Which diagnostic test would follow up after an initial virus isolation for ASF?

The correct answer is PCR, which stands for Polymerase Chain Reaction. This diagnostic test is used to detect and amplify the specific DNA or RNA sequences of the African Swine Fever (ASF) virus in a sample. Following an initial virus isolation, PCR serves as a highly sensitive and specific method to confirm the presence of the virus. It is particularly valuable for identifying the virus's genetic material, which can be critical in diagnosing ASF accurately and rapidly.

In contrast, histological examination focuses on the microscopic structure of tissues and may not provide direct evidence of the virus itself. Blood profiling and metabolic testing assess different physiological and biochemical parameters, which do not specifically target viral presence or confirm ASF. Therefore, PCR is the most appropriate follow-up diagnostic test after initial virus isolation for ASF, as it allows for a precise confirmation of the infection.