Brucellosis is a zoonotic disease (any disease or infection that is naturally transmissible from vertebrate animals to humans and vice-versa is classified as a zoonotic disease).It is also known as “undulant fever”, “Mediterranean fever” or “Malta fever” . Brucellosis is a disease of mainly cattle, swine, goats, sheep and dogs.
The infection is transmitted to humans by animals through direct contact with infected materials like afterbirth or indirectly by ingestion of animal products and by inhalation of airborne agents. Consumption of raw milk and cheese made from raw milk (fresh cheese) is the major source of infection in man. It is also an occupational disease for people who work in the livestock sector. It affects people of all age groups and of both sexes.
Initial symptoms include; fever, weakness, malaise, anorexia, headache, pain in muscles and joint and/or back, fatigue.
Some signs and symptoms may persist for longer period are-
Recurrent fever, arthritis, swelling of the testicle and scrotal area, swelling of the heart (endocarditis), chronic fatigue, depression, swelling of the liver and/or spleen.
Complications may affect any organ system.
Brucellosis is caused by different species of bacteria Brucella such as Brucella abortus,Brucella melitensis, Brucella suis, Brucella canis. They are shed in large numbers in the urine, milk and placental fluid of infected animals.
The infection is transmitted to humans by animals through three different ways-
- Infection may occur with direct contact with infected materials like afterbirth, blood, urine through broken skin, mucus membrane or conjunctiva.
- Infection may takes place indirectly by ingestion of animal products such as raw milk and cheese made from raw milk. It is the major source of infection in humans.
- Infection may also spread by inhalation of airborne agents.
Brucella spp. can survive for long periods in dust, dung, water, slurry, aborted fetuses, soil, meat and dairy products.
Human-to-human transmission is very rare.
Incubation period is highly variable. Usually 2-4 weeks, can be 1 week to 2 months or longer.
The clinical picture is not specific therefore diagnosis needs to be supported by laboratory tests.
- Rose Bengal test (RBT) for screening; positive tests to be confirmed by one of the tests mentioned below under Confirmatory diagnosis below;
- Standard agglutination test (SAT).
- Isolation of Brucella spp. from blood or other clinical specimen.
- A presumptive laboratory diagnosis based on detection of agglutinating antibodies (RBT, SAT) combined with detection of non-agglutinating antibodies through:
- ELISA IgG test,
- Coombs IgG.
Antibiotics are used to treat the infection and prevent the recurrence of disease. Longer courses of therapy may be needed if there are complications.
For further treatment seek medical advice.
The most rational approach for preventing human brucellosis is the control and elimination of the infection in animals.
- Vaccination of cattle is recommended for control of bovine brucellosis in enzootic (constant presence of a disease in animal population) areas with high prevalence rates.
- Eradication by testing and culling is the way to the elimination of brucellosis in regions with a low prevalence.
People should be educated to avoid consuming unpasteurized milk and milk derivatives and to cook meat adequately.
Barrier precautions for hunters and professionals at risk (butchers, farmers, slaughterers, veterinarians) with careful handling and disposal of afterbirths, especially in cases of abortion.