Detection and quantitation of fowl adenovirus genome by a real-time PCR assay

The purpose of the study was to develop a highly sensitive real-time polymerase chain reaction (PCR) assay to detect and quantitate fowl adenovirus (FAdV) DNA in chicken tissues, using FAdV-9 as a model. The assay had a dynamic range of 7 logs and minimum detection limit of 9.4 viral genome copies. It was shown to be highly specific, as tissues from uninfected chickens and other viral genomes, such as those of Marek's disease virus, fowlpox virus and infectious laryngotracheitis virus did not produce positive signal. The sensitivity of the real-time PCR was comparable with nested PCR and it was 100 times more sensitive than the conventional PCR. The assay was validated by testing DNA from tissues of chickens infected with FAdV-9 collected at different days post-infection. FAdV-9 DNA was detected in liver, bursa of Fabricius and cecal tonsil tissues in a range of 10(2)-10(7) copies per 100 ng of total DNA. High amounts of viral DNA were present in the cecal tonsils for a week after inoculation making this tissue an ideal sample source for the diagnosis of FAdV infection. This assay is an excellent research and diagnostic tool that provides high sensitivity, specificity and rapid post-PCR analyses.