in poultry rotavirus is a relatively new virus, first reported in 1977, triggered by the wheel Virus disease usually causes diarrhea. The virus does not spread between species, so rotavirus from poultry has no effect on human health.
Rotavirus belongs reoviridae only infect vertebrates, through fecal – oral route propagation. Rotavirus is a double-stranded RNA virus. Under an electron microscope, they look like a wheel with a wider hub and shorter spokes. Rotaviruses are classified into typical viruses and atypical viruses. In terms of antigenicity, they are usually distinguished by letters. Groups A, D, F and G of rotavirus have been found in poultry. Group A rotaviruses infect mammals and poultry, while group D, F and G rotaviruses only infect poultry.
1.2 rotavirus enteritis
rotavirus enteritis in common in the 6-week-old chicks, such as chickens, turkeys or pheasant young, young partridges, quail and young ducklings like. Various investigations of chicks with diarrhea show that a considerable part of chicks are infected with rotavirus. Infected poultry excrete a large amount of virus through feces, which is easy to spread horizontally. Some studies have shown that the virus can spread vertically. Studies have shown that small beetles can carry rotavirus. Older poultry have poor resistance to the virus or even lose resistance, so aging poultry sometimes recurs. The incubation period of the disease is generally 2 to 5 days. The infected poultry has drained feces and the anus is dirty. The mortality rate in a severe outbreak of the disease in small turkeys may be only 5%, but the incidence is very high.
1.3 Necropsy results
At necropsy, it is usually seen that there are watery contents in the small intestine and cecum, which may contain a lot of air bubbles. Secondly, it can be seen that sick chickens are dehydrated, grow slowly, anus is dirty, pecking anus, and there are litter hard shells on toes or feet. Rotavirus disease is similar to intestinal coccidiosis, with different strains colonizing in different parts of the small intestine. At the time of diagnosis, it is necessary to observe the intestinal contents or the presence of rotavirus in the stool through an electron microscope to confirm the diagnosis.
of rotavirus disease there is no effective treatment, and no commercial vaccine available. The best treatment is to strengthen the management of the environment, littering and feeding, and treat the symptoms accordingly.
2 duck hepatitis virus type Ⅰ
duck hepatitis virus type Ⅰ fatal disease in a rapid spread of the ducklings. The disease is caused by duck viral hepatitis virus, and the main feature is hepatitis. The disease was first discovered in 1945, but it was not until an outbreak occurred on Long Island, New York, that the pathogen was identified as duck viral hepatitis 1 virus. In that outbreak, more than 70 farms were severely affected. Ducklings of 2 to 3 weeks old are susceptible, and the mortality rate in some farms exceeds 95%.
duck hepatitis virus type Ⅰ virus is a small RNA virus. This virus has strong resistance and can survive in the environment for 2 to 3 months and 40 days in feces. The virus can survive longer at low temperatures, for example, the virus can survive 2 years or more at 4°C.
duck hepatitis virus type Ⅰ occurs mainly in ducklings, duck of the same adult ducks are not affected. In the wild, duck viral hepatitis I can spread rapidly among ducks with high mortality. The virus does not spread through eggs. If the farm is clean and hygienic, ducklings hatched from eggs laid by infected breeders will not be infected with the disease. Infected ducklings will detox for several months after recovery. Wild birds have a certain effect on the spread of the disease, but there is no evidence that wild waterfowl are infected with the virus.
2.3 Clinical symptoms
The disease developed rapidly, and the ducklings died 3 to 4 days after the onset. Infected ducklings like to squat with half-closed eyes, then fall to the ground, their legs are cramped, and when they die, they have an antagonist (head tilted back). Ducklings usually die within 1 h after the first clinical symptoms appear. The morbidity and mortality of young ducklings is close to 100%, the morbidity and mortality of 1-3 week-old ducklings are 50% or lower, and the morbidity and mortality of 4-5 week-old ducklings is very low or no disease.
2.4 pathological changes
of the disease occurs mainly in the liver disease, liver enlargement with minor bleeding, surface discoloration. The spleen is enlarged, sometimes with mottling, and the kidneys are usually enlarged.
ducklings infected with duck hepatitis virus type Ⅰ after rehabilitation can produce a strong immune system. If the breeding ducks are infected, their immunity can allow the offspring to obtain passive or maternal immunity. However, the use of blood tests to diagnose acute outbreaks of the disease is not very useful, because the formation of antibodies takes time, and diagnostic results can usually be obtained by other methods.
