Leptospirosis

leptospira
An electron microscopic image of Leptospira

Leptospirosis is an infection caused by bacteria called Leptospira. Human disease is usually acquired following environmental exposure to Leptospira shed in the urine of an infected animal. Infection is acquired during occupational or recreational exposure to contaminated soil and water, organisms gaining entry to the accidental human host via abrasions or less commonly the mucous membranes. Disease may also be acquired through direct contact with infected animals, and occurs in farmers, veterinarians and abattoir workers. The disease has a worldwide distribution but is most common in tropical regions where incidence peaks during the rainy season. Infection presents as an acute febrile illness associated with one or more of chills, headache, muscle pain, redness of the eyes and abdominal symptoms such as nausea, vomiting and diarrhoea. A minority of infections are severe (Weil’s disease) and may be fatal; this presents with jaundice and multi-organ involvement.

We study the incidence and clinical manifestations of leptospirosis in Udon Thani, Northeast Thailand. Leptospirosis is the most common identifiable cause of acute febrile illness in this region. An outbreak of leptospirosis in the northeast in the year 2000 that continued for several years was found by us to have been caused by a strain called L. interrogans serovar Autumnalis. We devised a typing scheme based on multilocus sequence typing, and using this designated the outbreak strain as sequence type 34. We have undertaken studies to define the optimal way to culture Leptospira from the blood of patients with leptospirosis. We have also defined how many people with leptospirosis develop clotting abnormalities. This is important for better understanding of complications that may occur and what investigations and management patients with severe leptospirosis require after admission to hospital.

Mortality from leptospirosis is less than 5%, and those people who die often have lung haemorrhage. We undertook a study to determine whether the addition of other treatments (high dose dexamethasone or vasopressin) to the standard antibiotic therapy could improve the mortality from severe leptospirosis associated with lung haemorrhage. Neither of the two extra therapies led to an improvement in outcome, and dexamethasone had the disadvantages that secondary bacterial infections occurred and led to a longer stay in hospital. Several antibiotics can be given to treat people with severe leptospirosis, but there was uncertainty as to whether one drug was superior to another. We undertook a study that showed that the efficacy of intravenous penicillin, doxycycline and ceftriaxone were similar. The oral antibiotic most often prescribed for milder leptospirosis or after intravenous treatment has finished is doxycycline, but this cannot be given to some patients groups, such as pregnant women. A study conducted by us showed that oral azithromycin is an effective alternative for uncomplicated leptospirosis.

subconjuctival_haemorrhage
Subconjuctival haemorrhage in a patient with leptospirosis