Low pathogenic avian influenza and Newcastle disease are also obstacles to the development of the layer industry
From the end of 2005 to the beginning of 2006, the domestic layer industry has been in a downturn due to the impact of bird flu; and the occurrence of “H9 subtype of low pathogenic avian influenza†or “Atypical Newcastle Disease†in some major layer-producing areas It has also become a major obstacle to the healthy development of the layer industry.
In view of this situation, Beijing Huadu Qikou Poultry Industry Co., Ltd., through calls, regional surveys, and on-the-spot diagnostics by veterinarian experts, has applied to 14 provinces, municipalities and autonomous regions including Beijing, Tianjin, Hebei, Shandong and Ningxia. More than 1,000 farmers surveyed and found new features of some poultry diseases.
Epidemiological features and pathological changes
The above two diseases in the investigated area were distributed to varying degrees, with egg-laying peak chickens aged from 180 to 300 days. The spread was rapid, the disease course was about 40 days, and the egg production dropped seriously. After recovery, the egg production rate was restored to 90% and the mortality rate was between 5% and 30%.
Tracheal mucosal hyperemia and hemorrhage; subcutaneous, abdominal cavity, coronal fat with bleeding; glandular and gastric bleeding is not common, common lesions are mainly concentrated in the reproductive system: follicular hyperemia, hemorrhage, deformation or degeneration, rupture of the formation of yolk peritonitis, fallopian tube white Jelly or cheese-like material.
Blood tests were performed to detect the level of antibodies in the chickens before and after the onset of illness. It was found that the H9 subtype antibody levels of Newcastle disease or avian influenza were low at the time of onset, and most of the chicken antibody levels were below the protective value, and antibody titers were dispersed and the dispersion was 5 or more. The antibody at the time of recovery increased by more than 3 to 5 titers and was higher than that produced by immunization.
Cause Analysis
From the analysis of the above-mentioned epidemic features, clinical symptoms and pathological changes, the disease that may have occurred may be "low pathogenic avian influenza H9 subtype" or "atypical Newcastle disease." The reason for this is as follows: The reason for the "low pathogenic avian influenza H9 subtype" is that it ignores H9 immunity. Some breeders are only protected from H5 subtype bird flu, and H9 subtypes are not considered to be H5N1-free, which also avoids H9; or H9 subtypes have fewer immunizations and are immunized only 1 or 2 times before egg production. After fear of affecting production, it is no longer immune, resulting in low antibody levels and insufficient protection.
The state attaches great importance to highly pathogenic avian influenza (H5N1) and vigorously promotes it, causing misunderstandings among some farmers and that the immunity of H9 is not important. In addition, some areas can not buy bird flu H9 single seedlings.
The cause of the atypical Newcastle disease is: lack of understanding, do not know that Newcastle disease protection requires humoral immunity + local immunity.
Many farmers do not perform antibody monitoring or antibody monitoring is not timely. The immunization method is not suitable, only drinking water, eye drops, or injection immunity. Although humoral immunity is better, local mucosal antibodies are not high, which means that the first line of defense against Newcastle disease virus infection is weak.
In addition, immunological numbness results from excessive immunity and short immunization intervals.
The best method for local immune response to Newcastle disease is aerosol.
Control measures
Immunization allows the birds to produce uniform and effective antibody levels.
In the prevention of bird flu, chickens that have not been immunized with the H9 subtype bird flu vaccine or who have immune but low antibody levels should be urgently replenished. Reference immunization program: 2~4 weeks old first immunization; 8~10 weeks old immunization; 120~130 days old three immunizations; immunization every 3~4 months after laying eggs.
For the prevention of Newcastle disease, we must attach importance to the role of local mucosal antibodies. It is the first line of defense against pathogen invasion and plays a very important role in anti-infection. Therefore, it takes the same attention as the humoral circulating antibody. Mucosal antibodies are mainly produced by immunization with live vaccines, and humoral antibodies are mainly produced by inactivated vaccines. Therefore, in the two most important stages of flock immunization, the two vaccines must be combined during the brooding and pre-laying period. use. After entering the egg-laying period, in order to maintain a high level of local mucosal antibodies, it must be guaranteed that live NDV vaccine should be administered 2 to 3 months.
The immune method, the first 3 weeks is best to use nasal drops, eye drops; 3 weeks after the use of aerosol methods; drinking water immune effect is poor, it is best not to adopt; if because of equipment problems can not use aerosol immunity method, the best use of nasal drops, Eyedrop method instead. Reference immunization procedure:
1st to 3rd day old live seedlings; 2nd to 7th to 10th day live seedlings; 3x17~21 day old live seedlings+inactivated seedlings; 4th free 8~10 week old live seedlings (air mist method) ; Five free 16 ~ 18 weeks old live vaccine + inactivated vaccine (air fog) method; egg production 2 to 3 months live vaccine once.
The detection of antibodies to these two diseases must be taken seriously. After immunizing chickens against Newcastle disease and bird flu, the body's antibody levels will gradually fall below the protection value as the immunization time increases. It is necessary to timely detect the level of antibodies in the flock to determine the timing of immunization, and timely check the rise of antibodies after completion of immunization to confirm the effect of immunization. Only the immunizations under the guidance of antibody detection will be “targeted†and effectively control the occurrence of these two diseases.
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