Isolation of Highly Pathogenic Avian Influenza H5N1 from Table Eggs After Vaccinal Break in Commercial Layer Flock

Abstract

In May 2009, during routine monitoring of a commercial layer flock of about 87,000 birds kept in cages in 4 different houses that had been vaccinated 3 times with an inactivated H5N1 vaccine at weeks 1, 7, and 16, highly pathogenic avian influenza (HPAI) virus of subtype H5N1 was isolated and detected by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) in tracheal and cloacal swabs collected from houses 3 and 4; 7 days after onset of clinical signs, there was an increase in mortality accompanied by a decrease in egg production and egg quality. In addition, using RT-PCR, the viral RNA could be detected from albumin and eggshell as well. Seven days after the onset of the clinical signs, the hemagglutination inhibition (HI) titers in the affected houses were 3.2 and 1.9 log2. In the other two houses, there were no clinical signs, and all tested samples were negative using virus isolation and real-time RT-PCR. The HI titers were 6.6 and 7.0 log2 in nonaffected houses. The isolated virus from egg albumin showed high nucleotides and amino-acid identities and clustered with viruses from recently H5N1-confirmed human infections and poultry from different places in Egypt. Moreover, several amino-acid substitutions of viral H5 protein were observed. The vaccinal break seems to be associated with immune escape mutants and/or improper vaccination. The role of contaminated eggs as a source of infection and as a vehicle for spread of the virus should be considered in area with avian influenza outbreaks.

A current review of avian influenza in pigeons and doves (Columbidae)

“…Despite the fact that several experimental studies and reports of natural infections prove that vertical transmission occurs in gallinaceous poultry (Cappucci et al, 1985;Bean et al, 1985;Kilany et al, 2010;Promkuntod et al, 2006;Pillai et al, 2010), there is no evidence to suggest that this occurs in columbids, and no experimental infections to investigate transmission of AIV in pigeon or dove eggs are documented. This is a topic that requires experimental investigation for a conclusion, emphasized by the observation of mild sporadic microscopic lesions in the ovarial thecal epithelial cells of H5N1 inoculated rock pigeons (Brown et al, 2009).…”

Comparison of the effectiveness of rHVT-H5, inactivated H5 and rHVT-H5 with inactivated H5 prime/boost vaccination regimes in commercial broiler chickens carrying MDAs against HPAI H5N1 clade 2.2.1 virus

“…Many HPAI vaccination breaks have been reported in commercial broiler, layer and breeder flocks Kilany et al, 2010Kilany et al, , 2013. These vaccination breaks happened as a result of the sub-optimal immune response in the vaccinated flocks which favours viral mutation and antigenic drift of field viruses from the vaccine strain Cattoli et al, 2011;Grund et al, 2011;Abdelwhab et al, 2012a).…”

High-Pathogenicity Avian Influenza Virus in the Reproductive Tract of Chickens

“…7 Although infection by low-pathogenicity AIV in domestic poultry can cause subclinical disease or mild respiratory signs with decreased egg production, infection with high-pathogenicity AIV (HPAIV) has been associated with severe systemic disease and accompanied by high mortality rates. 7 HPAIV replicates systemically in chickens, 3,4,6,7 and virus isolation has been reported to occur from the eggshell surface as well as within the egg yolk and albumin after experimental infection. 9 The presence of virus in the egg components and the decrease in egg production described in outbreaks of HPAIV in poultry [4][5][6] suggest that the virus can successfully replicate in the reproductive tract of affected individuals.…”

“…7 HPAIV replicates systemically in chickens, 3,4,6,7 and virus isolation has been reported to occur from the eggshell surface as well as within the egg yolk and albumin after experimental infection. 9 The presence of virus in the egg components and the decrease in egg production described in outbreaks of HPAIV in poultry [4][5][6] suggest that the virus can successfully replicate in the reproductive tract of affected individuals. However, very little is known regarding the pathobiology of HPAIV infection in the reproductive tract of chickens.…”