What Is Viral Arthritis?

Viral Arthritis is an important infectious disease in chickens caused by reovirus. The virus mainly attacks the synovial membrane, tendon sheath, and myocardium of the joint, causing swelling of the foot joints, inflammation of the tendon sheath, and subsequent rupture of the gastrocnemius tendon. Sick chickens are swollen and inflamed, have difficulty moving, limp or unwilling to move, have difficulty eating, and have stalled growth.

Chicken viral arthritis

Chicken viral arthritis (Viral Arthritis) is a

The feed utilization rate of chicken flocks has declined, and the elimination rate has increased, causing certain economic losses. Olson first reported the disease in 1957. Subsequently, the United States, Britain, Italy, the Netherlands, Japan, Hungary and other countries have successively reported cases of viral arthritis. From the mid-80s, I

The cause of viral arthritis is avian reovirus. The virus is basically the same as the reovirus in other animals. The virus particles have no capsule, are symmetrically arranged in icosahedron, have a diameter of about 75nm, and have a floating density in cesium chloride of 1.36 to 1.37 g / ml. Its genome consists of 10-segment double-stranded RNA.

Avian reovirus has a certain resistance to heat, and can tolerate 60 ° C for 8-10 hours. Not sensitive to ether. Resistant to H202, pH3, 2% Lysur, 3% formalin, etc. The virus can be inactivated with 70% ethanol and 0.5% organic iodine.

Reovirus can be grown in chicken embryos by inoculation of the yolk sac and chorioallantoic membrane (CAM). Inoculation through the yolk sac usually results in the death of chicken embryos 3 to 5 days after inoculation; inoculation through CAM usually results in the death of chicken embryos 7 to 8 days after inoculation. In addition to chicken embryos, Reov can grow in primary chicken embryo fibroblasts, liver, testis cells, and passage cells such as vero and BHK-21.

The lack of agglutination properties of red blood cells in many animals distinguishes Reov from other animals' reovirus. Reov strains share a common precipitation antigen, but the neutralizing antigen is obviously heterologous. Due to the different test methods used, the typing results of the strains are also different. Rosenberger et al. Believe that reovirus often starts with

Chicken reovirus exists widely in nature and can be isolated from many species of birds. But chickens and turkeys are the only animals known to cause arthritis by Reov. There are two ways in which the virus can spread in chickens: horizontally and vertically. Although data indicate that Reov can be transmitted vertically through breeding eggs, horizontal transmission is the main route of transmission of the disease. After the virus infects chickens, it first enters the blood after replication in the respiratory and digestive tracts, and appears after 24 to 48 hours.

Most field cases of this disease are recessive or chronic infections, which can only be determined through serological testing and virus isolation. In the case of acute infection, chickens show lameness, and some chickens are stunted. Lameness during chronic infection is more obvious, and a few sick chickens cannot move their sacroiliac joints. Sick chickens have decreased appetite and vitality, are reluctant to move, and sit on the joints, moving or reluctantly when driven, but the gait is unstable and then appears

1. Postmortem changes Swelling around the sacroiliac joints of the chicken, edema of the gastrocnemius tendon in the upper part of the joint can be seen, hyperemia or spotted bleeding is often found in the synovium, and the joint cavity contains pale yellow or bloody exudates. The output is purulent, similar to infectious synovitis lesions, which may be related to the secondary infection of certain bacteria. other

1. Initial diagnosis based on symptoms and lesions Although it is difficult to identify the symptoms of the disease, according to the characteristics of the symptoms and lesions, a preliminary diagnosis of the disease can be made in the clinic. The following points have diagnostic value:

(1) Sick chickens limp, and the sacroiliac joints swell.

(2) There is heterophage infiltration among myocardial fibers.

(3) In chickens with viral arthritis, some chickens often show dysplasia syndrome, sick chickens are pale, bone tungsten is incomplete, feather growth is abnormal, growth is retarded or growth stops.

2. Etiological diagnosis

(1) Isolation and identification of viruses: Isolation and identification of pathogens is the most accurate diagnostic method. Can be taken from swollen tendon sheaths, synovial fluid of the sacroiliac joint, trachea and bronchi, intestinal contents, spleen, etc.

There is currently no effective treatment for this disease, so prevention is the only way to control the disease. Due to the characteristics of the Reo virus and the high density of modern chickens, it is difficult to prevent flocks from being exposed to the virus. Therefore, vaccination is the most effective method to prevent chicken arthritis under current conditions. In order to prevent the epidemic, many kinds of attenuated vaccines and inactivated avian reovirus vaccines have been developed abroad, and corresponding immunization procedures have been developed. At present, attenuated vaccines applied abroad include the attenuated S-1133 attenuated by 72 generations of chicken embryos. They can drink water to immunize breeders at 30 or 10 to 17 weeks of age, and their offspring can resist oral challenge; the fully attenuated vaccine P100 Miao, this seedling is made by S-1133 strain passed 235 generations from chicken embryo, and then weakened by 100 generations of chicken embryo fibroblast culture. P-100 vaccine can be used for 1-day-old chicks, which can be subcutaneously inoculated. The immune chicks can resist the attack of homologous virus after 14 days. There is also a UMI-203 attenuated vaccine. Gai Miao has no pathogenicity to breeders of 8 to 18 weeks of age, but has strong virulence to chicks. The advantage of this vaccine is that the cross-immunity is stronger than that of S-1133 strain because of its wider antigenicity.

As chicks are most susceptible to the pathogenic Reo virus, and they do not have resistance to Reo virus until at least 2 weeks of age, providing immune protection to chicks should be the focus of epidemic prevention. Vaccination with weak live vaccines can effectively generate active immunity, and subcutaneous vaccination is generally used. However, when immunized with S-1133 attenuated vaccine and Marek's disease vaccine at the same time, S1133 will interfere with the immune effect of Marek's disease vaccine, so the two vaccines should be separated by more than 5 days. Reserve chickens without maternal antibodies can be immunized with live vaccines at the age of 6-8 days, and then boosted with live vaccines at 8 weeks of age. Inactivated vaccines are injected 2 to 3 weeks before the start of production, which generally allows chicks to Not infected for 3 weeks. This has proven to be an effective way to control chicken viral arthritis. Combining live vaccines with inactivated vaccines to immunize breeding flocks can achieve very good immune results. However, when using live vaccines, it should be noted that the toxicity of vaccine strains to chicks of different ages is different.

The general prevention method is to strengthen the sanitary management and regular disinfection of the house. Adopting the "all in and all out" feeding method, thoroughly cleaning and disinfecting the chicken house can prevent the infection of the virus left by the previous batch of infected chickens. Because the diseased chickens continuously detoxify for a long time, which is an important source of infection, the diseased chickens must be resolutely eliminated.