Present situation and countermeasures for fowl adenovirus infections in chicken
2019
Avian adenovirus belonging to the genera Aviadenovirus, Siadenovirus, and Atadenovirus, in the family Adenoviridae, can infect several species of birds. Fowl adenovirus (FAdV) is the all-inclusive name of adenoviruses isolated from chickens. There are 5 species of FAdV in the genus Aviadenovirus and it has 12 serotypes, FAdV-1 to -11, including -8a and -8b. Fowl adenovirus infections have been reported with increasing incidence, mainly in broilers, since around 2010. The main types of such diseases include inclusion body hepatitis, adenoviral gizzard erosion, and hydropericardium syndrome. More recently, cases of chicken adenoviral splenomegaly associated with Siadenovirus infection have been reported. In addition, cases of transmissible viral proventriculitis, suspected to be caused by an unknown adenovirus, have also been reported. Fowl adenovirus is highly resistant to physicochemical treatment, spreads in poultry farms at high rates, and is transmitted by vertical and horizontal infections. This makes it difficult to diagnose and control FAdV. Fowl adenovirus infections should be comprehensively diagnosed based on incidence, symptoms, gross necropsy findings, histopathological findings, serological tests, and microbiological tests. As a countermeasure against FAdV infections, vaccines are practically applied in Europe, America, and parts of Asia, in addition to general hygiene measures. However, FAdV vaccine is not approved in Japan. Therefore, the countermeasure, 'acclimatization,' is carried out in some poultry farms. However, acclimatization has disadvantages such as uncertainty of efficacy and risk of transmission of other pathogens. This situation highlights the need for the development and field application of anti-FAdV vaccines.
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