22 November 2017 - JOINT PRESS RELEASE

Usutu virus decreases the population of common blackbirds in the outbreak region

The Usutu virus endangers birds and has been circulating in Germany since 2010. However, estimating its impact on bird populations in the outbreak region has hardly been possible up to now. For the first time, researchers from the Bernhard Nocht Institute for Tropical Medicine, NABU (German Nature and Biodiversity Conservation Union), Friedrich-Loeffler-Institut (FLI), Kommunale Aktionsgemeinschaft zur Bekämpfung der Schnakenplage e.V. (KABS), German Center for Infection Research (DZIF) and the University of Bayreuth have published a study that enables concrete conclusions about the Usutu virus’ impact on German breeding birds. The data for this was obtained from dead birds as well as from the citizen science garden bird watch project “Stunde der Gartenvögel”.


Blackbird infected by the Usutu virus© Jutta Böhm-Wacker

“We have now managed to concretely evaluate the Usutu virus’ impact, 20 years after its first emergence in Europe,” emphasizes Dr Renke Lühken, ecologist from the BNITM who conducted the statistical analyses: “Although it has been confirmed that Usutu infections can lead to death in over 30 types of birds, only blackbirds are affected out of the 15 most common German garden birds. In regions where the Usutu virus emerged, blackbird populations decreased by on average 16 percent more than in other parts of Germany between 2011 and 20l6.”

The first time Usutu viruses caused blackbird death was in Tuscany, Italy, in 1996, as a retrospective analysis of historical samples demonstrated. In Germany, the first virus emerged in mosquitoes in 2010. In the following year, concerned German citizens provided critical information with regard to common blackbird death, reporting dead and diseased blackbirds to the KABS and NABU and also stating that blackbirds had disappeared from the northern Upper Rhine Plain.

“As we suspected that the blackbirds were suffering from a disease previously unknown in Germany, we turned to the Bernhard Nocht Institute to get to the bottom of this common blackbird death,” says Lars Lachmann, bird expert at NABU. Researchers from the BNITM and FLI were able to show that the condition was due to the mosquito-borne Usutu virus which originated from Africa.

Citizen science provides data basis

By means of press releases and the media, the NABU requested people to report suspicious-looking dead blackbirds online and, if possible, send them in for assessment so as to evaluate the pathogen’s effects on birds in Germany. Usutu virus infections were determined in a total of 230 birds between 2011 and 2015.

“However, the deaths alone do not permit conclusions about the impact of the Usutu virus on bird populations. It is important to know how the numbers of birds change both in and outside the outbreak regions over the course of several years,” explains Dr Renke Lühken. This was made possible by bird counts reported in the NABU garden bird watch project “Stunde der Gartenvögel” in which private people throughout Germany reported the numbers and types of birds they had seen in their gardens over a period of one hour on the second weekend of May. “According to 30,000 garden samples conducted annually, blackbirds are the second most common garden bird. Counts for the 15 most frequently reported types of birds were used for the analysis,” says Lars Lachmann.

Mathematical models were used in order to draw reasonable conclusions from the extensive data. “First, we created a map of Usutu virus distribution using laboratory confirmed cases of infection and nationwide temperature data. Subsequently, we compared the development of bird numbers in the Usutu affected regions and in Usutu free regions from 2011, i.e. just before the first outbreak, through to 2016,” describes Dr Renke Lühken.

Collaboration according to One Health

“In this project, we are working according to the One Health approach which observes both human and animal health in the environment,” says Prof Jonas Schmidt-Chanasit, DZIF scientist and Head of Arbovirology at the BNITM. “Analyses of the Usutu virus distribution in common blackbirds enable us to specifically work together with blood donation services so as to minimise the risk of Usutu virus transmission to humans.” In humans, the Usutu virus can cause encephalitis.

