Highlights of the FAO and OIE International Scientific Conference on Avian Influenza and Wild Birds
2006年5月30－31日

意大利罗马

May 30 - 31, 2006, Rome, Italy

Ward Hagemeijer
Introduction
At the end of the wild bird spring migration season 2006, more than 300 experts from around the world met to discuss the interface between avian influenza (AI), most notably highly pathogenic (HP) H5N1 or bird flu virus, and wild birds. The 2-day conference was sponsored by the Food and Agricultural Organization (FAO) of the United Nations and the World Organisation for Animal Health (OIE). The OIE, founded in 1924, is the international standard-setting body for animal health.

In his welcoming address, Dr. Gideon Bruckner[1] noted that the conference was bringing together representative experts from a variety of disciplines, including medical professionals, veterinarians, ornithologists, virologists, conservationists, and others. The stated purpose of the gathering was to share knowledge and expertise and to seek answers to the many unknown factors associated with AI, particularly those that are related to the role of wild birds in disease epidemiology. The transport of HPAI via migratory bird flyways, the sale of wild birds and other wildlife, and unmapped global trade were among some of the issues discussed by conference presenters and attendees.

The conference began with several overviews that set the scene for the more in-depth presentations that followed. Sessions were focused on the following aspects: ecology and virology; surveillance; sampling and risk analysis, including the risk transmission from wild birds to humans; and tools for disease management.

Abstracts and downloadable files of conference presentations are available at the FAO Web site.[2] This site also provides links to a number of background documents about AI. Additional information about FAO efforts to address the threat of AI can also be found at this Web site.[3]

The following report includes some of the most noteworthy information from a number of conference sessions.

AI — Global Overview
The meeting began with a historical perspective and an updated overview of the current global situation and developments in relation to HP H5N1. Calling it "an unprecedented crisis with complex epidemiological and socioeconomic impacts," Domenech[4] maintained that associated risks and impacts have extended beyond poultry systems to include the security of other foods and products, economic livelihood, and other zoonotic diseases.

The HPAI virus has been detected worldwide, with the exception of in the Americas. However, the situation overall seemed more stable at the end of May 2006, due to increased political and monetary support and to the increasing use of more efficient surveillance methods and tools for infection control.

The exception to the apparent current stability is the presence of HPAI in Africa, where poultry and/or wild birds in 8 countries are currently contaminated. Unlike other European, Asian, and Middle Eastern countries, most countries in Africa do not have sufficient resources to manage or eradicate the disease; thus, HP H5N1 could become endemic in areas of the continent.[4]

Wild birds have been strongly implicated in the spread of H5N1 westward from Asia and into the Middle East and Africa. However, how the spread has occurred remains unclear. More data are needed, particularly those that can be expressed through mapping of migratory routes. Furthermore, additional research is needed to determine whether wild birds are, or can become, permanent reservoirs of HPAI H5N1.[4]

FAO is concerned that international interest has been focused almost exclusively on the possibility of AI becoming epidemic in humans, with much less emphasis being placed on the potentially devastating impact on poultry (and subsequently, economic livelihoods) and other animals.[5] Domenech emphasized that the best way to protect people from AI is to control and try to eradicate the disease in animals.[4] Toward this end, an AI strategy developed by FAO/OIE includes targeted risk-based active surveillance, eradicating diseased animals, biosecurity, and movement control.

Surveillance and monitoring currently include poultry and other animals, followed by rapid reporting of any outbreaks to competent authorities and use of strict measures to limit disease spread. Limiting spread should entail the culling and secure disposal of sick poultry, and control of the movements of targeted poultry and related products.

Trade is considered the most frequent mechanism of spread of HPAI H5N1. This includes local, regional, and international trade of poultry and related products, and the trade of captive wild birds. Such activities take place both legally and illegally, with illegal trading being especially difficult to monitor.

Specifically, both movement of poultry to and from markets and the people involved in poultry production and marketing have been the main spreaders of disease to previously unaffected areas. Therefore, FAO is now urging farmers, traders, and others who come into close contact with poultry to be particularly careful to adhere to basic hygienic standards and for biosecurity measures in farm settings to be tightened.

Until more data about wild birds are available, the OIE recommends that control efforts be focused at the animal source (poultry) rather than on wild bird populations in general.[5] Bruschke[6] described the new OIE standard for international trade and notification of disease, emphasizing that it is aimed at facilitating transparent reporting, including reporting of viruses in wildlife, while not creating unjustified barriers to trade. Standard recommendations include having mechanisms in place to encourage the reporting of sick animals at the local and regional levels. However, on the basis of the belief that a pandemic can be prevented if the viral load in poultry can be reduced, the standard does not recommend any measures that extend beyond poultry.

Early detection of HPAI H5N1 in poultry is therefore crucial, and the OIE standard stresses implementation of early warning systems in all countries. Only 4 countries in the European Union (EU) have seen outbreaks among poultry.[7] Brown contended that this containment was at least partly attributable to the use of early warning systems and to implementation of increased biosecurity standards.[7]

Lubroth[8] specifically focused on AI in wild birds, and acknowledged that both migratory behaviors and the effects of different environments on the spread of H5N1 are not completely understood. Although it is known that transmission from wild birds to poultry can occur, transmission between wild birds is still undocumented. Additionally, a positive antibody test result reflects exposure but not carrier status, and virus isolation does not necessarily indicate that the animal being evaluated is a reservoir for HPAI H5N1; both of these "knowns" make determinations that are related to AI transmission more difficult.

Other barriers to obtaining data that could describe potential transmission include:

Most identification of virus has been made only in dead or sick birds, rather than in healthy birds;

Limited expertise and funding to support wild bird research; and

Various logistic problems related to sampling exist.
AI knowns in wild birds include:

The Z genotype of H5N1 dominates, and has expressed increased virulence and increased host range; and

Morbidity and mortality seem to have increased over time in Mallard (Anas platyrhynchos); excretion of<