1.2 Cattle diseases

The major cattle disease event in the period 1999-2005 was the detection of the first case of bovine spongiform encephalopathy (BSE) in a Danish-born cow in February 2000. In total, 17 cases of BSE had been confirmed in Danish cows by the end of 2005. Denmark maintained its status given by the European Union regarding bovine herds as officially free of brucellosis, tuberculosis and enzootic bovine leucosis. None of these diseases has been diagnosed in cattle for more than a decade. Denmark is also recognised as free from infectious bovine rhinotracheitis (IBR) by the European Union. However IBR was diagnosed in four herds and in one imported animal in 2002, and was diagnosed in one herd in 2003 and in one herd in 2005. Furthermore Denmark is in the final stages of the successful eradication of bovine virus diarrhoea.

Bovine spongiform encephalopathy (BSE)

The first case of BSE in a Danish-born cow was diagnosed in February 2000. In Denmark, 17 cases of BSE have been found in Danish-born cows, three of which were found in cattle exported to other countries. BSE was made notifiable in 1990, and the surveillance for the disease in 1999 was limited to testing of animals with clinical signs of BSE. After finding the first positive BSE case, the surveillance was extended to include random sampling of about 15,000 cattle from different risk groups (fallen stock, emergency slaughter etc.) for BSE testing. According to EU regulations, the surveillance programme was later altered to include:

• All healthy slaughter animals older than 30 months (ini-tiated on 1 January 2001). These animals must test negative for BSE before being released for consumption.
• All fallen stock older than 24 months (initiated on 1 July 2001).
• All emergency-slaughtered animals older than 24 months (initiated on 1 January 2001).
• AM animals older than 24 months (initiated on 1 July 2001). AM animals are cattle which, at the ante-mortem inspection at the slaughterhouse, are suspected of having a disease that can spread to other animals or humans, or which show signs of a disease that could make the meat unsuitable for human consumption.
• Animals imported from the United Kingdom (initiated in 1996). These animals were imported to Denmark before 1990, when importation from the United Kingdom was prohibited. Only one animal imported to Denmark from the United Kingdom is still alive.
• Feeding cohort animals (initiated in 2000). These animals are cattle born between 1 August 1995 and 31 July 1997 and have been fed the same feed as the livestock in which the first positive BSE case occurred in February 2000. Initially this cohort consisted of approximately 11,000 animals. Because all the remaining animals are now older than 30 months, they are automatically tested for BSE when sent for slaughter. So a special surveillance procedure for feeding cohort animals no longer exists.
• All animals above 24 months of age from a BSE-positive herd (initiated in 2001).
• Animals with clinical symptoms of BSE (initiated in 1990).

The removal of SRM from all slaughtered animals is considered to be the most important consumer protection factor.

The results of the surveillance programme for BSE for the period 2001-2005 are summarised in table 4.

Table 4: The Danish BSE surveillance programme, 2001-2005.

Target group	2001		2002		2003		2004		2005
	Neg.	Pos.	Neg.	Pos.	Neg.	Pos.	Neg.	Pos.	Neg.	Pos.
Fallen stock	20,296	2	34,289	2	38,037	0	36,163	1	36,224	1
Emergency slaughter	1,797	0	1,680	0	1,682	0	1,803	0	2,024	0
AM animals	99	0	24	0	16	0	7	0	9	0
Healthy slaughter animals	250,408	3	254,667	1	250,358	1	246,156	0	216,687	0
UK animals and animals from BSE suspected or positive herds	4,025	0	2,640	0	1,967	0	95	0	6	0
Clinical suspects	70	1	38	0	37	1	18	0	11	0
Total	276,695	6	293,338	3	292,097	2	284,242	1	254,961	1

Immediately after finding the first positive BSE case, Denmark started removing specified risk material (SRM) from carcases of slaughtered animals. The removal of SRM from all slaughtered animals is considered to be the most important consumer protection factor. Further consumer protection was obtained through a ban on mechanically recovered meat and a ban on pithing. On 1 January 2001, the Danish Veterinary and Food Administration introduced a total ban on feeding of processed animal protein (including meat and bone meal (MBM), fish meal, etc.) to animals that are kept, fattened or bred for the production of food. This total feed ban was a further tightening of the two previous feed bans prohibiting feeding ruminant MBM to ruminants (1990) and feeding mammalian MBM to ruminants (1997).

Additionally, all animal waste from cattle (including animals killed in the BSE eradication programme, SRM from slaughter animals, etc.) is processed as SRM at an incineration plant by high-pressure sterilisation using 133C for 20 minutes at a 3-bar pressure. The resulting fat and MBM is subsequently incinerated. SRM is not allowed to re-enter the food or feed chain.

The tests applied in the surveillance programme are tests approved by the European Union. In case of a suspicion of BSE, the herd of origin is immediately placed under movement restrictions, and movement restrictions are also imposed on animals with relation to this herd. Additionally, if a rapid test of a slaughter animal is found positive all parts of the animal are destroyed as SRM irrespective of the result of the verification test. The carcases of one animal before and two animals after the relevant animal in the slaughter line are also destroyed as SRM due to the risk of contamination with tissue from the animal tested positive in the slaughter process.

