Department of Viroscience
Department of Viroscience
Which species of bird does the virus affect?
- Wild bird species:
Mortality caused by the Usutu virus has been described for a wide range of songbirds in various countries. A high mortality has mainly been described among blackbirds and house sparrows.
- Captive birds:
Among captive birds mortality has mainly been described for owls, especially the great grey owl.
What effects can the virus have on bird populations?
After an initial introduction in an area, the mortality is always high and subsequently an equilibrium will arise and the mortality should decrease. It is difficult to predict how long the virus will remain in the bird population in the Netherlands, how large the mortality will eventually be, and how long it will take for the bird population to recover.
Where does the virus occur in Europe?
The virus originates from South Africa. The first outbreak among birds in Europe was in 1996, in Italy, followed by an outbreak in 2001 in Austria. Since then the virus has also been found in birds in Spain, Croatia, Hungary, Switzerland, the Czech Republic, Germany and Belgium. The virus can be introduced to new areas by birds and/or mosquitoes. The Usutu virus was first found in healthy, living Dutch birds in August 2016 from which samples had already been taken in April 2016. In September 2016 the virus was shown to be present in dead birds for the first time. These birds were investigated after it was found that the number of reports of blackbird mortality had increased since mid-August.
Which symptoms do infected/sick birds exhibit?
In general, it can be stated that if a bird is 'bloated', sluggish or no longer drinks then this indicates a disease. In the case of an infection with the Usutu virus the symptoms are:
general malaise, sluggishness, fever, bloatedness, no longer drinking, difficulty breathing, muscle weakness (e.g. inability to fly), and letting the wings droop. Which symptoms a bird exhibits depends on which organ has been affected (heart, brain, peripheral nervous system). As this clinical picture also fits other diseases, it cannot be stated with certainty whether a bird is infected with the Usutu virus or another disease based on the symptoms alone.
Is my dog/cat that has picked up or eaten a dead bird at risk?
The Usutu virus is an avian virus. In European countries where many birds have previously been infected with the Usutu virus, dogs and cats did not become ill. This indicates that the Usutu virus does not pose a threat to dogs or cats.
Can I prevent captive birds from becoming infected?
The best method is to try to reduce exposure to possibly infected mosquitoes. Avoid the presence of stagnant water in which mosquitoes can lay eggs.
Use mosquito nets on birdcages or accommodate birds inside and use insect screens in windows/doors. No vaccination for birds is available at present.
Can I treat sick captive birds?
No specific drugs are available. The treatment consists of controlling the symptoms. A vaccine is not yet available.
Does the virus pose a threat to people?
The virus is transmitted by mosquitoes, mainly those from the genus Culex. It is very rare for humans to become ill. Despite the major outbreaks among birds, in Europe only five patients with neurological symptoms have been described in whom an infection with the Usutu virus was diagnosed. The majority of these patients had a compromised immune system.
Which measures must be taken when dealing with ill or dead birds?
The general hygienic measures (in Dutch) for handling dead and sick birds should be adhered to. There is no reason to take extra measures.
What can I do if I find a dead blackbird or house sparrow?
You can report the finding of a dead bird to Dutch Centre for Field Ornithology (Sovon) or on the website of the Dutch Wildlife Health Centre (DWHC) via the link Submit a dead animal (in Dutch).