Clinical Evaluation of Latent Visceral Leishmaniasis in US Service Members Deployed to Operation Iraqi Freedom

Abstract

Background. Visceral leishmaniasis (VL) is a systemic vector-borne disease. In Iraq, VL is caused by Leishmania infantum, an intracellular parasite requiring a cell-mediated immune response. Most infections are asymptomatic, and evidence exists for latent disease that may activate, especially with immunosuppression. Since 2001, 22 cases of active VL have occurred among deployed service members and there is potential that many are latently infected. Methods. A recent surveillance study tested 112 asymptomatic US service members previously deployed to Iraq for latent VL with interferon gamma release assays (IGRA), enzyme-linked immunosorbent assays (ELISA), rK39 immunochro-matographic tests, and quantitative polymerase chain reactions (PCR). Persons with any positive result were ofered a clinical consultation to assess for exposure risks, immune-suppressing conditions, and evidence of active VL, as well as to obtain baseline laboratory studies and abdominal imaging, as needed, and to provide counseling. This is a case series of the 18 subjects who underwent clinical evaluation. Results. Among18 latent VL subjects evaluated, 14 were IGRA+, 4 ELISA+, 0 rK39+, and 1 PCR+ (3 parasites/ml). All were male and median age was 38.5 years. Initial deployments were in 2003-2008 and median total duration in Iraq was 17 months. Musculoskeletal disease was the most common comorbidity. Four subjects previously had cutaneous leishmaniasis. One subject had psoriatic arthritis and prior TNF-α inhibitor exposure, but no other substantial risks for immunosuppression were identified. There was no evidence of active VL, although one subject had thrombocy-topenia and two had elevated liver enzymes. There was no abnormal imaging. No subjects were treated and those that were PCR+ and ELISA+ are being followed clinically. Conclusion. This series highlights the first 18 US service members diagnosed with latent VL. No patients have active disease, most have an appropriate immune response (IGRA), four have a TH2 humoral immune response (one of whom is immu-nosuppressed), and one has evidence of ineffective immune control with circulating parasites. We have developed an approach to the assessment and counseling of latent VL. Further studies are needed to assess the natural history and treatment of latent VL.