Interference between avian corona and influenza viruses: The role of the epithelial architecture of the chicken trachea.

Respiratory viral infections are among the major causes of disease in poultry. While viral dual infections are known to occur, viral interference in chicken airways is mechanistically hardly understood. The effects of infectious bronchitis virus (IBV) infection on tissue morphology, sialic acid (sia) expression and susceptibility of the chicken trachea for superinfection with IBV or avian influenza virus (AIV) were studied.

Wild and domestic animals variably display Neu5Ac and Neu5Gc sialic acids.

Sialic acids are used as a receptor by several viruses and variations in the linkage type or C-5 modifications affect the binding properties. A species barrier for multiple viruses is present due to α2,3- or α2,6-linked sialic acids. The C-5 position of the sialic acid can be modified to form N-acetylneuraminic acid (Neu5Ac) or N-glycolylneuraminic acid (Neu5Gc), which acts as a determinant for host susceptibility for pathogens such as influenza A virus, rotavirus, and transmissible gastroenteritis coronavirus.

Influenza D binding properties vary amongst the two major virus clades and wildlife species.

The influenza D virus (IDV) uses a trimeric hemagglutinin-esterase fusion protein (HEF) for attachment to 9-O-acetylated sialic acid receptors on the cell surface of host species. So far research has revealed that farm animals such as cattle, domestic pigs, goats, sheep and horses contain the necessary receptors on the epithelial surface of the respiratory tract to accommodate binding of the IDV HEF protein of both worldwide clades D/Oklahoma (D/OK) and D/Oklahoma/660 (D/660). More recently, seroprevalence studies have identified IDV-seropositive wildlife such as wild boar, deer, dromedaries, and small ruminants.

Pathology and Pathogenesis of Eurasian Blackbirds () Naturally Infected with Usutu Virus.

The Usutu virus (USUV) is a mosquito-borne zoonotic flavivirus. Despite its continuous circulation in Europe, knowledge on the pathology, cellular and tissue tropism and pathogenetic potential of different circulating viral lineages is still fragmentary. Here, macroscopic and microscopic evaluations are performed in association with the study of cell and tissue tropism and comparison of lesion severity of two circulating virus lineages (Europe 3; Africa 3) in 160 Eurasian blackbirds (Turdus merula) in the Netherlands.

The contribution of the immune response to enhanced colibacillosis upon preceding viral respiratory infection in broiler chicken in a dual infection model.

Colibacillosis in chickens caused by avian pathogenic Escherichia coli (APEC) is known to be aggravated by preceding infections with infectious bronchitis virus (IBV), Newcastle disease virus (NDV) and avian metapneumovirus (aMPV). The mechanism behind these virus-induced predispositions for secondary bacterial infections is poorly understood. Here we set out to investigate the immunopathogenesis of enhanced respiratory colibacillosis after preceding infections with these three viruses.