Comparative study of the clinical manifestations and pathophysiology of leptospirosis and scrub typhus

Abstract

The study aims were to determine the prevalence of leptospirosis and scrub typhus in northeast Thailand, and to compare and contrast their clinical features and outcomes. Leptospirosis and scrub typhus accounted for 45% of acute febrile illness in 1249 prospectively studied patients presenting to Udon Thani hospital , northeast Thailand between October 2000 and December 2002, nearly 20% of who has leptospirosis and scrub typhus coinfection. A total of 311 patients had leptospirosis, 97 of who were culture-positive for Leptospira spp. The culture-positive group had fewer complications, including aseptic meningitis, jaundice, renal impairment, thrombocytopenia and pulmonary haemorrhage, compared with the culture-negative group. A total of 304 patients were diagnosed as having scrub typhus, one-fourth of who had putative reinfection based on the presence of an IgG response without detectable IgM. Patients with primary scrub typhus infection were significantly younger and presented to hospital later than patients with reinfection. Primary infection was associated with jaundice, liver impairment and gastrointestinal bleeding, but fewer patients had shock and confusion compared with patients with reinfection. Patients with leptospirosis had significantly more hepatic and renal impairment, thrombocytopenia and bleeding diathesis than patients with scrub typhus. Despite this, the morality rate was comparable at around 3% for each infection, and the major cause of death for both disease was pulmonary haemorrhage. Patients with concurrent leptospirosis and scrub typhus had more severe clinical features (shock, jaundice, renal failure, thrombocytopenia and bleeding diathesis) than patients with one of these diseases alone, but mortality was comparable. A leptospirosis-scrub typhus (LEST) score based on clinical features and routine laboratory tests was developed to predict the diagnosis of leptospirosis or scrub typhus. The score specificity approached 90% for both diseases. Further validation of the LEST score is required to determine its accuracy in routine clinical practice and in other geographic areas.