Brucellosis is a contagious zoonotic disease that is notifiable in livestock and can severely impact the livelihood of cattle farmers. It is caused by bacteria from the genus Brucella, which contains species of bacteria that cause brucellosis in a number of different animals including cattle, sheep, goats, pigs, camelids, dogs and cetaceans. Most Brucella species have a preference for specific mammalian species but are able to infect a variety (Garin-Bastuji and Blasco, 2018).
Brucellosis in cattle is usually caused by Brucella abortus, although Brucella melitensis and Brucella suis can also cause disease. Whilst the main effects are on the reproductive system, arthritis can occur as a result of the bacteria becoming localised in the joints. The major clinical signs are abortion in late pregnancy, premature births, stillbirths, retained foetal membranes, weak calves and poor reproductive performance (decreased fertility). In bulls, swollen testicles (orchitis) is sometimes seen. In most cases, infection is not obvious until the animal aborts, with abortion storms sometimes seen in affected herds. Cattle can appear to recover and can go on to have healthy calves but often remain infected and continue to shed bacteria, thus remaining a threat to other animals and humans.
The bacterium is present in high numbers in affected calves, foetal membranes and uterine fluids and can last in a cool damp environment for several months, infecting further cattle when ingested or through cuts and contact with mucous membranes (Garin-Bastuji and Blasco, 2018). It is typically spread when an infected animal gives birth.
B. abortus can also colonise the milk glands, causing the milk to be infectious. This has historically been a major cause of human infection and pasteurisation has been an important tool in reducing infection rates in people. Brucellosis can cause severe and debilitating disease in humans and prevention of outbreaks in animals is key to the protection of public health.
The UK is officially free of brucellosis (OBF) for cattle (Brucella abortus) and sheep and goats (Brucella melitensis) but there is a continual risk to the cattle population from importation of disease and subsequent spread.
UK OBF status for brucellosis in cattle (B. abortus)
Brucellosis in cattle (B. abortus) is listed in the World Organisation for Animal Health (OIE) Terrestrial Animal Health Code and when isolated must be reported to the OIE. Many EU member states are classified as officially free from brucellosis; current notable exceptions include regions of Spain and Italy, Portugal, Hungary, Bulgaria, Greece and Croatia. Brucellosis in Great Britain (GB) was eradicated in 1979 and OBF status was granted in 1985. Since eradication there have been two reintroductions via imported cattle (in 1993 and 2003) and an outbreak in Cornwall in 2004 which was contained to a single location, though the origin of infection remains unclear. Prompt action which prevented further disease spread in all cases has meant that this has not affected the GB OBF status. Northern Ireland gained OBF status in 2015 meaning that the entire UK is currently considered OBF. Moving into an era outside of the EU, it is more important than ever that the UK is demonstrably monitoring the national herd for brucellosis and maintaining its OBF status. A surveillance system was implemented throughout GB to meet the requirements to achieve OBF status and continues to ensure its maintenance. The rest of this article details how this surveillance is undertaken in GB (Box 1); separate arrangements apply in Northern Ireland and the Crown Dependencies.
Surveillance for Brucella abortus in Great Britain
To maintain GB’s OBF status farmers must report any cases they believe to be abortions or premature births
to the APHA who will confirm whether an investigation is required. The record of the number of cases reported and investigated is important to enable APHA to demonstrate that the GB surveillance strategy is effective (Foddai et al., 2020a). Also, due to the risk of reintroduction of disease in imported cattle, the strategy targets imported cattle from non-OBF countries for extra testing (Foddai et al., 2020b). These methods are backed up by regular bulk milk testing and the monitoring of bulls used for artificial breeding purposes.
Abortion reporting
Notification of abortions (Box 2) is an essential piece of the GB surveillance programme and it is the main way in which the brucellosis status of the GB beef herd (which constitutes a significant proportion of the whole GB herd) has been monitored since routine brucellosis testing of herds stopped in 2007. In the brucellosis incident in the South West of England in 2004, it was an abortion investigation that brought the presence of Brucella abortus to the attention of APHA who were then able to quickly bring the outbreak under control, eradicate disease on the premises and prevent spread to other holdings.
It is a legal requirement that anyone in charge of bovine animals, or anyone else that is aware of an abortion, should report any abortion or premature calving, whether the calf is dead or alive, within 24 hours (an abortion or premature calving is defined as that occurring less than 271 days after service or less than 265 after implantation for embryo transfer). APHA and policy leads are concerned that the number of statutory abortion notifications has been steadily decreasing since 2011. Only 1,238 abortions were reported across GB in 2019, from a national cattle population of just under 10 million animals, of which 2.88 million are adult females in breeding herds.
This drop in reporting may be because there is a misunderstanding regarding the need to report every abortion in all cattle (beef and dairy), a lack of appreciation of the risk of reintroduction, a misconception that abortion reports are not recorded or are rarely investigated or a combination of all of these.
APHA will investigate all reports in beef herds, all imported animals and all first calving heifers, as well as many other cows in dairy herds which they will risk assess when the report is made. Abortions should be reported by the owner/keeper or their vet. All abortion reports (whether they are investigated or not) are also recorded and form part of the evidence for GB’s OBF status.
A pilot scheme involving 12 practices is currently underway in the Wessex Veterinary Delivery Partnership area to investigate whether keepers are more likely to report abortions to their own vet rather than to APHA. Clients of these practices can report abortions directly to practice staff by calling their usual number. All other practices and their clients should phone APHA directly on 03000 200301 in England or 0300 3038268 in Wales. In Scotland they should contact the local field service office.
It is vitally important that APHA is able to continue to monitor brucellosis in the country and have sufficient data to demonstrate Great Britain’s OBF status. An inability to do this will put the national herd at risk and affect GB’s ability to trade – this will be more important than ever now we have left the EU. Early detection of disease is also important as a single case of brucellosis left undetected for any period of time could result in a major outbreak and will affect the livelihoods of our cattle farmers. Insufficient data from abortion reporting may lead to a need for an increase in on-farm check blood testing, and the extra costs and inconvenience that this brings. To help to avoid these outcomes please consider brucellosis as a differential for reproductive disease and encourage your clients to report all abortions or premature births.