Until 2005, Denmark used a herd culling strategy in the eradication of the disease. All animals on holdings where BSE was diagnosed were killed and incinerated as SRM together with animals related to these holdings. Due to the documented low prevalence of the disease, Denmark has altered the eradication policy in 2005 to cohort culling. This cohort culling was used when handling the 17th case of BSE in a Danish-born cow, which was diagnosed in September 2005. In Denmark, samples are taken from animals older than 24 months for BSE testing prior to the incineration. So far no animals in Denmark have tested positive for BSE in this group.

Table 5: Data regarding the 17 Danish BSE cases.

Case no.	Date of birth	Age in months	Surveillancecategory	Average age per year (months)	Year of diagnosis
1	1996-07-01	42	Clinical suspect	-	2000
2 3 4 5 6 7	1993-07-01 1997-02-08 1996-02-23 1996-03-12 1996-06-25 1998-05-23	90 48 65 65 64 41	Fallen stock Clinical suspect Healthy slaughter Fallen stock Healthy slaughter Healthy slaughter	62	2001
8 9 10 Exp. P* Exp. I**	1996-06-17 1996-01-03 1998-12-08 1999-03-15 1996-04-13	70 80 46 39 80	Healthy slaughter Fallen stock Fallen stock Healthy slaughter Healthy slaughter	63	2002
11 12 Exp. P*	1997-08-25 1996-03-01 1996-12-19	67 84 78	Clinical suspect Healthy slaughter Fallen stock	76	2003
13***	1990	168	Fallen stock	-	2004
14	1996-03-01	113	Fallen stock	-	2005

^* Export Portugal, ^** Export Italy, ^***Diagnosed as "Atypical BSE".

The Danish BSE cases break down into three clinical cases, seven fallen stock and seven healthy slaughter animals the youngest case being born in 1999 (healthy slaughter) and the oldest in 1990 (fallen stock). Most (10) of the Danish cases were born in 1996. Table 5 summarises data regarding the 17 Danish BSE cases, and figure 1 shows the geographical distribution.

Figure 1: The geographical distribution of BSE cases in Denmark.

The Danish BSE cases break down into three clinical cases, seven fallen stock and seven healthy slaughter animals the youngest case being born in 1999 (healthy slaughter) and the oldest in 1990 (fallen stock). Most (10) of the Danish cases were born in 1996. Table 5 summarises data regarding the 17 Danish BSE cases, and figure 1 shows the geographical distribution.

Compared to the other EU Member States, Denmark can document a low and significantly downward prevalence of the disease as illustrated by figure 2.

Figure 2: Bovine Spongiform Encephalopathy in the European Union, 2001-2005. Source: EU Commission.

The National Veterinary Institute has made a prognosis indicating that, as at 1 January 2006, the total number of new BSE cases for the period 2006-2010 will be 0.14.

Infectious bovine rhinotracheitis (IBR/IPV)

Denmark is recognised as free from infectious bovine rhinotracheitis (IBR) by the European Union (EC Commission Decision 2004/558/EC).

National control measures to prevent the infection from spreading were implemented in April 1984. As from February 1991, the infection was considered eradicated. In December 1992 Denmark was recognised as free from IBR by the European Union and has since then maintained this disease-free status.

A serological surveillance programme, sufficient to provide a 99% level of confidence of detecting IBR/IPV if present at a prevalence rate exceeding 0,2% of the cattle herds, is carried out by testing of bulk milk samples and blood samples from slaughterhouses. The sampling strategy was changed on the basis of an epidemiological evaluation of the surveillance programme and because a recently established on-line identification system at the slaughterhouses made it possible to select individual cattle for testing. The new sampling strategy was implemented in June 2004:

• Before June 2004 quarterly bulk milk samples from all dairy herds and blood samples from every sixth slaughter animal above eight months were tested.
• After June 2004 bulk milk samples from all dairy herds in Denmark (excluding Southern Jutland County) are tested four times a year, and bulk milk samples from all dairy herds in Southern Jutland County are tested each month. Monthly bulk milk samples from dairy herds that have imported livestock are tested in the six months following importation. Blood samples from slaughter animals above eight months of age, with a probability of random selection for testing of 15% in the summer half-year and 25% in the winter half-year, from all beef herds in Denmark (excluding Southern Jutland County) are tested. All beef herds in Southern Jutland County and all beef herds that have imported cattle within the last six months which have sent cattle for slaughter have to test one blood sample from an animal older than eight months per herd per month in the 2nd and 3rd quarters, and two blood samples from an animal older than eight months per herd per month in the 1st and 4th quarters.

The number of bulk milk samples and blood samples examined in each year is given in table 6.

Table 6: Number of bulk milk samples and blood samples examined under the surveillance programme for infectious bovine rhinotracheitis (IBR/IPV), 1999-2005.

Year	No. of bulk milk samples	No. of blood samples
1999	45,717	115,433
2000	47,533	109,015
2001	39,960	112,628
2002	38,425	116,547
2003	34,425	120,550
2004	32,296	65,560
2005	30,002	34,078

"In December 1992 Denmark was recognised as free from IBR by the European Union and has since then maintained this disease-free status.

