Outbreaks and results of the surveillance in 2006

Outbreak of highly pathogenic avian influenza H5N1 in 2006
The first outbreak of highly pathogenic avian influenza of the type H5N1 ever recorded in Denmark was confirmed on 18 May 2006. The outbreak occurred in a backyard holding in Funen Country.

The source of infection was probably wild birds, because the affected birds had not been kept in net-covered enclosures in order to minimize contact with the wild birds as prescribed in the Danish legislation at that time. The flock was close to the finding place of a wild bird isolate made a few weeks before. A magpie found dead on the affected premises was diagnosed with highly pathogenic avian influenza H5N1 on the 29 May 2006.

Protection and surveillance zones as well as A and B areas were immediately established on 18 May 2006 on the basis of the positive virologic result. All birds in the herd were immediately killed and sent to an approved rendering plant. Further to this, the infected holding were cleaned and disinfected. The zones were lifted on 30 June 2006 following an extended screening of poultry within the zones. This outbreak did not cause any secondary outbreaks, and reoccurrence of the disease has not been observed since then.  

Detection of low pathogenic avian influenza in poultry in 2006
The surveillance of poultry and game birds for restocking was intensified in February 2006. The surveillance was based on serology. PCR testing was only used for ducklings or chickens from game birds.

Nearly 2% of the herds examined in 2006 through this surveillance were found positive in serological tests. Further testing for circulating virus in these herds did not result in any positive findings.

However, the virological testing of offspring from mallards resulted in three herds with mallards for restocking found infected with low pathogenic avian influenza H5N2 and H5N3 in June and July 2006. These three herds were all killed. In two of these herds, the infection was thought to originate from contact with wild birds. In the third herd, the infection most likely originated from indirect contact with one of the other infected herds. There were no clinical signs in any of these herds, and in all three herds mallards were carrying the infection.

In all cases, restriction zones were immediately established on the basis of the positive PCR result. A further four herds with game birds for restocking were found positive in virological tests with subtypes other than H5 or H7 - one of these were H6N8, the others could not be typed.

Chronological overview of outbreaks of low pathogenic avian influenza H5 in poultry in Denmark in 2006

First administrative division	Name of location	Date of confirmation of LPAI (H5)	Affected population
Funen County	Tommerup	02/06/2006	Game bird holding.
Viborg County	Løvel	05/07/2006	Game bird holding.
Funen County	Illebølle	19/07/2006	Game bird holding.

Surveillance of wild birds in 2006
The survey programme for avian influenza in wild birds in 2006 consisted of a  surveillance for AI in wild birds found dead and a surveillance in waterfowl reservoirs and along migratory flyways. Additionally, an extraordinary survey with in total 1007 samples of fresh droppings from wild birds was established around the Danish high pathogenic avian influenza H5N1 outbreak.

In January and the beginning of February 2006, only very few dead birds were sent in for examination, but after the infection spread among wild birds in Europe from the middle of February, this changed considerably. The number of birds examined was highest in March falling to a lower level in May and June. This was due to both increased awareness towards avian influenza among the general public and the Danish Veterinary and Food Administration's call via the media for sending in dead birds. Many birds died during the winter, which was colder and lasted longer than normally.

The first finding of high pathogenic avian influenza H5 in wild birds in Denmark was confirmed on 14 March 2006. Subsequently, it was shown to be of the type H5N1, which had been found in wild birds in wild birds in large parts of Europe.

In total, 44 wild birds were found infected with HPAI H5N1 in six counties in March-May of 2006. Wild birds found infected with H5N1 were

• primarily ducks (60%)
• but also swans (16%),
• birds of prey (18%),
• crows (2%)
• and other waterfowl (4%).

The last case was confirmed on 29 May. In all cases, protection and surveillance zones were immediately established around the place of finding on the basis of positive PCR results. On the figure below the zones established in April at the height of the epidemic is shown.

 

In total, 1189 dead birds have been examined in 2006. The dead wild birds were sent in from the whole country, but the positive findings were concentrated in the south-eastern Denmark especially along the Baltic sea as illustrated on the figure below.

