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West Nile Virus Austria

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					         Food and Farming Group
         International Animal Health
          International Disease Monitoring
                                              Preliminary Outbreak Assessment
Ref: VITT 1200/WNV – AUSTRIA
Date: 16 October 2008


                                  West Nile Virus: Austria
Note: Defra’s International Animal Health (IAH) monitors outbreaks of specified disease around the
world. We also report on significant epidemiological developments for certain diseases. West Nile Virus
(WNV) is among those diseases.

1   Introduction

The Austrian veterinary authorities have reported two outbreaks of West Nile Virus (WNV) in
wild birds, one in North Austria and one in Vienna region (see Map 1). Two sparrow hawks,
one dead and one ill which later died, were found in North Austria. Both showed signs of
encephalitis at post mortem and tests revealed the presence of WNV. One Kea (Nestor
                                                                      notabilis) was found
                                                                      dead in Vienna and
                                                                      subsequently also
                                                                      tested positive for
                                                                      WNV. At the Standing
                                                                      Committee on the Food
                                                                      Chain and Animal
                                                                      Health (SCoFCAH)
                                                                      meeting in Brussels on
                                                                      15 October 2008,
                                                                      Austria reported that
                                                                      the virus isolated from
                                                                      the sparrow hawks was
                                                                      WNV lineage 2 with
                                                                      very high sequence
                                                                      homology with two
                                                                      strains found previously
                                                                      in Hungary in 2004 and
                                                                      2005.

The virus isolated from the Kea was also WNV lineage 2, but there were no details on the
sequence homology. Disease control measures have been put in place, along the same lines
as those used under the Avian Influenza framework. That is, all wild birds found dead in the
area will be investigated for WNV. Veterinary Authorities have been informed about the need
to check horses with signs of central nervous system disease for WNV infection and Health
Authorities have been advised about the clinical signs of human cases.

2   Situation Assessment

WNV is a mosquito borne disease and there is no direct transmission of the virus between
susceptible species. WNV has recently been isolated from horses and wild birds in Northern
Italy (Defra, 2008; map above). To date, there have been 14 outbreaks in 20 horses in Emilia
Romagna and Bologna regions (OIE 2008a). Seven magpies and six carrion crows were also
found to be infected during routine surveillance. Recently, Italy have also reported two human
cases in Emilia Romagna (Rossini and others, 2008). The local human population has been
advised to take appropriate measures to avoid being bitten by mosquitos. The distance
between these outbreaks in Italy and Austria is approximately 500km.

Horses are dead end hosts, in that infected animals produce very low levels of circulating
virus and do not contribute to the transmission cycle. There have been no reported cases of
infected horses in Austria. Nevertheless, in order to move between EU Member States,
registered equidae require official veterinary certification of freedom from clinical disease.
They also must not originate from a holding subject to disease control restrictions. EU rules
do not require testing for WNV.

West Nile viruses can be broadly split into two lineages: Lineage 1 is widely distributed
around the world, in North America, Asia, Europe and Africa, while Lineage 2 almost
exclusively contains viruses from Africa, but is carried into Europe by migrating birds (Lanciotti
and others, 2008). Generally WNV infection in Europe causes low mortality in wild birds in
contrast to the North American infections (Figuerola and others, 2008). However, recently
clinical signs have been observed in wild birds of prey in Spain (Hofle and others, 2008). In
the Austrian cases, mortality was high and pathophysiological signs of encephalitis were seen.
While sparrow hawks are native to Austria, the Kea is a non-native bird (a parrot native to
New Zealand) thus may have had no previous exposure to virus and hence be more
susceptible to this particular strain.

The Department of Health (DH) has published a contingency plan to cover surveillance,
diagnosis, prevention and control of WNV, should there be any change in risk (Dept of Health,
2004).

3    Conclusion

There is continuing risk of disease introduction through wild birds into the UK. Wild birds
continue to be tested for WNV in the UK according to the Defra surveillance framework (see
http://www.defra.gov.uk/animalh/diseases/notifiable/westnilevirus/index.htm).

Currently, we consider that there would be a negligible risk of introduction of the disease from
imported horses from Austria. It is expected that infected horses would either show clinical
signs or be asymptomatic. However, horses are demonstrated to harbour very low levels of
virus and are considered to be dead end hosts.

We will continue to monitor and review developments.

4    References

Defra (2008) West Nile Virus in Italy. http://www.defra.gov.uk/animalh/diseases/monitoring/pdf/wnv-
      italy.pdf Accessed 16 October 2008.

Defra (2008) Disease factsheet: West Nile Virus (WNV).
      http://www.defra.gov.uk/animalh/diseases/notifiable/westnilevirus/index.htm#6 Accessed 16
      October 2008.

Department of Health (2004) West Nile Virus: A contingency plan to protect the public’s health.
     Publication 40168: DH Publications, PO Box 777, London SE1 6XH. Available on-line at
     http://www.dh.gov.uk/assetRoot/04/08/33/33/04083333.pdf

Figuerola, J., Jimenez-Clavero, M.A., Lopez, G., Rubio, C., Soriguer, R., Gomez-Tejedor, C., Tenerio,
      A. (2008) Size matters : West Nile Virus neutralizing antibodies in resident and migratory birds in
      Spain. Veterinary Microbiology. 132: 39-46.
Hofle, U., Blanco, J.M., Crespo, E., Naranjo, V., Jimenez-Clavero, M.A., Sanchez, A., de la Fuente, J. &
      Gortazar, C. (2008) West Nile virus in the endangered Spanish imperial eagle. Veterinary
      Microbiology. 129: 171-178.

OIE. (2008). OIE Alert Message AUT 15-10-08. Received by e-mail 15 October 2008.

OIE (2008a) Follow-up Report No. 3. http://www.oie.int/wahid-
      prod/reports/en_fup_0000007423_20081013_162702.pdf. Accessed 16 October 2008

Rossini, G., Cavrini, F., Pierro, A., Macini, P., Finarelli, A.C., Po, C., Peroni, G., Di CAro, A.,
     Capobianchi, M., Nicoletti, L., Landini, M.P., Sambir, V. (2008) First human case of West Nile
     virus neuroinvasive infection in Italy, September 2008 – case report. Eurosurveillance 13: 19002.
     Available on line at http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19002. Accessed
     16/10/2008.

				
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