Brucellosis: what kind of disease is that?

Medically reviewed: 1, February 2024

What is Brucellosis?

Brucellosis is a bacterial infection that can affect humans and animals. Brucellosis is caused by different types of the Brucella bacteria, which can be passed from infected animals to people through contact with their bodies or things they produce, like milk, meat, or placenta.

Brucellosis has a long and complex history, and it is still a major public health problem in many parts of the world. In this text, I will provide a very long and comprehensive overview of brucellosis, its history, and its symptoms.

How disease was discovered?

The history of brucellosis dates back to ancient times, when it was probably known as a disease of cattle and sheep. The first recorded description of brucellosis in humans was by Hippocrates in the 5th century BC, who mentioned a fever that occurred among shepherds and herdsmen in Greece. The disease was later called Malta fever, after it was observed among British soldiers stationed in Malta in the 19th century. In 1887, a Scottish doctor named David Bruce discovered the germ that causes Malta fever.

He found the bacteria Brucella melitensis in the spleen of a soldier who had died. Bruce found out that goats and their milk can spread the disease too. In 1897, a Danish vet named Bernhard Bang found a new kind of Brucella bacteria. An abortion in cattle and their inability to have babies is called “abortus”.
Bang also showed that the disease could be transmitted to humans by drinking unpasteurized milk.

In 1914, Alice Evans, an American bacteriologist, confirmed that B. abortus and B. melitensis were closely related and belonged to the same genus. She also suggested that pasteurization of milk could prevent the spread of brucellosis. In 1920, the term brucellosis was coined by Stitt, an American naval surgeon, to honor Bruce and his work.

Since then, two more species of Brucella have been identified as human pathogens: B. suis, which infects pigs and causes swine brucellosis, and B. canis, which infects dogs and causes canine brucellosis. Brucellosis is also known by different names like undulant fever, Mediterranean fever, rock fever, and Bang’s disease. These names depend on where the infection comes from and what animal carries it.

What are the risk factors of Brucellosis?

The risk factors of brucellosis can be divided into two main categories: environmental and occupational. Environmental risk factors are things in the environment that can affect where and how a disease spreads among animals and people. Certain jobs or activities can put you at risk of getting sick from being around animals or things from animals.

Environmental risk factors

Brucellosis is a disease that can be found all over the world and is required to be reported in the majority of countries. It is a highly significant and widespread infectious disease that affects both humans and animals. However, the disease is more common and endemic in some regions than others, depending on the animal reservoirs, the control measures, and the socio-economic factors. According to the World Health Organization (WHO), the highest incidence rates of human brucellosis are reported in the Mediterranean Basin, the Arabian Peninsula, Central Asia, Africa, and Latin America.

These regions have large populations of sheep, goats, and cattle, which are the main sources of infection for humans.

Moreover, these regions have limited resources and infrastructure for animal vaccination, testing, and culling, as well as for human diagnosis, treatment, and prevention. Also, people in these areas have customs and diets that make them more likely to consume raw dairy products or meat, which can spread disease to humans.

To reduce the chances of getting brucellosis, we can take steps to control and eliminate the infection in animals. This can include vaccinating, testing, removing infected animals, keeping sick animals separate, and keeping an eye on the situation. Also, teaching people about the dangers of eating raw dairy or meat and making sure that food safety rules are followed can lower the chance of getting sick from animals.

Occupational risk factors

Brucellosis is a risk for people who work with animals on farms or in similar jobs. These people are more likely to get sick from touching or being around animals or their body parts that are infected with the disease.

The occupational risk factors of brucellosis include:

• Working in farms, ranches, slaughterhouses, meat-processing plants, or dairy factories, where exposure to infected animals or their products is frequent and prolonged.
• Working as veterinarians, veterinary assistants, animal health workers, laboratory personnel, or researchers, who may handle or examine infected animals or their specimens, or perform procedures such as artificial insemination, castration, or necropsy.
• Working as butchers, hunters, or wildlife workers, who may kill, skin, or process infected animals or their carcasses, or handle their trophies, such as horns, antlers, or hides.
• Working as military personnel, humanitarian workers, or travelers, who may visit or stay in endemic areas, or consume local food or water that may be contaminated with the bacteria.

The occupational risk factors of brucellosis can be reduced by adopting appropriate preventive measures, such as wearing gloves, masks, goggles, and protective clothing, washing hands and equipment thoroughly, disposing of waste properly, and avoiding contact with wounds or mucous membranes.

