L. tropica, a parasite endemic to the Persian Gulf, typically causes cutaneous leishmaniasis. At least eight PGW veterans developed viscerotropic leishmaniasis from L. tropica (N Engl J Med 328:1383-7, 1993). Viscerotropic leishmaniasis can be difficult to detect and can cause symptoms such as chronic fatigue and abdominal pain similar to those of veterans with PGW Unexplained Illness. To determine whether viscerotropic leishmaniasis might explain the health problems of some veterans with PGWUI, we assessed the frequency of immune reactivity to a L. tropica antigen among PGW veterans from Oregon and Washington.

Sera from the first 200 subjects participating in a population-based, case-control study of PGW veterans from a randomly selected population survey were tested for reactivity to a L. tropica recombinant protein using an ELISA. This assay was previously shown to be capable of detecting immune reactivity to L. tropica among veterans with documented viscerotropic leishmaniasis (Proc Natl Acad Sci, USA, 92:7981-85,1995). Samples with OD >3SD above the mean OD of sera from healthy, non-veteran controls were considered positive.

Positive serology by ELISA to the L. tropica recombinant protein was found in 18 of the 200 veterans (9%). Among cases of PGWUI, 10% had positive serologies while 6% of PGW veteran controls had positive serologies. None of the subjects with positive serology had abnormalities on physical examination or routine blood tests, including liver function and complete blood count. Subsequent follow-up on subjects with positive serologies by an infectious disease specialist failed to disclose evidence of clinically active leishmaniasis.

In conclusion, 5-10% of PGW veterans may have serologic evidence of exposure to L. tropica. None of the subjects with positive serologies in this study had evidence of active infection with L. tropica, suggesting that L. tropica infection is rarely a cause of significant health problems among PGW veterans.

This work was supported by a grant from the Department of Veterans Affairs to the PEHRC, a joint project of the Portland Veterans Affairs Medical Center and the Center for Research on Occupational and Environmental Toxicology, Oregon Health Sciences University.