Melioidosis

Melioidosis is due to infection by Pseudomonas pseudomallei, acquired mainly via skin penetration but also by the respiratory route and by drinking contaminated water.

Infective agent
Pseudomonas pseudomallei is a Gram negative, motile, non spore-forming bacillus

Habitat
Soil and warm waters of rivers, seas, plantation paddy fields etc.

Distribution
The disease has limited geographical distribution being confined to tropical areas. It is endemic in South-east Asia where it occurs in Malaysia, Myanmar, Thailand, Vietnam, Indonesia and the Philippines. It is also present in the northern regions of Australia and in Iran. Sporadic cases occur in the countries of West Africa and in some areas of South America. (e.g. Bolivia, Colombia and Ecuador.
In tropical endemic areas human melioidosis usually affects persons with underlying health problems ( diabetes mellitus, renal deficiencies, cirrhosis of the liver, immunodeficiency etc.) which may facilitate progression of infection towards clinical disease, and those occupationally at risk mainly in rural areas. (Stock keepers, agricultural workers, soldiers and others exposed to contaminated waters of rice paddies, drains, plantations and gardens.) Melioidosis has been reported in travellers to endemic areas and may therefore present, as an imported disease, in Western Countries. This can be soon or many years after being exposed to infection.

Personal prevention measures
The adoption of low-risk behaviour to limit exposure. Avoid bathing/walking in rice paddies, still waters, plantations and other water logged soils other than when wearing protective garments.

Illness acute and chronic disease occurs
The skin and soft tissue at the entry site can develop subcutaneous abscesses and cellulitis. In internal organs (liver, spleen, bones lung), melioidosis presents as localised abscesses. Severe manifestations may present as septicaemia with toxic shock syndrome. In this instance onset is abrupt, with shivering, high fever and signs of cerebral impairment. If acquired via the respiratory tract pneumonia, with cavitation, may be the presenting feature. Cough, purulent discharge and haemoptysis are the initial clinical signs.

Treatment
This requires bactericidal agents which are intracellularly active. The drug of choice is ceftazidime 120mg/kg/day in divided doses. Chloramphenicol 6G/day for the adult weight or cotrimoxazole with 2.4g of sulpha per day have also been effective.

Recommended for more information
'Lecture Notes on Tropical Medicine,' Dion R.Bell; Blackwell Publications; ISBN 0-632-0445-0.
'Mansons Textbook of Tropical Diseases' Ed.G.C.Cook; WB Saunders Company Ltd.ISBN 0-7020-1764-7
'Clinical Medicine'; Kumar and Clark; WB Saunders Company Ltd. ISBN 0-7020-4739-6