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.