What Is Brucellosis?

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Brucellosis is an infection caused by a type of bacteria called Brucella that can spread from animals to people. People are commonly infected by consuming raw or unpasteurized dairy products.

Although, the bacteria that cause Brucellosis can spread through the air or direct contact with infected animals. There are different strains of Brucella bacteria.

Some types are discovered in cows. Others were found in camels, dogs, pigs, sheep, and goats. Recently, scientists discovered new strains in the red fox and certain marine animals, like seals. Brucella in animals cannot be cured.

Brucellosis is not common in the U.S because of effective animal disease control programs. About 200 people get sick with the disease annually in the U.S. It is most often experienced in the spring and summer months in Texas, California, Virginia and Florida

Brucellosis is seen as a significant health threat in some parts of the world. According to the WHO, the disease has been reported in more than 500,000 people each year in 100 countries.

Causes of Brucellosis

Humans can get infected with Brucellosis when they come into contact with an animal or animal product infected with the Brucella bacteria. Brucellosis can affect many domestic and wild animals which include Bison, Goats, Camels, Sheep, Pigs and Wild hogs, Dogs, especially those used in hunting, Deer, Elk, Cattle, Caribou, Moose etc.

A strain of Brucellosis can also affect certain whale, harbour seals, and porpoises. The most common ways that Brucellosis can spread from animals to people are:

People can get infected by consuming unpasteurized dairy products. Brucella bacteria can be found the milk of infected animals can spread to humans in raw milk, ice cream, butter, and cheeses. The bacteria can also spread in raw or undercooked meat of infected animals.

People can get infected by inhaling contaminated air. Brucella bacteria can spread quickly into the air. Hunters, farmers, laboratory technicians, and slaughterhouse workers can inhale the bacteria.

Humans can get infected by touching the blood and body fluids of infected animals. Bacteria in the placenta, blood, semen, or urine of an infected animal can enter the bloodstream through a cut or other wound.

Although regular contact with animals like Playing touching, or brushing doesn’t cause infection, it is rare for pet owners to get Brucellosis from their pets.

Nonetheless, people who have weakened immune systems should avoid handling dogs or other animals known to have the disease.

It is unusual for Brucellosis to spread from person to person, but there have been few cases of women who passed the disease to their children during birth or through their breast milk. 

Oftentimes, the bacteria can spread from person to person. A nursing mother with Brucellosis can pass the bacteria to their baby through breastmilk. Brucella can also spread through sexual contact.

Bacteria can enter the body:

  • Through an injury or cut in the skin
  • When one eat or drink something contaminated with the bacteria, such as unpasteurized milk or undercooked meat
  • When one breathe in contaminated air (rare)

There are four strains of Brucella bacteria that cause the majority of brucellosis infections in humans:

B. melitensis. This strain causes most cases of human Brucellosis and is usually found in sheep and goats. It is most often found in:

  • India
  • Spain
  • Greece
  • Latin America
  • Middle East

B. suis. This type is found in wild pigs and is the most common strain of Brucella found in the U.S. Infections due to this type is often found in the Southeast and California. It is also in South America, Europe, and Southeast Asia.

B. canis. The infection from this strain of bacteria spreads from dogs.Dogs can become infected with Brucellosis canis.

Some pet owners have contacted Brucellosis this way, but the infection is usually not severe. There is one known case of a human getting infected with Brucellosis by a dog bite.

But this form of transmission of Brucellosis is uncommon. Most dogs infected with Brucella do not affect their owners with the bacteria. One is more likely to get Brucellosis if one comes in contact with blood or other bodily fluids from an infected animal.

Veterinarians are at increased risk of contracting Brucellosis. If one has a weakened immune system due to medications or certain diseases, one should avoid touching dogs infected with Brucella. It is most often seen in North, Central, and South America, Japan, Central Europe

B. abortus. This infection comes from cattle. It occurs worldwide. It has been wiped out in several European countries, Japan, Israel, Canada, Australia, and New Zealand.

Risk Factors 

In the U.S., Brucellosis is more prevalent in men, and people who become sick with the disease work or have worked around livestock.

Brucellosis is uncommon in children. One is more likely to get Brucellosis:

  • If one eat or drink unpasteurized dairy products gotten from goats, cows, or other animals that are infected with Brucellosis
  •  If one eats other unpasteurized dairy products like cheeses called “village cheeses.” These come from high-risk regions, like the Mediterranean
  • Work on a farm
  • Travel to areas where the infection is common
  • Work in a meat-processing factory or slaughterhouse

Brucellosis has also been reported in:

  • Hunters in the U.S.
  • Veterinarians who immunize cattle with the infection

Symptoms of Brucellosis

Symptoms of Brucellosis are often not specific and are identical to the flu. They can include:

  • Fever ( which is the most common symptom, with high “spikes” that usually happen in the afternoon)
  • Body-wide aches and pains
  • Reduced appetite and weight loss
  • Headache
  • Night sweats
  • Weakness
  • Abdominal pain
  • Cough
  • Chills
  • Sweats
  • Fatigue
  • Joint, muscle and back pain

Symptoms usually appear within five to thirty days after one comes in contact with the bacteria. 

How bad your symptoms depend on what type of Brucella one is infected with Brucella abortus usually induce mild or moderate symptoms, but they are more likely to become severe and long-lasting.

