Avian influenza H5N1 virus infections in vaccinated commercial and backyard poultry in Egypt

Abstract

In this paper, we describe results from a high-pathogenic H5N1 avian influenza virus (AIV) surveillance program in previously H5-vaccinated commercial and family-backyard poultry flocks that was conducted from 2007 to 2008 by the Egyptian National Laboratory for Veterinary Quality Control on Poultry Production. The real-time reverse transcription PCR assay was used to detect the influenza A virus matrix gene and detection of the H5 and N1 subtypes was accomplished using a commercially available kit real-time reverse transcription PCR assay. The virus was detected in 35/3,610 (0.97%) and 27/8,682 (0.31%) of examined commercial poultry farms and 246/816 (30%) and 89/1,723 (5.2%) of backyard flocks in 2007 and 2008, respectively. Positive flocks were identified throughout the year, with the highest frequencies occurring during the winter months. Anti-H5 serum antibody titers in selected commercial poultry ranged from <2 (negative) to 9.6 log(2) when determined in the hemagglutination inhibition test using a H5 AIV antigen. In conclusion, despite the nationwide vaccination strategy of poultry in Egypt to combat H5N1 AIV, continuous circulation of the virus in vaccinated commercial and backyard poultry was reported and the efficacy of the vaccination using a challenge model with the current circulating field virus should be revised.

Role of vaccination-induced immunity and antigenic distance in the transmission dynamics of highly pathogenic avian influenza H5N1

“…These studies show that use of vaccines that are antigenically distant to the circulating strains led to lack of protection due to low HI titres against the challenge strains. Upon closer examination however, it can be seen (where the data are available) that even HI titres against the vaccine strains were low in these vaccination programmes, thus indicating that the vaccine had failed to induce immunity to begin with [20,37,38]. In addition, reports from the field have emerged in which it is shown that in some cases where vaccination against HPAI is applied nationwide, the population coverage is extremely low, thus allowing transmission to take place in a seemingly vaccinated population [12,14,20].…”

“…It may be speculated that the variant strain was selected after many passages in animals, since field vaccination was applied at the same time that transmission of the viruses continued [37].…”

Natural infection with highly pathogenic avian influenza virus H5N1 in domestic pigeons (Columba livia) in Egypt

“…In the present study, H5N1 virus was isolated and identified from respiratory samples of naturally infected pigeons in Sharkia Province, Egypt during 2011. Based on the phylogenetic analysis of the HA gene sequences, the virus clusters into group 2.2.1/C isolated from backyard birds, the live bird market and human Hafez et al, 2010). Since pigeons commonly reside with humans on farms in Egypt, their role as potential carriers for H5N1 virus should not be neglected.…”

Surveillance on Avian Influenza H5N1 and H9N2 Subtypes In Egypt 2012-2013

“…showed that AIV infections were detected in 35/3,610 (0.97%), 27/8,682 (0.31%) of examined commercial poultry farms in these years respectively [22]. Also Hassan [15] isolated two AIV isolates from 49 examined chicken farms (4%) in 2012 -2103.…”