Sciensano is the Belgian National Reference Laboratory (NRL) for avian influenza. To tackle this virus, which is highly-contagious and likely to cause fatal epidemics in birds, we participate in active and passive monitoring of our Belgian flocks and we are developing tools to diagnose the disease quickly and effectively and thus to fight against its expansion.
Avian flu poses a significant threat to the poultry industry, with an enormous economic impact.
The HP H5N1 virus in Asia since 2001: an unprecedented event
The appearance and the circulation of the HP H5N1 virus in Asia was an unprecedented event in the history of influenza, due to :
- its distribution and highly-endemic nature
- its particularly high virulence
- its spectrum of susceptibility for other host species, such as mammals.
The lack of early warning systems and rapid control in Asian countries allowed the virus to circulate and to evolve, leading to:
- an increase in its virulence
- the adaptation to new hosts (primarily water fowl and mammals) and therefore accompanied by a zoonotic risk.
In this context, every movement can become and increased risk factor (trade, transport, migration etc.).
Following the globalization of highly-pathogenic avian influenza HPAI H5N8, reassorted from the HP H5N1, in the winter of 2014-2015, the epidemiological situation of HPAIs and of HP H5N8 in particular, has further evolved.
The global HP H5N8 virus throughout the winter of 2016-17
The crisis in the winter of 2016-2017 (HP H5N8) was exceptional for a number of reasons :
- its geographical spread, affecting 29 countries in Europe, as well as Africa
- its heightened virulence in wild birds and its wider spectrum of avian hosts
- its variable symptomatology without systematically leading to a sudden increase in mortality of chickens and turkeys as expected from an HPAI
- it unusual environmental persistence throughout the summer
- and finally, a post-infection recovery associated with a seroconversion HP H5N8 both in wild ducks and in chickens, which raised the concern that an immunity would be established that would foster the silent circulation of HPH5 viruses.
The H7N9 virus in 2013: humans are infected for the first time
Recently, an H7N9 virus emerged for the first time in humans. China has reported over 1,560 cases of the H7N9 infection since the appearance of the virus in humans in March 2013, and around 40% of contaminated patients died from it, according to WHO statistics. This virus had low pathogenicity in poultry, in which it induced few or no symptoms thus rendering its detection and control difficult. Since January 2017, a strain that is highly pathogenic for poultry has emerged and associated with it, a rise in human cases. However, as observed with the H5N1 virus, no sustained inter-human transmission, which is an essential condition for an influenza virus to become pandemic, had been demonstrated at this stage.
The need for monitoring
The avian flu viruses are very variable and for the most part, unpredictable in terms of the risks they pose to human health. They cannot be eradicated from wild bird reservoirs and, once introduced to domestic birds, their control is often difficult. By circulating in poultry and primarily chicken, they can acquire other properties such as an increase in virulence for birds and the adaptation to other species associated with an increase in virulence. For these reasons, they represent a considerable challenge to scientists, decision-makers and risk-managers, and accentuate the need for a collaboration between the public authorities and animal health authorities.
Numerous studies on the evolution of the avian flu virus and the acquisition of virulence during their circulation in chickens, have clearly demonstrated that each of the H5 and H7 viruses are potentially dangerous. The probability of a low pathogenic virus mutating into a highly pathogenic virus is uncertain and will depend on a number of factors.
Given the zoonotic potential of certain avian influenzas, monitoring the situation in the field and being prepared for a crisis are essential.
Thanks to monitoring, both of poultry and of wild birds, we can guarantee an early detection service and we follow potential threats, at a national and international level.
Based on our expertise, we advise health authorities continually to help them to control and combat this virus.
We have the necessary expertise and containment facilities to isolate the virus without the risk of external contamination. Our staff have experience of serological tests, of virus isolation and of the molecular diagnosis of the avian flu virus that comes from field samples.
Due to the highly contagious nature of the disease and the numerous mutations of the viruses, Sciensano studies pathogenic viruses and more specifically, conducts the following tasks:
- molecular, virological and serological diagnosis
- flock monitoring (clinical and serological) in wild birds
- development of diagnostic tools
- pathogenesis (adaptation, virulence)
- phylogeny (the study of evolutionary relationships between living organisms)
- measurement of immunity (innate and acquired).