Brucellosis Can Spread from Cattle to People through Raw Milk
Brucellosis is caused by bacteria of the Brucella genus and affects both animals and people. The bacteria can infect cattle as well as goats, sheep and pigs, and may be present in animal tissues and fluids. Human infection can follow the consumption of raw milk or dairy products made from contaminated milk that has not undergone pasteurisation.
People may also become infected through direct contact with infected animals or their secretions. This makes agricultural workers, veterinarians and abattoir staff particularly exposed groups. Handling blood, placentas, birthing materials and other animal fluids can create additional opportunities for transmission. The US Centers for Disease Control and Prevention also lists raw milk and other unpasteurised dairy products among routes of infection.
Symptoms can appear weeks or months after exposure
Brucellosis is not always easy to identify from symptoms alone. Signs may emerge weeks or months after exposure and can resemble those of several other infections. Fever may persist or return intermittently, a pattern associated with the disease’s alternative name, undulant fever.
Possible symptoms include tiredness, weakness, sweating—including at night—headache, muscle, joint or back pain, reduced appetite and general malaise. These symptoms do not establish a diagnosis by themselves. Medical assessment generally considers the person’s exposure history, such as recent consumption of raw milk or direct work with animals, and laboratory testing is needed to confirm infection.
Pasteurisation reduces the risk
The risk is linked to the absence of a processing step that can destroy dangerous microorganisms, rather than to milk as a food in itself. Pasteurisation uses controlled heating to reduce bacteria that may be present. Milk taken directly after milking can appear fresh and have a normal smell and appearance without providing the same protection as pasteurised milk.
Dairy products made with unpasteurised milk also require caution. Consumers are advised to choose pasteurised milk or products that have received an appropriate heat treatment, check the origin of cheese and other dairy goods, and avoid raw-milk products from unknown sources. Professionals working with animals should use protective equipment when handling potentially infectious fluids.
Medical evaluation is required
Recurring or persistent fever, fatigue and body aches after eating unpasteurised milk or cheese, or after risky contact with animals, should be assessed by a health professional. Brucellosis is treated with antibiotics, but the medicines and treatment length depend on medical evaluation and confirmation of the diagnosis. Person-to-person transmission is considered extremely rare.
