Melioidosis, also known in Thailand as “Soil Fever,” is an infectious disease caused by bacteria found in soil and water in tropical regions, including Thailand
It is commonly found in Southeast Asia and northern Australia, especially during the rainy season. It is a severe bacterial infection with a high mortality rate if not properly treated and is considered a significant public health concern.
What causes melioidosis?
Melioidosis is caused by infection with the bacterium “Burkholderia pseudomallei,” a gram-negative, rod-shaped, motile organism that is highly resilient in the environment. It naturally inhabits soil and water in tropical regions. The bacteria can enter the human body through several routes, including:
- Inhalation of contaminated dust or water droplets
- Consumption of contaminated food or water
- Skin contact, especially through cuts, abrasions, or broken skin
- Human-to-human transmission is very rare and typically occurs through exposure to contaminated needles or laboratory equipment
Who is at risk of melioidosis?
- People with diabetes (the most significant risk factor)
- Chronic alcohol users
- Patients with liver disease
- Patients with kidney disease
- Patients with thalassemia
- Patients with cancer or weakened immune systems
- Patients with chronic lung disease
- Individuals using immunosuppressive drugs, such as organ transplant recipients
- People with occupations or activities involving exposure to soil or contaminated water, such as farming, gardening, or construction work
What are the symptoms of melioidosis?
This disease presents with a wide range of symptoms similar to other conditions such as tuberculosis or pneumonia. The incubation period is typically 1–4 weeks after exposure, but in some cases, the bacteria may remain dormant for months or years before symptoms appear when immunity declines. There are four main clinical forms:
1. Localized infection (usually mild)
- Chronic inflamed wounds
- Skin lumps or abscesses
- Swollen lymph nodes that may be tender and produce pus
- Conjunctivitis or uveitis
2. Pulmonary infection (most common), ranging from bronchitis to severe pneumonia
- Cough, sputum production, shortness of breath, chest pain
- High fever
- Loss of appetite, fatigue
3. Bloodstream infection (common in high-risk individuals such as diabetics, with high mortality)
- High fever with chills
- Difficulty breathing
- Severe headache, drowsiness, confusion, seizures
- Multiple organ failure
- Low blood pressure, septic shock, potentially leading to death
4. Chronic infection (similar to tuberculosis)
- Prolonged fever
- Weight loss, fatigue
- Abscesses in the liver, spleen, prostate, joints, or bones
How is melioidosis diagnosed?
Standard diagnosis is made by culturing the bacteria from blood, urine, sputum, cerebrospinal fluid, or pus from abscesses or wounds. Antibody testing and DNA detection methods may also be used in certain cases.
Treatment of melioidosis
Treatment is prolonged and divided into two phases:
1. Intensive phase (2 to 8 weeks)
To control the infection, intravenous antibiotics are administered. The main drugs include Ceftazidime or Meropenem. In severe cases, Trimethoprim-sulfamethoxazole may be added.
2. Eradication phase (3 to 6 months)
To eliminate the bacteria and prevent relapse, oral antibiotics are prescribed. The main regimen includes Trimethoprim-sulfamethoxazole, with alternatives such as Amoxicillin/clavulanic acid or Doxycycline.
Patients must complete the full course of treatment. Incomplete treatment may lead to relapse, which often occurs within 1–2 years.
How can melioidosis be prevented?
Currently, there is no vaccine available. Prevention focuses on hygiene and behavioral measures:
- Wear protective equipment such as boots or rubber gloves when in contact with soil or water
- Avoid exposure to soil or water when having open wounds
- Drink clean water, either boiled or properly bottled
- Maintain personal hygiene; shower and wash with soap after work, and clean hands after contact with soil or water
- Avoid going outdoors during the rainy season to reduce inhalation of contaminated dust
- High-risk individuals, such as those with diabetes, should maintain good control of their underlying conditions
