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Animal disease Mass bird death by Usutu viruses
The so-called Usutu virus has once again triggered extensive bird death in parts of Germany this year. The German Nature Conservation Union (NABU) reports numerous reports of dead birds. The results of virus researchers have confirmed an expansion of the outbreak area.
For the first time, the tropical virus was detected in 2010 in mosquitoes in Germany. In 2011 and 2012, a mass extinction among local birds, especially under blackbirds, reported the NABU. After that, the situation calmed down again and there were no further major outbreaks. This year, however, the reported reports point to a significant increase in infections.
The Usutu virus has led to a mass extinction among native bird species, in particular, the blackbird population was sometimes almost completely eliminated. (Image: Bernd Wolter / fotolia.com) Usutu harmless to humans
Although the virus is harmless to humans, so far only five people have been proven to be infected with the Usutu virus throughout Europe - mostly people with previously compromised immune systems - according to NABU. But the bird population is threatened by the virus many times in their existence. In particular, the blackbird population was almost completely eliminated in the course of the previous outbreaks in some regions. "After a few years without major outbreaks, the virus will increase again in 2016," reports NABU. Since the end of July were reported sick and short time later deceased blackbirds at NABU.
611 suspected cases reported
As of September 23, NABU had called for online reporting of suspected bird diseases and in just 11 days, a total of 611 messages had been received. This is a remarkably high number of suspected Usutu cases compared to about 400 reports in the fall of 2011 and 1,040 reports in the entire outbreak year 2012, reports the NABU. This time, the largest number of reports of sick and dead blackbirds came from North Rhine-Westphalia, in particular from the Lower Rhine and from the Aachen area.
North Rhine-Westphalia hit hardest
In addition, many suspected cases from the areas along the Rhine from Freiburg to Cologne were reported to the NABU, where already in the years 2011 and 2012 a known breakout area was found. Furthermore, more and more reports were received from the Leipzig area and from Berlin as well as from the north of Lower Saxony and from Schleswig-Holstein. Once the reports received have been evaluated and other diseases have been excluded as triggers, the actual spread of the Usutu virus can be determined, reports the NABU.
Examination of dead birds at the BNI
In addition to the online report, it is also possible to send dead birds suspected of using Usutu to the Bernhard Nocht Institute for Tropical Medicine (BNI) in Hamburg. Twenty blackbirds and several other birds have already been examined here and "in total, the BNI and other laboratories have confirmed the suspicion of Usutu infestation in at least 21 cases," according to the NABU statement. Affected were 15 blackbirds and six captive bearded owls. Thus, the observation from the outbreak in 2011/12 confirmed that in addition to blackbirds, especially owls are affected by Usutu diseases.
Infections depending on the mosquito season
Usutu virus deaths occur during the mosquito season from May to November. The increased incidence of Usutu infections this year was certainly favored by the weather, reports the NABU. For a mild winter was followed by a damp early summer and a dry and warm late summer. These are ideal conditions for mosquitoes. Also, the current outbreak areas correspond largely to the areas with the highest late summer daytime temperatures in Germany, the NABU continues.
Infected birds usually die within a few days
Birds affected by the Usutu virus appear to be ill, become apathetic and no longer flee, reports the NABU. Most animals would die within a few days. Given the high proportion of blackbirds affected, the Usutu epidemic was also known as "blackbird dying". But other bird species would be affected by the virus and can die from it. Contrary to the epidemic in 2011/12, few reports of almost complete collapse of local blackbird populations have been reported this year. These come from areas in which the virus 2011/12 not yet occurred. With the onset of autumnal weather and a decrease in mosquito activity, a slow end to the eruption is to be expected.
Monitoring the spread of the Usutu virus
In the following years, according to the experts from April / May, a recurrence of the infections can be expected, with a periodic recurrence of larger Usutu outbreaks in the established range of the virus is likely. About the effects of the recent Blackbird dying on the stock of this species can only speculate at this time. Overall, the outbreak of Usutu infections in Germany represents a unique opportunity to track and analyze the spread and consequences of a new bird disease. "The NABU is working with scientists from the BNI to document and understand the spread of the virus and its effects on our bird life in order to assess this new type of risk of bird species compared to other sources of danger," said the Nature Protection Agency. (Fp)