Hepatitis E in laying hens
Release time:
Aug 20,2019
Avian hepatitis E, also known as hepatitis-Enlarged spleen syndrome. Avian hepatitis E virus (HEV) infection can cause hepatitis in laying hens and broiler breeders-Enlarged spleen, decreased egg production and even death. Dead birds have blood in the abdominal cavity, hepatosplenomegaly. Since the mid-1980s, the disease occurred in some parts of the United States, the disease has been called large liver and spleen disease, necrotizing hemorrhagic hepatitis, hepatitis-liver hemorrhagic syndrome, etc.
Epidemiology:
1991The disease was first reported in western Canada in, and now occurs in eastern Canada, California, and the Midwest and eastern United States. The disease has been reported in Australia. Serological investigation shows that there are also avian HEV in the UKInfection. Caged Laihang hens are susceptible, and the disease occurs frequently on some farms. It has also been reported in laying broiler breeders, and sporadic deaths in laying hens and small flocks raised on litter may be related to this. Under field conditions, chicken is the only host of avian HEV.
Route of transmission: dung-The feces of infected chickens are the main source of the virus, and vertical transmission of HEV can occur in hens.
Clinical symptoms:
From viral infection to discharge from feces, the incubation period of mouth-nose infection in chickens is 1-3Week. Morbidity and mortality are relatively low, with egg production falling by more than 20 per cent in some flocks with explosive disease, while others are unaffected. Egg-laying broiler breeders and 30-72The mortality rate of the disease was higher than that of normal laying hens at the age of 40-50 weeks, and the incidence rate was the highest at the age of 40-50 weeks. Mortality increases by about 0.3 percent per week during mid-laying and can sometimes exceed 1 percent. Sick chickens may have cockscomb, pale, gloomy flesh, loss of appetite, contamination of anal feathers or mushy faeces. Infected flocks produce small eggs with thin shells and light color.
Pathological changes:
Naturally, dead chickens usually have regressed ovaries, red fluid in the abdomen, and enlarged liver and spleen. Infected chickens before death are usually in good condition, accompanied by a disastrous failure of the crown and meat drape, but sometimes the chickens can be seen in poor condition. The liver is enlarged and bleeding or blood clots can be seen in the abdominal cavity. The liver is usually brittle, with colored spots and red, yellow, or yellowish brown foci, a subcapsular hematoma, and clots attached to the surface. Coagulation in the abdominal cavity and bleeding in the liver are often associated with hemorrhagic fatty liver syndrome (HFLS) confusion. HFLS usually occurs in laying hens, but hepatitis-Hepatic hemorrhagic syndrome (HS syndrome) The liver is not steatotic. The spleen of infected chickens is mildly to severely enlarged, sometimes with white lesions, and the ovaries of infected chickens are usually degraded.
Diagnosis: The initial diagnosis of the disease is based on clinical symptoms and general pathological changes or microscopic lesions. Hepatitis E syndrome HSmust be distinguished from hemorrhagic fatty liver syndrome (HFLS) because HSSyndrome A clot occurs in the abdominal cavity and causes bleeding in the liver, and the liver in HS syndrome is not fatty as in HFLS syndrome. Insecticide (anticoagulant) poisoning, the abdominal cavity or liver sometimes around the clot (or not). The differential diagnosis should also consider chicken trauma or liver hemorrhage or perihepatic hemorrhage.
Prevention and control measures:
1HEV to presentThere is no vaccine available. At present, there is no effective treatment for avian HEV infection. The use of liver and kidney protection, increase the immune function of the drug to help the recovery of the disease.
2The implementation of strict biosecurity measures on chicken farms can limit the spread of the virus.Adhere to the disinfection of the environment, especially with chicken disinfection, the use of iodic acid preparation and glutaraldehyde preparation alternately used better; early detection, early elimination of sick chickens, as far as possible to reduce the chance of transmission.
3,Because hepatitis E can be transmitted vertically, it is necessary to investigate whether hepatitis E has occurred in the chicken farm when entering the seedling,Strict selection of chicken source field, to prevent vertical transmission.
4Strengthen feeding management and use high-quality full-price feed.Adding Vitamin E to Feed and Drinking WaterVitamin C and liver protection drugs.
5Good control of immunosuppressive diseases, can reduce avian HEVof infection.
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