in waterfowl, especially geese, causing a large number of deaths. In addition, the occurrence of Newcastle disease in other poultry species is also frequently reported, and the farm is easy to isolate the virulent Newcastle disease. However, in the past five years, great changes have taken place in the epidemic situation of Newcastle disease in China. Liu Xiufan said that atypical Newcastle disease rarely occurs in immune chickens in China, clinical Newcastle disease symptoms of geese are controlled, and virulent virus is rarely isolated, while other poultry species, except pigeons, have fewer reported cases of Newcastle disease, and it is also difficult to isolate virulent Newcastle disease in large-scale farms.
"The state should seize the opportunity to formulate a Newcastle disease eradication plan to achieve the transition from immune disease-free to non-immune disease-free." Liu Xiufan believes that in recent years, the prevention and control of Newcastle disease in my country has been the best period, and it has been difficult to isolate the once rampant gene VII virulent virus across the country.
H9N2 subtype avian influenza is the most widespread, most effective and fastest spreading avian influenza in poultry in China, and it is also the most difficult to control at present. Since 1998, the epidemic characteristics of H9 subtype avian influenza are as follows: fast transmission speed and wide epidemic range; chickens of various ages are susceptible, and the clinical severity is quite different, but the economic loss is very large. The egg production of laying hens decreased by 10% ~ 60% or lost production, and the death rate of broilers, broilers or broilers ranged from 10% to 80%. There is a significant synergistic pathogenic effect with some other pathogens. In recent years, the vast majority of isolated strains have acquired aerosol transmission ability, and can still infect chickens under the condition of high antibody, resulting in a large number of virus replication and excretion. But at present, the epidemic trend of this type of influenza shows different characteristics. Liu Xiufan introduced that it is mainly the pathogenic synergy between H9 subtype avian influenza and other pathogens, such as avian Escherichia coli, avian infectious bronchitis, avian infectious laryngotracheitis, Newcastle disease or a variety of immunosuppressive pathogens, which need to be paid attention.
Speaking of the Asian H5N1 subtype of highly pathogenic avian influenza, Liu Xiufan said that the Asian H5N1(H5NX) subtype of avian influenza is by far the most widespread and longest-lasting in the world, and it is also the most harmful to the poultry industry. Highly pathogenic avian influenza. The evolutionary trend of this highly pathogenic avian influenza is mainly manifested in: evolution from H5N1
H5N2, H5N5, H5N6, H5N7, H5N8; Some branches of H5 subtype have completely disappeared in 2015. The two subbranches have continuously evolved new subbranches. HA receptor binding sites have evolved from avian sources to dual binding characteristics of avian and human sources, thus enhancing human infectivity. The transmission ability is enhanced.
H7N9 subtype avian influenza is an avian influenza that gradually changes from non-pathogenic to chickens to highly pathogenic. It is the avian influenza with the most human cases so far. Liu Xiufan said that this H7N9 subtype influenza has no survival advantage in poultry, especially compared with the H9N2 subtype virus. He said that in recent years, the test data show that the low pathogenic H7N9 virus in poultry is dying out.
In terms of the difficulties in preventing, controlling and eradicating avian influenza, Liu Xiufan believes that, first, because of the loss of the best extinguishing time, it has become a large-scale frequent epidemic; second, the breeding mode of China's poultry industry is complex, the level of biosafety is generally poor, and it relies too much on vaccines; third, the breeding of domestic waterfowl in China is huge and the ecological environment is complex, which is conducive to the sustainability and purification of influenza A virus in the environment; fourth, my country's animal epidemic control management system still has room for improvement, and the social ecological environment is not satisfactory, which needs to be further optimized and improved.
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