“Collecting sufficient data for this assessment was only possible thanks to the good collaboration with our longstanding partners from the BNITM, NABU, FLI and KABS,” says Prof Jonas Schmidt-Chanasit. “We will also analyse the current common blackbird death. Since July 2016, we have received 260 birds and could confirm Usutu infection in 62 of them. Here, we determined a marked spread in northern Germany—to both Bremen and Hamburg. However, only bird counts from the next years will enable us to determine whether blackbird populations are being as strongly affected as in the previous outbreak region and how persistent the impact is.”

Background information on the Usutu-Virus and blackbird death

·        www.bnitm.de/aktuelles/faq-zum-usutu-virus

·        Reporting project: www.nabu.de/usutu-melden

·        www.fli.de/de/aktuelles/tierseuchengeschehen/usutu-virus


Lühken R, Jöst H, Cadar D, Thomas SM, Bosch S, Tannich E, Becker N, Ziegler U, Lachmann L, Schmidt-Chanasit J (2017) Distribution of Usutu virus in Germany and its effect on breeding bird populations. Emerg Infect Dis. 23(12): 1994-2001 doi.org/10.3201/eid2312.171257

Press Contact

Dr Renke Lühken | BNITM
T +40 42818-862

Lars Lachmann | NABU
T +49 30 284984-1620

Dr Jessica Tiedke & Laura Zimmermann | BNITM
T +49 40 42818-264

Nicole Flöper | NABU
T +49 30 284984-1958

Elke Reinking | FLI
T +49 38351 7-1244

Karola Neubert | DZIF
T +49 531 6181 1170

About the project partners

The Bernhard Nocht Institute for Tropical Medicine (BNITM) is Germany’s largest establishment for research, healthcare and education in the field of typical tropical disease and emerging infections. Current research themes include malaria, haemorrhagic fever viruses, tissue worms and developing diagnostics. The institute has a BSL4 laboratory (highest biosafety level) for handling highly infectious viruses and infected insects as well as a safety insectarium (BSL3). The BNITM serves as a national reference centre for all tropical infectious disease pathogens and houses the WHO Collaborating Centre for Arbovirus and Haemorrhagic Fever. The Arbovirology research group investigates mosquito-borne viruses and monitors the spread of arboviruses and different types of mosquitoes in Germany together with its collaborating partners. www.bnitm.de

The NABU (German Nature and Biodiversity Conservation Union) has been dedicated to humans and the environment for 118 years. With over 620,000 members and sponsors it is the largest environment association in Germany. Alongside its commitment to bird and species protection, NABU is involved in global climate protection and is dedicated to sustainable European agricultural policy, cleaning oceans and many other things. NABU’s particular strength lies in its professional expertise and the practical environment protection work performed by its active members who are organised into 2,000 regional groups. Since 2005, the NABU has been organising the annual citizen science garden bird watch project “Stunde der Gartenvögel” and initiated a winter bird watch project “Stunde der Wintervögel in 2010. In these projects, participants count and report birds seen in gardens and parks on a specific weekend over a period of one hour. www.NABU.de

The Friedrich-Loeffler-Institut (FLI) is a national research centre dedicated to farm animal health and welfare. Its central tasks are preventing, diagnosing and, combating animal epidemics, improving animal farming and animal feed as well as sustaining and using animal energy sources. It is an independent higher federal authority under the Federal Ministry for Food and Agriculture. www.fli.de

The Kommunale Aktionsgemeinschaft zur Bekämpfung der Schnakenplage e.V. (KABS) is an affiliation of 100 municipalities along the Upper Rhine Region with the aim of fighting mosquito plagues biologically. In close collaboration with Heidelberg University, scientists at the KABS and the affiliated “Institut für Dipterolgie” have been involved in investigating mosquito biology, combating mosquitoes and researching their impact on humans for decades.www.kabsev.de

At the German Center for Infection Research (DZIF) approximately 500 scientists and doctors from 35 institutions throughout Germany jointly develop new approaches for preventing, diagnosing and treating infectious diseases. The aim is to translate research results into clinical practice quickly and effectively. With this, the DZIF paves the way for developing new vaccines, diagnostics and drugs against infections. www.dzif.de

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