Update on emerging avian influenza virus H5N8

In early March, 27 European countries declared outbreaks with the World Animal Health Organisation (OIE) of the H5N8 or H5Nx highly pathogenic avian influenza virus, responsible for a bird flu epizootic in many of these countries. ANSES is highly involved in surveillance of avian influenza and of the propagation of the H5N8 virus and closely related viruses in France, due to its participation in the Epidemiological surveillance platform for animal health (ESA Platform), its research and reference activities concerning bird flu, and its activities in the assessment of risks to animal health.

Since early December 2016, close to four hundred outbreaks of highly pathogenic avian influenza (HPAI) H5N8 and H5Nx have occurred in French farms, especially in southwestern France, one year after the start of the influenza epizootic that at the time was caused by other highly pathogenic viruses (H5N1, H5N2 and H5N9). Many European countries have ben affected, either by cases in wild birds or by outbreaks in domestic poultry (in early March, 27 European countries declared outbreaks with the World Animal Health Organisation (OIE)). Currently, water fowl farms are those most often affected.

This new virus, which cannot be transmitted to humans, was most likely introduced into France through wild birds. It is highly pathogenic in poultry farms, including water fowl farms, where it spreads rapidly. The health situation evolves differently depending on the area: while certain regulated areas created to control the virus' spread around detected outbreak points have been stabilised (in particular in the Tarn, Aveyron and Deux-Sèvres départements), the area in which the latest confirmed outbreaks have been focused, including the Gers, Landes, Hautes-Pyrénées and Pyrénées-Atlantiques départements, as well as the Lot-et-Garonne, has not yet been stabilised.

High avian influenza risk in France: risk assessment mobilised

Given this background, as soon as the first cases appeared in the countries neighboring France, the DGAL requested the issuing of an emergency opinion from ANSES on the circulation of HPAI viruses with the H5N8 subtype detected in Europe. The "HPAI" expert group, which has been working on this topic since the initial outbreaks of the preceding episode in late 2015, was quickly mobilised. Based on its report, the Agency published its opinion on 17 November, which considered that there is a "high probability" of infected wild birds entering metropolitan France in a unified fashion throughout all the country's wetland areas, including in Corsica, and that there is a "high probability" of an HPAI H5N8 outbreak in wild birds in these areas.  

Due to these conclusions, the Ministry of Agriculture, Agrofood and Forestry (MAAF) decided to raise the level of risk regarding the disease from "negligeable" to "high" in the areas particularly at risk (wetlands), and to "moderate" in the rest of France.

Due to the rapid evolution of the HPAI H5N8 situation in France and outbreaks of the disease in wildlife in the Nord-Pas-de-Calais département (call ducks) as well as in farms in the Tarn (water fowl), ANSES was once again asked to provide an emergency assessment of the situation in December 2016. The conclusions of its opinion brought about the publication of the Ministerial Order of 5 December 2016, in which the risk level for avian influenza was raised to "high" throughout metropolitan France.

The large numbers of outbreaks in water fowl farms and, to a lesser extent in other domestic bird species in the designated protection and surveillance zones in the Gers, Landes and northern Hautes-Pyrénées and Pyrénées-Atlantiques, have prompted the MAAF to adopt a new strategy. As of 5 January 2017, in order to put an end to the spread of this new virus as quickly as possible, the culling of all free-range water fowl in the previously cited zone is currently underway. Due to the large number of cases in domestic water fowl, the culling zone was extended in late February in order to ensure faster control of the infection and the possibility of restocking farms after a long period of prophylactic quarantine.

At the request of the MAAF, the HPAI expert group is pursuing its work in order to define a methodological strategy enabling the most responsive adjustment possible of risk levels, regardless of the HPAI viruses circulating and the epidemiological context.

Involvement of the Ploufragan/Plouzané Laboratory and the ESA Platform

ANSES's Ploufragan/Plouzané Laboratory is the National reference laboratory (NRL) for avian influenza and was highly mobilised by the emergence of this new virus. Since the start of this crisis in November 2016, the NRL has been mobilised seven days a week to sequence the genes of the H5N8 virus in several hundred samples in order to confirm the highly pathogenic nature of the viruses as confirmed by the veterinary analysis laboratories to which the NRL also supplies the reagents used for first line diagnoses.  

The Ploufragan-Plouzané Laboratory has also sequenced the full genome of two viruses from samples of the first outbreak in the Pas-de-Calais département (call ducks) and from the first case identified in domestic fowl in the Tarn département, followed by another outbreak identified in the Deux-Sèvres in a farmyard. The genome sequence of the first virus is similar to that of viruses detected in northern Europe, while that of the second virus is similar to a virus initially detected in Croatia. These initial results suggest that HPAI H5N8 was introduced into France by two different routes, probably by migratory birds. The virus sequence isolated in the Deux-Sèvres is in fact similar to that of the viruses detected in Northern Europe, thus proving that this outbreak is independent of those reported in south-western France.

The NRL also conducts research work to specify the genetic evolution of viruses, as well as the pathogenicity of newly detected viruses. Due to the absence of available data on the spread of the virus and its persistence in the environment, which is crucial information for risk managers, the Ploufragan-Plouzané Laboratory is also conducting research work on the virus's persistence in liquid duck manure and for developing a method to detect the virus in poultry and in their environment. Such a method would enable detection of the most highly contaminated areas and equipment in order to assess the effectiveness of the cleaning and disinfection measures implemented, prior to the resumption of activity and the reintroduction of animals to sites. Epidemiological investigations are also conducted in the field in the various départements concerned by the Ploufragan Avian Epidemiology team (EBEAC) alongside the departmental services in charge of population protection (DDecPP). These epidemiological investigations are coupled with the work of virologists and with epidemiological surveys conducted in areas where outbreaks are detected by the DDecPP services in the départements concerned.

An analysis of epidemiological links should help to better understand how the virus was able to break out and disseminate among farms and may contribute to defining and evaluating possible measures for improving control of these avian influenza epizootics about which the laboratory's virologists and epidemiologists are regularly questioned by the public authorities.  

The ESA platform, whose role it is to supply precise reliable information and analyses on the epidemiological situation for diseases present in France and developments in them, has also been strongly committed to monitoring the evolution of avian influenza and circulation of the H5N8 virus. Weekly situation updates are issued both for France, based on the results communicated by the NRL and the Directorate General for Food, and for the European continent through its international health watch scheme. These situation updates, which are published on the ESA platform's resource centre website (http://www.plateforme-esa.fr/), are very popular, with the number of monthly visits to the site quadrupling between October and December, from 5 000 to 20 000 visits per month. The ESA platform's notes are now being taken up by mainstream French media (ex. Le Monde, TV5 Monde) as well as by surveillance platforms (ex. Promed). ANSES has also contributed to the establishment of an information system for the decentralised services of the Ministry of Agriculture, Agrofood and Forestry (DDcePP and regional departments for food), which is updated daily and makes it possible to monitor developments with regard to outbreaks and restricted areas.