MELIOIDOSIS: CAUSES, SYMPTOMS, TREATMENT, PREVENTION AND MORE
Medically Reviewed by Dr. Rae Osborn, Ph.D. - August 8, 2024
Melioidosis, also known as Whitmore's disease, is a potentially life-threatening infection and disease caused by the bacterium Burkholderia pseudomallei.
This condition can affect people of all ages, with higher prevalence in adults aged 40-60 and increased risk for individuals with underlying health issues[1]. It is mainly seen in Southeast Asia and Northern Australia, however, has also been reported in other regions like South Asia, Africa, and South America. It does also occur in Puerto Rico and parts of Mississippi along the Gulf coast.[2]
This article discusses the causes, modes of transmission, risk factors, symptoms, treatment, and prevention of Melioidosis.
What is Melioidosis?
Melioidosis is an infectious disease caused by Burkholderia pseudomallei, a Bacillus bacterial species commonly found in soil, decaying matter, and water. Scientists theorize that it was initially a harmless soil bacterium that adapted to survive inside mammalian hosts.[3]
It can infect humans and animals, entering the body through cuts or wounds, inhalation, or ingesting contaminated water or soil. Direct contact with infected animals, particularly livestock and domestic pets, can also lead to Melioidosis transmission.
What makes Burkholderia pseudomallei unique is its remarkable survival ability. It can persist in soil, water, and extreme environments for over a year. In low-nutrient conditions without water, it can survive for up to 30 days.[4]
It is a significant public health concern in endemic regions owing to the following features:
- The bacterium Burkholderia pseudomallei demonstrates genetic resistance to harsh environmental conditions like extreme temperatures, pH variations, and desiccation.
- Burkholderia pseudomallei bacterium forms resilient biofilms, aiding their survival and persistence by creating microbial communities attached to surfaces.
- This bacterium releases toxins, enabling it to enter host cells, evade immune responses, replicate, cause tissue damage, and interfere with essential cell functions.[5]
- It can infect various cell types, leading to widespread symptoms and damage to multiple tissues and organs.
- Burkholderia pseudomallei causes cell enlargement, aggregation, and multi-nucleation[6].
- The pathogen confers resistance to many antibiotic types and is immune to lysosomal breakdown by the cell, making it difficult to treat without a proper diagnosis.
Burkholderia pseudomallei exhibits genetic diversity, leading to different strains with varying levels of antibiotic resistance[7] and virulence. Some strains may be more pathogenic than others, such as Burkholderia mallei, which leads to a more severe and lethal form of the condition known as glanders disease.[8]
Symptoms of Melioidosis
Melioidosis can manifest itself in a variety of forms, from acute or chronic localized infections to systemic sepsis. The symptoms of Melioidosis can vary following the severity and bacterial strain.
The incubation period for Melioidosis can range from 1 days to several years. In most cases, it can take up to 21 days for symptoms to manifest from exposure.
The three main types of Melioidosis are acute pneumonia, chronic melioidosis, and latent melioidosis.
Acute Pneumonia
Acute pneumonia is the most common form of Melioidosis, presenting with the following symptoms[9]:
- High fever
- Chest pain
- Difficulty breathing
- Coughing
- Headaches
- Appetite loss
- Rapid weight loss
- Night sweats
- Fatigue
- Muscle and joint pain
Acute Melioidosis may also occur in the skin or blood causing septicemia. Skin symptoms can include ulcers, sores, or abscesses with swollen glands. Systemic infections are similar to acute pneumonia, with changes to one's mental state.
Chronic Melioidosis (Disseminated)
Chronic Melioidosis is often less severe than the acute form but can still lead to long-term complications. Melioidosis that lasts for more than two months is defined as chronic and affects 10% of patients.
The symptoms of chronic melioidosis may include:
- Recurrent fever
- Weight loss
- Joint pain
- Skin infections
- Abscesses in internal organs
- Enlarged spleen or liver
Latent Melioidosis
Latent Melioidosis is a form of the disease where the bacterium remains dormant in the body without causing any symptoms. It can later become active and lead to acute or chronic melioidosis years after exposure to the original pathogen.
Reports have indicated that troops who returned from Vietnam to the United States have shown symptoms of latent melioidosis 10 to 20 years after their service.[10]
Latent activation can occur whenever the patient's immune system dips. Common triggers include:
- Trauma
- Burns
- Glucocorticoid use
- Comorbid illness such as COVID-19, cancer, or diabetes
- Infections such as pneumococcal disease, malaria, or influenza A
Risk Factors
Risk factors for Melioidosis include[11]:
- Occupations involving soil excavation, construction, agriculture, animal husbandry, veterinary professions, and water-related activities increase the risk of exposure to Burkholderia pseudomallei.
- Individuals with compromised immune function are at a higher risk of developing Melioidosis, such as those with thalassemia (a blood disorder), or cancer.
- People with kidney disease, liver disease, diabetes, cystic fibrosis, or chronic lung diseases like COPD are at a higher risk of developing Melioidosis, as the disease can worsen their condition and lead to complications.
