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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Background information about Avian Influenza and hints for ornithologists.
Auteurs :	Wolfgang Fiedler, Auteur ; Stefan Bosch, Auteur ; Anja Globig, Auteur ; Franz Bairlein, Auteur
Type de document :	Article
Dans :	Vogelwarte (43(4) NOV 2005)
Article en page(s) :	249-260
Langues:	Allemand
Résumé :	Waterfowl are known to be the major reservoir for all 16 H- and 9 N- Subtypes of low pathogenic avian influenza viruses (LPAIV), including the subtypes H5 and H7 being a serious economic threat to the poultry industry as well as H1, H2, H3 that are the main source for human influenza. LPAI neither cause any signs of disease in the infected wild birds nor in poultry. However, low pathogenic avian influenza virus of the subtypes H5 and H7 can be introduced into poultry holdings. Especially in industrial holdings with large numbers of highly susceptible animals, the previously stable viruses of low pathogenicity begin to evolve rapidly and may mutate into highly pathogenic avian influenza (HPAI) (known as fowl plague and also called "bird flu") causing up to 100% mortatlity in infected birds. Afterwards, infections of HPAI are usually spread by movement of stock, infectious feces, contaminated water or bird products. Free flying birds are usually also blamed to spread the disease, but this could be never proven to have happened. Since 1959 none of the outbreaks of HPAI has approached the size of the ongoing epizootic in Southeast Asia, which most probably originated in the late 1990 ies presumbly in captured ducks in Southern China and is caused by a new HPAI virus of the subtype H5N1. In 2005 the disease started to spread westwards and appears to be a threat for European poultry. The asian H5N1 cause serious public health concern for at least three reasons. These AIV isolates can cause heavy economic losses in the poultry industry and through loss of poultry may exaggerate to human food protein deficits in the developing world. In addition, they have the potential to cross the species barriers and cause human disease and death though only when connected to very close contacts with infected animals or raw consumption of infected birds (chicken, ducks). Last but not least there is the potential of the virus to change it's genetic structure - most probably by mixing with a human influenza virus (H1, H2, H3) that may achieve human-to-human spread by meeting the unprepared immune system of men resulting in a new human pandemia. Three pandemias during the 20 th century - all originating from HPAI viruses-emphasise the danger of the probability of H5N1 becoming the next pandemia virus. The role of migratory birds in the long range transportation of HPAI viruses is still controversely discussed. The patterns of occurrence of HPAI outbreaks and bird migration as well as the pattern of virus isolations in wild birds and HPAI outbreaks in many cases do not fit convincingly. Therefore the risk of transmission of HPAIV through man (legal and especially illegal trade of birds and bird products) appears to be as high as through migratory birds. There is still the unanswered question, whether a bird infected with HPAI virus H5N1 is able to perform migration flights at all. So far a HPAI virus H5N1 was never isolated from a clinical healthy wild bird and there is the evidence that the reported cases of HPAI virus H5N1 in wild birds origate from infected poultry. Subsequently, even wild birds died. However, as it is not known whether the virus may be transported by migratory wild birds that don't suffer from disease over long distances, it is recommended to monitor the situation carefully. Avian Influenza outbreaks in Turkey in mid October 2005 involved a virus type that was closely related to a H5N1 virus isolated from a dead "Grebe" (likely Podiceps sp.) in Siberia suggesting that this virus might have been transported by migratory birds.For ornithologists who potentially might be exposed to HPAI viruses we recommend the following precautions: (1) sufficient hand hygiene after all contacts with birds and bird excretions, (2) reduction of direct bird contacts to a minimum level (e.g. handling, ringing and measuring of captured wild birds by a single person only), (3) protection of hands, lungs and eyes from viruses; largest possible reduction of dust and splashes; wear of protective masks and glasses when necessary, (4) avoidance of direct contacts with suspect dead birds (use of plastic bags), (5) consequent separation of working space (e.g. on field stations) and rooms for eating and sleeping; avoidance of eating, sleeping, smoking and drinking in rooms were birds are measured, ringed or kept, (6) changing clothes and shoes after close bird contacts before entering other areas and avoid contact to domestic poultry for the next 3 days, (7) in case of suspicion of AI infection monitoring of body temperature during 7-10 days and instant seek of medical help when body temperature rises to more than 37.5 degrees C (information of medical personnel by phone before arrival), (8) instant report of suspicious dead birds to the local veterinary and health administrations. Vaccination against human influenza strains does not protect specifically against HPAI virus H5N1 but is nevertheless recommended. Prophylactic and therapeutic medication before or within 48 hours after emergence of influenza symptoms is possible by antiviral medicine containing e.g. Oseltamivir (Tamiflu (R)).

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