Brucellosis

Unique identifier / Notation

BI0202

Synonyms

Undulant fever Contagious abortion Malta fever Mediterranean fever

Brucellosis is a bacterial disease caused by various Brucella species, which mainly infect cattle, swine, goats, sheep and dogs. Humans generally acquire the disease through direct contact with infected animals (WHO, 2020).

Primary reference(s)

WHO, 2020. Brucellosis. World Health Organization (WHO). Accessed 25 May 2025.

WOAH. No date. Brucellosis. Accessed 28 May 2025.

Annotations

Additional scientific description

Human

Brucellosis is one of the most widespread zoonoses transmitted by animals and in endemic areas, human brucellosis has serious public health consequences. The expansion of animal industries and urbanisation, and the lack of hygienic measures in animal husbandry and food handling, partly account for brucellosis remaining a public health hazard (WHO, 2020).

Brucellosis is mainly caused by Brucella abortus, biovars 1-6, 9; B. melitensis, biovars 1-6; B. suis, biovars 1-5; and B. canis (WHO, 2001). Worldwide, B. melitensis is the most prevalent species causing human brucellosis, owing in part to difficulties in immunising free-ranging goats and sheep (WHO, 2020).

Although there has been great progress in controlling the disease in many countries, there still remain regions where the infection persists in domestic animals and, consequently, transmission to the human population frequently occurs. It is an important human disease in many parts of the world especially in the Mediterranean countries of Europe, north and east Africa, the Middle East, south and central Asia and Central and South America and yet it is often unrecognized and frequently goes unreported. There are only a few countries in the world that are officially free of the disease although cases still occur in people returning from endemic countries (FAO, OIE, WHO, 2006).

Brucellosis typically causes flu-like symptoms, including fever, weakness, malaise and weight loss. However, the disease may present in many atypical forms and which, in the absence of specific treatment, may persist for weeks or months. In many patients the symptoms are mild and, therefore, the diagnosis may not be considered. The incubation period of the disease can be highly variable, ranging from 1 week to 2 months, but usually 2 to 4 weeks (FAO, OIE, WHO, 2006; WHO, 2020). Human-to-human transmission is very rare (WHO, 2020).

Animal

Brucellosis is a bacterial disease of livestock with significant economic impact. In endemic areas, vaccination is often used to reduce the incidence of infection. Several vaccines are available. Most countries maintain a list of approved veterinary vaccines for use. For specific regulations, consult the country's veterinary authorities (Blasco et al., 2021; WOAH, no date).

Brucellosis affects cattle, swine, sheep and goats, camels, equines, and dogs. It may also infect other ruminants, some marine mammals and humans. The disease in animals is characterized by abortions or reproductive failure. While animals typically recover following the initial abortion, they may continue to shed the bacteria. The poor reproductive performance results in huge economic losses to dairy, sheep, goat and pig farmers. Brucellosis is typically spread when the animal aborts or gives birth. High levels of bacteria are found in the birth fluids of an infected animal. The bacteria can survive outside the animal in the environment for several months, particularly in cool moist conditions. They remain infectious to other animals which become infected by ingesting the bacteria. The bacteria also colonise the udder and contaminate the milk. Brucellosis is also an important disease in wildlife, infecting feral pigs, bison, elk and European hares (Wernery, 2014; WOAH, no date).

Brucellosis in cattle (B. abortus), sheep and goats (B. melitensis), and swine (B. suis) are diseases listed in the World Organisation for Animal Health (WOAH) Terrestrial Animal Health Code (WOAH, no date).

Metrics and numeric limits

Disability adjusted life years (DALYs) are used as a measure to evaluate the impact of the morbidity caused by brucellosis in humans.

Key relevant UN convention / multilateral treaty

International Health Regulations (2005), 3rd ed. (WHO, 2016).

WTO Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement) (WTO, 1994).

Collaboration between the World Trade Organization (WTO) and the World Organization for Animal Health (OIE) concerning the use of international standards in the context of the SPS Agreement (WTO, 2007). United Nations. 2023.

UN Recommendations on the Transport of Dangerous Goods - UN Model Regulations Model Regulations. https://unece.org/transport/dangerous-goods/un-model-regulations-rev-23.

Drivers

Human

Introduction of sub-clinically infected animals. The disease is also considered an occupational hazard for people who work in the livestock sector. People who work with animals and are in contact with blood, placenta, foetuses and uterine secretions have an increased risk of contracting the disease. This method of transmission primarily affects farmers, butchers, hunters, veterinarians and laboratory personnel (WHO, 2020).

Animal

Not Applicable

Impacts

Human

Brucellosis generates disease in humans after consuming unheated dairy products (e.g., raw milk); and trade implications. These may involve substantial economic losses, including loss of income and manpower, medical care costs, and loss of food due to inadequacy of processing or spoilage.

Animal

Huge economic losses to dairy, sheep, goat and pig farmers (WOAH, no date).

Multi-hazard context

Brucellosis is found globally and is a reportable disease in most countries. It affects people of all ages and both sexes. In the general population, most cases are caused through direct contact with infected animals, by eating or drinking contaminated animal products or by inhaling airborne agents. Most cases are caused by ingesting unpasteurized milk or cheese from infected goats or sheep (WHO, 2020).

Risk Management

Control activities must be coordinated and shared between both public health and animal health sectors. Administrative arrangements between the two sectors must facilitate immediate cross-notification of cases, as well as joint investigations and control. Control programmes must be promoted in goat-raising areas (FAO, OIE, WHO, 2006).

