Highly pathogenic avian influenza can occur all year round, but it occurs frequently in winter and spring. The main reasons are:
First of all, influenza virus is very sensitive to temperature. With the increase of environmental temperature, the survival time of the virus is shortened. In addition, the light intensity is relatively high in summer and autumn, and the ultraviolet rays in the sun have a strong killing effect on the virus.
Secondly, the ventilation intensity of poultry houses in summer and autumn is much higher than that in winter and spring. Good ventilation can greatly reduce the number of viruses in the henhouse environment, so the chances and number of viruses invading chickens are obviously reduced, and the probability of infection is reduced. At the same time, good ventilation also reduces the stimulation of bad gas to the respiratory mucosa of chickens, which is of great significance to maintain the resistance of respiratory mucosa.
Newcastle disease glandular stomach nipple bleeding, influenza not,
There is jujube stone necrosis at the end of duodenum, but not in influenza.
Pancreatic hemorrhage and necrosis, but not Newcastle disease,
Coronary artery fat bleeding, not Newcastle disease.
It is difficult to distinguish Newcastle disease from avian influenza simply by anatomical symptoms and clinical symptoms, and the diagnosis can only be made by laboratory diagnosis. However, it doesn't matter much if it can't be diagnosed. Anyway, the treatment schemes for these two diseases are similar.
Differential diagnosis and treatment of avian influenza and Newcastle disease
In recent years, avian influenza and Newcastle disease have posed a huge potential threat to the chicken industry in China. Especially in large-scale chicken farms, because chickens are generally immune to nd, the incidence of ND is atypical, and it is difficult to see the typical pathological changes of ND in clinical autopsy, which is difficult to distinguish from AI, which brings great difficulties to the diagnosis and prevention of AI and ND.
Differential diagnosis of 1 AI and nd
1. 1 etiology
Avian influenza virus belongs to orthomyxoviridae, Orthomyxovirus and influenza A virus (AIV). In addition to type A, influenza viruses also include types B and C. Types B and C are only found in humans, while type A can infect humans and animals. There are two important surface antigens on the surface of AIV, namely hemagglutinin (HA) and neuraminidase (NA). These two surface antigens can mutate independently or simultaneously, and HA has strong variability, which is the main reason for the variation of AIV. AIV consists of eight genome segments. When two different AIVs infect a cell at the same time, the viral genome fragments recombine, so it is possible to form a large number of virus subtypes without cross protection. These recombinant virus subtypes change their pathogenicity through gene rearrangement, exchange or functional complementarity, leading to the emergence of new highly pathogenic epidemic strains. This is the root cause of antigen drift of avian influenza virus.
ND virus is a single-stranded RNA virus, belonging to paramyxovirus family, with a fibrous envelope containing H (hemagglutinin), N (neuraminidase) glycoprotein and F glycoprotein. HN glycoprotein can recognize sialic acid receptor, bind to receptor (nonspecific) and promote cell fusion (specific). F glycoprotein precursor F0 has no antigenicity, and has membrane fusion activity after being hydrolyzed and split into subunits F 1 and F2 by host cell protease, which is related to the pathogenic effects of Newcastle disease virus (NDV) such as penetrating cells and dissolving red blood cells. The AA sequence of f glycoprotein F 1/F2 polypeptide cleavage site (residue112 ~117aa) is directly related to NDV virulence. Avian paramyxovirus has 9 serotypes, namely PMV 1 ~ 9, and NDV belongs to PMV 1. Although the popular NDV virus strains are PMV7, PMV8, etc. And HV glycoprotein and F glycoprotein have been mutated slowly, and no different serum subtypes of Newcastle disease virus strains have been found, indicating that the existing vaccines can still be used to control the current epidemic Newcastle disease.
