Leishmaniasis in the United States: Emerging Issues in a Region of Low Endemicity

Abstract

Leishmaniasis, a chronic and persistent intracellular protozoal infection caused by many different species within the genus Leishmania, is an unfamiliar disease to most North American providers. Clinical presentations may include asymptomatic and symptomatic visceral leishmaniasis (so-called Kala-azar), as well as cutaneous or mucosal disease. Although cutaneous leishmaniasis (caused by Leishmania mexicana in the United States) is endemic in some southwest states, other causes for concern include reactivation of imported visceral leishmaniasis remotely in time from the initial infection, and the possible long-term complications of chronic inflammation from asymptomatic infection. Climate change, the identification of competent vectors and reservoirs, a highly mobile populace, significant population groups with proven exposure history, HIV, and widespread use of immunosuppressive medications and organ transplant all create the potential for increased frequency of leishmaniasis in the U.S. Together, these factors could contribute to leishmaniasis emerging as a health threat in the U.S., including the possibility of sustained autochthonous spread of newly introduced visceral disease. We summarize recent data examining the epidemiology and major risk factors for acquisition of cutaneous and visceral leishmaniasis, with a special focus on implications for the United States, as well as discuss key emerging issues affecting the management of visceral leishmaniasis.

Keywords: asymptomatic visceral leishmaniasis; autochthonous leishmaniasis; climate change; immunosuppression; transfusion transmission; travel-related leishmaniasis.

Figure 1

Number of Returned Travelers Reported from a U.S. GeoSentinel Surveillance Network Site with a Diagnosis of Leishmaniasis from 2008–2019. CL = cutaneous leishmaniasis, ML= mucosal leishmaniasis, and VL = visceral leishmaniasis. (Data kindly provided courtesy of Dr. Michael Libman and the GeoSentinel Surveillance Network).