In 2002 IBR was diagnosed in four herds and in one imported animal:

• In April 2002, IBR was diagnosed in three dairy herds, which were located in the southern part of Jutland. All animals from the three herds were subsequently slaughtered and the holdings were cleaned and disinfected. The three infected herds were all found by serological tests. None of the animals showed any clinical signs. No common factor was found that explained the introduction and transmission of the infection to the three positive herds. All contact herds and all herds in a 2-km zone around the infected herds were tested and found to be IBR negative. The three outbreaks were diagnosed within 10 days; the distance from each herd to the German border is less than 21 km.
• On 15 August 2002, a calf imported from the Netherlands reacted seropositive for IBR and the farm was put under restrictions. The seropositive calf was slaughtered and all other cattle on the farm were tested 30 days later all with a negative result. The restrictions on the herd were subsequently lifted.
• On 14 November 2002, a cow was found positive for IBR by detection of antibodies for IBR in a slaughter blood sample. The herd of origin, a herd near Bylderup Bov in the southern part of Jutland, was placed under restrictions and all cattle in the herd were blood tested with a negative result. Thirty days after this first blood test, all the animals were tested again for IBR and again with a negative result. On 13 December 2002, the restrictions on the herd were lifted.

In 2003, IBR was diagnosed in one herd. The IBR-positive herd was detected on 8 September 2003. All animals in the herd were subsequently slaughtered and the holding was cleaned and disinfected.

On the 2 September 2005, a cow was found positive for IBR by detection of antibodies for IBR in a slaughter blood sample. The herd of origin was placed under restrictions and all cattle in the herd were blood tested with a negative result. Thirty days after this first blood test, all the animals were tested again for IBR and again with a negative result, and the restrictions on the herd were lifted.

Figure 3: Geographical distribution of the herd outbreaks of IBR in Denmark in 2002 (•), in 2003 (•), in 2005 (•) and location of the imported animal with IBR antibodies (•).

Bovine brucellosis

Since 1979 Denmark has been declared officially free of brucellosis as regards bovine herds by the European Union (EC Commission Decision 2004/320/EC).

The official eradication programme for bovine brucellosis began in 1948, and all cattle herds were registered as free from brucellosis in 1959. Bovine brucellosis has not occurred in Denmark since 1962.

Bovine tuberculosis

The eradication of bovine tuberculosis in Denmark was initiated already in 1893.

Since 1980 Denmark has been declared officially free of tuberculosis as regards bovine herds by the European Union (EC Commission Decision 2004/320/EC).

The eradication of bovine tuberculosis in Denmark was initiated already in 1893. A surveillance programme replaced the eradication programme in 1959 due to the fact that the eradication was so advanced that few outbreaks were diagnosed each year. In 1980 Denmark was declared officially free of tuberculosis as regards bovine herds by the European Union.

The Danish surveillance programme for demonstrating the absence of tuberculosis in cattle consists of clinical examination in conjunction with meat inspections and tuberculin tests of selected animals. All slaughter animals are examined in the meat inspection for possible clinical signs of tuberculosis. Furthermore, bulls are tuberculin tested prior to introduction into a bull station, and cattle are tuberculin tested prior to exportation.

Tuberculosis has not been diagnosed in cattle since 1988, when a cow with clinical symptoms of tuberculosis was identified at the meat inspection. The laboratory examinations confirmed the suspicion of bovine tuberculosis.

The herd of origin was examined, but the disease was not confirmed in any other animal from the herd.

In 1988 bovine tuberculosis was diagnosed in farmed fallow deer. The herd in question was heavily affected, and all animals were destroyed. A national programme for eradication of bovine tuberculosis in farmed deer was initiated, and during 1988 and 1989 the presence of the disease was confirmed in another 12 herds. One infected herd was found in 1991, one in 1993 and yet another in 1994, making a total of 16 infected deer herds. Restrictions have been lifted on all 16 infected premises, and at present no herds are considered infected. The Danish surveillance programme for demonstrating the absence of tuberculosis in farmed deer consists of clinical examination in conjunction with meat inspections, and all slaughter animals are examined in the meat inspection for possible clinical signs of tuberculosis.

Enzootic bovine leucosis

Enzootic bovine leucosis has not occurred in Denmark since 1990, and Denmark has been declared officially free of enzootic bovine leucosis since 1991 by the European Union (EC Commission Decision 2004/320/EC).

Enzootic bovine leucosis has been a notifiable disease since 1959, and a control programme was initiated the same year. In 1989 a few seropositive animals were identified in five herds. Since then no new reactors have been found. As a result of the control programme the country was declared free from enzootic bovine leucosis by the European Union in July 1991.

A serological surveillance programme for demonstrating the absence of enzootic bovine leucosis is carried out by testing of bulk milk samples and blood samples from slaughterhouses. The sampling strategy was changed on the basis of an epidemiological evaluation of the surveil

lance programme and because a recently established online identification system at the slaughterhouses made it possible to select individual cattle for testing. The new sampling strategy was implemented in June 2004:

• Before June 2004 bulk milk samples from all dairy herds were tested every third year and blood samples from every sixth slaughter animal above eight months were tested.
• After June 2004 bulk milk samples from all dairy herds are tested every third year, and bulk milk samples are tested six months after the introduction of imported cattle into dairy herds. Furthermore, blood samples from every sixth slaughtered animal above the age of two years are tested from all beef herds, and from all beef herds that have imported livestock and sent cattle for slaughter, a minimum of two samples per herd per month have to be tested in the following 12-month period.

The number of bulk milk samples and blood samples examined in each year is given in table 7.

Table 7: Number of bulk milk samples and blood samples examined in the surveillance programme for enzootic bovine leucosis, 1999-2005.

