Avian Influenza in the Year of the Rooster

Dr.Sali Bache, Pest IT Pty. Ltd.

Recent reports of the possibility of a pandemic (global outbreak) of bird flu resulting in the death of up to 150 million people have hit the headlines and provoked fear in the general community. Avian influenza is a zoonotic infection, transmitted from birds to humans. To date there are no confirmed cases where it has been contracted from human-to-human contact. Current likelihood of contraction is restricted to those that regularly interact with birds – no more so than Australian pest managers involved in bird control.

The H5N1 strain of bird flu has killed more than 60 people since late 2003. Because the H5 type of influenza is unusual in viruses that cause human flu the population has a very low immunity. Australia is to date free of this strain of bird flu. Actions Australia is taking include screening of airline passengers and patrols for migratory birds exhibiting disease symptoms in the north.

Neither the timing nor severity of the next pandemic can be predicted, though the present level of risk will not be easily diminished. Two of the three prerequisites for the start of a pandemic (a new virus to which the population has little or no immunity and lack of an effective vaccine) have been met. The third: the establishment of effective human-to-human transmission is not yet a reality. Several experts have stated that while the risk of this becoming a human disease is very real it is probably not immediate.

It has been long known that wild birds represent a traditional reservoir for avian influenza viruses worldwide. Unusually it appears that the currently circulating H5N1 strain is also highly pathogenic to wild migratory birds which are dying in large numbers. All birds are thought to be susceptible to infection though some species which are more resistant may be asymptomatic carriers. Of known susceptibility to the disease are quails, guinea fowl, ducks, geese, emus, ostriches, passerine birds (finches and sparrows), budgerigars, gulls, herons, crows, magpies and birds of prey. Avian influenza viruses normally infect only pigs and birds, but H5N1 is an exception, so far having infected humans as well as large felines.

To date almost all human cases have been in relation to people who have been closely associated with village or backyard poultry farming. Recommendations have been made for the installation of bird-proof facilities in these countries so as to prevent possible avian influenza transmission from wild and migratory birds. The primary approach in many areas has however been through the vaccination of poultry. Asian countries where H5N1 has been detected include Korea , Japan , Viet Nam , Thailand , Cambodia , Laos , Indonesia , Mongolia , China and Malaysia , as well as several in Eastern Europe . Influenza activity is likely to increase in Asia through the wet season of November to April.

Birds that survive infection can excrete the virus orally and in faeces for at least 10 days. Avian flu virus can survive on contaminated raw poultry, eggs or in faeces for as long as 35 days. Avian influenza viruses can survive on surfaces for several weeks and spread well in water. To contract it from birds at this stage “close contact” is needed. Importantly to the pest management industry, there is no evidence of any cases of H5N1 contraction by humans from non-poultry bird species. This may however be due in part to the fact that most human-bird interaction occurs primarily within a poultry farm environment.

Control of the disease in animals is the principle way to reduce opportunities for human infection. International bodies responsible for the issue all agree that the control of avian influenza infection in wild bird populations is not feasible, would not be effective and should not be attempted. Indeed the role of wild birds in the propagation, maintenance and dissemination of H5N1 remains poorly understood.

Largely because H5N1 has not yet been detected in Australia , there are no specific recommendations issued in regard to people who interact regularly and closely with birds. Indeed the Department of Health and Ageing states that “these industries do not need to take any additional precautions at present”. General recommendations from the US emphasize the importance of basic hygiene – washing hands in soap and water (20 seconds) and hand disinfectant procedures. Further suggested is the use of appropriate personal protection equipment including disposable gloves and disposable protective shoe covers or rubber/polyurethane gloves and boots that can be disinfected. Specifically recommended is the use of fit-tested disposable particulate respirators so as to ensure a tight seal. Proper discarding of disposable goods and careful washing of hands after disposal is also recommended.

General preventative measures should H5N1 reach Australian bird populations would likely include the vaccination of persons at high risk of exposure. No specific vaccine for H5N1 has to date been able to be developed so this would involve the use of existing vaccines effective against currently circulating human influenza strains. In addition exposed workers or suspected cases would be treated with anti-virals. Careful surveillance of those likely to have been exposed would be continued for at least one week as the incubation period in humans is though to be approximately 3-7 days. Symptoms include fever and cough, much like that of regular flu. Not all cases of H5N1 have typical flu symptom of a sore throat and runny nose and of greatest concern is severe respiratory distress.

The take home message is that at present there is a very low risk but a large amount remains unknown about avian influenza in particular the current strain. Regardless of H5N1, bird managers should as standard practice clean and disinfect all sites prior to the commencement of any bird work. Some degree of caution and vigilance in interactions with birds would be prudent.

Dr.Sali Bache is a Director of Pest IT Pty. Ltd. Dr Bache has a Bachelor of Science (hons) and a PhD in Public Policy and International Law.