Brucellosis

Sophie Matzik is a freelance writer for the medical team.

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Brucellosis is an infectious bacterial disease that is mostly transmitted from infected animals to humans. It manifests itself through unspecific symptoms such as fever and chills, but can also have serious organic consequences. Read here how to protect yourself from infection and how brucellosis is treated.

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. A23M49

Brucellosis: description

Brucellosis is an infectious disease caused by bacteria that occurs in humans and animals alike (anthropozoonosis). It is mostly transmitted from animals to humans.

Brucellosis can be caused by various bacteria of the genus Brucella. Depending on the pathogen, different types of brucellosis are distinguished, for example Mediterranean fever (undulating fever), Bang's disease, and pig and dog brucellosis.

Mediterranean fever is most common in humans, while swine and canine brucellosis are very rare.

The symptoms of brucellosis can vary widely. In about 90 percent of the cases, there are no signs of infection at all. In the remaining ten percent, the symptoms vary from unspecific signs of inflammation such as fever or headache to severe organ damage.

What happens with brucellosis?

The brucellosis pathogens enter the human body through the mucous membranes or small injuries in the skin. Once penetrated, cells of the immune system transport them to the nearest lymph nodes. There they can get from the lymph into the bloodstream and on to various organs (such as the spleen, liver) or into the bone marrow, where they cause inflammation.

Brucellosis: facts and figures

Around 40 new cases of brucellosis are reported in Germany each year, most of them imported from Turkey. Doctors worldwide estimate that there are around 500,000 affected people.

Most of the sick in Germany got infected with brucellosis while traveling abroad. Endemic areas are the Mediterranean countries, the Arabian Peninsula, Africa, Asia, Central and South America.

In Germany, according to the Infection Protection Act (IfSG), there is an obligation to report brucellosis. This means that the suspicion, the actual illness and the death from brucellosis must be reported by the doctor to the health department. Sick animals are also notifiable. The entire population of animals that could become infected (cattle, goats, sheep, horses, pigs, dogs) is officially considered brucellosis-free in Germany. Sick animals are mostly imported from abroad. There are also occasional outbreaks in free-range pigs that have contracted wild boars.

incubation period

The time between infection and the outbreak of brucellosis (incubation period) is very variable: it can only be five days, but it can also be 60 days and more than two years. On average, the incubation period is around four months, with Bang's disease usually only one to three weeks.

The pathogens can be passed on to other people during the entire incubation period.

Brucellosis: symptoms

In around 90 percent of all those affected, brucellosis runs with no or only mild symptoms (subclinical course). The doctor can then only recognize that there is actually brucellosis from evidence of antibodies against the pathogens (antibodies) in the blood.

In the other ten percent of cases, the disease is either acute or chronic. There are different symptoms:

Acute brucellosis

Acute brucellosis can begin slowly or suddenly. A gradual progression usually occurs in Bang's disease, a sudden onset in Mediterranean fever. The first symptoms are unspecific signs of illness such as:

• fever
• nausea
• fatigue
• Headache and pain in the limbs
• Night sweats

In acute brucellosis, the fever can last for one to three weeks. Especially with Mediterranean fever, there are often two to five-day fever breaks in between. Such a course is called undulating fever.

A slow heartbeat (bradycardia) and visibly swollen lymph nodes are symptoms of acute brucellosis.

Chronic brucellosis

If brucellosis is not recognized and not treated, chronic brucellosis can develop after the onset of acute symptoms and last for over a year. A chronic course occurs in about five percent of the cases. General symptoms are:

• decreased performance
• Sweats
• depressive phases

In addition, there are usually permanent foci of inflammation in the liver, spleen or bones. If the bone marrow is affected, blood formation is disturbed as a result.

Furthermore, various organs and tissues can become chronically inflamed in brucellosis. This includes:

• the meninges (meningitis)
• the lining of the heart (endocarditis)
• Testicles (orchitis) and epididymis (epididymitis)
• Gallbladder (cholecystitis)
• Pancreas (pancreatitis)
• Peritoneum (peritonitis)
• Lungs (pneumonia)
• Vertebral body (spondylitis)
• Eyes (uveitis)

More rarely there is an enlargement of the liver and spleen (hepatosplenomegaly).

Brucellosis: causes and risk factors

Brucellosis is caused by small, gram-negative rod bacteria of the genus Brucella, the so-called Brucelles. Depending on the causing Brucella species, a distinction is made between the following forms of brucellosis:

• Mediterranean or Malta fever: The pathogen is Brucella melitensis (mainly in goats, sheep and camels)
• Bang's disease, Bang's disease: caused by Brucella abortus (mainly in cattle)
• Pig brucellosis: due to Brucella suis
• Canine brucellosis: due to Brucella canis

The last two Brucella species and the pathogens Brucella ovis and Brucella neotomae are extremely rare in humans.

