Synonyms: undulant fever, contagious or infectious abortion, Malta fever, Maltese fever, Mediterranean fever, Crimean fever, Gibraltar fever, Bang's disease, Rock fever

What is it?

The brucelloses are a group of cosmopolitan bacterial diseases caused by species of the genus Brucella. Brucella species usually infect genital organs, causing abortion and infertility. Different Brucella species are observed in many wild and domestic mammals, some of them being infective to humans. As a consequence, brucellosis causes production losses in livestock and represents a public health threat. Brucella species are usually classified as rough and smooth, according to their appearance in culture. Only smooth Brucella are zoonotic: Brucella abortus, Brucella melitensis and Brucella suis. Brucella abortus and B. melitensis infect primarily cattle and small ruminants, respectively. They were also isolated in humans, small ruminants, camels, horses, pigs and dogs. Brucella suis is mostly found in pigs but humans, cattle, horses and dogs were reported to be infected by B. suis. Brucellosis is transmitted either through aborted fetuses and placenta, infected raw meat or through the consumption of milk and milk products originating from infected animals. As a consequence, human brucellosis is primarily an occupational disease of people working or living in close contact with animals or whose work involves processing raw meat. The consumption of raw (uncooked, unboiled, unpasteurized)  milk and products made from raw milk also presents a high risk of infection.

Simplified text

Brucellosis Disease Card (English, French and Spanish)

Brucellosis Surveillance. WHO (English only)

Brucellosis. Veterinary Faculty, Egypt (English, Arabic)

Brucellosis: An overview. AVIS Consortium (English only)

Simplified video

Brucellosis in Egypt (3'01; Arabic only)

Technical text

Brucellosis WHO/OIE/FAO (English only)

Brucellosis abortus, Iowa State University (English only)

Brucellosis melitensis, Iowa State University (English only)

Global burden of human brucellosis (English only)

OIE terrestrial manual, cattle (English only)

OIE terrestrial manual, small ruminants (English only)

How to recognize it

In animals, brucellosis causes late stage abortion (last third of pregnancy), stillbirth and placental retention in pregnant animals. Subsequent gestations are usually problem free. Males may develop orchitis when testes are infected. Hygromas (swollen joints) are sometimes observed in chronic infections. Abortions might either be sporadic or epizootic (abortion storm), depending on the immune status of the herd.  Diagnosis can be confirmed through the isolation of Brucella from the fetus or from the placenta. Serological tests are available: rose Bengal plate test, Wright’s slow agglutination test, fixation of complement, indirect ELISA and competitive ELISA. Serological tests are relatively specific but may lack sensitivity. Cross-reactions with Yersinia enterocolitica were reported, particularly in pigs, and vaccinated animals may turn positive to a serological test. Skin tests using brucellin as antigen are more specific but less sensitive than serological tests.

Simplified text

Brucellosis Disease, AVIS consortium (English only)

Brucellosis. Veterinary Faculty, Egypt (English, Arabic)

FAO manual on meat inspection for developing countries (English only)

Simplified video

Brucellosis in Egypt (3'01; Arabic only)

Technical illustrations

Brucellosis abortus, Iowa State University (English, Spanish and Thai)

Technical text

Brucellosis Diagnosis, AVIS consortium (English only)

Brucellosis abortus, Iowa State University (English only)

Brucellosis melitensis, Iowa State University (English only)

OIE terrestrial manual, cattle (English only)

OIE terrestrial manual, small ruminants (English only)

Technical video

Indian video on isolation and diagnosis of brucellosis in animals (5'36; English)

In humans, brucellosis causes a flu-like febrile syndrome: intermittent and relapsing fever, sweating, body aches, joint pain, fatigue, weakness, dizziness, headache, depression, irritability, loss of appetite, weight loss, cough, difficulty breathing, chest pain, abdominal pain, enlarged liver and/or spleen. The disease is generally chronic with different levels of severity. Unlike animal brucellosis, human brucellosis does not cause abortion or infertility. Orchitis (inflammation of the testes) has been reported in humans but is infrequent. Endocarditis (an infection of the inner lining of the heart ) also occurs rarely but is the most feared because it is the main cause of death from brucellosis. Serological tests can be used to detect specific antibodies. Bacterial isolation from clinical specimens can also be attempted.