Birds infected with HPAI H5N1 were found in areas, where the density of wild ducks and swans normally are high in winter/early spring.

In 2006, 5530 samples of bird droppings (active surveillance) were analysed by PCR. All samples were negative for high pathogenic H5N1, except one pool of samples from five herring gulls collected near the twon Bisserup in the County of Storstrøm. The gulls had not shown any clinical signs at the time the samples were conducted. The location, where the samples were taken, was in an already established zone due to the finding of a positive wild dead bird.

Other avian influenza virus subtypes isolated in the active surveillance were two H2N3 (LP), one H13N6 (LP) and one H14N5 (LP).

Chronological overview of the detections of highly pathogenic avian influenza (HPAI H5) in wild birds in Denmark in 2006

First administrative division	Name of location	Date of confirmation of HPAI (H5)	Affected species
Storstrøms Amt	Svinø	14/03/2006	1 common buzzard (Buteo buteo)
Fyns Amt	Ærøskøbing	17/03/2006	9 tufted ducks (Aythya fuligula)
Fyns Amt	Ærøskøbing	19/03/2006	7 tufted ducks (Aythya fuligula)
Frederiksborg Amt	Frederikssund	21/03/2006	1 whooper swan (Cygnus cygnus)
Storstrøms Amt	Præstø	22/03/2006	1 tufted duck (Aythya fuligula)
Fyns Amt	Ærøskøbing	22/03/2006	3 tufted ducks (Aythya fuligula)
Fyns Amt	Drejø	24/03/2006	1 peregrine falcon (Falco peregrinus)
Fyns Amt	Svendborg	25/03/2006	1 greylag goose (Anser anser)
Storstrøms Amt	Guldborgsund	25/03/2006	1 tufted duck (Aythya fuligula)
Fyns Amt	Fåborg	27/03/2006	2 mute swans (Cygnus olor) 1 tufted duck (Aythya fuligula)
Storstrøms Amt	Nysted	27/03/2006	1 common buzzard (Buteo buteo)
Storstrøms Amt	Stubbekøbing	27/03/2006	1 tufted duck (Aythya fuligula)
Frederiksborg Amt	Skibby	27/03/2006	1 rough-legged buzzard (Buteo lagopus)
Sønderjyllands Amt	Sønderborg	29/03/2006	1 common buzzard (Buteo buteo)
Sønderjyllands Amt	Kegnæs	30/03/2006	1 tufted duck (Aythya fuligula)
Bornholms Amt	Vang	31/03/2006	1 mute swan (Cygnus olor)
Vestsjællands Amt	Skælskør	31/03/2006	1 tufted duck (Aythya fuligula)
Storstrøms Amt	Bandholm	01/04/2006	1 tufted duck (Aythya fuligula)
Fyns Amt	Fåborg	01/04/2006	1 common buzzard (Buteo buteo)
Storstrøms Amt	Nysted	06/04/2006	1 whooper swan (Cygnus cygnus)
Fyns Amt	Ullerslev	07/04/2006	1 common buzzard (Buteo buteo)
Frederiksborg Amt	Hornbæk	07/04/2006	1 common buzzard (Buteo buteo)
Storstrøms Amt	Præstø	10/04/2006	1 whooper swan (Cygnus cygnus)
Frederiksborg Amt	Skibby	10/04/2006	1 mute swan (Cygnus olor)
Sønderjyllands Amt	Gråsten	02/05/2006	1 great crested grebe (Podiceps cristatus)
Fyns Amt	Kerteminde	26/05/2006	1 magpie (Pica pica)

 

Cases of HPAI in wild birds in 2006 distributed by species group

Group	Number of infected birds	Number of dead birds tested	Proportional mortality rates
Ducks	26	170	15%
Swans	7	181	4%
Birds of prey	8	415	2%
Gulls and terns	0	119	-
Crows	1	60	2%
Other water fowl	2	110	2%
Other birds	0	65	-
Total	44	1120	4%

 

Contact

Animal Health Division - 1kontor@fvst.dk