Epidemiology of avian influenza in wild aquatic birds in a biosecurity hotspot, North Queensland, Australia.

Migratory birds may introduce highly pathogenic H5N1 avian influenza from Southeast Asia into Australia via North Queensland, a key stopover along the East Asian-Australasian Flyway, with severe consequences for trade and human health. A 3-year repeated cross sectional study on the epidemiology of avian influenza in Australian nomadic wild aquatic birds was conducted in this potential biosecurity hotspot using molecular and serological techniques. Avian influenza virus subtypes H6 and H9 were commonly present in the studied population. It is likely that one of the H6 viruses was newly introduced through migratory birds confirming the perceived biosecurity risk. The matrix gene of another H6 virus was similar to the Australian H7 subtypes, which suggests the reassortment of a previously introduced H6 and local viruses. Similarly, a H9 subtype had a matrix gene similar to that found in Asian H9 viruses suggesting reassortment of viruses originated from Australia and Asia. Whilst H5N1 was not found, the serological study demonstrated a constant circulation of the H5 subtype in the sampled birds. The odds of being reactive for avian influenza viral antibodies were 13.1(95% CI: 5.9-28.9) for Pacific Black Ducks over Plumed Whistling Ducks, highlighting that some species of waterfowl pose a greater biosecurity risk. Antibody titres were slightly higher during warm wet compared with warm dry weather. Routine surveillance programmes should be established to monitor the introduction of avian influenza viruses from Asia and the interactions of the introduced viruses with resident viruses in order to better detect emerging pathogens in aquatic birds of North Queensland. Surveillance should be targeted towards highly susceptible species such as the Pacific Black Duck and carried out during favourable environmental conditions for viral transmission such as the wet season in northern Australia.

Risk factors for H7 and H9 infection in commercial poultry farm workers in provinces within Pakistan.

A cross sectional survey was conducted involving 354 farm poultry workers on 85 randomly selected commercial poultry farms in high density poultry farm areas in Pakistan to estimate the sero-prevalence of H5, H7 and H9 and to identify the potential risk factors for infection with the avian influenza virus. A haemagglutination inhibition test titre at 1:160 dilution was considered positive, based on WHO guidelines. The estimated sero-prevalence was 0% for H5, 21.2% for H7 and 47.8% for H9. Based on a generalized linear mixed model, the significant risk factors for H7 infection were area, type of farm and age of poultry worker. Risk of infection increased with the age of poultry workers. Compared with broiler farms, breeder farms presented a greater risk of infection (odds ratio [OR]=3.8, 95% confidence interval [CI]: 1.4, 10.1). Compared with the combined Khyber Pakhtunkhwa Province and Federal area, North Punjab had higher observed biosecurity measures and presented a lesser risk of infection (OR=0.3, 95% CI 0.1, 0.9). Biosecurity should therefore be enhanced (especially in breeder farms) to reduce the occupational risks in poultry farm workers and to decrease the risk of emergent human-adapted strains of AI H7 and H9 viruses.

Molecular epidemiology of influenza A (H5N1) viruses, Bangladesh, 2007-2011.

To investigate the origins, evolution and patterns of spread of HPAI H5N1 outbreaks in Bangladesh, we performed a phylogenetic reconstruction analysis using Bayesian methods. The analysis was conducted using 81 hemagglutinin (HA) gene sequences from the H5N1 viruses isolated in Bangladesh from 2007 to 2011, together with 264 publicly available HA sequences of clade 2.2, 2.3.2 and 2.3.4 retrieved from GenBank. Our study provides evidence that clade 2.2.2 viruses that caused outbreaks in Bangladesh were lineages independent from the viruses introduced earlier into India. Furthermore, the Bangladesh clade 2.2.2 descendents subsequently spread to India and Bhutan. This has implications for avian influenza control in southern Asia suggesting multiple routes of entry of the virus including one pathway that spread to neighboring countries via Bangladesh.