1.2 epidemic characteristics
AI is mainly in horizontal transmission, where sick birds excrete virus through digestive tract and respiratory tract, and it spreads through dust, feed, drinking water and poultry, so it spreads quickly. Once infected, it is easy to cause an outbreak of the whole flock of chickens, and even spread to neighboring flocks. The disease can occur all the year round, but mostly in winter and spring, and windy weather can promote the spread of the disease. Chickens of different ages, breeds and sexes can be infected. Laying hens are frequent, and many avian influenza pandemics in history were first caused by laying hens. The incidence of moderate and weak strains (such as H9N 1 and H9N3) can reach 100%, but most of them are within 80%. There is no secondary infection, and the mortality rate is generally within 10%. Combined or secondary bacterial infection may not only aggravate the damage to the body, but also increase the enzyme that can cut AI hemagglutinin in the body, and indirectly enhance the virulence of the virus. Avian influenza virus strains with abnormal virulence are rarely seen in clinic. It is generally believed that the incidence and mortality of avian influenza infection in chickens are higher than that in waterfowl. However, recent research shows that waterfowl is no longer just the storage host of avian influenza, and some waterfowl are often reported to be infected with avian influenza or even die.
ND can occur in any season, but it is more common in spring and autumn (day trading and communication of chickens). Through the digestive tract, respiratory tract and other birds. After atypical ND occurred in chickens, the symptoms and pathological manifestations were very different, most of them showed respiratory symptoms in different degrees, and some showed nervous system symptoms. The morbidity is 5% ~ 85%, and the mortality is 15% ~ 80%. The duration of atypical ND is too long, during which a few chickens always die sporadically. Chickens of all ages are susceptible to infection, among which chickens of 40 ~ 90 days old are extremely susceptible to infection. The symptoms and pathological changes of adult chickens are not obvious due to repeated vaccination. Typical ND has the characteristics of acute high lethality, but it is rare in recent years.
1.3 Clinical symptoms
Avian infected with AIV will show extremely complicated clinical symptoms due to the differences of virus virulence, poultry species and poultry health status, including asymptomatic subclinical infection, mild respiratory symptoms, decreased egg production and acute septicemia with 100% death. Chickens with high body temperature, dyspnea, listlessness, loss of appetite or disuse, and empty capsules filled with water or air. Increased nasal secretions, swollen sinuses, runny nose, swollen eyelids, conjunctival congestion, tears, large conjunctival cysts, and sticky or cheese-like secretions in the eyes. Diarrhea, sulfur and loose stools, light gray-green or light yellow in some cases, and increased urate, mainly manifested in different degrees of liquid white urate in the ureter. Some chickens have edema in the head, the comb and moustache are purple-black, the moustache on one or both sides is thickened and hardened, the heat sensation is enhanced, and there are purple bleeding spots on the hairless parts of the legs. The mortality rate mainly depends on the virulence of the virus, but if there are mixed infections with other diseases, it will often aggravate the condition and lead to higher mortality. Laying hens and laying ducks will drop in different degrees, and the laying rate of some chickens can drop from more than 90% to 20% within 3 days after onset, or even stop production, generally falling by 20% ~ 50%. In the same area, the laying rate of the first-onset chickens decreased greatly, and the laying rate of the later-onset chickens decreased slightly, and at the same time, soft-shelled eggs, preserved eggs, faded eggs and deformed eggs were produced. Generally, it drops to the minimum after 7 ~ 10, and slowly rises after staying at the lowest point for 7 ~ 70 days. The speed of egg laying recovery is related to the virulence of infected strains, feeding and management conditions and whether drugs are used. It usually takes 10 ~ 60 days to recover. When it is found that a large number of chickens die, and there are symptoms such as head edema, congestion in the comb and wattle, purple-black, thickening and hardening of one or both wattles, hairless legs and purple bleeding spots on scales between feet. It should be suspected that it is a highly pathogenic avian influenza virus infection.
Typical ND is the most acute and acute. The initial body temperature can rise to 44℃. Loss of appetite, listlessness, loose feathers, eyes closed and neck narrowed, like drowsiness; There is a lot of mucus in the oropharynx, which sometimes flows out; Dyspnea, wet snoring, blue beard, yellow-green or dark green foul-smelling thin feces, and some sick chicken crops are full of sour and smelly liquids. Subacute and chronic manifestations are neurological symptoms, such as paralysis of one or both legs or wings, limping or inability to stand, and drooping wings; Some have dyskinesia, often turning over on the ground, and some have their heads tilted back or bent to one side, semi-paralyzed or completely paralyzed. Atypical ND mainly occurs in vaccinated chickens. The clinical diagnosis showed mild respiratory symptoms, white eggs (some of which were slightly deformed), decreased egg production and low mortality.