- A history of traveling to endemic regions where Melioidosis is prevalent raises the risk of exposure to Burkholderia pseudomallei, especially in regions where untreated water sources are used for drinking and cooking.
- Glucocorticoid use
- Excessive alcohol consumption
- Male gender
To protect against Melioidosis, individuals should understand the characteristics of Burkholderia pseudomallei, differentiate between strains, recognize transmission modes, and identify risk factors.
Diagnosis
Melioidosis is often referred to as the "great mimicker" due to its ability to imitate other diseases[12], such as tuberculosis or septic shock, making it challenging to diagnose.
Therefore, healthcare providers must consider Melioidosis as a differential diagnosis in regions where the disease is endemic, especially in patients with risk factors or a history of travel to affected areas. Prompt recognition and suitable treatment are critical for preventing mortality and long-term complications.
Some methods used to diagnose Melioidosis include[13]:
- Blood Culture: A culture from a blood sample can reveal the presence of the bacterium to diagnose Melioidosis.
- Serological Tests: These tests look for the patient’s antibody response to the bacterium which can confirm a Melioidosis diagnosis.
- Molecular Diagnostics: Tests like polymerase chain reaction (PCR) can detect the bacterium in a sample for Melioidosis diagnosis.
- Imaging Studies: X-rays and CT scans can locate abnormalities in the lungs or affected organs for Melioidosis diagnosis. Abscesses may occur in the liver, spleen, prostate, and parotid glands.
Melioidosis Treatment
Melioidosis is a complex disease that requires careful management to prevent complications. Patients with Melioidosis may need long-term antibiotic therapy (up to 20 weeks) to eradicate the bacterium from their system.
The type of antibiotic used will depend on the severity of the infection.
Additionally, frequent follow-up consultations with a healthcare provider are necessary to oversee treatment progress and address any new signs of disease.
In severe cases, hospitalization may be required for intravenous antibiotics. Treatment may also include draining any abscesses that have formed. Surgical abscess removal is indicated in some patients, while organ transplantation may help in other instances.
Patients should also be vigilant about practicing good hygiene and taking precautions to prevent reinfection. By staying informed and proactive, individuals can effectively manage Melioidosis and improve their overall quality of life.
Complications and Prognosis
If left untreated, Melioidosis can lead to severe complications, including sepsis, pneumonia, and abscesses in the liver, spleen, prostate, lungs, and other internal organs. Severe complications may result in sepsis, organ failure and death.
The prognosis for Melioidosis depends on the infection severity, the timeliness of treatment, and the individual's overall health including factors like age and comorbid conditions. Before available treatment, it had a very high mortality rate of over 90% once the disease became septicemia. The prognosis is good with timely intervention, averaging mortality rates as low as 10%. Most patients undergo treatment for five months or more before the infection resolves.
Living with Melioidosis
Living with Melioidosis can be challenging, particularly for those with chronic or latent forms of the disease. It is essential to follow the treatment plan your doctor prescribes and take precautions to avoid any future infections.
Prevention and Precautions
There is currently no vaccine for Melioidosis, emphasizing the critical nature of prevention. Several safety measures can lower infection risk[14]:
- Avoiding contact with contaminated soil and water
- Wearing protective gear when working in high-risk environments
- Properly cleaning and disinfecting any cuts or wounds, especially in those with diabetes
- Boiling or filtering water before drinking it
- Avoiding eating raw or undercooked food
Latest Research and Advancements
Research is ongoing to develop a vaccine for Melioidosis. In recent years, there have been advancements in the development of several vaccines, some of which have entered phase I clinical trials set to start in 2024.[15]
Vaccine mechanisms currently under exploration to elicit protective immune responses against Burkholderia pseudomallei include:
- Live attenuated vaccines: Live attenuated vaccines use weakened or modified forms of the bacterium to stimulate immune responses without causing severe disease. These vaccines can elicit a broad and robust immune reaction, providing long-lasting protection against Melioidosis.
- Subunit vaccines: Subunit vaccines involve using specific pieces, or subunits, of the bacterium (such as proteins or polysaccharides) as vaccine antigens. These subunits can mimic the presence of the whole bacterium, triggering an immune response and conferring protection against melioidosis.[16]
Other research areas are investigating better antibiotic treatments, rapid diagnostic tools, and alternative strategies to target Melioidosis, such as phage therapy.
Phage therapy utilizes bacteriophages, which are viruses that infect and kill bacteria. Studies show the potential of using phages to target and eliminate Burkholderia pseudomallei, the causative bacterium of Melioidosis. Phage therapy provides an alternative approach to combat resistant strains, as phages can adapt and evolve to target specific bacterial strains.[17]
More research is required to explore the safety and efficacy of phage therapy for treating Melioidosis.
Conclusion
Melioidosis is a potentially life-threatening infectious illness prevalent across tropical and subtropical regions. Until an approved vaccine emerges, timely detection and treatment are critical for ensuring a good prognosis. By taking precautions and following proper hygiene practices, those at risk can protect themselves from contracting Melioidosis.
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