This information may be of interest to some-( Usutu, I understand, is a flavivirus with a bird/mosquito cycle like Murray Valley encephalitis virus)
Robin Hide
USUTU VIRUS - NETHERLANDS
*************************
A ProMED-mail post <http://www.promedmail.org>
ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>
Date: Thu 10 Nov 2016
Source: Euro Surveill [edited] <http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=22635>
Citation: Rijks J, Kik M, Slaterus R, Foppen R, Stroo A, IJzer J, et al. Widespread Usutu virus outbreak in birds in the Netherlands. Euro Surveill. 2016;21(45):pii=30391.
Abstract
--------
We report a widespread Usutu [USUV] virus outbreak in birds in the Netherlands. Viral presence had been detected through targeted surveillance as early as April 2016 and increased mortality in common blackbirds and captive great grey
owls was noticed from August 2016 onwards. Usutu virus infection was confirmed by post-mortem examination and RT-PCR. Extensive Usutu virus activity in the Netherlands in 2016 underlines the need to monitor mosquito activity and mosquitoborne infections in
2017 and beyond.
Discussion
----------
There is a widespread USUV outbreak in wild blackbirds and captive great grey owls in the Netherlands. Although USUV circulated in neighbouring countries, it had not been detected in the Netherlands before 2016, despite scanning surveillance
for bird mortality since 2008 and a targeted study in dead blackbirds based on convenience sampling in 2012. USUV emerged in Europe in Italy 20 years ago; however, introductions from Africa probably started several decades earlier and continue to occur. The
virus has been detected in mosquitoes, birds and bats in 8 European countries (Austria, Belgium, Czech Republic, Germany, Hungary, Italy, Spain, Switzerland) and is presumably maintained in enzootic mosquito-bird transmission cycles.
Birds of 14 orders can be infected. In the current outbreak in the Netherlands, live bird monitoring showed the presence of the virus in wild birds already months before the detection of unusual death rates among blackbirds and great
grey owls. USUV outbreaks also occurred in birds in neighbouring countries, Belgium and Germany, in 2016 (personal communication: M Garigliany and J Schmidt-Chanasit, August 2016). A comprehensive genetic study including strain data from affected neighbouring
countries is under way to elucidate the origin of events and patterns of spread.
High mosquito abundance may have been one of the factors contributing to the occurrence and scale of the outbreak in the Netherlands. In Europe, the _Culex pipiens_ mosquito is considered an important vector for USUV. The _Culex pipiens/torrentium_
complex is found throughout the Netherlands between April and October. June 2016 was extremely wet and, together with unusually high temperatures in September [2016], may have furthered and prolonged mosquito activity. The event demonstrates the need for long-term
standardised datasets on mosquito abundance in the Netherlands and their analysis in relation to climate. The samples of captured mosquitoes could be one pillar in a molecular surveillance programme for USUV and other mosquitoborne zoonotic viruses.
In birds, fatal infections occur mostly in Passeriformes and Strigiformes. Hepatosplenomegaly is a common finding. Histological lesions include encephalitis and necrosis in heart, liver, spleen and kidney, with lymphoplasmacytic inflammation.
In this outbreak, the pathological findings raised 2 questions. Firstly, many of the birds were co-infected with _Plasmodium_ spp. Mosquitoes are the vectors of both USUV and _Plasmodium_ spp., which may explain the high number of dual infections. Alternatively,
a fatal outcome of USUV infection may be more probable in co-infection. Secondly, while skin lesions during USUV outbreaks have been reported earlier, causal association is unknown and needs to be studied.
We used citizen science data to identify the area where the virus probably circulated most intensively up to 23 Sep 2016. Infected blackbirds maintain virus circulation, and the observed pattern will partly reflect the density of resident
blackbird populations. Ongoing wild bird counts will provide insight into the impact of USUV on resident bird populations.
The emergence of USUV in the Netherlands illustrates the continuous geographical expansion of zoonotic arboviruses in Europe, documented elsewhere. It serves as another warning of the expanding geographical range of regions suitable
for sustained arbovirus circulation. In areas with endemic circulation, human infections seem to occur very rarely with only 13 human cases described in literature until now.
Human clinical cases present with neurological signs, fever, rash, jaundice or combinations thereof. Subclinical human USUV infections are a concern in blood transfusions or organ transplants, and recent data from Italy suggest that
subclinical cases in regions with sustained USUV circulation may be commoner than previously thought.
The same study showed that USUV was the cause of previously unexplained encephalitis cases, indicating that USUV should be included in the differential diagnosis of such cases in endemic areas.
These recent public health findings suggest that USUV diagnostic capability and adequate USUV surveillance with molecular typing are warranted in regions shown to be suitable for USUV circulation.
Although the 2016 mosquito season is coming to an end, physicians should be aware of putative USUV infection in cases of viral encephalitis of unknown aetiology, and vigilance should be maintained in the coming mosquito season in 2017.
--
communicated by: ProMED-mail <>
[USUV appears to be spreading across Europe. There was an outbreak in Germany in 2011-2012. Originating from Africa in the summer of 2011, USUV virus was cause of a mass die off of blackbirds in south west Germany. Again in the summer
of 2012, dozens of birds died and USUV was found in mosquitoes (_Culex pipiens_) in Germany.
As Mod.AS noted in the ProMED-mail post [Usutu virus - Germany (02): birds, conf.
http://promedmail.org/post/20110916.2827] of 16 Sep 2011, "USUV 1st detection outside Africa took place in Vienna, Austria, in 2001, causing deaths in blackbirds (_Turdus merula_) and great gray owls (_Strix
nebulosa_). In 2002, USUV was still circulating in Austria, demonstrating that USUV has managed to overwinter in a local bird-mosquito cycle in central Europe. More recently, USUV-specific RNA or antigen was also detected in birds or mosquitoes in Hungary,
Switzerland, Italy and Spain. In the summer of 2009, USUV-related illnesses were reported in 2 immunocompromised patients in Italy. Antibodies were detected in UK in wild birds in 2002."
Usutu is a member of the mosquito transmitted flaviviruses belonging to the Japanese encephalitis virus group.
Reference
---------
Vazquez A, Jimenez-Clavero M, Franco L, Donoso-Mantke O, Sambri V, Niedrig M, et al. Usutu virus - potential risk of human disease in Europe. Euro Surveill. 2011;16(31). pii: 19935. Available at <http://www.eurosurveillance.org/images/dynamic/EE/V16N31/art19935.pdf>.
- Mod.TY
