Calogero Terregino

In October 2022, an outbreak in Europe of highly pathogenic avian influenza (HPAI) A(H5N1) in intensively farmed minks occurred in northwest Spain. A single mink farm hosting more than 50,000 minks was involved. The identified viruses belong to clade 2.3.4.4b, which is responsible of the ongoing epizootic in Europe. An uncommon mutation (T271A) in the PB2 gene with potential public health implications was found. Our investigations indicate onward mink transmission of the virus may have occurred in the affected farm.

Newcastle disease (ND) remains a constant threat to the poultry industry and is a limiting disease for poultry producers worldwide. The variety of clinical presentations and the emergence and spread of new genetic variants make recognition and diagnosis challenging. The current review details the pertinent features of the clinicopathologic disease in the main susceptible species, including chicken, turkey, duck, goose, pigeon, and other birds such as cormorants, psittacines, and canaries. Furthermore, the available and emerging laboratory diagnostic methodologies for the detection and typing of the virus are reviewed, including traditional techniques such as virus isolation and immunohistochemistry as well as rapid procedures based on molecular tools, such as real-time polymerase chain reaction, gene sequencing, and microarrays. The relevant genetic variability of ND viruses probably represents the major limitation in the validation and application of the current, advanced diagnostic molecular techniques. This underscores the importance of a multidisciplinary and comprehensive diagnostic approach, which should include, next to the new generation assays of the genomic era, the more traditional techniques such as histopathology, immunohistochemistry, and virus isolation.

The present paper reports of the development and validation of a control strategy for avian influenza infections in poultry. The "DIVA" (Differentiating Infected from Vaccinated Animals) strategy is based on the use of an inactivated oil emulsion vaccine containing the same haemagglutinin (H) subtype as the challenge virus, but a different neuraminidase (N). The possibility of using the heterologous N subtype, to differentiate between vaccinated and naturally infected birds, was investigated through the development of an "ad hoc" serological test based on the detection of specific anti-N1 antibodies. This was achieved using a baculovirus expressing a recombinant N1 protein. The A/ck/Pakistan/H7N3 virus was used as a vaccine and birds were challenged with the HPAI A/ty/Italy/4580/V99/H7N1 strain. The homologous H group ensured a clinical protection of 93% regardless of the vaccination scheme used, and was able to prevent viraemia and muscle colonization in the clinically healthy challenged birds. However, it was not able to prevent viral shedding. The "ad hoc" serological assay was developed as an indirect immunofluorescence test, and was validated using 608 field sera, and showed an "almost perfect agreement" (Kappa value) with the HI test, with relative sensitivity and specificity values of 98.1 and 95.7, respectively. The results of the present investigation suggest that the "DIVA" control strategy may represent a tool for the control of avian influenza infections in poultry.