Melioidosis, also known as Whitmore Disease, is a largely tropical or subtropical disease caused by the bacteria Burkholderia pseudomallei. Burkholderia pseudomallei is endemic in Southeast Asia, Australia, Africa, the Middle East, China and India with isolated occurrences in South America, Hawaii and Georgia. The highest percentage of melioidosis cases is reported by Thailand where 3.6-5.5 persons per 100,000 acquire melioidosis.
The disease is spread by ingestion, inhalation, and through cuts in the skin. Person-to-person transmission is rare. Melioidosis symptoms resemble those of glanders. Burkholderia pseudomallei can survive for long periods in soil and water, but can be deactivated by moist heat (at 121 degrees Celsius for 15 minutes) or dry heat (160-170 degrees Celsius for 1 hour). The Burkholderia pseudomallei bacteria are also deactivated by disinfectants such as sodium hypochlorite, ethanol or formaldehyde.
History of Melioidosis
Septicaemic melioidosis was first described in 1911-1912 by Captain Alfred Whitmore, a British pathologist serving in Burma, and his assistant C.S. Krishnaswami. The bacteria were isolated from morphine addicts in Rangoon, Burma. Autopsies of the morphine addicts revealed consolidation in the lungs and abscesses in the liver, spleen, kidneys, and beneath the skin. They noted that the disease resembled glanders but the morphine addicts were not exposed to equine hosts that typically carried glanders. When cultivated on peptone agar and potato slopes, the bacterial colonies grew faster than glanders bacteria (Burkholderia mallei), were motile, and when the bacterium was injected into guinea pigs, there was a lack of the Strauss reaction characteristic of Burkholderia mallei. The disease was named 'Whitmore Disease' after the pathologist who discovered it.
In Malaysia at the Institute for Medical Research, bacteriologist Ambrose Thomas Stanton and pathologist William Fletcher began to study an outbreak of "distemper-like" disease in animals. In 1917, the two scientists identified the bacteria that cause the disease as Burkholderia psuedomallei. In 1932, Stanton and Fletcher named the disease 'melioidosis.' In Greek, melis translates to 'distemper of asses,' and eidos translates to 'resemblance.' Over the next 10 years, Stanton and Fletcher documented 39 cases of melioidosis in humans and several cases in wild and domestic animals.
Following Stanton and Fletcher's discoveries, the disease was found in Vietnam, Sri Lanka, and Indonesia, and particularly affected the French troops stationed in Indochina and the American troops that followed them. During the French occupation of Vietnam between 1948 and 1954, over 100 cases of melioidosis were diagnosed. During the American occupation, over 300 cases were diagnosed. Soldiers acquired the disease by directly exposing wounds to soil or water carrying the Burkholderia pseudomallei bacteria or through inhalation. Melioidosis was known as the "Vietnamese Time Bomb" due to its potentially long incubation period; soldiers experience symptoms long after their return home. The longest documented period of latency was 26 years. Experts estimated that 225,000 American personnel who served in Indo-China were exposed to melioidosis.
Burkholderia pseudomallei is resistant to various antibiotics including penicillin, ampicillin, cephalosporius, and rifampicin. In 1989, effective antibiotic treatment became available and reduced mortality from melioidosis by 50%. The current treatment of choice is ceftazidime with or without trimethoprim-sulfamethoxazole (120 mg per kilogram per day) or imipienem (60 mg per kilogram per day).
Melioidosis as a Biological Weapons Agent
The Center for Disease Control (CDC) classified melioidosis as a Category B biological weapons agent. Burkholderia pseudomallei presents a stable, sturdy, easily obtainable, easily manufactured potential biological agent. In addition, due to its flu-like symptoms and potentially long incubation period, melioidosis can be difficult to accurately diagnose.
The United States and Soviet Union biological weapons programs both studied melioidosis as a possible biological weapons agent. Reports suggested that the Egyptian biological weapons program also researched melioidosis as a possible biological weapons agent.
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