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Dr Ed Feil
Dr Ed Feil

Internal News - 14 November 2007

New gene technique helps discover cause of recent leptospirosis outbreak

A single disease-causing clone of the bacterium Leptospira interrogans was behind the recent sustained outbreak of leptospirosis in Thailand, according to a new collaborative investigation by researchers in Thailand, Australia and the UK.

Leptospirosis (also known as Weil's disease, nanukayami fever and seven-day fever) is a relatively rare bacterial infection, commonly transmitted to humans by allowing fresh water that has been contaminated by animal urine to come in contact with unhealed breaks in the skin, eyes or with the mucous membranes.

Symptoms are varied but may include severe headache, chills, muscle aches, vomiting, jaundice, red eyes, abdominal pain, diarrhoea and a rash.

The disease is found worldwide but is most common in tropical regions where incidence peaks during the rainy season. A sustained leptospirosis outbreak occurred in northeast Thailand from 1999 to 2003, but the cause was unknown.

To investigate the cause, researchers including Dr Edward Feil from the Department of Biology & Biochemistry at the University of Bath identified patients with leptospirosis presenting to Udon Thani Hospital in northeast Thailand from 2000 to 2005, and isolated the causative organisms from the blood.

The researchers used a special molecular biology technique for identifying the organism - a form of bacterial genotyping known as multilocus sequence typing. This approach has advantages over existing schemes in that the data generated can undergo detailed evolutionary analysis, and are readily comparable via the internet.

Their results, published in the journal PLoS neglected tropical diseases, provided evidence that the human outbreak was associated with a biologically successful clone of Leptospira interrogans, called ST34. It was also demonstrated that the bandicoot rat was an animal host for this disease-causing bacterium.

“Previous studies of human outbreaks have largely relied on the study of blood serum to confirm clinical cases and define the infecting organism,” said Dr Feil.

“These provide a broad idea of groups responsible for leptospirosis in a given geographic area with an accuracy of less than 50 per cent.

“Our new study clearly demonstrates the advantages of bacterial isolation, in that it permits detailed typing studies to understand local populations and outbreaks.

"The existence of this strain collection now provides the opportunity to study the basis for pathogenicity and disease acquisition."