Pathological changes of 1.4
AI has no characteristic pathological changes visible to the naked eye, and it is difficult to distinguish it from ND because of the different virulence and infection period of the virus. Some may not see obvious changes with the naked eye after autopsy, but some can see systemic hemorrhagic lesions. The following diseases are common: congestion and bleeding of trachea, and the bronchi on both sides of the first branch of trachea are filled with yellow cheese-like substances; Glandular gastric mucosa and nipple tip bleeding, cherry red, duodenal mucosa bleeding, showing diffuse and dense spots, tubal bleeding is sometimes serious, chest and leg muscles, epicardium, skull bleeding, pancreas often has gray necrosis points; There is typical peritonitis with a large amount of cheese-like exudate.
Typical ND crop edema, tracheal ring bleeding, glandular gastric papilla basal bleeding, dark red, obsolete, cloacal mucosa warm congestion and bleeding, small intestinal mucosa with jujube pit or irregular bleeding ulcer, cecal tonsil swelling, bleeding and necrosis. Atypical nd only found edema, rectal and cloacal bleeding, intestinal mucosal bleeding or ulcer in the glandular stomach, especially 3 cm behind the yolk navel, which has more clinical diagnostic significance. Some sick chickens will have pneumonia, pulmonary congestion, tracheal ring bleeding and other diseases.
2 Prevention and control measures of avian influenza and Newcastle disease
2. 1 avian influenza and Newcastle disease prevention principles
Strengthen feeding management to minimize the occurrence of stress factors such as cold, thief wind, transportation and group rotation; Environmental purification, pay special attention to the ventilation of henhouses, reduce the concentration of harmful gases such as NH3, CO and SO2, and reduce dust pollution; Strengthen air disinfection; Do a good job in immunization.
2.2 Prevention and control measures for avian influenza
2.2. 1 It is the most basic countermeasure to prevent and control AI to do epidemic prevention and health work well and keep the virus out of the chicken farm. When choosing a chicken farm, try to stay away from other chicken farms, duck farms and goose farms. Strengthen the control of vehicles and personnel. Strictly manage the live poultry trading market and try to trade in places far away from chicken houses. It is an effective measure to disinfect chickens regularly. Because although strict preventive measures have been taken, sometimes viruses can still enter chicken farms through flowing air and bird droppings, but the entry of viruses does not mean the occurrence of diseases. Any pathogenic microorganism needs a certain amount to make sensitive chickens sick. Regular spray disinfection can eliminate or reduce the virus that may exist in the small ring to a minimum, and avoid or reduce the occurrence of diseases.
2.2.2 Be vigilant and strengthen prevention. It is necessary to strengthen the port quarantine of live birds, ornamental birds, wild birds and their products to prevent the introduction of avian influenza from abroad, especially to prevent the introduction of highly pathogenic avian influenza. Once suspected avian influenza is found in China, it should be reported in time, and personnel should be organized for early diagnosis, and the serum subtype, virulence and pathogenicity of the isolated avian influenza virus should be identified. Delineate epidemic areas, strictly block, cull all poultry infected with HPAIV virus, and thoroughly disinfect them. Feasible measures should be taken for food with positive serum, and the flow direction should be paid close attention to to prevent the spread of infectious sources.
2.2.3 About vaccine immunization. Because of the diversity of AIV antigens, there are some antigenic differences among subtypes, and there is a lack of strong cross-protection between subtypes. There is still a danger of mutation and recovery after the use of attenuated vaccine, so it is difficult to immunize AI. However, domestic experiments show that the outbreak and epidemic of avian influenza in China can be basically prevented as long as the prevention of H9 and H5 subtype avian influenza is well done. At present, it is necessary not only to immunize chickens on a large scale, but also to do a good job in the epidemic prevention of H5 subtype avian influenza in waterfowl. At present, the incidence of H5 subtype avian influenza in waterfowl is on the rise, so it is of great significance to do a good job in waterfowl epidemic prevention, both to reduce the incidence of waterfowl itself and to reduce the spread to chickens. Broilers can be immunized at 7- 12 days old; Laying hens and broiler breeders were immunized at 2, 20 and 40 weeks respectively. In areas with severe epidemic situation, immunization can be strengthened once at the age of 12 weeks. However, the export of meat and poultry does not advocate AI immunity.
