Introduction and enzootic of A/H5N1 in Egypt: Virus evolution, pathogenicity and vaccine efficacy ten years on.

It is almost a decade since the highly pathogenic H5N1 avian influenza virus (A/H5N1) of clade 2.2.1 was introduced to Egypt in 2005, most likely, via wild birds; marking the longest endemic status of influenza viruses in poultry outside Asia. The endemic A/H5N1 in Egypt still compromises the poultry industry, poses serious hazards to public health and threatens to become potentially pandemic. The control strategies adopted for A/H5N1 in Egyptian poultry using diverse vaccines in commercialized poultry neither eliminated the virus nor did they decrease its evolutionary rate. Several virus clades have evolved, a few of them disappeared and others prevailed. Disparate evolutionary traits in both birds and humans were manifested by accumulation of clade-specific mutations across viral genomes driven by a variety of selection pressures. Viruses in vaccinated poultry populations displayed higher mutation rates at the immunogenic epitopes, promoting viral escape and reducing vaccine efficiency. On the other hand, viruses isolated from humans displayed changes in the receptor binding domain, which increased the viral affinity to bind to human-type glycan receptors. Moreover, viral pathogenicity exhibited several patterns in different hosts. This review aims to provide an overview of the viral evolution, pathogenicity and vaccine efficacy of A/H5N1 in Egypt during the last ten years.

Infection and cross-protection studies of winter dysentery and calf diarrhea bovine coronavirus strains in colostrum-deprived and gnotobiotic calves.

OBJECTIVE: To investigate in vitro antigenic relations, in vivo cross-protection, and isotype antibody responses to a winter dysentery (WD) and calf diarrhea strain of bovine coronavirus (BCV). DESIGN AND ANIMALS: Gnotobiotic and colostrum-deprived calves were inoculated oronasally with a WD (DBA) or a calf diarrhea (DB2) BCV, and were challenge exposed with the heterologous BCV. PROCEDURE: Nasal swab and feces specimens and blood samples were collected. Fecal and nasal specimens were assayed for BCV shedding by antigen-capture ELISA or immune electron microscopy. Bovine coronavirus antigens were detected in nasal epithelial cells by immunofluorescence. Antibody titers to BCV in serum were assayed by virus neutralization (VN), and BCV antibody isotype titers in feces and sera were quantitated by ELISA. RESULTS: All calves developed diarrhea and shed BCV nasally and in feces, then recovered and were protected from BCV-associated diarrhea after challenge exposure with the heterologous BCV. After challenge exposure with either strain, fecal shedding of DBA was detected in 1 of 4 calves and nasal shedding of DB2 was detected in 2 of 4 calves. Immunoglobulin M was the principal coproantibody to BCV early, followed predominantly by IgA. Immunoglobulin G1 coproantibody titers to BCV were low, but increased after challenge exposure. Immunoglobulin G1 antibodies were predominant in serum. After challenge exposure, all serum antibody isotype titers increased except IgG2. The VN antibody responses paralleled serum IgG1 antibody responses. CONCLUSIONS AND CLINICAL RELEVANCE: Immunoglobulin A coproantibodies at challenge exposure were associated with protection against diarrhea. Nasal shedding of BCV after challenge exposure confirmed field data documenting reinfection of the respiratory tract of cattle, suggesting that, in closed herds, respiratory tract infections constitute a source of BCV transmission to cows (WD) or young calves.

Isolation of coronaviruses antigenically indistinguishable from bovine coronavirus from wild ruminants with diarrhea.

Diarrheal feces from three sambar deer and one waterbuck in a wild animal habitat and one white-tailed deer on a wildlife farm in Ohio contained coronavirus particles which were agglutinated by antiserum to bovine coronavirus (BCV) in immune electron microscopy. Three coronavirus strains were isolated in human rectal tumor cells from the feces of the sambar and white-tailed deer and the waterbuck, respectively. Hemagglutination, receptor-destroying enzyme activity, indirect immunofluorescence, hemagglutination inhibition, virus neutralization, and Western blot (immunoblot) tests showed close biological and antigenic relationships among the isolates and with selected BCV strains. Gnotobiotic and colostrum-deprived calves inoculated with each of these isolates developed diarrhea and shed coronavirus in their feces and from their nasal passages. In a serological survey of coronavirus infections among wild deer, 8.7 and 6.6% of sera from mule deer in Wyoming and from white-tailed deer in Ohio, respectively, were seropositive against both of the isolates and selected BCV isolates by indirect immunofluorescence tests. These results confirm the existence of coronaviruses in wild ruminants and suggest that these species may harbor coronavirus strains transmissible to cattle.