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Everything You Need to Know About Melioidosis

What is melioidosis?

Melioidosis is also called Whitmore’s disease. It’s a deadly condition that can affect both humans and animals. The cause of this infection is the bacterium Burkholderia pseudomallei, which can be spread through contact with contaminated water and soil.

The disease is rare in the United States, but it’s a public health problem in Southeast Asia, northern Australia, and other places with a tropical climate. Melioidosis has the potential to spread to areas where it’s not typically found. For that reason, B. pseudomallei, the cause of melioidosis, has been identified as a potential biological weapon.

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Symptoms

Symptoms of melioidosis

The symptoms of melioidosis vary depending on the type of infection. Types of melioidosis include pulmonary (lung), bloodstream, local, and disseminated infections.

In general, it takes two to four weeks for symptoms to appear after exposure to the bacterium. However, symptoms may take hours or years to appear, and some people have the disease without having symptoms.

Pulmonary infection

The most common way melioidosis shows up in people is through a lung infection. A lung problem can arise independently, or it can result from a blood infection. Lung symptoms can be mild, like bronchitis, or severe, including pneumonia and leading to septic shock. Septic shock is a serious blood infection that can rapidly lead to death.

Symptoms of pulmonary infection may include:

  • cough with normal sputum (the mixture of saliva and mucus that can rise into the throat from coughing) or no sputum, called a nonproductive cough
  • chest pain during breathing
  • high fever
  • headache and general muscle soreness
  • weight loss

Pulmonary melioidosis infection can mimic tuberculosis because they both can lead to pneumonia, high fever, night sweats, weight loss, bloody sputum, and pus or blood in the lung tissues. X-rays of lungs with melioidosis may or may not show empty spaces, called cavitations, which are a signature of tuberculosis.

Bloodstream infection

Without fast, appropriate treatment, a pulmonary infection can progress to septicemia, which is an infection of the bloodstream. Septicemia is also known as septic shock and is the most serious form of melioidosis. It’s common and life-threatening.

Septic shock usually occurs quickly, though it may develop more gradually in some. Its symptoms include:

  • fever, especially with shivers and sweating (rigors)
  • headache
  • sore throat
  • breathing problems, including shortness of breath
  • upper abdominal pain
  • diarrhea
  • joint pain and muscle tenderness
  • disorientation
  • sores with pus on the skin or internally in the liver, spleen, muscle, or prostate

People with these specific conditions have a higher risk of developing a melioidosis bloodstream infection:

People older than age 40 may also have a higher risk of contracting a melioidosis blood infection and developing more serious symptoms than younger people.

Local infection

This type of melioidosis affects the skin and organs just under the skin. Local infections can spread to the bloodstream, and bloodstream infections can cause local infections. Symptoms may include:

  • pain or swelling in a contained (localized) area, such as the parotid glands, which are most commonly associated with mumps and are located below and in front of the ear
  • fever
  • ulcerations or abscesses on, or just below, the skin — these may start as firm, gray or white nodules that become soft and inflamed, and then look like wounds caused by flesh-eating bacteria

Disseminated infection

In this type of melioidosis, sores form in more than one organ and may or may not be related to septic shock. Symptoms may include:

  • fever
  • weight loss
  • stomach or chest pain
  • muscle or joint pain
  • headache
  • seizures

Infected sores are most commonly located in the liver, lung, spleen, and prostate. Less commonly, infections occur in the joints, bones, lymph nodes, or brain.

Causes

Causes of melioidosis

People and animals who have direct contact with soil or water that’s contaminated with the bacterium B. pseudomallei can develop melioidosis. The most common ways of direct contact include:

  • breathing in contaminated dust or water droplets
  • drinking contaminated water that hasn’t been chlorinated
  • touching contaminated soil with the hands or feet, especially if there are small cuts in the skin

It’s very rare for one person to spread the infection to another, and insects aren’t thought to play a significant role in transmission.

The bacteria can live for years in contaminated soil and water.

