Brucellosis: how to spot and report the disease

Brucellosis is a highly contagious disease of livestock caused by brucella abortus or brucella melitensis and is characterised by abortions or reproductive failure in cattle, sheep, goats and pigs.

Animals may recover from the disease, however they can continue to shed the bacteria causing spread of the disease with significant economic impact through reduced production in livestock.

Brucellosis is still present in several other European Union areas, including Northern Ireland, and it is important therefore to maintain an effective level of surveillance.

Clinical signs

Brucella abortus is primarily a disease of cattle. The most common clinical sign of brucellosis is high incidence of abortion or premature calving of recently infected animals. The foetus, placenta and uterine fluid contain large quantities of brucella abortus bacteria which can infect other cattle coming into contact with an infected animal around the time of calving. The organism continues to be excreted in the milk. Breeding bulls which are infected, can transmit the disease to cows at the time of service by infected semen.

Brucella melitensis can affect most species of domestic animals but mainly causes ovine brucellosis (of sheep and goats). Reproductive failure with abortion is the most common clinical sign of the disease. Infection is normally by inhalation and via abraded skin, and transmission between species occurs easily. The post-partum discharges (after-birth) of infected females contain large numbers of bacteria whether or not the animal has aborted. After abortion, infection may persist in the uterus for many months, and in the udder for years.  

The level of infection in milk and uterine discharges is probably lower in sheep than in goats. As with brucella abortus, viable offspring from infected females may also be infected but seronegative and may discharge infection following birth or abortion. These animals would thus be a significant risk when imported into an uninfected flock or herd and it is essential that animals be added only from flocks/herds of known free status.

How brucellosis is spread

The disease is spread by contact with infected material that contains the bacteria.

For humans this can include:

• contact with the placenta of infected animals after they give birth or have abortions 
• contact with discharge from genitals of infected animals
• drinking raw (unpasteurised) milk or eating dairy products made from raw milk of infected animals

For animals this can include:

• drinking water or eating feed that has been contaminated with the bacteria
• licking discharge from the genitals of infected animals
• drinking milk of an infected animal

Human health implications

Brucellosis is a zoonotic disease, meaning it can be transmitted from animals to humans. It causes flu-like symptoms and/or persistent headaches. It affects people of all ages and both sexes. If left untreated the disease may persist for weeks or months and can affect any organ in the body.

How to control the disease

If the disease is confirmed the outbreak will be controlled in line with the contingency plan for exotic notifiable diseases.

Legislation

Brucella abortus
On the basis of Directive 64/432/EEC (as amended by Directive 97/12/EC) Great Britain was declared officially free of bovine brucellosis in 1985.

The Brucellosis (Scotland) Order 2009 , Brucellosis (Scotland) Amendment Order 2011, Brucellosis (Scotland) Amendment Order 2014 and the Brucellosis (Scotland) Amendment (No2) Order 2014 are currently in place to implement Directive 64/432 EEC in relation to monitoring and testing for brucella abortus in cattle.

The changes to the Zoonoses Order also include an amendment to add dogs to the list of animals in which detection of Brucella is reportable, this means that detection of brucellosis in dogs is reportable. 

The Animal Health (Notification and Control Measures) (Miscellaneous Amendments) (Scotland) Order 2021

Brucella melitensis
The UK was recognised as officially free by Commission Decision 93/52EEC.

Biosecurity

Biosecurity is about being aware of the ways disease can spread and taking every practical measure to minimise the risk of disease spreading. The advice details practical things you can do on your farm to help prevent the introduction and spread of brucellosis to and from your animals.