Simplified text

Brucellosis Disease, AVIS consortium (English only)

Brucellosis Surveillance. WHO (English only)

Technical text

Brucellosis WHO/OIE/FAO (English only)

Health-seeking behaviour of human brucellosis cases in rural Tanzania (English only)

Lancet : Human brucellosis (English only)

How to control it

Many industrialized countries eradicated brucellosis from livestock using vaccination followed by a test-and-slaughter strategy (regular testing of all animals and slaughter of those testing positive). Reintroduction through importation of live animals or contaminated objects (fomites) should be avoided. Surveillance and investigation of the causes of abortions should continue since reintroduction in livestock from the wild or from abroad cannot be ruled out. Bringing new animals into a disease free herd should be done with caution: animals should only come from brucellosis-free herds and be quarantined and tested before they are mixed with the herd.

Animals cannot be treated against brucellosis. Young stock can be vaccinated against Brucella abortus and Brucella melitensis using live attenuated vaccines (B19 and Rev 1, respectively).  Vaccination has the disadvantages of inducing the production of antibodies that may interfere with diagnostic tests, causing healthy but vaccinated animals to test positive for the disease.   Vaccination can also cause abortion in pregnant animals and vaccines may accidentally infect humans through needle inoculation. The more recent RB51 B. abortus vaccine was developed to avoid cross-reactions with serological tests. Livestock vaccination significantly reduces the incidence of abortion and the risk of transmission to humans but fails to eliminate the disease. Complete elimination can only be achieved through a strict and long-lasting test-and-slaughter scheme. Such schemes are expensive because they require compensations for the animals that are slaughtered. Compensation is absolutely necessary to obtain the support of the livestock owners.

In case of suspicion of animal brucellosis, aborted fetuses and placentas should be destroyed and the place where the animal has given birth should be disinfected to reduce the risk of transmission. Farmers and veterinarians can reduce the risk of being infected by using protective clothing (gloves and a mask) when assisting an animal with a difficult birth. Butchers and hunters also need to protect themselves when dressing potentially infected meat.

The consumption of raw milk or products made of raw milk originating from endemic areas should be avoided. Ideally, milk should be pasteurized, sterilized or cooked before it is used for human consumption. This measure is often not very well tolerated by the communities because it is cumbersome, requires a lot of energy (fire wood) and may interfere with the preparation of milk products.

When diagnosing humans it is not easy to distinguish brucellosis from other diseases. Its main clinical sign, recurrent fever, means that in malaria-endemic zones it is almost always initially diagnosed as malaria and many human patients are never correctly diagnosed with brucellosis. Veterinary services should be informed when cases of human brucellosis are observed so that appropriate control measures can be implemented in livestock.

Human brucellosis can be treated with antibiotics such as doxycycline, gentamicin, rifampin, and streptomycin. Combinations of drugs cause fewer relapses. Treatment regimens are long, lasting a minimum of 6 weeks and several months if complications occur.

