Guangdong Animal Husbandry and Veterinary Association is a provincial social organization with legal personality approved by the Civil Affairs Department of Guangdong Province, an integral part of the Guangdong Science and Technology Association, a bridge and link between the party and the government and animal husbandry and veterinary science and technology workers, and an important social force for the development of animal husbandry and veterinary medicine in our province.
Duck viral hepatitis is a fast-spreading, highly lethal, clinical symptoms of horn arch reversal, with hepatitis as the main lesion of infectious diseases in young ducks. The disease has caused serious economic losses to China's duck industry.
Today, Zhengye Special Duck Doctor Lecture Hall will take you to learn more about the epidemic, diagnosis and prevention of duck viral hepatitis in the--- series of waterfowl disease prevention and control series.
Duck hepatitis A virus types 1 and 3 and duck astrovirus are the culprits of duck viral hepatitis
The pathogen of duck viral hepatitis is duck hepatitis virus, which has 3 serotypes, namely I., II., III. The results of the study showed that duck viral hepatitis was caused by duck hepatitis A virus and duck astrovirus. China is mainly duck hepatitis A virus, which belongs to the genus avian liver virus of the family RNAviridae, which contains 3 serotypes, namely duck hepatitis A virus type 1 (that is, dhv traditional serum type I.), duck hepatitis A virus type 2 isolated in Taiwan, and duck hepatitis A virus type 3 isolated in South Korea and China. Recently, the International Committee on The Classification of Viruses has classified it as a new virus species name, Avian Liver Virusa. Duck astroviruses include duck astrovirus type 1 (i.e., dhv traditional serum type II) and duck astrovirus type 2 (i.e., traditional serum type III).
Duck viral hepatitis in China is mainly caused by duck hepatitis A virus type 1, duck hepatitis A virus type 3 and duck star virus type 1, and duck hepatitis A virus type 2 has not been isolated in mainland China. Duck viral hepatitis is susceptible to ducks under 6 weeks of age (including Peking duck, Cherry Valley duck, fan duck and other species), clinical manifestations of drowsiness, ataxia, angle arch reversal, and rapid death; the incidence of 100%, can cause 95% to 100% of the young duck death, adult ducks can be infected and most do not occur, but can be detoxified through feces. In the case of natural infection, the disease does not circulate in flocks of chickens, turkeys and geese.
The disease is mainly transmitted through the digestive tract and respiratory tract through contact with sick ducks or contaminated people, tools, feed, bedding, drinking water, etc.; rats and fish can also carry the virus as a source of infection; there is currently no evidence that the disease can be transmitted vertically. The disease occurs throughout the year, and improper feeding management, such as low temperature and humidity in duck houses, excessive density, poor sanitary conditions, or lack of nutrients in feed, can cause the disease to occur in young ducks.
Neurological symptoms, enlarged and fragile liver are typical symptoms of duck viral hepatitis
The main clinical features of the disease are that the young ducks in the early stage of the disease show depression, loss of appetite, low head drooping, and finally general convulsions, dorsal neck and other neurological symptoms, manifested as motor disorders, the body fell to one side, the wings drooped, and the feet spasmodically kicked repeatedly. Autopsy diseased and dead ducks, can see the liver is enlarged, brittle, fragile, with hemorrhagic ecchymosis, the liver of ducks under 10 days of age is often earthy yellow, 10 to 30 days old often gray-red or yellow-red. The gallbladder is oblong-ovoid, filled with bile, and the bile is brown or dark green. He staining reveals massive hepatocyte necrosis, bile duct hyperplasia, bleeding, and exudation of inflammatory cells, swelling of the spleen and kidneys, and vascular obstruction.
Fig. 1 Dead ducklings are inverted with horned bows
Fig. 2 Enlarged liver, superficial and brush-like bleeding
(1) Clinical diagnosis
A preliminary diagnosis is made based on epidemiology, typical symptoms, and pathological features such as significant bleeding spots or bleeding spots in the liver. Symptoms of the disease may not be apparent in older or immunized ducks and should be isolated and identified. Clinical attention should be paid to the differential diagnosis with duck plague Rimerellosis, duck cholera, duck paratyphoid fever, aspergillosis, etc.
(2) Laboratory diagnosis
Laboratory diagnostic methods are mainly serological diagnostic techniques, including neutralization tests, enzyme-linked immunosorbent tests, fluorescent antibody technologies, agar diffusion tests, colloidal gold techniques and molecular biology techniques.
Vaccine antibodies plus Chinese and Western medicines, comprehensive prevention and treatment of duck viral hepatitis
To prevent viral hepatitis in ducks, the following measures can be used:
(1) General management measures
(1) Adhere to self-breeding: do not buy ducks from epidemic areas or epidemic farms, usually strengthen hygiene and disinfection, and regularly use 10% lime milk or 3% to disinfect duck house utensils.
(2) Isolation and disinfection: strict isolation of sick ducks, dead ducks using harmless treatment, duck houses, equipment, utensils, etc. are fully cleaned, and then disinfected with 5% sodium hydroxide solution, and the whole group of ducks is disinfected with 0.3% peracetic acid spray every day.
(2) Immunization: improve the awareness of epidemic prevention and carry out specific prevention. Before entering the hatching, it is necessary to understand the immunity of the breeding duck farm to the disease.
(1) Breeding duck immunization program: 1 to 3 days old, subcutaneous neck, injection of chicken embryonic duck hepatitis virus vaccine 0.5 ml / only; intramuscular injection once a month before the start of labor, the dose of 0.5 ~ 1 ml / only, after 2 weeks interval, strengthen immunity once; maternal antibodies are not enough to protect the offspring of the chicks completely without hepatitis, but can delay the onset of the day.
(2) Commercial duck immunization program: 1-day-old commercial ducks inject chicken embryonic duck hepatitis virus vaccine 0.5 ml under the skin of the neck, and after 5 to 7 days after immunization, the antibody can reach the peak and maintain it for 2 months without decreasing.
Treatment: antibody immunity plus drug prevention and control
Immediately after the onset of illness, isolation treatment, and add minerals and multivitamins to the feed, subcutaneous injection: (1) rehabilitation duck serum or high exempt duck serum 0.5 ~ 1 ml / only. (2) High egg-free yolk antibody 0.5 ~ 1 ml / only. At the same time, antibacterial drugs such as cefotafuroxime sodium, cefixime, and amikacin are used to control secondary bacterial infections. Or for traditional Chinese medicine prevention and control, the addition of Chinese herbal medicines such as large green leaves, astragalus, plate blue root and other Chinese herbs or antiviral drugs such as astragalus polysaccharides to prevent it can reduce the incidence.