Undulant fever is a term that describes the disease we now call brucellosis. It characteristically causes rising and falling fevers.
The bacterial genus Brucella, responsible for the infectious disease known as brucellosis, was first discovered in the mid-1800s. Since its discovery, Brucellosis had had many different names determined by the geographical locations where outbreaks occurred. Some examples include Mediterranean fever, Malta fever, Rock fever, Crimean fever, and Gibraltar fever. Other names come from the symptoms it causes, like undulant fever or gastric remittent fever.
Brucellosis is a zoonotic infection, which means transmission occurs from animal to human, either from ingestion of infected foods or direct contact with an infected animal; the infection can also spread through the air or contaminated wounds.
How common is Undulant fever or Brucellosis in Humans?
Thanks to veterinary control measures in domestic livestock, now there are less than 140 human brucellosis cases a year in the United States. Of those few cases, most occur in people that work closely with livestock or raw foods. The worldwide situation is quite different from that of the United States; there are approximately 500.000 thousand brucellosis cases each year. Most cases occur in underdeveloped countries. According to the European Union, no countries with a GDP of over 90% (the world’s wealthiest countries) have an annual rate higher than 10 cases per million habitants.
The disease is more common in the Mediterranean peninsula (Spain, Italy, Portugal), south and central America, and the Arabian peninsula. Because in many countries reports are not entirely reliable, authorities estimate 70 cases a year for 100.000 habitants of endemic areas. Brucellosis is more common in adults over the age of 20 and uncommon in infants. There is no significant difference in the frequency among different genders and races.
How do you become infected with brucellosis or undulant fever?
Brucella bacterium lives in the reproductive organs of mammals. When animals are infected, Brucella produces infertility and abortions. As you may have guessed by its location, animals shed Brucella specimens through their milk, urine, and placental fluids.
Most infected humans get it from domesticated animals (particularly livestock). However, the bacteria can also infect wild animals like wild boar, bison, or elk. There are different kinds of Brucella, and each kind tends to infect a particular type of animal:
- Melitensis Brucella: Found in sheep, it causes the most severe infections.
- Suis Brucella: Found in sheep, causes severe infection but less severe than Melitensis Brucella.
- Abortus Brucella: found in cattle, tends to generate a more moderate infection.
- Canis Brucella: From dogs, it also causes moderate disease.
Common ways of getting infected include the following:
- Eating unpasteurized milk or cheese
- Helping animals give birth without adequate protection equipment
- Eating raw meat products
- From person to person (rare)
- Through casual contact with pets (extremely rare)
Can Brucellosis be sexually transmitted?
Transmission from person to person is rare. In a few cases, it does happen; it is thanks to breastfeeding and sexual contact. There are very few reported cases, but there is definite proof of sexual transmission in those few isolated cases. Most cases of human to human transmission happen through breastfeeding (over 61%).
What are the symptoms of undulant fever or brucellosis?
Brucella symptoms vary a lot from patient to patient, and there isn’t a particular symptom specific to Brucella. It can produce heart symptoms, respiratory symptoms, urinary symptoms, neurologic symptoms, gastrointestinal symptoms, as well as bone and joint symptoms.
The most constant symptom that most patients have is fever. Brucellosis causes a particular type of fever called undulant fever. It is an intermittent fever with constant ups and downs with chills. In patients in non-endemic areas, fever of unknown origin tends to be the first diagnosis before the doctors realize it is actually brucellosis.
Other symptoms include:
- Bone and joint symptoms: Joint pain, lower backaches, and joint swelling.
- Neurologic symptoms: Headache, depression, fatigue. A few severe cases can have altered mental status, coma, or seizures.
- Gastrointestinal symptoms: Besides fever, gastrointestinal symptoms are the most common ones; they include abdominal pain, indigestion, constipation, diarrhea, and vomiting. Liver abscesses are a common complication.
- Respiratory symptoms: cough and dyspnea
- Heart symptoms: Endocarditis is a common complication that can be fatal in some cases; other cardiac complications are less common.
- Weight loss
What is chronic Brucellosis or undulant fever?
In a minority of patients with acute brucellosis, symptoms persist for more than a year. These patients can continue experiencing on and off symptoms for years, even with treatment. The most common long-term symptoms include recurrent undulant fever, fatigue, an inflammatory arthritis of the joints, and endocarditis.
Chronic Brucellosis patients are extremely hard to diagnose without a previous diagnosis of acute Brucellosis. The symptoms of chronic Brucellosis are very unspecific and are common to many other different diseases. Furthermore, the on and off nature of symptoms makes diagnosis more complicated. Chronic fatigue syndrome is the most common misdiagnosis.
Why are Brucella’s symptoms so varied?
Brucella bacteria have a special ability to infiltrate inside of cells and avoid an immune system response. They come inside the interior of immune cells called neutrophils and are distributed from there to any organ in the body. After they reproduce, they break outside of the cell, killing it in the process.
What are the symptoms of Brucellosis in animals?
As you may imagine, symptoms in animals are very different from those of a human and can be very hard to detect. The bacteria is easily transmitted among cattle animals. Therefore, if one animal on a farm has it, it is likely that most animals on that same farm have the disease.
The bacteria lives in the reproductive system of cattle; uterine fluids and urine of infected animals contain the bacterium.
