A Stealth Parasite: Prevalence and Characteristics of Risks for Latent Visceral Leishmaniasis in a Cohort of US Soldiers Deployed to Operation Iraqi Freedom

Abstract

Leishmaniasis is a zoonotic parasitic disease transmitted by sand fly bites. Visceral leishmaniasis (VL) is a chronic intracellular infection which, when symptomatic, can be fatal without therapy. Subclinical or latent VL may occur in a majority of those infected with lifelong risk of activation when immunosuppressed. Symptomatic VL has been described in Soldiers deployed to Operation Iraqi Freedom (OIF). We report the prevalence and risk characteristics of latent VL infection in OIF Soldiers. Healthy soldiers deployed during summer months (2002–2011) to VL endemic areas of Iraq were recruited from Fort Bliss, Texas. Responses to a risk factor survey and blood samples were obtained. Leishmania research diagnostics were performed on serum and/or white blood cells to include ELISA, rk39 immunochromatography, qPCR, and interferon gamma release (IGRA) assays. Analyses included descriptive percentages and other summary statistics. Fisher’s exact test and logistic regression were used for group comparisons. Out of 88 subjects enrolled, 76/88 (86%) were male with median age 39 years and deployment duration of 365 days. The prevalence of latent VL was 10.2% (CI 4.8%-18.5%) with seven IGRA positive and two ELISA positive. Travel to Ninewa governate correlated with VL, P < 0.05. No significant differences were noted in occupation, personal protective measures, deployment timeframe, or sleeping conditions between VL positive and negative individuals. In persons with latent VL, 4/9 (44.4%) and 6/9 (66.7%) deployed to Ninewa and Baghdad respectively, 7/9 (77.8%) were outdoors most nights, 5/9 (55.6%) slept on the ground during deployment, 5/9 (55.6%) were medical personnel, 7/9 (77.8%) slept in less than full uniform, and 8/9 (88.9%) never or rarely used insect repellent. Latent VL was identified in asymptomatic OIF Soldiers (10.2%). Travel to Ninewa governate correlated with VL infection. In the latent VL group, many were healthcare workers, slept on the ground or in less than full uniform, and rarely used insect repellent. Further studies are needed to inform risk of reactivation disease in latently infected US Soldiers and to target measures for broader surveillance and safety, such as the screening of military blood donors. All authors: No reported disclosures.