The incidence of leprosy is increasing in the southeastern United States (Case report)

Aug 3, 2023 | Diseases & Drugs

In a recent case report, the authors from the US have warned about an increase in the incidence of leprosy cases without traditional risk factors in Florida, and rising evidence that leprosy has become endemic in the southeastern United States. The authors also presented a case of lepromatous leprosy in a man from central Florida, without risk factors for known transmission routes.

From the 1980s through 2000s, there was a drastic reduction in the annual number of documented cases of leprosy in the US. But, since then, reports have shown a gradual increase in the incidence. According to the National Hansen’s Disease Program, there were 159 new cases in the United States in 2020. Central Florida had 81% of the cases reported in Florida and almost one fifth of the cases reported nationally.

Leprosy, or Hansen disease, is a chronic infectious disease caused by the acid-fast bacilli Mycobacterium leprae, which have a unique tropism for peripheral nerves, skin and mucous membranes of the upper respiratory tract. Humans are the main natural reservoir for M. leprae. Armadillos are the only confirmed sources other than humans, although other animal and environmental sources may exist. Most scientists believe that disease is transmitted from person to person through nasal droplets and secretions.

According to cellular responses and clinical findings, leprosy is classified to: tuberculoid, lepromatous and borderline. People with tuberculoid leprosy typically have a strong cell-mediated immune response, which limits disease to a few skin lesions. A disease is milder, and less contagious. People with lepromatous or borderline leprosy typically have a poor cell-mediated immunity to M. leprae and have a more severe, systemic infection with widespread bacterial infiltration of skin, nerves, and other organs (e.g., nose, kidneys, testes). They have more skin lesions and the disease is more contagious.

Case Report

A 54-year-old man was admitted to a dermatology clinic for a painful and progressive erythematous rash. The lesions started on the distal extensor part of legs, and progressed to his trunk and face. The results of biopsies from multiple sites revealed a diffuse dermal infiltrate composed of disorganized aggregates of foamy histiocytes and lymphocytes. Acid-fast bacilli were found within histiocytes and cutaneous nerve twigs, a pathognomonic finding of leprosy.

Images from original article of Bhukhan A. et al. A, B) Leonine facies with waxy yellow papules. C) Violaceous nonblanching macules coalescing into patches along dorsum of feet.

He was referred to an infectious disease specialist who, under the guidance of the National Hansen’s Disease Program, prescribed triple therapy with dapsone, rifampin, and clofazimine.

The patient denied any domestic or foreign travel, exposure to armadillos, prolonged contact with immigrants from leprosy-endemic countries, or connection with someone who had leprosy. He has lived in central Florida for his entire life, works in landscaping, and spends long periods of time outdoors.

The National Hansen’s Disease Program conducted the contact tracing and found no associated risk factors, such as travel, zoonotic exposure, professional association, or personal contacts. The absence of traditional risk factors in numerous recent cases of leprosy in Florida, such as the presented one, supports the hypothesis that environmental reservoirs could be a potential source of transmission.

Leprosy in the US has previously affected individuals who have immigrated from leprosy-endemic areas. According to the Centers for Disease Control and Prevention, the incidence of leprosy has been increasing, but, the rates of new diagnoses in persons born outside the US have been declining since 2002. Approximately 34% of new cases during the period 2015–2020 appeared to have acquired the disease locally. This suggests that leprosy has become endemic in the southeastern US.

This article was published in Emerging Infectious Diseases, The Centers for Disease Control and Prevention.

Journal Reference

Bhukhan A. et al. Case Report of Leprosy in Central Florida, USA, 2022. Emerging Infectious Diseases •   Vol. 29, No. 8, August 2023