Melioidosis

Melioidosis! Heard about this disease before? Well, it is prevalent in this part of the world!

Melioidosis (also called Whitmore's Disease) is an infectious disease caused by a bacterium called Burkholderia pseudomallei (previously known as Pseudomonas pseudomallei). The bacteria are found in contaminated water and soil and spread to humans and animals through direct contact with the contaminated source. It  is also passed to humans from infected domestic animals like sheep, goats, swine, horses, cats, dogs and cattle. Melioidosis can spread from person to person as well.

Melioidosis is most frequently reported in Southeast Asia and Northern Australia. It also occurs in South Pacific, Africa, India, and the Middle East. The bacterium that causes the disease is found in the soil, rice paddies, and stagnant waters of the area. People acquire the disease by inhaling dust and water droplets contaminated by the bacteria and when the contaminated soil comes in contact with abraded (scraped) area of the skin. Infection most commonly occurs during the rainy season.

The time between an exposure to the bacteria that causes the disease and the emergence of symptoms is not clearly defined, but may range from one day to many years; generally symptoms appear two to four weeks after exposure. Patients with latent melioidosis may be symptom-free for decades; the longest period between presumed exposure and clinical presentation is 62 years.

Recently it was found that the deadly bacteria that can be picked up by a simple sniff can travel to the brain and spinal cord in just 24 hours, researchers in Australia have stated (2). 

Melioidosis symptoms most commonly stem from lung disease where the infection can form a cavity of pus. The effects can range from mild bronchitis to severe pneumonia. Patients may also experience respiratory distress, fever, headache, disorientation, loss of appetite, cough, chest pain, joint pain, muscle soreness and seizures. The effects can also be localized to infection on the skin (cellulitis). It can spread from the skin through the blood to become a chronic form of melioidosis affecting the heart, brain, liver, kidneys, joints, and eyes. Symptoms may last months.

Neurological melioidosis is particularly prevalent in northern Australian patients and involves brainstem infection, which can progress to the spinal cord (2).

Melioidosis is said to be able to affect any organ in the body except the heart valves (endocarditis). Although meningitis has been described secondary to ruptured brain abscesses, primary meningitis has not been described. Less common manifestations include intravascular infection, lymph node abscesses, pyopericardium and myocarditis, mediastinal infection, and thyroid and scrotal abscesses and ocular infection.

The diagnosis of melioidosis is made with a microscopic evaluation of a blood, urine, sputum, or skin-lesion sample in the laboratory. The disease is mostly misdiagnosed [as tuberculosis] and treated with inappropriate antibiotics. India has recently set up lab facilities to identify the cases correctly.

The treatment of melioidosis involves antibiotics and depends on the location of the disease. Patients who are more severely ill are given a combination of two or more antibiotics for three to six months. Untreated, melioidosis is fatal. When treated with antibiotics, severe forms of the illness have an overall mortality rate of approximately 40%.

Surgical drainage is usually done for prostatic abscesses (a swollen area within body tissue, containing an accumulation of pus) and septic arthritis, may be indicated for parotid (salivary gland) abscesses, and is not usually indicated for hepatosplenic abscesses (affecting the liver and spleen). In bacteraemic (the presence of bacteria in the blood) melioidosis unresponsive to intravenous antibiotic therapy, splenectomy (surgical procedure to remove one's spleen) will be done, but only anecdotal evidence supports this practice.

Patients with melioidosis usually have risk factors for disease, such as diabetes, thalassemia, hazardous alcohol use, liver or renal disease, AIDS, cancer and various lung diseases and frequently give a history of occupational or recreational exposure to mud or pooled surface water.

In counties where melioidosis occurs, people with compromised immune systems should avoid contact with soil and contaminated water, especially in farm areas. Those who perform agricultural work should wear boots, which can prevent infection through the feet and lower legs. Health care workers can use standard contact precautions (mask, gloves, and gown) to help prevent infection.

References:

1. http://www.nature.com/articles/nmicrobiol20158

2. http://iai.asm.org/content/early/2016/06/28/IAI.00361-16