Moreover, seeking medical attention promptly and receiving prophylactic antibiotics in case of exposure or injury can prevent or treat the infection.

Symptoms of Brucellosis

The signs of brucellosis can be different depending on the kind of Brucella bacteria, how the person got infected, how well their immune system works, and how long the illness lasts. Brucellosis starts slowly with fever, chills, sweats, weakness, and body aches. It can go away in a few weeks or last for a long time. The fever goes up and down every day.

The sweats are often profuse and have a characteristic foul, moldy smell. The joint and muscle pain are migratory, meaning that they move from one location to another. The illness can also harm different parts of the body, causing problems like joint pain, heart infection, brain infection, testicle swelling, liver infection, enlarged spleen, and bone infection. Brucellosis is diagnosed by looking at the symptoms, what the person has been around, and doing some tests in the lab. The tests done in the laboratory check the blood, use serology, polymerase chain reaction (PCR), and imaging studies.

The symptoms of brucellosis can be divided into two phases: acute and chronic.

Acute symptoms

The acute phase usually occurs within a few days to a few months after exposure to the bacteria, and lasts for several weeks to months. The chronic phase may occur after the acute phase, or after a period of latency, and lasts for months to years, or even indefinitely. The chronic phase may also recur after treatment or remission.

The acute phase of brucellosis is characterized by a flu-like syndrome, with fever, chills, sweats, weakness, fatigue, headache, loss of appetite, weight loss, and pain in the muscles, joints, and back. The fever is typically undulant, meaning that it rises and falls in a daily pattern. The sweats are often profuse and have a distinctive foul, moldy smell. The pain is migratory, meaning that it moves from one location to another. The symptoms may vary in intensity and duration, and may resolve spontaneously or persist for a long time.

Chronic symptoms

The chronic phase of brucellosis is characterized by recurrent or persistent symptoms, which may affect various organs and systems of the body. The most common complications of brucellosis are:

• Arthritis: inflammation of the joints, especially the knees, hips, ankles, wrists, and spine. It may cause pain, swelling, stiffness, and reduced mobility.
• Spondylitis: inflammation of the spinal bones, which may cause back pain, stiffness, and nerve compression. It may also lead to spinal deformity or fracture.
• Sacroiliitis: inflammation of the joints where the spine and the pelvis connect, which may cause lower back pain, buttock pain, and sciatica.
• Endocarditis: infection of the inner lining of the heart chambers and valves, which may cause fever, heart murmur, chest pain, shortness of breath, and embolism. It may also damage the heart valves or cause heart failure.
• Meningitis: infection of the membranes that cover the brain and spinal cord, which may cause fever, headache, stiff neck, nausea, vomiting, confusion, and seizures. It may also cause brain damage or death.
• Encephalitis: infection of the brain tissue, which may cause fever, headache, confusion, drowsiness, personality changes, and neurological deficits. It may also cause coma or death.
• Orchitis: infection of the testicles, which may cause pain, swelling, and infertility.
• Epididymitis: infection of the tube that carries sperm from the testicles, which may cause pain, swelling, and infertility.
• Hepatitis: infection of the liver, which may cause jaundice, abdominal pain, and liver failure.
• Splenomegaly: enlargement of the spleen, which may cause abdominal pain, anemia, and increased risk of infection.
• Osteomyelitis: infection of the bone, which may cause pain, swelling, and bone loss. It may also cause abscess or fracture.

Diagnostics of Brucellosis

The diagnosis of brucellosis is based on the clinical presentation, the history of exposure, and the laboratory tests. The laboratory tests include:

• Blood culture: a test that grows the bacteria from a blood sample. It is the most definitive test, but it may take several weeks to obtain the results.
• Serology: a test that detects the antibodies against the bacteria in the blood. It is a quick and simple test, but it may not be reliable in the early or late stages of the disease, or in people who have been vaccinated or treated.
• Polymerase chain reaction (PCR): a test that amplifies the DNA of the bacteria from a blood or tissue sample. It is a sensitive and specific test, but it may not be widely available or standardized.
• Imaging studies: tests that use X-rays, ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) to visualize the affected organs or tissues. They may help to identify the complications or rule out other causes of the symptoms.

