Affected birds show depression and pallor. The bursa of Fabricius and thymus are smaller than normal and the bone marrow of the long bones is pale, appearing ochre colored. There is no effective treatment for the prevention or cure of the disease.
Etiology:
The anemia virus of the chicken (VAP) is about 25 nm, is a virus icosaédrico, without capsule, with a single-stranded circular DNA.
The proposed classification for VAP is a new family of viruses called the Circoviridae.
There are antibodies against VAP in chickens worldwide, and this disease has been described in most of the countries that have a poultry industry. It is unknown whether VAP infects other birds besides chickens.
Transmission:
VAP is transmitted horizontally by direct contact or contaminated fomites (fecal/oral route) and vertically through embryonated eggs.
The majority of the breeding farms are infected and develop antibodies against the VAP before you begin to lay fertile eggs.
If groups of seronegative breeding birds are infected, VAP will be transmitted vertically and during the viremia period (1 to 3 weeks) of the hen, infesting the chicks.
The proportion of vertically infected chicks is less than 5%, and these chicks quickly infect the rest of the susceptible animals through horizontal transmission. If the hens are seropositive, the antibodies passed on by the mother usually protect the offspring against the disease, but not against infection.
Chicks <1 week of age with no VAP antibodies can become infected and develop the disease.
The resistance by the age of the disease (but not infection) starts in the first week and complete 2 weeks after opening the hatch.
However, the protective effects of maternal antibodies and age-related resistance can be overcome by co-infection of VAP with immunosuppressive agents, such as infectious bursal disease virus (p. 2164), Marek’s disease herpesvirus (p. 2176), and reticuloendotheliosis virus (p. 2180).
Have antibodies against VAP, many groups of chickens specifically free of microorganisms.
You have not described the spread of the infection embryos or cell cultures from vaccines and biological agents contaminated.
When inoculated the VAP intramuscularly into chickens sensitive from 1 day of life, the viremia appears in 24 hours.
The virus can remain in most organs and in rectal contents for up to 35 days after inoculation.
The main sites for the replication of the VAP are the precursors of T-lymphocytes from the thymus cortex and the hemocitoblastos of the bone marrow.
Anemia results from the destruction of these cells.
The infection VAP has adverse effects on the response of proliferation of the lymphocytes of the spleen and the production of the growth factor of T cells and interferon on the part of the splenocytes. In addition, the VAP modified negatively some functional properties of macrophages.
You can watch neutralizing antibodies to 21 days after infection and the clinical parameters, hematological, and pathological return to normal 35 days after infection.
Clinical symptoms and lesions:
When chickens adults seronegative se infectan con VAP, no se producen síntomas de enfermedad ni efectos adversos sobre la producción de huevos.
However, the clinical disease is manifested in the progeny of 12 to 17 days after hatching and persists until you interrupt vertical transmission of the virus. The chickens have anorexia, lethargy, depression, and pallor.
The hematocrit is decreased (in chicks, anemia is defined as a hematocrit of 50%.
The organs are pale and the size of the thymus and the bursa of Fabricius is small. The bone marrow is pale or yellowish.
There may be hemorrhage in the skin or under it, in the skeletal muscle and other organs. Histologically, we observed a significant reduction of the populations of lymphoid cells in lymphoid organs primary and secondary.
The granulocyte and erythrocyte compartments of the bone marrow are atrophic or hypoplastic.
Diagnosis:
The preliminary diagnosis is based on history, symptoms, and the macroscopic findings and pathology.
The confirmation requires the detection of the antigens of the virus or the virus DNA in the thymus or the bone marrow.
Can also be done by isolation of the virus, but this technique is slow and high economic cost. To isolate the VAP, the laboratories must maintain crops MOCC-MSB-1 (a cell line lymphoblastic from the tumor of the Marek's disease) or have chicks sensitive of a day in the life (with results negative for antigens and antibodies) or chicken embryos.
Marketing:
An ELISA test is currently available that can detect the presence of serum antibodies against VAP; this test can be used to identify breeding flocks in which laying hens are seronegative and to monitor the vaccine’s efficacy.
Treatment:
There is No specific treatment. Secondary bacterial infections can be treated with antibiotics. In EE. UU.
Still, there are no vaccines, although in Europe it is used a live vaccine that is administered in the drinking water.
In some areas, it has been moved by the garbage facilities are not contaminated and has been added to a homogenate of crude tissue from infected chickens to the drinking water, to ensure the infection and seroconversion of breeding before they begin to lay eggs and, thus, reduce the risk of transmission to eggs.
However, these procedures have some risks and may not be recommended without reservation. Due to the synergy between VAP AND other viruses suppress the immune system, the control of the latter is also important.
Prevention:
From the point of view sub-clinical, there is no known way to prevent these losses.
Horizontally acquired VAP infection by broiler progeny from seropositive parents is associated with significant impairment of economic performance. At present, there is no known way to prevent these losses.
