SUMMARY Respiratory infections are a common cause for increased mortality rates in poultry worldwide. To improve intervention strategies, circulating pathogens have to be identified and further characterized. Because of the lack of diagnostic tools, it was not known what pathogens contribute to the high mortality rates in association with respiratory disease in Algeria. Our objective was to determine if primary pathogens including Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), avian influenza virus (AIV), infectious bronchitis virus (IBV), and avian metapneumovirus (aMPV), known to be present in neighboring countries, can also be detected in Algerian chicken and turkey flocks. Results demonstrate the circulation of the investigated pathogens in Algerian poultry flocks as multi-infections. Phylogenetic characterization of the Algerian IBV strains confirmed the circulation of nephropathogenic viruses that are different from the strains isolated in neighboring countries. This could suggest the exis... RESUMEN Reporte de caso- La co-infección con múltiples patógenos respiratorios contribuye al aumento de la mortalidad en parvadas avícolas en Argelia. Las infecciones respiratorias son una causa común para el aumento de las tasas de mortalidad en las aves comerciales en todo el mundo. Para mejorar las estrategias de intervención, se tienen que identificar y caracterizar adecuadamente los agentes patógenos circulantes. Debido a la falta de herramientas de diagnóstico, se desconocía qué patógenos contribuyen con las altas tasas de mortalidad asociada con enfermedades respiratorias en Argelia. Nuestro objetivo fue determinar si los patógenos primarios incluyendo Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), el virus de la influenza aviar (AIV), el virus de la bronquitis infecciosa (IBV) y el metapneumovirus aviar (aMPV), que se conoce están presentes en los países vecinos, también se pueden detectar en parvadas de pollo y pavo en Argelia. Los resultados demuestran que los patógenos investigados en...

The chicken represents a valuable model for research in the area of immunology, infectious diseases as well as developmental biology. Although it was the first livestock species to have its genome sequenced, there was no reverse genetic technology available to help understanding specific gene functions. Recently, homologous recombination was used to knockout the chicken immunoglobulin genes. Subsequent studies using immunoglobulin knockout birds helped to understand different aspects related to B cell development and antibody production. Furthermore, the latest advances in the field of genome editing including the CRISPR/Cas9 system allowed the introduction of site specific gene modifications in various animal species. Thus, it may provide a powerful tool for the generation of genetically modified chickens carrying resistance for certain pathogens. This was previously demonstrated by targeting the Trp38 region which was shown to be effective in the control of avian leukosis virus in chicken DF-1 cells. Herein we review the current and future prospects of gene editing and how it possibly contributes to the development of resistant chickens against infectious diseases.

Significance: Genetically modified animals are crucial for functional studies and translational biomedical research. However, the generation of genome-edited large animals is time consuming and inefficient. Here, we report the generation of transgenic pigs and chickens that ubiquitously express Cas9 nuclease. The functionality of Cas9 was demonstrated for different target genes, a variety of cell types, and in vivo for the heart and the developing brain. Genome editing can now easily be carried out in vivo in specific organs or tissues without the need to generate germline-modified animals. These Cas9 transgenic animals provide an innovative and efficient resource for in vivo genome editing in biomedical and agricultural sciences.

Avian metapneumovirus (aMPV) is a pathogen with worldwide distribution, which can cause high economic losses in infected poultry. aMPV mainly causes infection of the upper respiratory tract in both chickens and turkeys, although turkeys seem to be more susceptible. Little is known about virus–host interactions at epithelial surfaces after aMPV infection. Tracheal organ cultures (TOC) are a suitable model to investigate virus–host interaction in the respiratory epithelium. Therefore, we investigated virus replication rates and lesion development in chicken and turkey TOC after infection with a virulent aMPV subtype A strain. Aspects of the innate immune response, such as interferon-α and inducible nitric oxide synthase mRNA expression, as well as virus-induced apoptosis were determined. The aMPV-replication rate was higher in turkey (TTOC) compared to chicken TOC (CTOC) (P < 0.05), providing circumstantial evidence that indeed turkeys may be more susceptible. The interferon-α response was down-regulated from 2 to 144 hours post infection in both species compared to virus-free controls (P < 0.05); this was more significant for CTOC than TTOC. Inducible nitric oxide synthase expression was significantly up-regulated in aMPV-A-infected TTOC and CTOC compared to virus-free controls (P < 0.05). However, the results suggest that NO may play a different role in aMPV pathogenesis between turkeys and chickens as indicated by differences in apoptosis rate and lesion development between species. Overall, our study reveals differences in innate immune response regulation and therefore may explain differences in aMPV – A replication rates between infected TTOC and CTOC, which subsequently lead to more severe clinical signs and a higher rate of secondary infections in turkeys.

Genome editing technology provides new possibilities for animal breeding and aid in understanding host-pathogen interactions. In poultry, retroviruses display one of the most difficult pathogens to control by conventional strategies such as vaccinations. Avian leukosis virus subgroup J (ALV-J) is an oncogenic, immunosuppressive retrovirus that causes myeloid leukosis and other tumors in chickens. Severe economic losses caused by ALV-J remain an unsolved problem in many parts of the world due to inefficient eradication strategies and lack of effective vaccines. ALV-J attachment and entry are mediated through the specific receptor, chicken Na⁺/H⁺ exchanger type 1 (chNHE1). The non-conserved amino acid tryptophan 38 (W38) in chNHE1 is crucial for virus entry, making it a favorable target for the introduction of disease resistance. In this study, we obtained ALV-J-resistance in a commercial chicken line by precise deletion of chNHE1 W38, utilizing the CRISPR/Cas9-system in combination with homology directed repair. The genetic modification completely protected cells from infection with a subgroup J retrovirus. W38 deletion did neither have a negative effect on the development nor on the general health condition of the gene edited chickens. Overall, the generation of ALV-J-resistant birds by precise gene editing demonstrates the immense potential of this approach as an alternative disease control strategy in poultry.