2.3 Second Control Countermeasures
2.3. 1 according to the local epidemic situation, the immune status of chickens, feeding management and other actual conditions, formulate and adjust the nd immunization program.
Monitoring the maternal antibody level of Newcastle disease in chickens to determine the first immunization time. Newcastle disease antibody (commonly used HI test) was regularly monitored in chickens to determine the immunity and virus infection in the field, and to provide basis for formulating immunization procedures.
The maternal antibody of chicks increased day by day after hatching, reached the peak in 5-7 days, began to decrease after 9 days, and gradually disappeared after 28 days. The average half-life of maternal antibody is 4.5 days. When the HI titer of chicks is lower than 1: 8, the humoral immune response ability can only be achieved through immunization; Chickens can only have a slight immune response when the titer is above 1: 32. For cHIcks 1 day after hatching, 0. 1% blood was collected to check the hi antibody titer. The optimum day age for the first immunization of chicks =4.5×( 1 day age HI-4 logarithm) +5. If the HI titer of 1 day-old chicks is lower than 1: 16, the first immunization should be carried out at 1 day-old chicks. CHIckens with high maternal antibody did not increase the titer of hi antibody after immunization, but decreased in different degrees, and the higher the maternal antibody level, the greater the decline. If the maternal antibody is not uniform, when the titer of HI antibody in most chicks is above 1: 16, the protection rate is above 60%, and the surviving chickens often become carriers of virulent virus. Some people think that the first immunization can be carried out in advance until 20% of maternal antibodies fall to the critical value.
Local broiler breeds: 1 day-old for the first immunization, with eye drops of clone -30-MA5 or IV vaccine,15-20 days-old for the second immunization, 45-50 days-old for the third immunization, and 80 days-old for the fourth immunization. Fast-growing broilers: First immunization at 1 day, eye drops and nasal drops of clone -30-MA5 or IV vaccine, second immunization at 25-30 days, intramuscular injection of I vaccine (if there is an epidemic nearby, it can be immunized with IV vaccine once before and after 15 days).
2.3.2 Strengthen feeding management, reduce stress and do a good job in air purification of the environment. 5% glucose and 0. 1% vitamin c are added to drinking water, and appropriate antibiotics and vitamins are mixed into feed to prevent secondary infection.
2.3.3 Strengthen blockade, isolation and disinfection; Emergency blockade and isolation of sick henhouses, and strict disinfection of personnel and articles entering and leaving; Disinfect pollutants such as feces in time; The whole environment is disinfected, and chickens are disinfected with chickens.
2.3.4 Rapid control of atypical ND chickens with 3 times dose of Clone-30 vaccine; Inject or drink water to the chicken muscle with 3 ~ 5 times of IV vaccine, and give each chicken a shot as much as possible. At the peak of laying eggs, the disease can be controlled at 1 week by intramuscular injection or drinking 5 ~ 8 times of IV epidemic water and then mixing it with cod liver oil.
Treat mild avian influenza and Newcastle disease.
3. 1 mild treatment
r:
1) Qingankang 100g/ bottle, mixed with 200kg of water, and the whole group drank water for 3-5 days.
2) Poultry Gansukang 500g/ bag, mixed with 250kg.
In addition, 500 g /250 kg feed was added to mix with Huchuankang with respiratory symptoms; For particularly severe fever, 500g/250g of Du Wen Su Kang can be added.
Kilogram; 3-5 days;
3) In addition to the above measures, emergency intramuscular injection of Wanpukang, 0.5 ml 1 time each time, once a day 1 time, twice in a row, was given to chickens that did not eat or drink and died seriously.
Time.
point out
1) after taking the medicine according to the above course of treatment, drink 3-5 times of Newcastle disease L water to prevent secondary Newcastle disease. If the condition is basically controlled, it is best to take Weikang with your heart.
