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Melioidosis agent identified in samples

In the United States, the Centers for Disease Control and Prevention (CDC) announced on July 27, 2022 the identification, in household environmental samples, of the bacterium Burkholderia pseudomallei responsible for a rare and serious disease called melioidosis. For the first time, the bacterium has been identified in soil and water samples taken from the coastal region of the Gulf of Mississippi.

Two unrelated people living in close geographic proximity in the Gulf Coast region of the southern United States fell ill with melioidosis two years apart – in 2020 and 2022 – prompting the state health officials and the CDC to take samples and test household products, soil and water in and around the two patients’ homes, with their permission.

Three of the soil and water samples taken from puddles in 2022 tested positive to the CDC for B. pseudomalleiindicating that the environmental bacterium was the likely source of infection for both individuals and had been present in the area since at least 2020.

Reminder on melioidosis:

Melioidosis (also called Whitmore’s disease) is an infection caused by Burkholderia pseudomallei (or Whitmore’s bacillus) an environmental bacterium found in surface water, mud, wet clay soils, especially during the flooding of rice fields and the planting of rice at the beginning of the monsoon season.

Melioidosis is considered endemic or potentially endemic in Australia (North Queensland, Western Australia, Torres Strait region, Kimberley region), Thailand, Singapore, Malaysia, Myanmar (Burma), Viet Nam, South China, Hong Kong, Sultanate of Brunei, Laos, Cambodia, Taiwan and India. Sporadic cases have been reported in many countries (non-exhaustive list) in Asia (Indonesia, Bangladesh, Japan, Philippines, Pakistan, Sri Lanka, Nepal), on the American continent and in the Caribbean (Aruba, Guadeloupe, Guyana, Martinique , Puerto Rico, Ecuador, Panama, El Salvador, Haiti, Brazil, Costa Rica, Mexico, Venezuela, Honduras, Guatemala, United States, Trinidad, Dominican Republic, Virgin Islands, Peru), in the Pacific (Guam, Fiji, Papua -New Guinea, New Caledonia) in Africa and the Middle East (Iran, Uganda, Sierra Leone, Gambia, Madagascar, Kenya, Nigeria).

The annual number of cases is estimated at 165,000, including 89,000 deaths. The disease can occur in endemic areas in an epidemic mode and its incidence is directly linked to the rainy season and floods. It preferentially affects people working in agriculture, mining and construction. Outside endemic areas, imported cases are regularly reported among tourists and migrants. Ecotourists and adventurous travelers are more at risk.

Melioidosis can be contracted in three ways:

  • transcutaneously when a wound or skin abrasions are in contact with contaminated soil or water,
  • by air by contaminated aerosols,
  • through the digestive tract when ingesting untreated contaminated water.

Human-to-human transmission has been described but is exceptional. Besides humans, many animal species can be infected.

The clinical picture of melioidosis resembles that of many other diseases, which often leads to diagnostic delays.
The time between exposure to the bacteria and the onset of symptoms is not clearly defined. The average incubation period is estimated to be nine days (1-21 days), but symptoms may begin sooner (<24 hours) after inhalation.

  • Most patients develop acute melioidosis after a recent infection (85% of cases). The bacterium is present in the blood in 50% of cases and 20% of patients develop septic shock. The infection can present as a lung infection (50% of adults, 20% of children) or skin infection (60% of children versus 13% of adults), in the form of abscesses in different organs (liver, kidney, spleen, prostate), damage to the central nervous system or a bone or joint infection. Other localizations are rarer (mycotic aneurysm, pericarditis, mediastinitis).
  • In approximately 10% of cases, chronic melioidosis develops resulting in symptomatic lung or skin involvement for more than 2 months, generally associated with general signs.
  • About 4% of cases develop latent pulmonary reactivation of disease, sometimes decades after the initial infection.
  • A relapse of the primary infection may also occur (1 to 2% at 1 year in the event of well-conducted treatment, approximately 10% of cases at 10 years).

Mortality due to acute melioidosis varies from 10 to 50%, but may be higher when medical resources are limited or when the patient has risk factors (diabetes, chronic liver or kidney disease, thalassemia, immunosuppression, pulmonary diseases chronicles). The rates would be lower for imported cases (6% in a European series).

Treatment is with antibiotics given for several months. It begins with intravenous treatment (ceftazidime or meropenem) followed by prolonged oral antibiotic therapy (trimethoprim-sulfamethoxazole, amoxicillin/clavulanic acid).

Prevention for the traveler: There is no vaccine against melioidosis.

The risk of contracting melioidosis is low unless you are involved in agricultural work or humanitarian interventions during flooding. The following measures can reduce the risk of exposure:

  • Avoid swimming in fresh water and contact with soil or mud during the rainy season in endemic areas, especially if you have wounds or skin abrasions.
  • Clean and disinfect any skin lesions.
  • When traveling in wet areas, wear closed shoes and protect any skin lesions with bandages.
  • Travelers with diabetes or chronic kidney disease are more prone to melioidosis and should avoid contact with soil and standing water.
  • People doing agricultural work should wear boots.

Those at high risk should consider postponing travel if it is planned during hyperendemic times, such as during monsoon rains.

Source : Outbreak News Today.


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