Year	No. of bulk milk samples	No. of blood samples
1999	11,534	115,433
2000	0	109,015
2001	0	112,628
2002	8,645	116,547
2003	0	121,852
2004	0	46,944
2005	5,830	20,053

Bovine virus diarrhoea (BVD)

A voluntary control programme for bovine virus diarrhoea was implemented in Denmark in 1994. The voluntary programme was replaced in 1996 by a compulsory programme carried out jointly by the Danish Veterinary and Food Administration and the Danish Cattle Federation. The legislation has been continuously adjusted according to the evolution in the BVD programme. The decrease in the number of infected herds is presented in figure 4.

Figure 4: The number of bovine virus diarrhoeainfected herds in Denmark, 1999-2005.

Table 8: The year of last recorded occurrence of other OIE cattle diseases in Denmark.

Bovine anaplasmosis*	Never recorded
Bovine babesiosis*	Suspected to be present
Bovine cysticercosis	Reported present1
Bovine genital campylobacteriosis*	1995
Contagious bov. pleuropneumonia	1886
Dermatophilosis*	Never recorded
Haemorrhagic septicaemia*	Never recorded
Malignant catarrhal fever*	Known to be present
Rinderpest	1782
Theileriosis*	Never recorded
Trichomonosis*	1990
Trypanosomosis*	Never recorded

^* The disease is not a notifiable disease in Denmark.
¹ The disease occurs with a low sporadic prevalence.

1.3 sheep and goat diseases

Denmark is recognised as being officially free of Brucella melitensis by the European Union and the disease has never been recorded in Denmark. The only OIE sheep and goat diseases that have occurred in Denmark from 1999 to 2005 are Maedi-visna and Caprine arthritis/encephalitis. Both diseases are included in the voluntary control programme for Lentivirus.

Caprine and ovine brucellosis (Brucella melitensis)

The disease has never been recorded in Denmark, and since 1995 Denmark has been recognised as being officially free of Brucella melitensis by the European Union (EC Commission Decision 94/877/EEC). A serological surveillance programme for demonstrating the absence of B. melitensis is carried out by testing of blood samples collected under the voluntary control programme for Maedi-visna. The number of blood samples examined in each year is given in table 9.

Table 9: Number of blood samples examined in the surveillance programme for Brucella melitensis, 1999- 2005.

Year	No. of blood samples
1999	7,245
2000	6,540
2001	5,839
2002	5,829
2003	4,731
2004	4,588
2005	4,492

Caprine arthritis-encephalitis

The disease, which has an enzootic occurrence, is mostly recorded as serological findings, as it is included in the voluntary control programme for Maedi-visna (cf. below).

Maedi-visna

A voluntary control programme for lentivirus (Maedivisna in sheep and caprine arthritis-encephalitis in goat) has existed since 1979. The programme is run by the agricultural organisations. Sheep and goat herds can gain a free status by repeated serological examinations.

It requires at least two years to gain the free status. At present, approximately 3,000 herds of sheep and goats have free status.

Transmissible spongiform encephalopathy (TSE)

Scrapie was made notifiable in 1988. The naturally occurring TSE in sheep and goat is scrapie and is not believed to threaten humans, although experiments have shown that BSE can be passed on to small ruminants with the risk of spreading the disease to man.

In 1995 a voluntary surveillance programme for scrapie was initiated, resulting in testing of a number of small ruminants from holdings that wanted to export animals to other EU countries. In the period 1999-2005 the surveillance underwent several alterations. In 2002, the national surveillance programme was initiated on the basis of EU legislation in the field. The national surveillance programme included testing of a random sample of fallen stock and healthy slaughter animals. In October 2003, Denmark applied to the EU Commission for approval of an extended national surveillance programme including testing of all fallen ovine and caprine animals older than 18 months in Denmark and excluding testing of healthy slaughter animals. The EU granted the permission in January 2004, and by the end of 2004 the surveillance for TSE in sheep and goats in Denmark included testing of all animals with clinical symptoms of TSE and all fallen stock older than 18 months. The diagnosis of a French goat with BSE in the beginning of 2005 resulted in an amendment of the TSE regulations requiring a TSE test of all healthy slaughter goats. By the end of 2005, the Danish surveillance programme included TSE testing of all fallen stock older than 18 months, all healthy slaughter goats older than 18 months and all animals with clinical symptoms of TSE.

Table 10: The Danish TSE surveillance programme for sheep, 2002-2005.

	2002		2003		2004		2005
	Neg.	Pos.	Neg.	Pos.	Neg.	Pos.	Neg.	Pos.
Fallen stock	369	0	1,152	0	5,253	0	3,986	0
Animals for slaughter	563	0	880	0	91	0	60	0
Clinical suspects	6	0	3	0	5	0	0	0
Total	938	0	2,035	0	5,349	0	4,046	0

The results for the period 2002-2005 for sheep and goats are summarised in tables 10, page 28 and table 11, page 29.

Table 11: The Danish TSE surveillance programme for goats, 2002-2005.

