Risk Estimation, 31.03.2017
Assessment of the situation
The detection of HPAIV H5N8 in 29 European countries (listed chronologically by date of report: Hungary, Poland, Croatia, Switzerland, Austria, Germany, Denmark, the Netherlands, Sweden, Finland, France, Romania, Serbia, Great Britain, Greece, Bulgaria, Montenegro, Slovak Republic, Italy, Ireland, Czech Republic, Slovenia, Spain, Portugal, Macedonia, Belgium, Bosnia and Herzegovina, Lithuania) and the rapid distribution of the virus indicate a highly dynamic spatial spread of the infection. For the first time since onset of the current fowl plague epidemic the number of reports in wild birds has decreased considerably; in contrast, new outbreaks are reported almost daily from the German region with the highest poultry density in Lower Saxony. This is the most severe and most long-lasting fowl plague epidemic in Europe and Germany since outbreaks have been recorded.
POULTRY AND ZOOS/ANIMAL PARKS
In Germany, HPAI outbreaks have been reported from 90 poultry holdings and 15 zoos/animal parks. Almost all of these holdings are located in areas where increased numbers of dead HPAIV-positive water birds have been found. In the affected animal parks, mostly water birds with possible contact to wild waterfowl have been affected. In most poultry holdings, direct or indirect introduction via contaminated material (shoes, vehicles, objects) is the most likely route of infection. The risk of introduction by purchased poultry, feed and drinking water has been negligible in all outbreaks investigated epidemiologically by the FLI. Until March 2017 almost all outbreaks in affected holdings were primary outbreaks which did not spread any further; however, one outbreak in Brandenburg and outbreaks at three sites belonging to one holding in Schleswig-Holstein are highly likely to be secondary outbreaks. Since 02.03.2017, a series of 23 outbreaks in fattening turkeys has occurred in the district Cloppenburg, one of the regions with the highest poultry density in Germany. It is assumed that in these cases a spread of the virus between holdings plays an important role. Further single outbreaks were reported in the districts Oldenburg (turkey hens) and Ammerland (ducks). An alarming event is the outbreak in parent ducks in the district Ammerland, as the adult animals only showed a reduced laying performance but no increased mortality. An endemic establishment of the virus in water birds kept in captivity may lead to similar series of outbreaks as observed in France, Hungary, Romania and the Czech Republic where the virus seems to have found a niche in waterfowl populations.
While in the 2014/2015 outbreak HPAIV H5N8 was only sporadically detected in healthy appearing wild birds (three mallard ducks, one common teal and one sea gull), this epidemic is characterized by detection of a large number of dead water birds and carrion-eating birds of prey, e.g. buzzards, white-tailed eagles and sea gulls. So far, the virus has been detected in at least 53 different bird species including species belonging to the categories diving ducks, grebes, sea gulls, swans, in isolated cases dabbling ducks (mallard duck), geese, birds of prey, owls and also carrion-eating songbirds (e.g. crows). The fact that HPAIV H5 has also been detected in healthy water birds or in their feces leads to the assumption that wild birds can excrete the virus without developing disease or dying. Infected but asymptomatic wild birds as well as birds during the incubation period continue to be mobile virus carriers. Furthermore, predators (mammals such as foxes and martens, but also birds of prey and crows) may break up carcasses of dead waterfowl and carry away parts of the carcasses or inner organs with high virus loads, thus causing a considerable contamination of the environment. Persons and vehicles accessing contaminated areas may spread the virus and introduce it into poultry holdings.
Since mid-March, the number of HPAI H5 cases reported in wild birds which still continued to increase considerably at the end of February has been decreasing strongly (Fig. 1).
After the beginning of spring migration of nordic waterfowl in February and more prominently since March, strong migratory movements within Europe from the West and Southwest to the East and Northeast are observed (geese, swans, ducks, grebes). In most bird species, return migration to the breeding grounds does not take as long as fall migration. Due to the mild winter 2016/2017 spring migration of many water and shore birds, in particular geese, ducks, swans, gulls and pewits, already has fully started. Some species of these groups overwinter in Southwestern France, i.e. in the regions where currently the highest number of outbreaks in domestic poultry is reported. This applies to dabbling ducks such as mallards, common teals, diving ducks (common pochards, tufted ducks) and greylag geese which now return from these overwintering areas to their nesting grounds in Central and Northern Europe (including Germany). During the nesting season from March to June the birds do not commute. The activities of the breeding birds are restricted to their own limited territory. In general, water birds are rather reclusive during nesting season. In populations of cranes, white storks, but also many Anatidae species (ducks, geese, swans) there is a certain but hard to quantify percentage of non-breeding birds. These may migrate on a small scale depending on the food supply.
HPAI infected wild birds are still reported (Fig. 1), in particular birds of prey and waterfowl species which breed in Germany (e.g. greylag geese, mute swans), so that it must be assumed that the virus is still present in waterfowl and in the environment (bird carcasses) in areas where local epidemics have occurred.