Brucella canis symptoms can come and go. They are identical to Brucella abortus infection, although people affected with Brucella canis experience vomiting and diarrhoea.

Brucella suis can cause abscesses in different parts of the body. Brucella melitensis can cause sudden and chronic symptoms, which can lead to disability.

Brucellosis affects thousands of people and animals globally. Some people with chronic Brucellosis can experience symptoms for years, even after treatment.

Long-term signs and symptoms can include recurrent fevers, arthritis, inflammation of the heart (endocarditis), inflammatory arthritis that affects the spine and nearby joints (spondylitis ), and fatigue.

Diagnosis of Brucellosis

 The doctor will examine the patient for:

  • A rash
  • A swollen liver
  • Swollen lymph nodes
  • Joint swelling and pain
  • A swollen spleen
  • Unexplained fever

Blood tests will be carried out to diagnose the infection and determine what strain of Brucella is the patients affected with, Proper identification of the bacteria can pinpoint the source of the disease.


Brucellosis can be complicated to treat. If one has Brucellosis, the doctor will prescribe antibiotics. Some Antibiotics commonly used to treat Brucellosis are:

  • Ciprofloxacin (Cipro) or ofloxacin (Floxin)
  • Doxycycline (Acticlate, Monodox, Vibra-Tabs, Vibramycin)
  • Tetracycline (Sumycin)
  • Rifampin (Rifadin, Rimactane)
  • Sulfamethoxazole/trimethoprim (Bactrim) 
  • Streptomycin

It is advisable, generally, for one to take doxycycline and rifampin together for 6-8 weeks.

One must take antibiotics for many weeks to prevent the disease from recurring. The chances of reinfection following treatment is 5-15% and usually occurs within the first six months after treatment.

Recovery can take weeks, even months. Patients who get treatment within a month of infection can be cured of the disease. 

Complications of Brucellosis

Brucellosis can affect almost any part of the human body, including the central nervous system, reproductive system, liver, and heart. Chronic Brucellosis can cause complications in just one organ or throughout the body. Possible complications include:

Infection of the heart’s inner lining (endocarditis). This is one of the most severe complications of Brucellosis. Untreated endocarditis can destroy the heart valves and is the leading cause of brucellosis-related deaths.

Arthritis. Joint infection is marked by pain, stiffness, and swelling in your joints, especially the knees, hips, ankles, wrists, and spine. Spondylitis — inflammation of the joints between the bones (vertebrae) of your spine or between your spine and pelvis — can be particularly hard to treat and may cause lasting damage.

Inflammation and infection of the testicles (epididymo-orchitis). The bacteria that cause Brucellosis can infect the epididymis, the coiled tube that connects the vas deferens, and the testis. From there, the infection may spread to the testicle itself, causing swelling and pain, which may be severe.

Inflammation and infection of the spleen and liver. Brucellosis can also affect the spleen and liver, causing them to enlarge beyond their standard size.

Central nervous system infections. These include potentially life-threatening illnesses such as meningitis, an inflammation of the membranes surrounding the brain and spinal cord, and encephalitis, inflammation of the brain itself.

Brucellosis complications can also cause:

  • Infection of the central nervous system
  • Liver abscess

Brucellosis can provoke long-lasting symptoms that are identical to systemic exertion intolerance disease. This is previously known as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

The symptoms can cause disability. They can include:

  • Fatigue
  • Fevers that come and go
  • Joint pain

Brucellosis in a pregnant woman can lead to:

  • Congenital disabilities in the baby
  • Miscarriage
  • Death from Brucellosis is uncommon. 


To reduce the risk of contracting Brucellosis, one should take these precautions:

  • Avoid unpasteurized dairy foods: Cases witnessed by Brucellosis witnessed in recent years in the United States, have been linked to domestic herds’ raw dairy products. Still, it’s advisable not to consume cheese, unpasteurized milk, and ice cream. It is also advisable to avoid all raw dairy food when travelling to other countries.
  • Cook meat properly: All meat should be cooked until it attains an internal temperature of 145 to 165 F (63 to 74 C). When eating outside the house, order beef and pork at least medium cooked. It’s unlikely that meat in the United States carries brucella bacteria, but proper cooking can destroy other harmful bacteria like salmonella or Escherichia coli. When travelling abroad, one should avoid buying meat from street vendors, and ask that all meat be cooked properly.
  • Wear gloves as a slaughterhouse worker veterinarian, farmer, or hunter also when taking care of sick or burying dead animals or animal tissue or when helping an animal giving birth.
  • Take safety precautions in high-risk workplaces like a laboratory, by handling all samples under appropriate biosafety conditions. Workers in slaughterhouses should also follow protective measures, such as separating the killing floor from other processing areas and working with protective clothes, gloves etc.
  • Vaccinating of domestic animals: In the United States, there is an aggressive vaccination program that has almost eliminated Brucellosis in all domestic animals. Any handler who has an accidental needle stick while vaccinating livestock should be tested and treated.

When to see a doctor

Brucellosis can be difficult to identify, especially in the early stages, when it’s symptoms can be indistinguishable from other conditions, such as the flu.

One is advised to see a doctor if they experience unusual weakness, rapidly rising fever, muscle aches and if they have any risk factors for the disease, or if they suffer from persistent illness.


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