Brucellosis – Symptoms and Causes
Brucellosis is a bacterial disease caused by various Brucella species , which primarily infect cattle, pigs, goats, sheep, and dogs. Humans generally contract the disease through direct contact with infected animals, by eating or drinking contaminated animal products, or by inhaling airborne agents. Most cases are caused by ingestion of unpasteurized milk or cheese from infected goats or sheep.
Brucellosis is one of the most widespread zoonoses transmitted by animals and, in areas where it is endemic, human brucellosis has serious consequences for public health. The expansion of animal industries and urbanization, as well as the lack of hygienic measures in animal husbandry and food handling, partly explain why brucellosis continues to be a danger to public health.
Who is exposed to risk?
Brucellosis is a disease that occurs worldwide and is subject to notification in most countries. It affects people of all ages and both sexes. In the general population, most cases are caused by the consumption of raw milk or its derivatives such as fresh cheese. Most of these cases are due to products of ovine and caprine origin.
The disease is also considered an occupational hazard for people working in the livestock sector. People who work with animals and are in contact with blood, placenta, fetuses, and uterine secretions are at increased risk of contracting the disease. This method of transmission primarily affects farmers, butchers, hunters, veterinarians, and laboratory personnel.
Worldwide, Brucella melitensis is the most prevalent species causing human brucellosis, due in part to difficulties in immunizing free-range goats and sheep.
Transmission from person to person is very rare.
Prevention and Control
Prevention of brucellosis is based on surveillance and prevention of risk factors. The most effective prevention strategy is elimination of the infection in animals. Vaccination of cattle, goats and sheep is recommended in enzootic areas with high prevalence rates. Serological or other testing and culling may also be effective in low-prevalence areas. In countries where eradication of the disease in animals by vaccination or removal of infected animals is not possible, prevention of infection in humans relies primarily on awareness raising, food safety measures, occupational hygiene and laboratory safety.
The pasteurization of milk for direct consumption and for the production of derivatives such as cheese is an important step to prevent transmission from animals to humans. Education campaigns on the need to avoid unpasteurized dairy products can be effective, as can policies on their sale.
In agricultural and meat processing tasks, protective measures and the correct handling and disposal of the placenta, animal carcasses and internal organs are an important prevention strategy.
treatment and care
Brucellosis often causes flu-like symptoms, such as fever, weakness, malaise, and weight loss. However, the disease can present in many atypical forms. 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 and range from one week to two months, although it is normally between two and four weeks.
One of the therapeutic options is doxycycline 100 mg twice daily for 45 days, plus streptomycin 1 g daily for 15 days. The main alternative therapy is doxycycline 100 mg twice daily for 45 days, plus rifampicin 15 mg per kilogram per day (600-900 mg) for 45 days. Experience indicates that streptomycin can be substituted with 5 mg gentamicin per kilogram per day for 7 to 10 days, but no studies directly comparing the two regimens are currently available. The optimal treatment for pregnant women, newborns, and children younger than 8 years has not yet been determined; for children, options include trimethoprim/sulfamethoxazole (cotrimoxazole) combined with an aminoglycoside (streptomycin, gentamicin) or rifampicin.
WHO provides technical advice to Member States by providing standards, information and guidance for the management of brucellosis in humans and animals. The Organization works to support the coordination and exchange of information between the public health and animal health sectors. In collaboration with the Food and Agriculture Organization of the United Nations (FAO), the World Organization for Animal Health (OIE) and the Mediterranean Zoonoses Control Program (MZCP), WHO supports countries in disease prevention and management through the Global Early Warning System for Major Animal Diseases (GLEWS).