Prevention and control of white crown disease in autumn chickens
Release time:
Sep 03,2019
Chicken white crown disease is a seasonal epidemic disease of chickens, also called white blood cell protozoa, mostly occurred in late summer and early autumn. The pathogen is Leukocelia carinii, which usually parasitizes in the red blood cells and mononuclear cells of chickens, thus causing anemia in chickens. The bloodsucking insects Culicoides and gnats are the main vectors of transmission by biting chickens. Chickens of all ages can be infected with the disease, especially in the late stage of breeding and laying, which causes a decline in egg production rate and even death, resulting in serious economic losses.
1. Epidemiology
The occurrence of this disease has obvious seasonality. It starts in June in places with more rain in the south and occurs in August to October in North China. The life history of leukocyte protozoa is divided into two stages: sexual reproduction and asexual reproduction. Sexual reproduction is completed in the body of Culicoides or blackflies, generating invasive spores and distributing them in the saliva of Culicoides or blackflies, invading chickens through their bites or blood-sucking, parasitizing in red blood cells and monocytes and starting asexual reproduction, causing chicken disease.
The incubation period of the disease is 6 to 10 days, and it is found that 1 to 2 days after symptoms can cause death. The morbidity and mortality of chicks aged 3 to 6 weeks are higher, and the mortality rate of breeding and laying hens is lower, but the egg production rate of laying hens after infection is greatly reduced, and the serious cases are reduced by more than 50%.
2. clinical symptoms
The main symptoms are the color of cockscomb and meat droop, pale, decreased egg production rate, soft feet and green thin feces. Loss of appetite or waste, loose feathers, emaciation and weakness of the body, often lying on the ground, followed by sporadic deaths, with a daily mortality rate of 1% ~ 2%. Most sick chickens convulse and convulsion before and after death, and some chickens have mucus or bleeding from the mouth and nose before and after death. About 10% ~ 20% of the chickens in the flock show pale crowns and meat, sometimes pale roots and yellow or white upper parts. The laying rate of laying hens dropped sharply, and there were red particles on the soft shell eggs and thin skin egg shells. Some sick chickens can be found diarrhea, discharge green or yellow-green loose stool, often bloody stool. Some dead chickens shed blood or sputum with blood.
3. pathological anatomy
The blood of sick chickens is thin, light in color and not easy to coagulate. Muscle color is pale, chest and leg muscles, pancreas, mesentery, intestinal canal outer surface, heart, liver, spleen surface and abdominal subcutaneous fat surface have many miliary-sized hemorrhage or gray nodules, with obvious boundaries. Liver enlargement, sometimes white nodules, spleen enlargement 2~4 times, bleeding spots, gray nodules, and clear boundaries with surrounding tissues. Some dead chickens have blood clots or yellow turbid ascites in the abdominal cavity, obvious blood stasis in the lungs, blood-like mucus in the trachea, enlarged and bleeding in the kidneys, and bleeding spots and gray white nodules in the myocardium. Sick chicken some visible tubal mucosa with red bleeding papules.
4. preventive measures
The prevention of white crown disease is the key to cut off the transmission route. It is suggested that during the epidemic season, chicken farmers can spray drugs with less toxicity to chickens, such as permethrin or malathion, inside and outside the chicken house and on screen windows to kill mosquitoes. Remove weeds around the chicken house, smooth the stinking sewage breeding ditch, and keep the manure away from the chicken house to reduce mosquito breeding and cut off the transmission route.
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