Genetic analyses show a similarity to H5N8 viruses which were first detected in Southern Russia in the summer of 2016. These viruses show clear genetic differences to H5N8 viruses which occurred in Europe in 2014/2015. Therefore, the virus has been newly introduced, most likely by the same route as in 2014, i.e. via Russia by wild birds. Phylogenetic analyses lead to the assumption that on the way from Central Asia to Central Europe reassortment events with at least one other avian influenza virus have taken place. Direct introduction from China or the neighboring Asian countries by poultry and poultry products is very unlikely, as in this case other genetic patterns of the virus would have to be expected. The results of epidemiological outbreak investigations did not provide any indications for direct connections between the holdings affected in Germany and the endemic regions in East or Southeast Asia. (It must be mentioned that import bans on poultry and poultry products are in force for all countries affected from HPAI). The observed increased virulence in waterfowl correlates with the modified composition of the genome segments of the currently circulating H5N8 compared to the virus which circulated in 2014/2015.
Since mid-December 2016 a further subtype, H5N5, has been circulating in wild birds, which now has first been introduced into a poultry holding. This virus is a reassortant based on the original H5N8. Mixed viruses, so-called reassortants, of avian influenza viruses are generated, if several virus subtypes are present in one infected animal and exchange genetic material during replication. First analyses of the H5N5 virus also showed a relationship with HPAIV H5N8 precursor viruses from the Russian-Mongolian border region. It seems to have evolved in parallel with or shortly after HPAIV H5N8, but shows genetic differences and was then also introduced to Germany. Generation of reassortants always must be expected when different high and low pathogenic influenza viruses are circulating in one population. Thus, a further diversification of the viruses is to be expected given the multitude of currently circulating high and low pathogenic influenza strains.
So far, no cases of HPAIV H5N8 or HPAIV H5N5 infection in mammals, including humans, have been reported.
Conclusions and recommendations
It remains to be seen whether the number of HPAI cases in wild birds will continue to decrease over the next weeks. At present, single cases still are reported sporadically from different federal states (mainly inland states). Massive outbreak series in domestic poultry holdings caused by different high and low pathogenic H5 subtypes in France and some Balkan states (Table 2) are considered to be problematic, as the virus can be reintroduced into the wild bird population as long as the epidemic lasts, if infected domestic water birds come into contact with wild waterfowl. Therefore, the risk of introduction by wild birds into domestic poultry holdings and birds kept in zoological gardens in Germany by direct and indirect contacts between wild birds and domestic poultry in areas where HPAI H5 infected wild birds are found is considered to be high. In other areas where HPAI H5N8 has not been detected in wild birds for a longer period of time and where no waterbirds gather the risk is considered to be low.
In Lower Saxony, particularly in the district Cloppenburg, the risk of introduction due to a spread of the virus between poultry holdings is considered to be high.
For waterfowl kept in captivity the risk of an unrecognized circulation of HPAI H5 viruses and of a spread between poultry holdings is considered to be high.
Protection of domestic poultry holdings from infection with HPAIV H5N8 is the highest priority. It is essential to prevent a spread of infections between poultry holdings. This requires the implementation of strict biosafety measures, particularly consistent cleaning and disinfection of equipment and vehicles. Revision, optimization and strict implementation of biosafety measures are of utmost importance. Poultry farmers are obliged by law to observe basic biosafety rules. The creation of a physical and functional barrier between wild bird habitats where cases of HPAI have occurred and domestic poultry holdings remains important. Risk-based indoor housing of poultry and other biosafety measures minimize the risk of direct and indirect contact with infected wild birds. In particular, indirect introduction routes, e.g. contaminated food, water or contaminated litter and objects (shoes, wheelbarrows, vehicles etc.) must be taken into account. These routes must be cut off and adequate disinfection measures must be taken.
In detail, the following recommendations are made:
- Increased virological and/or serological surveillance of water bird holdings to ensure early detection of a possibly unrecognized circulation of HPAI.
- Observance of strict biosafety measures in all poultry holdings, also small-scale holdings, zoological gardens, animal parks and shelters, if necessary by means of check lists
- Joint use of equipment, carcass containers and vehicles by poultry holdings should be avoided
- Access of vehicles and persons to poultry holdings should be limited as far as possible. After entering a poultry holding persons who regularly take care of the animals in one holding should refrain from visiting other poultry holdings for the following 72 hours. Veterinarians and other professionals who visit poultry holdings should interrupt their tour and observe the recommended quarantine period after accessing a holding where clinical signs or losses indicate an outbreak of HPAI.
- Risk-based restriction of free-range husbandry (mandatory indoor housing) of poultry (at least in regions with a high wild bird density, a high poultry density, in the vicinity of wild bird resting and gathering areas, or locations where HPAIV H5 has been detected)
- Poultry holdings which have been exempt from mandatory indoor housing should be investigated clinically and virologically at three-week-intervals maximum
- Prevention of access of free-range poultry to natural bodies of water
- Notification of the responsible veterinary authority in case of dead or ill wild birds and mammals in areas where increased numbers of dead wild birds have been found
- Increased investigation of dead wild birds or wild birds living on or around water for avian influenza viruses
- No contact of hunters who have been in contact with game birds with domestic poultry; in areas where fowl plague has been detected in wild birds ban on game bird hunting
- Avoidance of direct contact between humans and pet animals and dead or ill wild birds
- Assessment of practicability of the measures foreseen in the animal disease emergency plans and, if necessary, revision of plans.
Full-length risk estimation dated March 31, 2017 (in German language only)