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Updated August 09, 2015.
In 2014, a lab in Louisiana reported monkeys were infected with Burkholderia Pseudomallei. An investigator, thought to have been exposed, was found to have antibodies, but did not become ill. This splashed across the news.
Why did this matter?
Meliodosis causes a rare disease which, if allowed to progress, can be fatal. It is considered a potential bioterrorism agent. This in part because it is a potentially fatal disease that can be acquired from inhalation.
It is hard for labs to diagnose, in part because it is not usually found in the US. It can persist in the environment for years and still be infectious. Its treatment is long and oftentimes cumbersome.
This disease is sometimes called the "Great Mimicker". Because the disease seemed like so many others - and is rare in the US, many are not diagnosed quickly enough. The Vietnam War saw veterans return with the infection - possibly as many as 225,000 were silent carriers. They may carry the infection unaware, which often reappears many years later. Veterans may develop the deadly disease years later earning the disease a reputation for being a "Time Bomb". It can occur in troops even after brief exposures. World War II veterans from the South Pacific also developed infections years later.
What is the disease like?
Meliodosis is often mistaken for TB. It is a disease that can appear years after exposure and may have similar symptoms. Of those who develop the severe symptoms, as many as 1 in 2 can die.
It can be an acute disease (most) or chronic disease.
There are different forms, which can overlap or progress from one to another:
Localized infection usually involves an ulcer, nodule, or skin abscess that results from direct exposure to the skin. It can cause fever and muscle aches. It can remain localized or it can lead to wider infections.
Pulmonary infection is common and can be a mild bronchitis or a severe pneumonia. It often resembles Tuberculosis with upper lobe infiltrates and cavitary lesions on Chest X-Ray after a couple of months of illness. It frequently causes chest pain and a cough that is dry or productive of sputum. It is usually associated, like TB, with constitutional symptoms like fever, loss of appetite as well as muscle soreness and headache.
Bloodstream infection is a very severe form. It can present rapidly and patients can be found to have abscesses throughout their bodies (liver, spleen, prostate). It can lead to septic shock and death. It may be marked by difficulty breathing, disorientation, fever, headache, abdominal pain, joint and/or muscle pain.
Disseminated Infection may be an acute or chronic infection and involves abscesses which may or may not lead to bloodstream infection. These abscesses are often in liver, lung, spleen, and prostate. This may involve joints, bones, lymph nodes, skin, brain. Patients may have pain in any of these locations, as well as weight loss and fever. It can resemble TB or cancer for some doctors.
How is the disease transmitted?
Melioidosis is often transmitted through direct contact with contaminated soil and surface waters. This can occur when walking through Rice Fields. Skin abrasions may be a portal of entry for many.
Some may acquire the infection through inhaling contaminated dust or water sprays, drinking contaminated water or other ingestions. This may occur when someone has an exposure through a near-drowning.
Rarely is the infection spread from person-to-person, but it happens. It has included mother-child contact and potentially from sex with someone with prostatic infection.
The infection can take 1 day to 3 weeks to develop acutely. The size of the exposure may play a role.
Where is it acquired?
The disease is usually acquired in Southeast Asia in the rainy season.
Thailand has the largest burden, with at least 2-3000 cases a year. Rice Fields are common sources of exposure, with more than half of rice field samples positive in certain areas. In Thailand, 1 in 5 cases of septicemia, or blood poisoning, is caused by Burkholderia pseudomallei.
Most cases are acquired in:
- Thailand
- Malaysia
- Singapore
- Northern Australia
Other cases have been found in the Indian subcontinent, southern China and Hong Kong and Taiwan, Papua New Guinea, Vietnam, Indonesia, Cambodia, Myanmar, and Laos. Other cases have rarely been found in Central and South America, the Caribbean, Sri Lanka, and the Pacific region.
Recently in Louisiana, 5 monkeys in a research lab became infected with Burkholderia Pseudomallei through an unknown source. This may have exposed a person (a federal investigator) who visited the lab, but did not lead to any clear illness. There was concern that more would be infected, but there have not been any further concerns about human infections.
It is pretty common in some parts of the world. Up to 80% children in northeast Thailand are exposed by age 4.
How is treated?
The treatment for Melioidosis is very specific to the disease. The duration of treatment is long, to avoid relapses, and depends on the type of infection. Treatment usually involves close to 2 weeks of IV treatment followed by 3-6 months of oral antibiotic treatment.
The antibiotics choosen are very specific to the disease. Melioidosis does not respond to many antibiotics that are given empirically for other similar infections. Because it can be hard to diagnose Melioidosis this can lead to dangerous delays in treatment.
The antibiotics used for initial IV treatment are: Ceftazidime or Meropenem IV (either treatment often requires 3-4 IV doses a day). Oral treatment may be Trimethoprim-sulfamethoxazole (Bactrim, Cotrim, Septa) or Doxycycline.
The rate of relapse is high.
Bukrholderia is resistant to a number of antibiotics - either intrinsically or through acquired means.
How is it diagnosed?
The bacteria can be grown from cultures of blood, abscesses, or sputa. A PCR test can be used as well.
How risky is it for lab workers?
Safety precautions are stringent when handling Burkholderia pseudomallei. The problem is lab workers don't always know they are handling the dangerous bacteria.
In 2013, a patient died of Melioidosis in Los Angeles before the laboratory identified the pathogen. 17 lab workers were exposed; none became ill. All were given 3 weeks of antibiotics as a precaution. They were monitored and the CDC investigated.
Is this the same as Glanders?
Glanders is an infection caused by a related bacteria - Burkholderia mallei and primarily affects horses, donkeys, and mules, but can affect humans.
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