The history of Brucellosis in Northern Ireland

The page provides a summary of the history of Brucellosis in Northern Ireland over the decades.

Brucellosis during the 2010s

Following extensive testing and other initiatives disease levels began to fall in the 2010s.

Nothern Ireland was awarded Officially Brucellosis Free (OBF) status on 6th October 2015.

Changes were made in the testing regime for Brucellosis: pre-movement and pre-export (to other Member States) test requirements were abolished; and the age of eligibility for testing of female cattle and bulls was lifted to 24 months.  Routine test frequency was reduced.


Brucellosis during the 2000s

The level of Brucellosis rose again in the late 1990s and early 2000s. To counteract this, a series of new measures was introduced.

In January 2001 annual testing was reintroduced in the Armagh, Enniskillen, and Newry divisional areas. Also in 2001, the Brucellosis Bulk Milk ELISA (Enzyme Linked ImmunoSorbent Assay)(BrBME) was intoduced for sampling dairy herds and cull cow sampling was introduced at meat plants. In late 2004 pre-movement testing was introduced.

Brucellosis during the 1990s

The early nineties saw a 'mopping up' operation when the few residual pockets of infection were dealt with and by 1993 the only Brucellosis being detected was in recently imported cattle. There followed a 14-month period in 1995 - 1996 during which no Bbrucellosis was detected in the province.  

Brucellosis during the 1980s

The disease control measures implemented through the 1980s had the desired effect of reducing disease to a low level and on 26th July 1982 Northern Ireland's cattle herds were declared 'Officially Brucellosis Free' (OBF). Throughout the 1980s, the prevalence of the disease continued to be reduced and on the 13th April 1988 an EC decision recognised that since our herds had been OBF for more than four years and that at least 99.8% of herds were free from disease, the annual checks could be replaced by biennial herd tests.  

Brucellosis during the 1970s

Various control measures, dealing mainly with the control of movement of cattle within Northern Ireland and to / from infected herds, were introduced during 1972 and 1973 in order to limit infection or the spread of infection. In the years 1970 to 1979 all of the controls were tightened up considerably but the incidence of the disease persisted. The policy decision to buy-out confirmed infected herds was taken in 1978.  

Brucellosis during the 1960s

By 1960 less than 40% of the heifer calf replacements for the national herd were being vaccinated and occasional abortion storms began to reappear. The experience gained in the pilot eradication scheme was used to set up a voluntary scheme in August 1960. The response to this was limited, probably because the main cost of testing to enter the scheme had to be borne directly by the farmer.

Herdowners were allowed to retain reactors until disposed of by themselves but they were required to isolate the animals and cleanse and disinfect relevant areas after their disposal. Valuations were carried out by part-time Department staff. A panel of independent valuers was in existence and was allowed to continue.
Up until 1960, no Brucellosis register was kept and any herd could, on request, be tested for Brucellosis. A comprehensive survey, carried out to determine the extent of Brucellosis, was conducted in Northern Ireland in 1960 and a register of attested herds from which Brucellosis had been eradicated was established. These herds were issued with a Certificate of Registration. Movement permits were required for these voluntary register herds.

A survey based on milk ring testing of milk supplied to dairies in 1962 showed that approximately 12% of dairy herds were infected. A more limited survey based on the serum agglutination test of non-dairy (in other words breeding suckler herds) indicated that about 5% of these herds were infected. The wide difference in disease levels between the 2 types of herd is thought to have been due to the fact that there was much more purchasing of stock in dairy herds whereas the majority of breeding herds, particularly the smaller ones, were self-contained. The larger breeding herds, where purchasing of stock was more common, were found to be infected more frequently.

The results of these surveys provided the basis for a decision to introduce a compulsory eradication programme on 1 January 1963. At that time the national herd consisted of approximately 18,000 dairy herds and 28,000 breeding herds. 

1960s - Compulsory eradication

A compulsory eradication scheme for dairy herds was introduced in January 1963. Letters were sent to all herd owners explaining details and procedures of the Brucellosis Scheme. Milk samples collected by the creameries were submitted and tested at 6-monthly intervals. Where three consecutive clear tests were obtained, these herds were placed on the register. Failing this, one blood sample was sufficient if clear.

Adult vaccination with S19 vaccine was discontinued and only calves aged 4 to 8 months were allowed to be vaccinated. The main effort at the outset of the eradication programme was directed towards those dairy herds from which milk samples taken at creameries had proved to be positive and those dairy and breeding herds which showed clinical evidence of infection (in other words, abortions).

The objective was to deal with known infection at source as quickly as possible thus curtailing spread within these herds and preventing its spread to neighbouring herds. Other herds were also tested on a geographical pattern. The testing of all dairy herds showed that about 20% were infected. This was a much higher level than had been indicated by the survey based on milk churn supplies to milk depots in 1962.

The testing of all breeding herds showed that the results of the survey based on the serum agglutination test had provided a reasonably accurate estimate of the level of infection in those herds. 

1960s - Vaccination

For some years prior to the introduction of compulsory eradication the vaccination of adult animals with Strain 19 had been discouraged since it created difficulties in test interpretation and vaccination of adults was prohibited from 1 January 1963.

The vaccination of calves between 4 and 8 months old caused few difficulties in interpretation but it too was prohibited from 29 March 1972 partly because infection had by then been reduced to a very low level and partly because the United Kingdom became a member of the European Community.

The most advantageous status - Officially Brucellosis Free (OBF) Herds - could only apply to herds which contained animals which had not been vaccinated within the previous 3 years. The use of Strain 45/20 vaccine had never been permitted in Northern Ireland.  

Brucellosis during the 1950s

It became apparent during the 1950s that active infection was still present throughout the national herd and in 1959 a pilot eradication scheme was carried out on about 150 herds which were selling bottled, unpasteurised milk. All breeding cattle over 12 months of age were subjected to serum agglutination, whey agglutination and vaginal mucous tests at three-monthly intervals until three negative herd tests were obtained.

Cattle judged to have positive titres were purchased at market value and slaughtered. The results of this scheme showed that:


  • 70% of these herds were free from brucellosis
  • 23% of herds were positive but had no clinical disease
  • 9% of the animals were positive to the test
  • 7% of the herds had clinical disease with 33% of the animals in these herds positive to the test

Once cleared of infection, herds within this scheme were subsequently blood tested at 12-monthly intervals and milk tested at six-monthly intervals. Movement into the herds was restricted to animals which were confirmed as Brucellosis free.  

Brucellosis during the 1940s

The vaccination of calves with Strain 19 vaccine was introduced in the mid 1940s. This represented the first effective method of combating the disease and was used in the majority of herds on a voluntary basis for a number of years. Unfortunately a fall in the number of abortions, which followed the use of the vaccine, created an illusion that the disease had been eliminated but vaccination only prevented the signs of the disease and did not eliminate the pathogenic organism. 

Brucellosis during the 1930s

The prevalence of Brucellosis in cattle herds in Northern Ireland constituted a major disease problem during the 1930s with about 60% of all herds being affected. A major factor in the spread of the disease was the movement of cattle between herds which resulted from an expansion of the dairy herd in the province.  









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