Treatment of Brucellosis

The treatment of brucellosis consists of prolonged courses of antibiotics, usually a combination of two or more drugs, such as tetracyclines, rifampin, streptomycin, and doxycycline. The treatment aims to eradicate the bacteria, relieve the symptoms, prevent relapse, and avoid complications. To avoid getting brucellosis, don’t touch animals or their products if they are sick. Make sure to heat milk and dairy products before drinking them, cook meat all the way through, wear gloves and protective clothing, and give domestic animals a vaccine.

The duration of the treatment may vary from six weeks to six months, depending on the type of bacteria, the severity of the disease, and the response to the therapy. The treatment may have side effects, such as nausea, vomiting, diarrhea, rash, and liver toxicity. The treatment may also interact with other drugs, such as oral contraceptives, anticoagulants, and antacids.

Treatment of brucellosis in animals

The treatment of brucellosis in animals depends on the species of the animal, the type of the bacteria, the stage of the infection, and the availability of the drugs. The main goals of the treatment are to eliminate the infection, prevent the transmission, and reduce the economic losses. The treatment options include:

1. Vaccination: This is the most effective and economical way to prevent and control brucellosis in animals. Vaccination can protect the animals from infection, reduce the shedding of the bacteria, and enhance the immune response. Different types of vaccines are available for different species of animals, such as cattle, sheep, goats, pigs, and dogs. The vaccines are usually administered to young animals, before they reach sexual maturity. The vaccines may have some side effects, such as abortion, inflammation, or allergic reactions. The vaccines may also interfere with the diagnosis of the infection, as they may induce antibodies that can be detected by the tests.
2. Antibiotics: This is the alternative or complementary way to treat brucellosis in animals. Antibiotics can kill or inhibit the growth of the bacteria, and reduce the symptoms and complications. However, antibiotics have some limitations, such as high cost, low efficacy, long duration, and risk of resistance. Antibiotics are usually given in combination, such as oxytetracycline, streptomycin, rifampin, and enrofloxacin. The dosage and duration of the treatment may vary depending on the species of the animal, the type of the bacteria, and the severity of the infection. The treatment may also require frequent monitoring and testing, to evaluate the response and the outcome.
3. Culling: This is the last resort or the mandatory measure to treat brucellosis in animals. Culling involves the identification and removal of the infected animals, and the disposal of their carcasses and products. Culling can prevent the spread of the infection, and reduce the reservoir of the bacteria. However, culling has some drawbacks, such as ethical, social, and economic implications. Culling may also require the compensation and support of the owners, and the enforcement and regulation of the authorities.

Treatment of brucellosis in humans

The treatment of brucellosis in humans depends on the type of the bacteria, the route of the infection, the immune status of the host, and the duration of the disease. The main goals of the treatment are to eradicate the bacteria, relieve the symptoms, prevent relapse, and avoid complications. The treatment options include:

1. Antibiotics: This is the standard and effective way to treat brucellosis in humans. Antibiotics can kill or inhibit the growth of the bacteria, and reduce the fever, pain, and inflammation. However, antibiotics have some challenges, such as high dose, long course, and risk of resistance. Antibiotics are usually given in combination, such as doxycycline, rifampin, streptomycin, and gentamicin. The dosage and duration of the treatment may vary from six weeks to six months, depending on the type of the bacteria, the severity of the disease, and the response to the therapy. The treatment may also require regular blood tests, dosage adjustments, and precautions.
2. Symptomatic treatment: This is the supportive and palliative way to treat brucellosis in humans. Symptomatic treatment can alleviate the discomfort and distress caused by the disease, and improve the quality of life. Symptomatic treatment may include painkillers, anti-inflammatory drugs, antipyretics, and fluids. Symptomatic treatment may also involve the management of the complications, such as surgery, drainage, or valve replacement. Symptomatic treatment may have some side effects, such as nausea, vomiting, diarrhea, rash, and liver toxicity. Symptomatic treatment may also interact with other drugs, such as oral contraceptives, anticoagulants, and antacids.

Prevention of Brucellosis

The prevention of brucellosis involves avoiding contact with infected animals or their products, pasteurizing milk and dairy products, cooking meat thoroughly, wearing gloves and protective clothing, and vaccinating domestic animals.

The prevention also involves educating the public about the risks and symptoms of the disease, and enforcing the food safety and animal health regulations and standards. The prevention also requires the cooperation and coordination of the human and veterinary health authorities, as well as the international organizations, such as the WHO, the Food and Agriculture Organization (FAO), and the World Organisation for Animal Health (OIE).