Contagion from animals and food

Humans are usually infected through contact with infected animals (especially their faeces and urine) and through the consumption of infected, raw meat or other uncooked or unpasteurized animal products such as milk or cheese. The pathogen can also enter the body via the conjunctiva, the airways or damaged skin. In Germany all animals are officially brucellosis-free. The infection therefore mostly takes place abroad, where brucellosis is still widespread with regional differences.

Travelers to the Mediterranean region should note that pets and farm animals such as goats, sheep and pigs are often infected with the pathogen causing Mediterranean fever. Pig brucellosis occurs mainly in North America, Bang's disease mainly in the cattle breeding areas of the tropical zone.

Agricultural and veterinary surgeons as well as laboratory staff belong to the occupationally exposed risk groups.

Contagion from person to person

In rare cases, the transmission takes place directly from person to person. Infected mothers can pass brucellosis pathogens on to their children through breast milk. Brucellosis has very rarely been infected in the past through bone marrow transplants, blood transfusions and sexual intercourse.

Brucellosis: examinations and diagnosis

The diagnosis of brucellosis is very difficult because each disease has different symptoms or no symptoms at all. In addition, other diseases that cause the same unspecific signs of inflammation must be excluded in the diagnosis.

First of all, the medical history (anamnesis) is asked for during the examination. This provides the doctor with possible indications of brucellosis.

If there is any suspicion, a blood test is carried out in the laboratory. In the event of an infection, specific defense substances (antibodies) against the pathogen can be detected in the blood serum.

Depending on where in the body there are signs of inflammation, pathogens causing brucellosis can also be found in other tissues and fluids. These include, for example, spinal fluid (liquor), urine, liver, spleen and bone marrow.

The evaluation of the (blood) tests takes a few days.

Brucellosis: treatment

If there is a justified suspicion of brucellosis, therapy must be started immediately.

As a rule, brucellosis is treated with a combination of different antibiotics. In an acute course, a combination of doxycycline and rifampicin is given for six to twelve weeks. If the course is chronic, antibiotic therapy can be extended to up to six months. The success of the therapy is monitored with regular blood tests. Monotherapies are always contraindicated.

If the brucellosis pathogens have already attacked internal organs, the therapy is also extended.

If the nervous system is affected (neurobrucellosis) or the inner lining of the heart (inflammation of the heart skin = endocarditis), additional medication may be prescribed for significantly longer periods of time, usually antibiotics such as amoxicillin and chloramphenicol.

In rare cases, brucellosis pathogens affect the bones or heart valves, and surgery may be necessary.

In children under nine years of age and pregnant women, cotrimoxazole is given in combination with rifampicin for six weeks to treat brucellosis.

Herxheimer reaction

In antibiotic therapy, the pathogens break down. As a result, many inflammatory messengers are released in a fairly short time. The body reacts to this with symptoms such as fever and chills, or by worsening the original symptoms. Headache and body aches, fatigue, difficulty concentrating and depression can also occur. This reaction of the body is called the Herxheimer reaction, also called the Jarisch-Herxheimer reaction or Her for short. It can be different in each patient, but it is a normal part of therapy and does not worsen the disease.

Brucellosis: prevention

A vaccination against brucellosis is not yet possible in humans. The focus is therefore on combating the pathogen in animals. In Germany, all animals are officially brucellosis-free according to the so-called Brucellosis Ordinance. This does not apply to many other countries.

You should therefore absolutely avoid eating raw meat in countries where the pathogen is still widespread (endemic areas). Drink only boiled milk and only eat cheese and other dairy products made from pasteurized milk.

In addition, it is essential to avoid contact with animals in endemic areas.

People who spend a lot of time with animals should clean and disinfect their hands thoroughly and change their clothes after each contact. Veterinarians are advised to always wear gloves and use a skin-protecting cream during surgery.

Women with brucellosis are not allowed to breastfeed; however, their milk may be given to the child in a boiled state.

Brucellosis: disease course and prognosis

The course and prognosis of brucellosis are different for each patient. Depending on the type of pathogen, the severity of the disease and the stage at which brucellosis is diagnosed, each person affected has a very individual prognosis.

If therapy begins too late, undulating fever can become chronic and drag on for up to 20 years. A chronification of brucellosis occurs in about five percent of all patients after the acute symptoms have subsided. If brucellosis is not treated properly, the relapse rate (recurrence rate) is very high; this means that even years later, fever attacks can suddenly occur again.

On average, no more than two percent of all those affected die from brucellosis. Most deaths occur in patients with Mediterranean fever, which, if the disease goes unnoticed and untreated for a long time, can develop inflammation of the inner lining of the heart (endocarditis).

If brucellosis is detected early and treated consistently, the prognosis is favorable and those affected can usually be completely cured.

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