	2002		2003		2004		2005
	Neg.	Pos.	Neg.	Pos.	Neg.	Pos.	Neg.	Pos.
Fallen stock	95	0	317	0	1,294	0	826	0
Animals for slaughter	51	0	94	0	26	0	241	0
Clinical suspects	4	0	3	0	0	0	3	0
Total	150	0	414	0	1,320	0	1,070	0

" The diagnosis of a French goat with BSE in the beginning of 2005 resulted in an amendment of the TSE regulations requiring a TSE test of all healthy slaughter goats.

Scrapie has never been diagnosed in Denmark, and the population of sheep and goats is quite small. Nevertheless the potential human health risk is among the reasons for introducing preventive measures and establishing surveillance and breeding programmes for small ruminants.

Some of the preventive measures for BSE in cattle (see chapter 1.2) also apply to small ruminants. The removal of specified risk material (SRM) from carcases of slaughtered animals was also implemented for small ruminants in 2001. Furthermore the feed bans applied for cattle are also valid for sheep and goats.

When a small ruminant in Denmark is suspected of having TSE, all animals in the herd and all contact animals and contact herds are placed under movement restrictions. So far all Danish suspicions have been disproved, but in the case of verification all animals will be killed and incinerated as SRM. In addition, small ruminants will not be allowed on the holding of the infected animal and contact holdings for a period of several years.

Table 12: The year of the last recorded occurrence of other OIE sheep and goat diseases in Denmark.

Contagious agalactia*	Never recorded
Contagious caprine pleuropneumonia*	Never recorded
Enzootic abortion of ewes*	Never recorded
Nairobi sheep disease*	Never recorded
Ovine epidedymitis (B. ovis)	Never recorded
Ovine pulmonary ademonatosis	1998
Peste des petits ruminants	Never recorded
Salmonellosis (S. abortus ovis)	Never recorded
Sheep pox and goat pox	1879

^* The disease is not a notifiable disease in Denmark.

1.6 Poultry diseases

The major poultry disease event in the period 1999-2005 was the Newcastle disease epidemic in 2002. A total of 135 outbreaks were registered during the epidemic, but despite the many outbreaks the disease was successfully eradicated using a stamping out policy within one and a half months after the initial detection of the disease. Newcastle disease also occurred in 2005, when a single outbreak was confirmed. A screening programme for avian influenza was initiated in 2003. The presence of low pathogenic avian influenza was detected in September 2003 in a holding with mallard ducks, but highly pathogenic avian influenza has never been reported in Denmark. All other poultry diseases listed by OIE, except mycoplasmosis, occurred in Denmark in the period 1999-2005. However all these diseases have a low sporadic occurrence, and the diseases mainly occur in ornamental, hobby and backyard birds.

Newcastle disease (ND)

In the summer of 2002 a Newcastle disease epidemic oc-curred in Denmark. At that time, the disease had notbeen diagnosed in Denmark since February 1998. A total of 135 outbreaks were registered during the epidemic.Four primary outbreaks and 131 secondary outbreaks were identified. Most outbreaks were found in the central and southern parts of Jutland, but a single outbreak occurred on the Island of Sejerø in the County of West Zealand (figure 5). Most outbreaks (126) were observed in backyard flocks. Only nine commercial flocks were infected.

Figure 5: Geographic distribution of the outbreaks of Newcastle disease in Denmark in 2002. Blue dots indicate locations of outbreaks and the hatched areas are the 10-km surveillance zones around the outbreaks.

The first outbreak was confirmed by virus isolation and ICPI-determination on 26 July 2002, and the last outbreak was confirmed on 28 August 2002. However, eradication of infected flocks, establishment of protection and surveillance zones and restrictions on poultry movements were initiated for precautionary reasons already on 16 July, i.e. 10 days before the first virological confirmation was obtained. The preliminary diagnosis was based on clinical signs and serological reactions. Positive serology could be used as an indicator of ND infection because at that time Denmark applied a non-vaccination policy for ND. All poultry on holdings on which the disease was diagnosed were killed and destroyed.

In most of the outbreaks, no obvious clinical symptoms were observed. Among all 135 outbreaks, only poultry in 13 outbreaks revealed clinical symptoms such as ataxia, torticollis and egg drop. Seven of these were outbreaks in commercial flocks. The pathological lesions were also limited, as was the spread by any other means than movement of pullets already infected.

As a consequence of the very slow in-vitro growth of the virus involved, the diagnostic methods were primarily based on serology in order to ensure rapid eradication of the outbreaks. Avian paramyxovirus-1 (APMV-1) was isolated from three flocks of commercial poultry, but not from any of the backyard flocks. The two isolates tested both belonged to antigenic group C1 viruses.

Based on the epidemiological investigations, one of the primary outbreaks was linked to all of the 131 secondary outbreaks. This was due to the involvement of two poultry dealers, and the infection was spread among backyard flocks through trade in infected pullets. Thereby, this primary outbreak and the related contacts comprised one large epidemiological cluster of infected flocks.

The epidemiological investigations did not succeed in identifying a common source of infection with regard to the four primary outbreaks in commercial flocks. These were all situated less than 2 km from the coastline. The waterfowl populations in the vicinity of these holdings were investigated in attempt to locate the potential source of infection, but the results were inconclusive.

Following preliminary cleaning and disinfection of the affected premises, a serological screening of the more than 600 flocks in the vicinity of the outbreaks was carried out. A limited prevalence of low serological titres was found in 39 of these flocks, and no virus could be isolated.

