Leishmaniasis: A Persistent Threat in a Changing Operational Environment

New insights highlight evolving risks, diagnostic advances, and the urgent need for better treatments and vaccines.

June 9, 2026 by Sharon Holland

A recent review in The New England Journal of Medicine underscores a reality that military and global health professionals know well: some of the most persistent threats are also among the least visible. Leishmaniasis-a parasitic disease transmitted by sand flies-continues to evolve in ways that demand renewed attention from the medical community, particularly those operating in austere and high-risk environments, according to Uniformed Services University professor Dr. Naomi Aronson, the lead author.

Leishmaniasis is not a single condition, but a group of diseases caused by protozoan parasites that invade and multiply in host immune cells. It presents in three primary forms. Cutaneous leishmaniasis, the most common, causes skin lesions that can ulcerate and scar. Mucosal leishmaniasis leads to destructive lesions of the nose, mouth, and throat, visceral leishmaniasis, the most severe form, spreads to internal organs and is often fatal if untreated, and symptomatic visceral leishmaniasis is often fatal if untreated.

While cutaneous disease may resolve over time, it can result in permanent disfigurement and significant psychological impact. Visceral leishmaniasis, by contrast, carries a mortality rate as high as 75-95% without treatment.

More than one billion people worldwide are at risk of leishmaniasis, with an estimated 700,000 to 1 million new cases each year. Although historically concentrated in parts of Africa, Asia, Latin America, mid-East and Mediterranean littoral regions, the disease is now expanding into new regions.

Several factors are driving this shift: climate change, which is expanding the habitat range of sand flies; urbanization and deforestation, altering vector behavior and increasing human exposure; population displacement and conflict, which disrupt protective infrastructure; and global travel and migration, introducing cases into non-endemic regions.

For military forces operating globally, these dynamics increase the likelihood of exposure in both traditional and emerging theaters.

"Conflict and leishmaniasis go hand in hand. In recent operations in Iraq and Afghanistan over 2,500 cases of cutaneous leishmaniasis were diagnosed, and in USU research studies the rate of asymptomatic visceral leishmaniasis, a decade after return from theatre, was 19.5%. Providers trained in the US are often not familiar with leishmaniasis syndromes leading to delay in diagnosis and appropriate management. In the U.S. southwest, cutaneous leishmaniasis is now endemic and moving northward where potentially transmission competent vectors exist," said Aronson.

Advances in diagnostics are transforming how leishmaniasis is identified and managed. While traditional methods relied on microscopy and culture, newer approaches now leverage molecular tools such as Polymerase Chain Reaction (PCR) to detect parasite DNA directly from tissue samples. PCR is a common laboratory method used to amplify small, targeted segments of DNA, generating enough material for detailed analysis. These methods not only improve sensitivity but also allow clinicians to identify the specific infecting species-an increasingly important capability, given that treatment response varies significantly across species.

Despite decades of research, treatment options for leishmaniasis remain limited and imperfect. Current therapies-including liposomal amphotericin B, miltefosine, and pentavalent antimonial agents-are often toxic or poorly tolerated, expensive or difficult to access, require prolonged or parenteral administration, and increasingly threatened by drug resistance.

Encouragingly, combination therapies for visceral leishmaniasis are improving outcomes and reducing treatment duration in some regions. However, no universally effective, easily administered treatment yet exists.

Perhaps the most promising development is progress toward a vaccine. Although no human vaccine is currently available, two candidates are advancing toward clinical testing. Modeling suggests that even a moderately effective vaccine-around 50% efficacy-could eliminate visceral leishmaniasis within a decade in some regions.

Early-stage research, including CRISPR-based live attenuated vaccines, is showing encouraging results in preclinical studies.

For military medical professionals, leishmaniasis represents more than a tropical disease-it is a readiness issue. The combination of environmental change, operational deployments, and evolving epidemiology means that clinicians must be prepared to recognize and manage cases in diverse settings.

Prevention remains the first line of defense. Ways to help prevent contracting leishmaniasis include avoiding sand-fly exposure, particularly from dusk to dawn; using insect repellents and treated clothing; and maintaining awareness in endemic and emerging risk areas.

But as the disease continues to shift geographically and clinically, preparedness must also include diagnostic capability, treatment access, and ongoing research investment.

Leishmaniasis remains a complex and adaptive threat-one shaped by biology, environment, and human activity. While progress in diagnostics and therapeutics offers reason for optimism, significant gaps remain.

"For the Military Health System and global partners, addressing these gaps will require sustained focus, innovation, and collaboration," said Dr. Eric Elster, dean of USU's School of Medicine. "In an era of increasingly complex operational environments, even a sand fly can shape the readiness landscape."