Diagnosis and Prevention of Newcastle Disease in Chicken
Newcastle disease is an acute, hot, septic and highly contagious disease caused by Newcastle disease virus. It is characterized by high fever, dyspnea, diarrhea, neurological disorders, mucosal and serosal hemorrhage. With a high incidence and mortality, it is a major infectious disease that threatens the poultry industry and belongs to a class of infectious diseases.
First, the clinical symptoms of the disease incubation period of 2 to 15 days or longer, an average of 5 to 6 days. The Terrestrial Animal Health Code stipulates 2 l days.
According to the length of disease Newcastle disease is divided into the most acute, acute and chronic three types:
The most acute type: This type is more common in chicks and the early stages of the epidemic. Sudden onset, rapid death without characteristic symptoms. The diet was often observed the night before and was found dead the next morning.
Acute type: There are abnormalities in the respiratory tract, digestive tract, reproductive system, and nervous system. It starts with respiratory symptoms and then squats. Initially, the body temperature increased to 43-44 °C, respiratory symptoms showed cough, increased mucus, breathing difficulties and lead to open mouth, breathing sound, chicken cocks and meat palate was dark red or purple. Spiritual ted, loss of appetite or loss, thirst for desire, feather loose, do not want to move, down neck, wings, drooping wings, cocks and mink purple, eyes closed or closed, like a lethargy. Hens lay eggs or soft shell eggs. The sick chicken coughs, has a sticky nasal fluid, and has trouble breathing. Sometimes it stretches its head, breathes open mouth, wheezes its gurgling sounds, or has a sudden groan. A large amount of mucus flows out of the mouth, and the head is shaken or swallowed to remove mucus. There is a liquid content inside the hernia sac and a lot of sour dark gray liquid is often poured out from the mouth. The yellow-green or yellow-white water samples are loose and sometimes have a small amount of blood. Later fecal samples were egg white. In some cases, there are neurological symptoms such as fins, paralysis, standing instability, waterfowl, birds, etc., that cannot fly and lose balance. Finally, the body temperature drops and soon dies in a coma with a mortality rate of more than 90%. The disease duration of young birds within one month of age is not obvious and the mortality rate is high.
Chronic: Occurred in late adult birds. Over-acquired diseased birds are often dominated by neurological symptoms. The initial symptoms are similar to those of the acute type. Soon afterwards the symptoms are improved. However, neurological symptoms such as paralysis of the wings, lameness, or unsteady standing are observed. The head and neck are twisted backward or to one side. , often rotating, repeated attacks. Everything is normal during the interval and it looks like it is healthy. However, if they are disturbed by stimuli or rush to eat, they will suddenly have a seizure. The head and neck will bow and the body will twitch, and it will return to normal within a few minutes. Eventually it may become awkward or semi-paralysed, or it may gradually become thin and eventually die, but the mortality rate is lower.
The incubation period for natural infection is 3 to 4 weeks, ranging from several months. The Terrestrial Animal Health Code stipulates 4 months.
According to clinical symptoms, there are four kinds of neurological, visceral, eye, and skin types, which sometimes occur in combination.
Nervous: mainly manifested as gait instability and ataxia. Symptoms are characterized by paralysis or paralysis of one or more limbs, forming a leg that stretches forward and one leg stretches to the rear, and the wings are paralyzed (commonly known as the big cockroach). The paralysis of the neck causes the head and neck to be skewed, and the hernia sac expands due to paralysis (commonly known as the big louse). The necropsy showed that the injured nerves became thicker and swollen. They often occurred in the sciatic nerve, cervical vagus nerve, brachial plexus, celiac plexus, and mesenteric nerve plexus. The transverse stripes of nerve fibers disappeared and were grayish or yellowish-white.
Visceral: often inflicted on young chickens, the mortality rate is high. The necropsy shows that there are grayish white lymphocyte tumors in the internal organs. Common in the gonads (especially the ovary), followed by kidney, spleen, heart, liver, lung, pancreas, mesentery, glandular stomach, intestine, muscle and other organ tissues.
Eye type: mainly against the iris, unilateral or binocular disease, vision loss, and even blindness. Visible iris proliferation fading, pale turbid gray (commonly known as gray eyes or silver eyes). Pupils contract and the edges are not serrated.
Skin type: characterized by the formation of small nodules or tumors on the skin's hair follicles. It was originally found in the neck and both wings of the skin, and later spread throughout the body's skin.
Second, the diagnosis sign. Gland swelling, bleeding, or ulceration of the papillary glands, especially at the junction with the esophagus or muscle and stomach. Duodenal mucosa and small intestine mucosal bleeding or ulcers, sometimes visible "islands or jujube-like nuclear ulcers," the surface is covered with yellow or gray-green cellulose membrane. Cecal tonsil enlargement, hemorrhage, and necrosis.
