Physiological Changes in Chicken Embryos Inoculated with Drugs and Viruses Highlight the Need for More Standardisation of This Animal Model

Several works have been developed using the Gallus gallus embryo as an experimental model to study the toxicity of drugs and infections. Studies that seek to standardise the evaluated parameters are needed to better understand and identify the viability of chicken embryos (CE) as an experimental model. Therefore, we sought to verify whether macroscopic, histopathological, blood count, metabolites and/or enzymes changes and oxidative stress in CE of different ages are peculiar to the model. To achieve this goal, in ovo assays were performed injecting a virus ( Gammacoronavirus ) and two drugs (filgrastim and dexamethasone) that cause known changes in adult chickens and other animals. Embryo response to virus and drug challenges may not occur as expected for adult chickens and even different species. While macroscopic and microscopic damage was visible in the case of viral infections, the white blood cell count and inflammation biomarkers did not change. Filgrastim (FG) testing did not result in the expected effects for CE. On the other hand, with dexamethasone (DX), changes in blood parameters and biomarkers were inherent to the model and depended on the stage of CE development. Our work reinforces the importance of standardization and correct use of the model so that the results of infection, toxicity and pharmacokinetics are recorded.