Symptoms in animals include:
- Weak Calf born
- Retention of fetal membranes
- Swollen testicles (particularly in bulls)
There is no treatment for animals. Therefore having infected cattle can represent a substantial economic loss. Early detection and prevention are essential. Regularly testing the herd is now routine in most developed countries. This probably explains why the disease is so rare in countries with a high GDP. Although the animal vaccine doesn’t completely remove the risk of infection, it is significantly more unlikely.
How is brucellosis or undulant fever diagnosed?
Because symptoms are such an unspecific diagnosis, at first glance is difficult. The definitive diagnosis requires very specific tests, including blood or bone marrow cultures or serologies.
Before ordering cultures or serology, doctors usually order routine blood tests for infectious diseases. Characteristic Brucellosis findings in routine laboratory testing include:
- Low white blood cell count (a high white blood cell count is also possible but rarer)
- Anemia (in 75% of patients)
- Low platelets (in 40% of patients)
- Elevated liver enzymes
These are still unspecific findings and can also occur in patients with dengue fever, malaria, infectious mononucleosis, among others. However, your clinical symptoms combined with a history of exposure to cattle, raw milk, or meat and typical laboratory findings should prompt your doctor to test for Brucellosis.
Nowadays, the most common way of diagnosing Brucellosis is through serologies. An undulant fever serology is a blood test that searches for antibodies against Brucella species in the blood. A negative result means the person has not been in contact with brucella. However, during the early stages of the disease, the test might turn out negative.
If clinical suspicion for Brucellosis is high, your doctor may order another test 10 days or three weeks later. Furthermore, infections with other bacteria and certain vaccines can produce false negatives.
Cultures provide a more accurate diagnosis. Samples are commonly taken from the blood or the bone marrow. Bone marrow cultures are less likely to give a false negative than blood cultures. In patients with urinary symptoms, having a urinary culture might also be very helpful.
What is the differential diagnosis for brucellosis or undulant fever?
As previously stated, the signs, symptoms, and laboratory findings of brucellosis can resemble many other diseases. Some diseases with similar findings include:
- Malaria fever
- Dengue fever
- Viral Hepatitis
- HIV infection
- Typhoid fever
- Urinary tract infection
- Chronic fatigue syndrome
- Unspecific back pain
How is Brucellosis treated?
Brucellosis is a bacterial infection, and as such, requires antibiotic treatment. Brucella species are resistant to many different antibiotics, and only a few have shown to be clinically effective. These antibiotics include:
Single-drug therapy with doxycycline used to be the most common treatment. However, several studies revealed a relapse rate of around 40% with doxycycline alone. Therefore other options like rifampin are commonly added to the mix.
Brucellosis treatment is quite long. To prevent relapses, patients must take their medication every day for at least two weeks.
How is the treatment in pregnant women?
In pregnant women, Brucellosis treatment represents a fundamental challenge to both patients and physicians. Due to adverse effects during pregnancy, doxycycline is not an option for these patients.
Most regimens for pregnant women include Trimethoprim-sulfamethoxazole or rifampin. However, in some cases, Trimethoprim-sulfamethoxazole has caused adverse reactions in newborn children when used at the end of pregnancy.
Some patients may require surgical interventions—particularly those with joint effusions or spinal abscesses. Patients with endocarditis might require a surgical valve replacement.
How can I prevent Brucellosis?
Brucellosis is a preventable disease. People who live or travel to endemic areas like Mexico or southern Europe can avoid it by following these simple steps:
- Avoid consuming raw meat.
- Avoid consuming unsterilized milk or cheese.
- For whatever reason, if you must be in contact with animal blood, try using protective equipment such as gloves and protective glasses. It is especially important to cover any open wounds.
- Although there is no Brucellosis vaccine for humans, there is a vaccine for animals. If there are no infected animals, the risk of occupational exposure decreases to cero.
What is the prognosis or possible outcomes for someone with Brucellosis or undulant fever?
Although initial symptoms in the acute phase can be debilitating, the disease’s overall prognosis is excellent. If patients receive appropriate and early treatment, the disease is easily curable.
The risk of relapse or having a chronic disease is scarce. Initial improvement after the initial phase usually takes a few weeks. During this phase, bed rest has proven to speed up recovery, while physical activity tends to worsen the prognosis.
Patients with central nervous system brucellosis may suffer from psychological alterations that do not improve with the antibiotic system. Psychotherapy provides some improvement, but in some cases, the changes are irreversible.
Mortality is pretty low; experts estimate below 2%. Most Brucellosis deaths result from endocarditis that leads to valve destruction and congestive heart failure or a complicated central nervous system infection (meningoencephalitis, for example). Cases of chronic brucellosis are a minority. However, it may continue to cause trouble for patients for up to 25 years.
What happens if brucellosis or undulant fever goes untreated?
Most cases of acute brucellosis go into complete remission with or without treatment in 2 to 6 months. Nevertheless, untreated patients have a higher risk of suffering relapses, chronic brucellosis, and fatal complications such and endocarditis and meningitis. Therefore, the medical community recommends antibiotic treatment in all confirmed Brucellosis cases.
Do you have symptoms of undulant fever or brucellosis?
This tool is a Brucellosis Symptoms Checker. It gathers the most important signs, symptoms, and risk factors for this disease. Therefore, the tool would tell anybody who uses it the likelihood of their symptoms because of undulant fever or brucellosis. Also, using this tool is free and would only take a few minutes.