Use of immunohistochemistry (IHC) in the detection of Newcastle disease virus (NDV) in experimentally and naturally infected birds

The objective of the present study was to standardize an immunohistochemical reaction (IHC) for the diagnosis of Newcastle disease virus (NDV) in tissue samples. In order to achieve this aim, pigeons (Columba livia) and chicken (Gallus gallus) were experimentally infected with a pathogenic sample of NDV (São Joao do Meriti strain). The IHC reaction was standardized and tested in samples of lung, liver, spleen and trachea of the experimentally infected birds, and the results showed that from the 20 infected birds, 17 were positive for Newcastle disease antigen immunomarking in the trachea and 11 were positive in the spleen. NDV detection was not achieved in samples of lung and liver, and these tissues are not indicated in NDV detection in the present study.After that, the standardized technique was used in the detection of NDV in samples of trachea and spleen of 46 free-living birds which belonged to 11 different bird orders. The virus was detected in 24 individuals. The order Caprimulgiforme was the only one that did not show any positive animal. These NDV strains circulate in bird populations, generally without causing the disease, in a parasite vs. host balance. Outbreaks may occur when these free-living birds get in contact with commercial birds, with considerable losses to countries that raise and export poultry and poultry products. In conclusion, IHC is a diagnostic tool that may be used in locations that do not have biosafety levels for virus isolation, or that are even not able to perform molecular assays.