EVALUATION FOR LEPTOSPIROSIS DURING SURVEILLANCE OF ROYAL NEPALESE ARMY VOLUNTEERS IN AN EFFICACY TRIAL OF A HEPATITIS E VACCINE

Leptospirosis is a cosmopolitan infection with a wide geographic distribution. Nepal is thought to have serovars of leptospira circulating that are capable of causing human disease, though no national surveillance program exists to establish its incidence. The U.S. Army Medical Component of the Armed Forces Research Institute of the Medical Sciences (USAMCAFRIMS), Bangkok, Thailand, is currently completing an efficacy study of a Hepatitis E vaccine in 2000 Royal Nepalese Army volunteers garrisoned in the Kathmandu Valley and intermittently deployed elsewhere in Nepal. After a 3-dose vaccination schedule (50% having received placebo), each volunteer was evaluated for clinical hepatitis (fever, headaches, chills, myalgias, jaundice and/or abdominal complaints plus biochemical abnormalities) through surveillance at the single medical treatment facility designated to receive all such patients. As part of the evaluation for etiology of hepatitis, all cases were evaluated by Leptospira ELISA IgM (PanBio, Brisbane, Queensland, Australia). The ELISA detected 51 patients with evidence of possible leptospirosis. Confirmatory testing utilized a Leptospira microscopic agglutination test (MAT) using a battery of 24 serovars from 19 serogroups common in Asia. A “definite” leptospirosis case was defined as an illness clinically compatible with leptospirosis associated with a four-fold rise in MAT titer. A “probable” leptospirosis case was defined as clinically compatible with leptospirosis associated with MAT of > 200 in one or more serum specimens. Using these criteria, one patient had “definite” leptospirosis and 12 had “probable” leptospirosis. These results demonstrate that soldiers in Nepal are at risk for leptospirosis and suggest that the disease may affect the general population. Further studies are warranted to define the epidemiology, clinical disease and circulating serovars responsible for these infections. 13th Asia Pacific Military Medicine Conference (APMMC). Bangkok, Thailand. 11-16 May 2003.