3 fungal diseases
Some tissue invasion by fungi and damage can cause poultry disease. Avian aspergillosis is a good example of this type of disease. Aspergillosis in chicks or turkeys is usually related to litter such as rice husk and straw.
The most common pathogen is avian aspergillosis Aspergillus fumigatus (Aspergillus fumigatus), other Aspergillus, such as Aspergillus flavus and Aspergillus niger, sometimes causing animal disease. These fungi usually live in soil and can easily grow in organic matter (such as feed, litter, rice husk or straw) under warm and humid conditions. These fungi can also be found in environments similar to hatcheries, such as fungi can be isolated on ventilation ducts and damaged eggs. Fungi have a typical growth cycle and then form spores. Both stages prefer warm conditions, but the former prefers higher humidity, while the latter prefers slightly lower temperature.
Avian aspergillosis usually occurs in the first week after the chicks emerge. The chicks can be infected in the hatchery or immediately after being transferred to the farm. When old hens and turkeys are exposed to air with a large number of Aspergillus spores, Aspergillus pneumonia and air sacculitis can occur. For example, if there is a cornfield near the chicken house, dust will enter the chicken house through the combine harvester fan. Generally speaking, old chickens are more resistant to Aspergillus. In the hatchery, if the Aspergillus spores enter the air sacs of the breeding eggs through cracks or micro cracks in the eggshell, so-called “fungal air sacs” will be formed during the incubation process. In this case, a lot of fungi will grow in the air sacs of the hatched egg. If these eggs are broken, they may become a source of infection when the chicks emerge.
3.3 pathogenesis of
the Aspergillus spores are inhaled poultry, will remain in the respiratory tract and mucous membrane surface of the lungs, germination and growth. Local tissue reactions can cause granulomas or nodules. This infection can spread through the blood to deeper organs such as the brain, heart sac, kidney and bone marrow. A large number of lesions in the lower trachea or bronchi can cause respiratory distress and asphyxia. Chronic diseases can destroy the function of the heart, followed by ascites. This situation is mainly seen in turkeys.
3.4 clinical symptoms of
a symptom chicks or chickens infected with avian aspergillosis aging of respiratory distress, for chicks, hatched after the first 3 weeks there will be a biphasic death. Tolerant chickens usually show chronic respiratory symptoms and growth arrest. In chicks, the first stage of increased mortality (hatchery infection) occurs in the first 5 days after hatching.
incidence of erysipelas is characterized by the sudden death of poultry or occurrence of diarrhea and death characterized by a short illness. The disease is common in turkeys and is also seen in free-range chickens in some areas. The head of the sick turkey is cyanotic (purple) and the skin tumor is swollen. Sick duck webbed hyperemia. The mortality rate is 50%.
in addition to the above-mentioned skin lesions, diseased turkeys systemic congestion. Needle bleeding (peechia) is seen in the myocardium, heart fat, epicardium, mesenteric, gizzard inner membrane, liver, and other internal organs. If there is enteritis, the typical manifestation is intestinal catarrhal inflammation. In the case of acute sudden death, the chicken may not show any disease.
Chronic erysipelas often manifests as nutritional endocardial disease and fibrous septic arthritis.
based on clinical manifestations incidence of poultry, Isolation and identification of pathogens and pathological changes Erysipelothrix rhusiopathieae diagnose. Sick poultry may have a history of contact with sheep or pigs. Erysipelas erysipelas is an elongated gram-positive bacillus, which can be quickly identified by staining tissue smears. When cultivating Erysipelothrix erysipelas, the agar plate should be incubated for at least 2 days.
4.3 prevention and control of
health of the most important in the poultry field erysipelas have a history of keeping poultry house clean is essential. In addition, rodent prevention and anti-rodent work should be done. Most strains of Erysipelas erysipelas are sensitive to penicillin, erythromycin and clindamycin, and treatment with amoxicillin is usually effective. For turkeys, it is sometimes necessary to combine long-acting and quick-acting penicillin for injection.
in farm infection again, usually the turkey and scattered chicken inoculated with the bacteria or a live vaccine. For breeding turkeys, it is recommended to vaccinate every month, 2 servings (or more) each time. It should be noted that the bacterial vaccine will make the mycoplasma agglutination test false positive, so avoid blood testing for Mycoplasma gallisepticum or Mycoplasma turkey within 3 to 4 weeks after vaccination.