Leprosy cases in Florida suggest infection is endemic in Southeast US
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Key takeaways:
- One in five cases of leprosy in the United States is reported in Florida.
- Although the number of U.S. cases continues to increase, the risk for U.S. residents is relatively low.
Nearly one in five U.S. cases of leprosy is reported in Florida, with roughly 81% of cases in the state reported in central Florida, according to a study.
Many leprosy cases reported in Florida and Georgia in recent years have lacked zoonotic exposure or recent residence outside the U.S., suggesting the infection is endemic to the region, researchers wrote in a case study published in Emerging Infectious Diseases.
Data derived from Bhukhan A. et al. Emerg Infect Dis. 2023;doi:10.3201/eid2908.220367
“Our case adds to the growing body of literature suggesting that central Florida represents an endemic location for leprosy,” the authors wrote. “Travel to this area, even in the absence of other risk factors, should prompt consideration of leprosy in the appropriate clinical context.”
Leprosy, also known as Hansen's disease, is caused by Mycobacterium leprae, is known to be transmitted through aerosols between close contacts and can be spread by asymptomatic patients, according to previous research. However, overall risk for the disease among humans is relatively low and long-term direct contact with an infectious source is thought to be required for infection.
M. leprae is known to infect armadillos, red squirrels in the United Kingdom and chimpanzees in some areas of West Africa, in addition to likely surviving for years in soil and water inside of amoeba, John S. Spencer, PhD, associate professor in Colorado State University’s Mycobacteria Research Laboratories, who was not involved with the new study, told Healio.
Brazil, India and Indonesia report roughly 80% of new leprosy cases in the world each year, according to Spencer, with less than 200 cases occurring per year in the U.S.
According to the authors, leprosy in the U.S. has generally affected people who have newly immigrated to the country or who spend considerable time living outside the U.S., but about one-third of cases reported from 2015 to 2020 were in patients who “appear to have locally acquired the disease.”
They also report that a 54-year-old central Florida man sought treatment in 2022 with a painful and progressive rash, with lesions on his extremities, body and face. Although the man works in landscaping and spends a lot of time outdoors, he denied any recent travel, exposure to armadillos, prolonged contact with people recently relocated from leprosy-endemic countries or interacted with somebody who has leprosy.
The man was treated with triple therapy of dapsone, rifampin and clofazimine under the direction of the National Hansen’s Disease Program.
About 69% of U.S. leprosy cases occur in seven states — California, Florida, Hawaii, Louisiana, New York, Oregon and Texas — according to the National Hansen’s Disease Program.
The number of leprosy cases has been trending up in Florida since 2015, when the state saw a threefold increase from the year before in the number of reported cases, according to previous research, with much of it linked to armadillos.
Spencer said the cluster of leprosy cases in humans and armadillos has been reported on in previous research, and specifically on the growing number of cases in central Florida over the last several years — including many that note patients had contact with living or dead armadillos — and that “each time a new case like this arises, it makes some headlines.”
“For at least 10 years, the number of new cases in the U.S. has been less than 200 per year, so the risk of contracting leprosy in the U.S. is incredibly low,” Spencer said. “Contrast this with Brazil that sees 25,000 or more new cases per year for the last 10 years.”
M. leprae is also so slow at dividing, he said, that it often takes 3 to 7 years from the time of infection for skin lesions and nerve damage to develop.
Spencer added that genetics also play a key role in susceptibility or resistance to infection, with estimates suggesting more than 90% of all humans have natural immunity to mycobacterial infection, including tuberculosis, leprosy and nontuberculous mycobacteria.
Bhukhan and colleagues noted in the case study that a high percentage of leprosy cases in the southeastern United States, including in Florida, involved the same unique M. leprae strain carried by armadillos, “suggesting a strong likelihood of zoonotic transmission.” They add that increasing awareness and strengthening the reporting of new cases could help further identify how the infection is being transmitted.
“The absence of traditional risk factors in many recent cases of leprosy in Florida, coupled with the high proportion of residents, like our patient, who spend a great deal of time outside, supports the investigation into environmental reservoirs as a potential source of transmission,” the researchers wrote.
References:
- Bhukhan A, et al. Emerg Infect Dis. 2023;doi:10.3201/eid2908.220367
- Domozych R, et al. J Am Acad Dermatol. 2016;doi:10.1016/j.jdcr.2016.03.004
- Sharma R, et al. Emerg Infect Dis. 2015;doi:10.3201/eid2112.150501
- HRSA. National Hansen’s Disease (Leprosy) Program caring and curing since 1984. https://www.hrsa.gov/hansens-disease. Accessed August 3, 2023.
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