Equally important, complementary control of animal and human brucellosis activities on the ground at the community level, where local veterinary and public health services interact and collaborate, is key to ensuring the application of adapted approaches for improving surveillance, enhancing community awareness, promoting milk pasteurisation and hygiene practices and delivering effective vaccination campaigns (FAO, 2014).

Guidance on brucellosis surveillance and standards is available from the Food and Agriculture Organization of the United Nations (FAO), the World Health Organization (WHO), the World Organisation for Animal Health (WOAH), and the United States Centres for Disease Control and Prevention (CDC).

The FAO has produced guidelines for coordinated human and animal brucellosis surveillance. The purpose of these general guidelines on surveillance in both human and animal populations is to provide a set of principles and techniques that can be used to develop and monitor new or existing brucellosis control programmes. The guidelines can also help in assessing the effectiveness of regulatory and advisory measures designed to safeguard public health (FAO, 2003).

The WHO provides technical advice to member states through the provision of standards, information and guidance for the management of brucellosis in humans and animals. The WHO works to support the coordination and sharing of information between the public health and animal health sectors. In collaboration with the FAO, the OIE and the Mediterranean Zoonoses Control Programme (MZCP), the WHO supports countries in the prevention and management of the disease through the Global Early Warning System for Major Animal Diseases (GLEWS) (WHO, 2020).

The OIE Terrestrial Animal Health Code provides guidance on infection with Brucella abortus, B. melitensis and B. suis, specifically Article 8.4 on the mitigation of the risk of spread of, and the risk to human health from, Brucella abortus, B. melitensis and B. suis in animals (OIE, 2019).

The CDC Brucellosis Reference Guide: Exposures, Testing, and Prevention is an example of a country approach. This guide includes the Brucella species as one of the biological agents and toxins that may pose a severe threat to public health, stating that the Brucella species are easily aerosolised and have a low infectious dose, cited at levels of between 10 and 100 microorganisms (CDC, 2017).

Human

Prevention of brucellosis is based on surveillance and the prevention of risk factors. The most effective prevention strategy is the elimination of infection in animals. In countries where eradication in animals through vaccination or elimination of infected animals is not feasible, prevention of human infection is primarily based on raising awareness, food-safety measures, occupational hygiene and laboratory safety. (WHO, 2020).

Pasteurization of milk for direct consumption and for creating derivatives such as cheese is an important step in preventing transmission from animals to humans. Education campaigns about avoiding unpasteurized milk products can be effective, as well as policies on its sale (WHO, 2020).

Risk management includes movement control and treatment with antimicrobials. It also involves routine surveillance, particularly among high-risk groups (farmers, shepherds, workers in slaughterhouses, butchers, veterinarians, and laboratory personnel). Another element of risk management is the mandatory early case-based reporting by health care providers or laboratories to upper levels of the public health sector as well as to the appropriate level of the animal health sector. In endemic countries where investigation of all reported cases may not be feasible, a representative proportion of reported cases should be investigated routinely.

Animal

Movement control; tracing back/forward of infected animals, depopulation of infected herds; vaccination of animals. Vaccination of cattle, goats and sheep is recommended in enzootic areas with high prevalence rates. Serological or other testing and culling can also be effective in areas with low prevalence. Abortion of affected animals is also a risk reduction approach. Public health education should be included among the essential activities to be performed within the framework of brucellosis control programmes or even as an independent activity (FAO, OIE, WHO, 2006).

Monitoring

The table below offers an overview of monitoring for brucellosis. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management.

Which institution(s) produce(s) Disaster Risk Data/Information?

Ministry of Health, Ministry of Agriculture, Ministry of Livestock, WHO, FAO Reference Centres, WOAH Reference Centres

How is the Hazard Observed/Monitored/Forecast?

Through its global early warning system, FAO has been supporting Members with risk monitoring, assessment and forecasting for animal health threats to enhance preparedness and response to animal health threats:

The Global Animal Disease Information System, EMPRES-i+, plays a crucial role in supporting countries with early warning and early detection of animal disease outbreaks. By providing a comprehensive platform for real-time disease tracking, EMPRES-i+, enables to monitor and analyse animal health threats effectively, collaborating closely with countries and regions on disease information sharing. This supports the dissemination of risk assessments and alerts for evidence-based decision-making.
FAO develops and maintains decision support tools that provide risk maps of existing and predicted risks of animal disease emergence, as well as other threats to the agri-food chain.
Additionally, FAO collaborates closely with international organizations like WHO and WOAH to verify disease information through integrated mechanisms such as the Epidemic Intelligence from Open Sources (EIOS), and the Global Early Warning System (GLEWS+), and through the World Animal Health Information System (WAHIS) for WOAH-listed diseases. These collaborations allow for the dissemination of early warning alerts and risk assessments to Members, to enable timely responses to potential outbreaks.

FAO empres-i+ https://empres-i.apps.fao.org/diseases

WOAH WAHIS https://wahis.woah.org/#/event-management

WHO supports countries to conduct all-hazards strategic risk assessment in the contexts of health emergencies and disasters, which results in the development of a country's risk profile. Empowered with the country risk profile, inclusive of a seasonal risk calendar, countries can anticipate potential emergencies before they occur to trigger early alerts and inform early actions (WHO, 2021).

WHO's Early Warning, Alert and Response System (EWARS) has been designed to improve disease outbreak detection in emergency settings, such as in countries in conflict or following a natural disaster. It is a simple and cost-effective way to rapidly set up a disease surveillance system. EWARS is deployed during an emergency as an adjunct to the national disease surveillance system. WHO works with Ministries of Health and health sector partners to train local health workers to use the system. After the emergency, EWARS should re-integrate back into the national system (WHO, 2023).