During the progress of the eradication process, six regionalisations of Denmark were carried out in order to successively re-open the export of live poultry and hatching eggs from ND-free regions of Denmark. All restrictions were lifted by 1 January 2003 and Denmark regained its ND-free status according to the Office International des Epizooties (OIE) standards by 1 March 2003.

" In July 2004, the Danish Ministry of Food, Agriculture and Fisheries decided to change the control strategy for Newcastle disease from a non-vaccination strategy to a vaccination strategy.

In July 2004, the Danish Ministry of Food, Agriculture and Fisheries decided to change the control strategy for Newcastle disease from a non-vaccination strategy to a vaccination strategy. The implementation of the vaccination strategy began in the autumn 2004, and approximately one year later the poultry population in Denmark was vaccinated. The change of control strategy was based on a risk analysis, which was performed because the Danish poultry industry wished to change the control strategy after the outbreaks of Newcastle disease in Denmark in 2002.

In October 2005, an outbreak of ND occurred in a layer poultry flock with 41,000 hens. The flock was established before the beginning of the implementation of the Danish ND-vaccination strategy. The outbreak was confirmed by virus isolation and ICPI-determination (ICPI=1.79) on 28 October 2005. However, eradication of infected flocks, establishment of protection and surveillance zones and restrictions on poultry movements were initiated for precautionary reasons already on 21 October 2005. The preliminary diagnosis was based on clinical signs, serological reactions and PCR results. Culling of the infected herd was finalised on 24 October 2005, and the establishment was subsequently cleaned and disinfected. Six farms were examined for Newcastle disease, because they had received day-old chickens from the infected establishment. The results of these investigations did not show any evidence (neither clinical nor laboratory) that the disease had spread to these farms. All restrictions were lifted by 4 December 2005 and Denmark regained its ND-free status according to the Office International des Epizooties (OIE) standards by 25 April 2006.

Further information about the Newcastle disease outbreaks in Denmark in 2002 is available in a final report of the whole epidemic, which can be downloaded from DVFA‘s website: www.dvfa.dk

Avian influenza

Highly pathogenic avian influenza has never been reported in Denmark.

The first screening programme for avian influenza in Denmark was carried out in the autumn of 2002 and was performed on samples taken in connection with the epidemiological investigations of the Newcastle disease outbreaks. The screening included samples from backyard flocks and wild birds. The backyard flocks were examined both serologically and by virology. Blood samples from 53 backyard flocks that had been sampled in August 2002 were tested, and none was positive. In addition, 102 backyard flocks were examined virologically in August 2002, and the virus isolation performed did not show any presence of virus in the samples. The screening of the wild birds included 1,730 fresh droppings collected from wild birds (cormorants, geese, seagulls, jackdaws, rooks and crows) near the four primary outbreaks of Newcastle disease and 240 cloacal swabs from hunted game birds (mallards and pheasants). The bird droppings were sampled in September and October 2002, and the cloacal swabs were sampled in December 2002. The samples were pooled in pools of five samples and tested virologically. Avian influenza virus could be isolated from three of the 394 pools, and the avian influenza virus subtypes found were H2N3 (mallard) and h16N3 (seagull and cormorant).

" The first screening programme for avian influenza in Denmark was carried out in the autumn of 2002 and was performed on samples taken in connection with the epidemiological investigations of the Newcastle disease outbreaks.

The screening programme for avian influenza in poultry was considerably more comprehensive in 2003, when the screening programme was expanded to include samples from the major poultry types in Denmark, i.e. fattening turkeys, chicken breeders, broilers, layers and ducks (table 16). The screening programme in poultry was only slightly revised in 2004, the two changes being that only free range broilers were sampled and ducks were examined serologically. The screening programme in poultry was also only slightly revised in 2005, when the main change was that all holdings with free range laying hens were examined. All test results from the screening programme for avian influenza in poultry were negative (table 16).

Table 16: Number of samples examined in the screening programmes for avian influenza in poultry in 2003, 2004 and 2005. All samples were examined serologically for subtypes H5 and H7, except for ducks in 2003, which were examined virologically.

Type of poultry	2003		2004		2005
	Nsamples	Npositive	Nsamples	Npositive	Nsamples	Npositive
Fattening turkey	120	0	320	0	300	0
Chicken breeders	690	0	480	0	440	0
Broilers	578	0	601	0	501	0
Layers	40	0	550	0	1858	0
Ducks	3302	3	540	0	806	0

¹ Only free range broilers were sampled in the screening in 2004 and 2005.
² Five samples were pooled and examined virologically.

The screening programme for avian influenza in wild birds was also more comprehensive in 2003, with both a wider temporal and geographic covering. Bird droppings were sampled in both spring/summer (March to June) and autumn/winter (September to December) and were sampled from 20 locations. The bird droppings were collected from cormorant, lapwing, Bewick‘s swan, mallard, widgeon, teal and six different goose species. The samples were pooled in pools of five samples and tested virologically (by both virus isolation and RT-PCR). Avian influenza virus was detected by RT-PCR in 34 of 579 pools and could be isolated in 15 pools (table 17). The avian influenza virus was mainly found in the duck species in the autumn months. Neither H5 nor H7 subtypes of avian influenza virus could be isolated, but low pathogenic H5 and H7 subtypes were detected with RT-PCR (table 17). The following avian influenza virus subtypes isolated in the 15 pools were: H1N1, H3N2, H3N6, H3N8, H4N6, H6N5, H6N8 and H10N7.

