Epidemiology, Production Losses, and Control Measures Associated with an Outbreak of Avian Influenza Subtype H7N2 in Pennsylvania (1996–98)

Abstract

An outbreak of H7N2 low-pathogenicity (LP) avian influenza (AI) occurred in a two-county area in Pennsylvania from December of 1996 through April of 1998. The outbreak resulted in infection of 2,623,116 commercial birds on 25 premises encompassing 47 flocks. Twenty-one (one premise with infection twice) of the twenty-five infected premises housed egg-laying chickens and one premise each had turkeys, layer pullets, quail, and a mixed backyard dealer flock. Despite dose proximity of infected flocks to commercial broiler flocks, no infected broilers were identified. Experimentally, when market age broilers were placed on an influenza-infected premise they seroconverted and developed oviduct lesions. The outbreak was believed to have originated from two separate introductions into commercial layer flocks from premises and by individuals dealing in sales of live fowl in the metropolitan New York and New Jersey live-bird markets. Source flocks for these markets are primarily in the northeast and mid-Atlantic areas, including Pennsylvania. Mixed fowl sold include ducks, geese, guinea hens, quail, chukar partridges, and a variety of chickens grown on perhaps hundreds of small farms. Infections with the H7N2 AI virus were associated with variable morbidity and temporary decreases in egg production ranging from 1.6% to 29.1% in commercial egg-laying chickens. Egg production losses averaged 4.0 weeks duration. Mortality ranged from 1.5 to 18.3 times normal (mean of 4.3 times normal). Duration of mortality ranged from 2 to 13 weeks (average of 3.9 weeks) in flocks not depopulated. Lesions observed were primarily oviducts filled with a mucous and white gelatinous exudates and atypical egg yolk peritonitis. Quarantine of premises and complete depopulation were the early measures employed in control of this outbreak. Epidemiological studies suggested that depopulation furthered the spread of influenza to nearby flocks. Thereafter, later control measures included quarantine, strict biosecurity, and controlled marketing of products.

Molecular characterization and epidemiology of the highly pathogenic avian influenza H5N1 in Nigeria

“…Field data which are supported by these phylogenetic analyses indicated that outbreaks caused by this group of viruses were found in locations as distant as 954 km from an infected LBM infection. Previous studies have similarly confirmed the role of wet markets, LBMs and movement of poultry and poultry products without recourse to biosecurity in the viral ecology and spread of avian influenza and other viruses [14][15][16].…”

Identification of risk factors associated with highly pathogenic avian influenza H5N1 virus infection in poultry farms, in Nigeria during the epidemic of 2006–2007

“…Sales of live poultry (a common practice in Nigeria and most parts of Africa) are associated with rapid dissemination of infections through slaughter, evisceration, improper disposal of visceral, flying feathers and contaminated equipment used by farmers (Henzler et al, 2003).…”

“…Although previous studies have provided an epidemiologic framework for investigation of risk factors for HPAI H5N1 virus in poultry (Henzler et al, 2003;Thomas et al, 2005;Bouma et al, 2009;Busani et al, 2009), study findings and proposed prevention strategies may not apply to the conditions of Nigeria in view of variations in climatic conditions, poultry practices, and the socioeconomic and cultural orientations of agricultural populations in this geographic region. The aims of this study were to investigate and identify risk factors for HPAI H5N1 virus infection in poultry farms in Nigeria during 2006-2007.…”

Development and Evaluation of an Influenza Virus Subtype H7N2 Vaccine Candidate for Pandemic Preparedness

“…Viruses of the H5 and H7 subtypes have caused outbreaks in commercial poultry in the Americas (1,7,11,16,17). These viruses constitute a lineage that is genetically and antigenically distinct from the European and Asian lineages which currently circulate in that hemisphere.…”