What Causes Brucellosis?

Brucellosis, also known as 'Mediterranean Fever,' is a contagious disease that develops from exposure to a bacteria called Brucella. There are several different types of this bacteria, and it is carried by animals such as cows, sheep, dogs, goats, pigs, and camels. New strains of the Brucella bacteria have recently been found in foxes and seals. All of these animals can transmit the brucella bacteria to humans, leading to brucellosis. Typically, the disease begins with a fever, joint and back pain, extreme tiredness, and loss of appetite. As brucellosis progresses, it may lead to arthritis, more frequent fevers, depression, chronic fatigue, and swelling of the liver, spleen, or heart.

Blood tests are required for diagnosis, and the ailment is, thankfully, treatable. There are approximately one hundred cases of brucellosis in the United States each year, and the World Health Organization estimates 500,000 individuals worldwide are diagnosed annually. Many of those who have been successfully treated will go on to experience another episode of the disease in the future.

Unpasteurized Dairy Products

Around the world, consuming raw milk, cheese known as 'village cheese,' and other unpasteurized dairy products is a major cause of brucellosis. Typically, these foods are contaminated with either the Brucella melitensis or the Brucella abortus strains of the bacteria. The bacteria then enter the body when the dairy is ingested. Unpasteurized goat's milk, cow's milk, and sheep's milk are common sources of the brucella contaminant.

While the Brucella abortus strain, which originates in cattle, has been eradicated in several countries, the Brucella melitensis strain is responsible for the majority of brucellosis cases. It is commonly carried by sheep and goats and is prevalent in South America, the Middle East, India, Spain, and Greece. Rarely, other strains of brucellosis bacteria from unpasteurized products have been linked to the disease. These include Brucella suis and RB51, which can be resistant to some antibiotics.

Inhalation Of Bacteria

Although uncommon, brucellosis can be transmitted to humans through inhalation of the bacteria. This method of infection is referred to as inhalational brucellosis. Brucella bacteria are typically inhaled in areas where large numbers of livestock are concentrated, such as slaughterhouses and farms where cattle, pigs, sheep, and goats are raised. The bacteria can also be airborne in laboratories that conduct research on dogs or large livestock animals. To minimize the risk of inhalation, face masks or full protective suits are sometimes worn, and laboratory workers can use biological safety cabinets to contain specimens with a high risk of splashing.

Direct Contact With Bacteria

Direct contact with the bacteria frequently spread brucellosis. The disease is not present on the skin of infected animals; thus, simply touching or petting an animal with brucellosis will not transmit the disease to humans. However, Brucella bacteria are present in the placenta, blood, semen, and other bodily fluids of infected animals, and direct contact with these fluids can pass the illness to humans. For example, while very rare, there has been a reported case of a man getting brucellosis after being bitten by his dog.

This shows the Brucella bacteria can enter the skin through a tiny cut, scratch, or puncture wound. Generally, this is more likely to occur when helping animals give birth or when conducting animal experiments. Nevertheless, dog owners who have compromised immune systems, such as those undergoing cancer treatment, are recommended to avoid touching or petting them if the animal has a confirmed case of brucellosis.

Work In High Risk Occupations

Certain professions that involve close contact with domestic animals and livestock pose a higher than normal risk of exposure to, and potential infection with, strains of the Brucella bacteria. While there is a vaccine available for animals, no vaccine against brucellosis currently exists for humans; therefore, it is important for all individuals who face increased exposure take appropriate precautions in their work. Work in high-risk occupations is a central cause of brucellosis. Veterinarians, livestock and dairy farmers, meat-packing industry workers, hunters, laboratory technicians, microbiologists, and clinicians treating brucellosis patients all have a higher than normal risk of getting the disease themselves.

All workers at high risk should wear protective gear such as gloves, safety goggles, and face masks. Additionally, it is recommended that laboratory workers use primary barriers such as safety caps on centrifuges combined with secondary barriers such as closing external windows and doors and restricting laboratory access. For the protection of farmers, it is recommended for livestock to be vaccinated against brucellosis.

Travel To Areas With High Risk

Some areas of the world have higher incidences of brucellosis, and travel to these areas can increase an individual's chance of exposure to the disease. While brucellosis cases occur across the globe, areas of particularly high risk are generally those countries with less established health programs for both public and animal health. At present, Asia, Africa, the Caribbean, the Middle East, Eastern Europe, and Central and South America are all classified as high-risk regions. Additional countries with increased risk include Mexico, and the area referred to as the Mediterranean Basin, which includes Portugal, Spain, Greece, Italy, and southern parts of France. Individuals who plan to visit or work in these areas should avoid eating or drinking unpasteurized dairy products and uncooked or undercooked meats.

Those intending to work with livestock or animals in these areas should ensure any cuts or scratches are covered, and gloves, protective eyewear, and masks are worn as appropriate. Travelers returning from high-risk areas should be aware of the symptoms of brucellosis and should contact their doctor immediately if they believe they may have signs of this illness. The incubation period for brucellosis is approximately five to thirty days, and travelers should be especially vigilant about monitoring themselves for possible symptoms during this period.