Or treat the secondary infection of Escherichia coli and Salmonella for 3-5 days with flumetol to prevent secondary bacterial diseases;
2) If it is mixed Newcastle disease, it should be immunized with Newcastle disease and L-5 strain first, and then treated according to the above scheme after 24 hours.
3) Resume using Mu Yi Egg-increasing Essence and Jinji Vita for 7- 10 days;
3.2 treatment of Newcastle disease
r:
1) Drink 5-8 times the amount of NdIV vaccine once every 2-4 days.
2) Qingankang, 100g mixed with water, 200kg drinking water. If there is mycoplasma infection, mix it with huchuanning.
3) 500g of fast-growing avian influenza or fast-growing epidemic virus mixed with 250kg.
point out
Criteria for judging mixed infection of avian influenza and Newcastle disease
Immunize Newcastle disease for more than 40 days; The inner wall of the intestinal wall at the navel of the second egg yolk has oval swelling; Diffuse three small intestines
Bleeding; 4. The feed intake decreased significantly.
Management principles of mixed infection of Newcastle disease, avian influenza, Escherichia coli and mycoplasma;
The mixed infection of nd, AI, Escherichia coli and mycoplasma can be treated according to the treatment principle of ND and AI, and must be exempted first.
Newcastle disease, and then combined with drugs selectively according to the condition, such as severe mixed infection of Escherichia coli, can be used for poultry and Gankang.
Jia fu le mei; If there is mycoplasma infection, add Hukexing or Huchuanning; If Escherichia coli and mycoplasma are not serious,
First, viral diseases were treated for 5 days, and then Escherichia coli and mycoplasma were treated.
4 Special preventive measures
4. 1 Because the symptoms and pathological changes of AI are unstable, it is difficult for veterinarians who lack clinical experience to rely on respiratory rales, myogastric glands and stomach at the scene.
Bleeding, etc. It is easy to be diagnosed. When suspicious cases appear, the first thing to consider is whether it is chicken ND.
4.2 If AI is misdiagnosed as nd at the scene and has been vaccinated with multiple doses of ND vaccine, the mortality rate often rises sharply on the second day after vaccination, especially.
Almost all chickens died within 1 week after vaccination with strain ⅰ vaccine.
Second, the symptoms:
1, avian influenza (AI) swollen head and swollen eyes, Newcastle disease (ID) not;
2, AI foot scales have bleeding, ID does not;
3, AI feces are yellow-white, yellow-green, ID is green and smelly;
4, AI has a purr when breathing, and ID has a purr.
Third, lesions:
1, there is jelly-like exudation in the swollen head and neck of AI, and the ID is not;
2.AI has diffuse bleeding of the whole trachea with much mucus, and ID only has laryngeal bleeding;
3, AI thymus bleeding is serious, ID bleeding is light;
4.ID crops have serious inflammation, more mucus and less AI;
5. There are bleeding spots or spots on the surface of Ai liver, and the ID is generally absent;
6.AI has more bleeding points in coronary fat and less ID;
7, Ai Shen swollen blood, ID number;
8, AI stomach surface fat has bleeding point, ID generally does not; AI bleeds more between the base of glandular stomach and nipple, while ID bleeds more at the nipple of glandular stomach.
9, ai pancreatic bleeding necrosis, tax number;
10, AI has more diffuse bleeding in the small intestine, but generally there is no lymphatic follicular bleeding in the small intestine, while ID has more swollen bleeding in the lymphatic follicles, with large bleeding spots or spots, and the thickness of the intestine varies, and there is yellow colloidal secretion in the cut thick intestine;
1 1, Ebstein's bursa bleeding, ID is not;
12, AI has bleeding spots or spots under the skin of chest and abdomen and leg muscles, and there are bleeding spots at the root of leg and abdominal fat, without ID;
13, AI lung congestion and edema, ID is generally missing.
Fourth, epidemiology:
AI comes on quickly, recurs in a short time after mild recovery, and produces immunity for a long time after ID recovery. AI can cause diseases in ducks and geese, but ID can't.
In this series of differences, the most significant differences between avian influenza and Newcastle disease are: AI swollen head and swollen eyes, leg scale bleeding, pancreatic bleeding and necrosis, renal enlargement, massive bleeding in bursa of fabricius, and serious changes in visceral bleeding.