Another blackbird death by Usutu viruses

Researchers expect another blackbird death

04/19/2012

The Bernhard Nocht Institute for Tropical Medicine (BNI) was able to prove the Usutu virus in wintering mosquitoes, which had led to a massive blackbird mortality last year. In a joint press release, the BNI, the German Nature Conservation Association (NABU) and the Community Action Group for the Control of Snaring (KABS) warn against a renewed spread of the pathogens.

„We have proved that the Usutu virus has overwintered in native mosquito species and thus in the early summer again blackbirds in Germany can be infected“, explains the scientific director of KABS, Norbert Becker, in the current release. Last year, the Usutu virus caused the deaths of thousands of blackbirds, with songbirds nearly wiped out in some regions of the Rhine plain. The pathogens can cause the so-called Usutu fever in humans. However, such infections are extremely rare and especially affect immunocompromised people.

Experts warn against another blackbird mass extinction
The BNI in Hamburg, the NABU and the KABS warn in view of the detection of Usutu viruses in overwintering mosquitoes from another blackbird mortality. Although no corresponding pathogens have been detected in the dead birds examined so far this year, the mosquito season has not yet begun. Last year, scientists from the BNI were able to detect the African virus in dead blackbirds from Birkenau in Hesse for the first time, thus establishing a clear connection between the enigmatic mass bird dying and the pathogen. Above all, southern Hesse, Baden-Württemberg and Rhineland-Palatinate were affected. For example, in Rhineland-Palatinate the population of blackbirds declined by almost 50 percent compared to 2010, the experts report. According to the NABU, songbirds have almost completely disappeared in the northern Upper Rhine plain. The North German region, however, has so far been spared by the tropical virus.

Usutu viruses detected in overwintering mosquitoes
According to the latest press release, the BNI had „Dead blackbirds from Baden-Württemberg, Hesse and Rhineland-Palatinate were again received in the spring to study the tropical Usutu virus.“ So far, all test results were negative. „Our quick test results on Usutu viruses were all negative for the 25 dead birds sent in“, stressed the head of virological diagnostics at the BNI, Dr. med. Jonas Schmidt-Chanasit. But this is no reason to be all-clear, as the pathogens were detected in overwintering mosquitoes. In the summer months, the experts expect therefore with another blackbird dying. „An outbreak is expected depending on the weather in late spring or summer“, said the physician and ornithologist Dr. med. Stefan Bosch from Naturschutzbund Germany. It could be the Usutu virus „Depending on the mosquito population, it can also be transferred to birds of other neighboring areas“, so the statement of Dr. Bosch in the press release „Renewed blackbird mortality due to tropical virus is expected in the summer“.

Usutu virus can also infect humans
The Usutu virus originated in Africa, where the pathogen was discovered in 1959. Outside of Africa, Usutu viruses first appeared in Vienna in 2001. Presumably, the viruses were introduced by migratory birds. The pathogen may also be dangerous to humans, as evidenced by the infection of two immunocompromised patients in Italy in 2009. Those affected suffered a potentially life-threatening meningitis in addition to the common symptoms of Usutu fever, such as headache, rash, and fever. In 2010, the experts of the BNI showed the pathogens in Germany for the first time in mosquitoes, in 2011 succeeded in the detection of dead blackbirds. The songbirds were apparently particularly susceptible to the pathogens, with infected blackbirds often having symptoms like one „shaggy plumage in the neck and head area“ accompanied by „bright coloring, apathetic behavior and movement disorders“ showed, explained the NABU speaker, Markus Nipkow.

Population called for assistance
According to a joint statement by BNI, NABU and KABS, it applies „First of all, to geographically isolate the areas affected by the outbreak and to fight the carrier mosquito there, also to minimize the risk of human infections.“ In order to check the spread of Usutu viruses, according to the experts, as many animals as possible must be examined by virology. For that reason should „Dead blackbirds and other birds are sent as soon as possible to the BNI, the KABS or a local veterinary office“, explain the doctors and environmentalists. Also in the fight against the carrier mosquito each individual can help by: „all unnecessary water retention will be eliminated“, because here „many hundreds of house mosquitoes develop as larvae into pupae to avian insect“, so the message of the BNI, NABU and the KABS. Furthermore, the experts advise „frequent nesting sites (eg rain barrels, gullies, manure pits) with Culinex Bti tablets“ to treat. These tablets are based on a protein of Bacillus thuringiensis israelensis, which kills only the mosquito larvae, but does not harm other animals and humans. „One to two tablets kill the mosquitoes for two to four weeks in a rain barrel“, so the statement in the current release. (Fp)

Picture: Jens Bredehorn