The initial diagnosis can be made based on the typical clinical symptoms and pathological changes. The diagnosis should be further laboratory diagnosis.
Pathogen examination: 1 virus culture identification: after treatment, the sample is inoculated with 9 to 10 days old SPF chicken embryos, incubated at 37 °C for 4 to 7 days, collected allantoic fluid for HA test titer, with specific antiserum (chicken antiserum ) or I test to determine the presence of ND virus. 2Virulence assay: Determination of the ICPI (inflammation index), the IVPI (intravenous inoculation index), and the mean embryonic death time (MDT) in chicks at 1 week of age.
Serological tests: viral hemagglutination test (HA), viral hemagglutination inhibition test (HI), enzyme-linked immunosorbent assay (ELISA) for on-site diagnosis, epidemiological investigations, and screening for quarantine at ports of entry and exit.
Sample collection: For virus isolation, brain, lung, spleen, liver, heart, kidney, intestine (including contents) or mouth and nose swabs can be collected from sick or dead dead birds, except that the contents of the intestines need to be treated separately. Samples can be collected individually or mixed. The collection of swabs from live birds and cloacal swabs, chicks or rare birds can cause damage, and fresh feces can be collected instead. The above samples are immediately sent to the laboratory for processing or stored at 4°C for inspection (not more than 4 days) or stored at -30°C for inspection. Samples used for serological tests are generally collected in serum.
Third, control
Vaccination is the main measure to prevent this disease. The key to prevention is regular immunization of healthy chickens. Peacekeeping regulations should be strictly enforced in peacetime to prevent contact with viruses or infectious sources and vulnerable chickens.
When this disease occurs, it shall be dealt with in accordance with the “Animal Epidemic Prevention Law†and related regulations. Kill culprit birds and the same group of birds, bury or burn corpses deeply; pollute materials must be treated in a detoxified manner; thoroughly disinfect the contaminated utensils, objects and environment. Healthy chickens in affected and threatened areas are immediately vaccinated.
Fourth, treatment
The treatment of Newcastle disease in the past is the first use of vaccine after the use of drugs, generally with ND4, C30, C88, Xin Wei Ling, VH and other serious plus new epidemic Kang; the effect is very good. However, I have found that a large number of people said that Newcastle disease cannot be treated with lyophilized vaccines. Otherwise, it will cause widespread death or worsen the condition. In fact, these phenomena were not easily seen two years ago (except for the ND1 series). Why? What happened in these 2 years? This is the intensity of Newcastle disease, which was not very serious at the beginning of the disease. The result of a freeze-dried vaccine was severe. Actually, I see this problem in this way. Even if people do not use vaccines, they will have to die in large numbers. This only shows that general vaccines, including imported vaccines, are not effective or effective; or they cannot be said to be deaths or aggravations caused by vaccines. The condition. If it is found that the local intensity of Newcastle disease is popular, as long as Newcastle disease is discovered, it must be treated according to the intensity of treatment. Do not use simple or unreasonable measures to treat it, otherwise it will cause misunderstandings and delay the disease. The intensity of Newcastle disease is really difficult to treat. In the past year, the imported vaccine New Weiling or other new and new epidemics had doubled the drinking or injection of adult chickens. After one day, they used highly effective anti-virus Chinese herbal ingredients. Western medicine water basically solved all problems after 5 days. Symptoms; but not this year! Need to use imported New Welling or VH and Xin Xie Kang each 3.5-4 times the amount of one day after the use of highly effective anti-virus Chinese herbal ingredients, Western medicine drinking water for 5 days to control death. For chickens that do not have secondary infections for typical Newcastle disease, the effectiveness of conventional vaccines is not good or even effective; however, the disease, including death, will not be increased due to the consumption of vaccines. If you first switch to antiviral respiratory medicine for 4 days, then the Newcastle disease 4 Series will soon be significantly improved. In the past, it was definitely the first use of vaccines after the use of drugs, or no drug effect is very significant. Therefore, I suggest that you should encounter typical Newcastle disease in order to avoid misunderstanding by farmers, you can use drugs for 3-4 days (anti-influenza virus drugs), and after stopping for a day, the effect of using a simple ND4 or C30 is significant. . These issues should be properly and flexibly grasped. In the end, I would like to correct one common point: the point of view that Newcastle disease does not dare to use vaccines. This is terrible and inaccurate. Real Newcastle disease cannot fully recover a flock without proper vaccine; otherwise, it is not Newcastle disease. That is to say, the single use of drugs for treatment can be completely restored. It can be said that it is not Newcastle disease and you have not been diagnosed properly.
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