The screening programme for avian influenza in wild birds was slightly revised in 2004, when bird droppings were sampled in September to December from 16 locations. The bird droppings were only collected from mallard, widgeon, teal and pintail. The samples were pooled in pools of five samples and tested by both virus isolation and RT-PCR. Avian influenza virus was detected by RT-PCR in 131 of 696 pools and 65 individual samples and could be isolated in 14 samples (table 17). Low pathogenic avian influenza virus subtype H5N2 was isolated from two pools, and low pathogenic avian influenza virus subtype H5 could be detected with RT-PCR in 13 pools. The H7 subtype was neither isolated, nor was it detected with RT-PCR. The following avian influenza virus subtypes isolated in the 15 pools were: H2N3, H3N2, H3N8, H5N2 (low pathogenic), H6N2, H8N1 and H8N4.

Table 17: Results of the screening programmes for avian influenza in wild birds. Five samples were pooled and examined virologically.

	2002	2003	2004	2005
Number of pools	394	579	761	558
(Number of samples)	(1,970)	(2,895)	(3,545)	(2,790)
AIV isolation (No. of pools)	3	15	14	16
LPAI subtype H5 or H7	0	0	2	3
AIV detection by RT-PCR (No. of pools)	-	34	131	140
LPAI subtype H5 or H7		6	13	27

The screening programme for avian influenza in wild birds was slightly revised in 2005, when the bird droppings were sampled in August to December from two locations. The bird droppings were collected from mallard, teal, widgeon, goose and pheasant. The samples were pooled in pools of five samples and tested by both virus isolation and RT-PCR. Avian influenza virus was detected by RT-PCR in 140 of 558 pools and could be isolated in 16 samples (table 17). Low pathogenic avian influenza virus subtype H5 or H7 was isolated from three pools, and low pathogenic avian influenza virus subtype H5 or H7 could be detected with RT-PCR in 27 pools. All the H5 and H7 positive findings were from mallards. The following avian influenza virus subtypes isolated in the 16 pools were: H1N1, H1N9, H3N8, H4N6, H5Nx (low pathogenic), H7N5 (low pathogenic), H7N7 (low pathogenic), H9N1 and H11N9.

In addition to the results from the screening programme, the presence of LPAI was detected on 4 September 2003 in a holding with mallard ducks, which was examined due to elevated mortality. The presence of LPAI subtype H5N7 was detected by virus isolation during the laboratory diagnostic examination of the holding. There were 11,000 mallard ducks on the holding, which were raised for restocking for hunting purposes. The elevated mortality was noted on 25 August 2003. The infected flock was further examined by virus isolation and serology. The Danish Veterinary and Food Administration decided for precautionary reasons to cull and destroy the affected flock. All free range poultry flocks within a radius of 10 km from the infected holding were clinically examined and serologically tested. Furthermore, all contact flocks were traced and clinically inspected and examined by virus isolation and serology. All tests were negative for avian influenza virus, and none of the inspected animals showed any signs of disease. This and other evidence supports the assumption that the clinical signs found in the flock of mallards were not caused by the LPAI virus strain. Isolation of the H5N7 strain is considered to be a coincidental event.

Other poultry diseases

All other poultry diseases listed by OIE, except mycoplasmosis, occurred in Denmark in the period 1999-2004 (table 18, page 46 and table 19). However these diseases have a low sporadic occurrence (table 18, page 46), and the diseases mainly occur in ornamental, hobby and backyard birds.

Table 18: Number of outbreaks of other OIE poultry diseases that are notifiable, 1999-2005. The year of last occurrence (in brackets) if no outbreaks of a disease occurred in a year.

Poultry disease	1999	2000	2001	2002	2003	2004	2005
Avian infectious laryngotracheitis	5	9	2	11	8	4	4
Avian tuberculosis	4	7	4	3	1	(2003)	2
Fowl cholera		1	1	(2001)	(2001)	1	(2004)
Fowl pox	(1996)	(1996)	2	1	(2002)	1	(2004)
Fowl typhoid	(1994)	(1994)	(1994)	1	(2002)	(2002)	(2002)
Avian clamydiosis	21	19	15	8	8	16	11
Pullorum disease	2	1	2	4	2	5	5

Table 19: Occurrence of other OIE poultry diseases that are not notifiable, 1999-2005.

Avian infectious bronchitis	Known to be present1
Duck virus hepatitis	Known to be present1
Duck virus enteritis	Known to be present
Infectious bursal disease (Gumboro)	Reported present2
Marek‘s disease	Known to be present1
Mycoplasmosis (M. gallisepticum)	1967

¹ Has a low sporadic occurrence and is controlled by vaccination.
² Last known occurrence in Denmark was in 2003.

1.7 Lagomorph diseases

Myxomatosis

Myxomatosis, which had not been diagnosed during the period from 1962 to 1984, reappeared in 1985, and since then there has been a limited number of outbreaks of the disease in small rabbit farms.

Table 20: Number of outbreaks of myxomatosis, 1999-
2004.

Year	No. of outbreaks
1999	0
2000	2
2001	0
2002	2
2003	5
2004	2
2005	0

Tularaemia

Tularaemia has never been recorded in Denmark.

Rabbit haemorrhagic disease

Rabbit haemorrhagic disease has not been recorded in Denmark since 1990.