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Incidence

Incidence of melioidosis

Where melioidosis occurs

Experts believe cases of melioidosis are greatly unreported in many tropical and subtropical areas. The areas with the most reported cases of melioidosis are:

  • Thailand
  • Malaysia
  • Singapore
  • northern Australia

It’s also common in Vietnam, Papua New Guinea, Hong Kong, Taiwan, and much of India, Pakistan, and Bangladesh. It’s been less commonly reported in Central America, Brazil, Peru, Mexico, and Puerto Rico.

Weather’s role in transmission

Outbreaks of melioidosis are most common after a heavy rainfall, typhoon, monsoon, or flooding — even in arid regions. Pneumonia is a common first symptom during these periods. There may be other ways the bacterium is spread environmentally that haven’t been discovered.

People with the highest risk

People most likely to come in contact with B. pseudomallei in water or soil include:

  • military personnel
  • workers in construction, farming, fishing, and forestry
  • adventure travelers and ecotourists, including those who’ve spent less than a week in an area where the disease is prevalent

Animals most affected

Many animals are susceptible to melioidosis. In addition to contact with contaminated water and soil, animals can pick up the bacterium from infected animals’ milk, urine, feces, nasal secretions, and wounds. The most commonly affect affected animals are:

  • sheep
  • goats
  • swine

Cases have also been reported in horses, cats, dogs, cattle, chickens, marsupials, tropical fish, iguanas, and other animals. It has killed some zoo populations.

Diagnosis

How melioidosis is diagnosed

Melioidosis can affect almost any organ and can mimic many other diseases. That’s why it’s sometimes called “the great imitator.” But a misdiagnosis can be fatal.

Culturing the bacterium B. pseudomallei is considered the gold standard diagnostic test. To do this, doctors get small samples of a person’s blood, sputum, pus, urine, synovial fluid (found between joints), peritoneal fluid (found in the abdominal cavity), or pericardial fluid (found around the heart). The sample is put on a growing medium, such as agar, to see if the bacteria grows. However, culturing isn’t always successful in all cases of melioidosis.

Sometimes during outbreaks, experts get samples from the soil or water. The Centers for Disease Control and Prevention offers diagnostic help.

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Treatment

Melioidosis treatment

Treatment may vary depending on the type of melioidosis.

The first stage of treatment for melioidosis is a minimum of 10 to 14 days of an antibiotic given by intravenous (IV) line. Treatment with this antibiotic may last as long as eight weeks. Doctors may prescribe either:

  • ceftazidime (Fortaz, Tazicef), given every six to eight hours
  • meropenem (Merrem), given every eight hours

The second stage of treatment is three to six months of one of these two oral antibiotics:

Relapses don’t occur as often as they once did. They occur mostly in people who don’t complete the full course of antibiotics.

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Prevention

How to prevent melioidosis

There are no vaccines for humans to prevent melioidosis, though they are being studied.

People who live in or are visiting areas where melioidosis is common should take these actions to prevent infection:

  • When working in soil or water, wear waterproof boots and gloves.
  • Avoid contact with soil and standing water if you have open wounds, diabetes, or chronic kidney disease.
  • Be vigilant about avoiding exposure by inhalation during severe weather events.
  • Healthcare workers should wear masks, gloves, and gowns.
  • Meat cutters and processors should wear gloves and regularly disinfect knives.
  • If drinking dairy products, be sure they are pasteurized.
  • Get screened for melioidosis if you’re about to start immunosuppressive therapy.
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Outlook

Outlook for melioidosis

Even with newer IV antibiotic treatments, a significant number of people still die from melioidosis each year, particularly from sepsis and its complications. Death rates are higher in areas with limited access to medical care. People traveling to at-risk areas should be aware of melioidosis and take steps to limit their potential exposure. If travelers develop pneumonia or septic shock upon returning from tropical or subtropical areas, their doctors need to consider melioidosis as a possible diagnosis.

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