Simplified text

Brucellosis Surveillance. WHO (English only)

Brucellosis control, AVIS consortium (English only)

Brucellosis. Veterinary Faculty, Egypt (English, Arabic)

Simplified video

Brucellosis control in Tajikistan (4'17; English)

Brucellosis in Egypt (3'01; Arabic only)

Brucellosis monitoring in Mongolia (5'29; local language with English subttile)

Brucellosis vaccination in Egypt (No language)

Technical text

Brucellosis WHO/OIE/FAO (English only)

Brucellosis in terrestrial wildlife

Brucellosis: 'One Health' challenges and opportunities (English only)

FAO paper on production losses due to bovine brucellosis in Africa (English only)

Human health benefits from livestock vaccination for brucellosis: case study in Mongolia (English only)

OIE terrestrial manual, cattle (English only)

OIE terrestrial manual, small ruminants (English only)

Cultural and geographical specificities

Brucellosis is, in all countries, a reportable animal disease requiring the implementation of control measurs if cases are reported. However, brucellosis surveillance is rarely carried out in Africa and animal brucellosis is, in many countries, not controlled at all. The capacity to diagnose it in humans is often limited to a few hospitals and health centers, so that in humans the disease is massively underdiagnosed.  Thus although it appears that brucellosis is of limited public health impact, its real extent is unknown.   In indigenous livestock breeds, the disease has usually been present for some time in herds, so that abortion storms are rare, and animals are instead chronically infected.  Current evidence indicates that some specific situations do require attention, for instance in dairy farms using high-grade cattle and pastoralist communities. Vaccination of young stock should be proposed in all identified risk situations.  In most African situations, a test-and-slaughter policy is impracticable.  Compensation would be difficult to organize, and livestock keepers in the traditional sector need to retain all their breeding animals in order to maintain their herds in the face of drought and disease. 

Pastoralist communities

Pastoralists live in close proximity to their animals. As a consequence, they are heavily exposed to Brucella released after an abortion or during a delivery. Milk, almost always consumed raw, is an important component of pastoralists’ diet, which in some areas may also include raw blood.  Persuading people to change their nutritional habits is always a difficult and long drawn out process, nevertheless advice on avoiding the consumption of untreated milk and raw blood should be given.  Pastoralists are usually open to livestock vaccination. Introducing the brucellosis vaccine of young stock, combined with other veterinary vaccines is probably the most efficient way of reducing the incidence of human brucellosis.

Technical text

Health-seeking behaviour of human brucellosis cases in rural Tanzania (English only)

Postgraduate thesis: Prevalence and factors associated with brucellosis among febrile patients attending Ijara District Hospital, Kenya (English only)

Quantifying risk factors for human brucellosis in rural northern Tanzania (English only)

Communities in northern Africa and the Sahel region

Many farming systems with different breeds ranging from local to high-grade can be found in northern Africa and the Sahel. The introduction of high-grade dairy cattle in small farms and villages presents a high risk of B. abortus infection as they appear to be more susceptible. B. melitensis could be of concern in sheep, goat and camel herds, especially if people consume raw milk from these animals.   Brucellosis is also a concern in peri-urban dairy farms, whether based on indigenous or exotic cattle.  In traditionally managed herds with local breeds, prevalences obtained from surveys tend to be low, although occasional areas with higher levels of the disease are found.

Simplified video

Brucellosis in Egypt (3'01; Arabic only)

Technical text

A large seroprevalence survey of brucellosis in cattle herds under diverse production systems in northern Nigeria (English only)

Brucella infection among hospital patients in Makurdi, North Central Nigeria (English only)

Seroprevalence of brucellosis in animals and human populations in the western mountains region in Libya (English only)

Mixed farming communities in more humid regions

Numerous studies in central and southern Africa have revealed very low prevalences of brucellosis in traditionally reared indigenous animals, suggesting that the risk of human infection is very low. Very few cases are reported by the medical services in these areas. However, studies occasionally show higher prevalences in some localities.  It is also clear that commercial dairy farms tend to be more seriously affected, sometimes with prevalences of over 20%, and brucellosis appears to be an important occupational disease among farm workers and butchers and abattoir workers

Wildlife in game reserves may also be affected by brucellosis (abortion and hygroma can be observed) and therefore can infect humans when hunted.  In some areas brucellosis is also thought to be transmitted between wildlife and domestic animals.

Technical text

Zoonotic tuberculosis and brucellosis in Africa (English only)