In 1990, rabbit haemorrhagic disease was diagnosed for the first time in two rabbit farms. One of the rabbit farms was located in the southern part of Jutland, and the other one on the island of Lolland. All rabbits on the two farms were killed, and the premises were subsequently cleaned and disinfected.

Serological examination of wild rabbits has revealed seroreactors in the wild population of rabbits in the southern part of Jutland in 1990, and on the island of Lolland in the years of 1990, 1991 and 1992. No seroreactors have been reported since 1992.

1.8 Fish diseases

Denmark has 378 freshwater trout farms and 37 marine fish farms where the main production is rainbow trout. A few land-based marine fish farms have a minor turbot production, and in addition to these there are 12 eel farms. Since 1970, Denmark has had an official disease surveillance programme on all fish farms in the country. Since common EU legislation on animal health conditions governing the placing on the market of aquaculture animals was introduced with Council Directive 91/67/EEC, the surveillance programme has been conducted according to the provisions laid down in this directive.

Viral haemorrhagic septicaemia (VHS)

Since 1970, Denmark has conducted an official surveillance and eradication programme for VHS, which has made it possible to eradicate the disease in 327 of the 378 Danish freshwater fish farms. As a result of this programme, the northern part of Jutland containing 159 fish farms obtained the status of being an approved VHS-free zone in 1992 (figure 6). The programme is run in close collaboration with the aquaculture industry.

Figure 6: Distribution of VHS in Denmark. EU-approved VHS-free zone (dark area) and VHS-infected watercourses (orange lines)

During the period 1999-2005 a varying number of out- breaks occurred (table 21). In August 2000 an outbreak occurred in one remote trout farm in the centre of the EU-approved VHS-free zone. The source of the outbreak remains unknown. The other outbreaks were in fish farms in the unapproved zone and mainly in the western part of the zone Skjern and Omme where the disease has been difficult to eradicate.

Table 21: Number of VHS outbreaks in Denmark.

Year	No. of outbreaks
1999	6
2000	13
2001	9
2002	16
2003	18
2004	8
2005	6

Infectious haemorrhagic necrosis (IHN)

IHN has never been recorded in Denmark and the country has the status of EU-approved continental zone free of IHN.

Infectious pancreas necrosis (IPN)

Since 1970 Denmark has conducted a voluntary IPN surveillance programme and has so far registered 44 IPNfree fish farms. Most of these farms are situated along small river systems and their water source is mainly well water. Twenty-six of the 44 IPN free farms have brood stock and deliver eggs, fry and fingerlings to Danish trout farms as well as for export.

Spring viraemia of carp (SVC)

Denmark has three carp farms registered as free of SVC. Denmark reported one outbreak of SVC in 2002 and two in 2003. All these outbreaks were in imported ornamental carps. SVC-infected fish have not been released into Danish freshwater sources.

Table 22: Number of outbreaks of fish diseases in Denmark, 1999-2005.

Viral haemorrhagic septicaemia	761
Infectious haemorrhagic necrosis	Never recorded
Spring viraemia of carp	32
Epizootic haematopoietic necrosis	Never recorded
Oncorhynchus masou virus disease	Never recorded

¹ One case in the EU approved VHS-free zone in 2000.
² In imported ornamental carps.

1.9 Mollusc diseases

For decades, there has been an intensive commercial fishery on natural mussel stocks (Mytilus edulis) with annual landings of 90,000-100,000 tons. Natural stocks of European flat oyster (Oestrea edulis) only exist in the Limfjord. Through the 1990s, the oyster stock increased due to optimal climatic conditions for reproduction. In 2002, the stock had reached a size at which commercial utilisation was allowed, and in 2003 approximately 2 million oysters were landed. Aquaculture production of mussels and oysters started on an experimental basis in 2000 and the experience gained from these experiments began being transferred to a commercial scale from 2003.

Bonamiosis (Bonamia ostreae) and
Marteiliosis (Marteilia reføringens)

In the middle of the 1990s, commercial interests in utilising the flat oyster as a resource for aquaculture purposes were considered. This was the background for establishing a scientifically based disease surveillance programme for Bonamiosis and Marteiliosis in the Limfjord in 1996. This surveillance programme focused on the wild oyster population, as there had been no aquaculture activities in this field until the middle of 2000.

Since the autumn of 2000, when the first experiments of artificial cultivation of oysters were launched, an official disease surveillance programme for Bonamiosis and Marteiliosis has been conducted on the cultivated as well as on wild stocks following the provisions laid down by the EU Commission. The programme was conducted in order to obtain an official EU-approved Bonamiosis and Marteiliosis-free status for the Limfjord.

During the first two years, biannual sampling of 150 oysters from three different sites was conducted. The sampling was either from aquaculture production sites or from the natural stock if the number of active aquaculture production sites was insufficient. From the autumn of 2002, the sampling was reduced to two annual samplings of 30 oysters from three sites according to Directive 91/67/EEC.

Bonamia ostreae or Marteilia reføringens have never been detected in the flat oyster stock of the Limfjord.

Table 23: Mollusc disease

Haplosporidiosis1	Never recorded
Perkinsosis1	Never recorded
Microcytosis	Never recorded
Iridovirosis1	Never recorded
Marteiliosis	Never recorded
Bonamiosis	Never recorded

¹ Host not present in Denmark