Melioidosis

Synonym: Whitworth's disease.

This disease is very similar to glanders. Glanders is caused by Burkholderia mallei whilst meliodosis is cause by Burkholderia pseudomallei.
It is possible that in the past, both organisms have been developed for biological warfare, and used by the Japanese in China in the 1940s. The Health Protection Agency thinks this is unlikely that it is currently available as a biological weapon.¹ Nevertheless, they have produced guidelines for such an eventuality.²

• The bacteria of meliodosis are found in water, soil, or plants. They may also be transmitted from infected animals.
• The bacteria thrive in tropical climates, and the disease is endemic in Southeast Asia, especially Thailand. It infects both humans and animals. Melioidosis is also endemic in Northern Australia. It has been observed in the South Pacific, Africa, India, the Middle East, and Central and South America.³ It is difficult to know its true extent as in many of the areas there are not laboratories capable of identifying the bacterium.⁴ It is rare in Western Europe but a few cases a year may appear from immigrants, travellers, and IV drug abusers. Cases identified in temperate climates are almost invariably imported from the tropics.
• In the United Kingdom, 29 cases were diagnosed in the 17 year period from 1988 to 2004.¹

Transmission

Melioidosis is transmitted to humans through direct skin contact or ingestion of contaminated soil, water or infected animal tissue. Ingestion can include dust inhalation. Transmission between humans is rare but has been documented.

Clinical forms

• In the localised form bacteria enter the skin through a laceration or abrasion and an ulcer develops. Incubation period is 1 to 5 days. There may be regional lymphadenopathy. Bacteria that enter the host through mucous membranes can cause increased mucus production in the affected areas.
• A pulmonary form occurs when bacteria in aerosol form enter the respiratory tract by inhalation or by haematogenous spread. Pneumonia, pulmonary abscesses, and effusions can occur. The incubation period is 10 to 14 days. Abscesses can spread to skin but they may take months to appear.
• Bacteraemia and septicaemia can occur if immunity is reduced by diseases such as diabetes or HIV infection. The patient develops respiratory distress, headaches, fever, diarrhoea, pus-filled lesions on the skin, and abscesses throughout the body. Septicaemia may be overwhelming, with a 90% fatality rate and death occurring within 24 to 48 hours.
• The chronic form involves multiple abscesses, which may affect the liver, spleen, skin, or muscles. Melioidosis can also become resurgent many years after the primary infection.

Symptoms

• Symptoms include fever, rigors, night sweats, myalgia, anorexia, and headache.
• Depending upon the route of infection there may also be chest pain, cough, photophobia, lacrimation, and diarrhoea.

Signs

• Examination may show fever, cervical lymphadenopathy, papular or pustular lesions of the skin, hepatomegaly, or splenomegaly.
• Septicaemia is associated with flushing, cyanosis, and a disseminated pustular eruption. Pustules are often associated with regional lymphadenitis, cellulitis, or lymphangitis.
• Rarely lesions such as ecthyma gangrenosum and skin abscesses that sometimes ulcerate may appear.

• Anthrax
• Plague
• Other causes of pneumonia

• FBC shows a mild leukocytosis.
• Gram stain and culture of blood, sputum, urine, and skin lesions may possibly demonstrate the organism.
• Blood cultures are usually negative.
• Agglutination tests may be positive after 7 to 10 days, but interpretation is difficult in endemic areas.
• Complement fixation tests that show a 4-fold increase in the titre for melioidosis are considered positive.
• CXR may demonstrate bilateral bronchopneumonia, miliary nodules, segmental or lobar infiltrates, and cavitating lesions.

Non-Drug

• Precautions should be taken to prevent spread of infection.
• IV rehydration may be required in the severely ill.

Drugs

• Long courses of antibiotics are required, possibly with more than one agent. The regimen depends upon the type of condition. Co-amoxiclav, tetracycline, co-trimoxazole and ceftazidime are all used. There is limited evidence-base about the best form of treatment and duration.
• For localised disease, oral co-amoxiclav, tetracycline, or co-trimoxazole may be used for between 2 and 5 months.
• If there is localised disease but some toxicity, combine 2 of the 3 regimens for 1 month and then switch to monotherapy with co-amoxiclav or co-trimoxazole for 2 to 5 months.
• Suppurative disease outside the lungs requires prolonged treatment for 6 to 12 months. Drain abscesses surgically. For severe disease or septicaemia, give parenteral therapy for 2 weeks followed by oral therapy for 6 months. A typical combination is ceftazidime with co-trimoxazole.
• Add streptomycin if plague cannot be excluded.
• Postexposure prophylaxis with co-trimoxazole may be attempted but its efficacy is unproven.

Surgical

Surgical drainage of pus is beneficial

Possible complications include septicaemia, osteomyelitis, meningitis and abscesses in brain, liver or spleen.

• Before antibiotics, the death rate for septicaemia was 95%. It is still above 50% for septicaemia and 5% for localised disease despite treatment.⁵
• Overall, mortality is 40%.
• Awareness is essential to allow early diagnosis and to reduce morbidity and mortality.⁶

• No vaccine is available for human glanders or melioidosis.
• Where melioidosis is endemic, people with impaired immunity should avoid contact with soil and standing water and wearing boots and gloves during agricultural work.
• Recognition of cutaneous manifestations may be very important, especially in identifying biological attack.⁷
• Pathology specimens and corpses should be treated with due care. Undertakers and pathologists must be informed and post mortem examinations kept to a minimum.