Epidemiological Findings of Outbreaks of Disease Caused by Highly Pathogenic H5N1 Avian Influenza Virus in Poultry in Egypt During 2006
January 6, 2009
M. M. Aly, A. Arafa,A and M. K. Hassan
National Laboratory for Veterinary Quality Control on Poultry Production, P.O. Box 246-Dokki, Giza, Egypt 12618
Received 31 October 2007; Accepted and published ahead of print 1 February 2008
SUMMARY. This paper describes the first threats of H5N1 avian influenza outbreaks in Egypt recorded from February to
December 2006 in commercial and domestic poultry from different species and summarizes the major characteristics of the
outbreak. There were 1024 cases from different poultry species (rural and commercial chickens of different breeding types, turkeys,
ducks, geese, and quail) either in commercial breeding or in backyards from different locations in Egypt. All tested positive for the
H5N1 subtype. From these cases only 12 avian influenza A viruses were isolated and characterized from samples collected during
outbreaks. All isolates were characterized, and the data confirmed that the isolated viruses belong to highly pathogenic avian
influenza of subtype H5N1. Full hemagglutination gene (segment 4) sequencing was also done, and isolates were compared with
other strains from Russia, Africa, and the Middle East. The data revealed that all Egyptian strains were very closely related and
belonging to subclade 2.2 of the H5N1 virus of Eurasian origin, the same one circulating in the Middle East region and introduced
into Africa at the beginning of 2006. This study showed evidence of the wide spread of H5N1 virus infection in domestic poultry in
Egypt within a short time. The most obvious features of these outbreaks were severe clinical signs and high mortalities as well as
very rapid and widespread occurrence within the country in a very short time. The possible causes of its rapid spread and prospects
of disease control are discussed.
Infected chickens and turkeys usually showed cyanosis of comb and wattles (or snout), facial edema, conjunctivitis, subcutaneous hemorrhages in the shank, and diarrhea; nervous signs such as lack of coordination, head shaking, abnormal gait, loss of balance, and recumbency were also recorded. Mortality and morbidity were varied and commonly reached 100% within a few days, especially in layer flocks. Clinical signs in other species, especially in rural ducks, were less severe and usually accompanied with nervous signs and sudden death. Usually no clinical signs were seen in geese except sudden death. The only reported case from commercial quail was from meat of slaughtered birds from an infected farm, so the data on clinical signs were not reported. Sometimes there was no prominent lesion at post mortem because the birds died quickly before development of gross lesions.
However, in most cases a variety of types of congestion and hemorrhages were noticed. The internal organs (liver, spleen, kidneys, intestine) were hemorrhagic. Mild to severe hemorrhagic tracheitis was also recorded, and hemorrhages in the proventriculus and caecal tonsils were observed.
Clinical signs in other species, especially in rural ducks, were less severe and usually accompanied with nervous signs and sudden death. Usually no clinical signs were seen in geese except sudden death.
Sounds much like major waterfowl die offs in North America.
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