Highlights
- Leprosy, also known as Hansen’s disease, is a chronic infectious disease that attacks the skin and nerves. Symptoms include a wide variety of skin lesions like those that are reddish or pale and can be numb to the touch.
- The number of leprosy cases has risen in Florida over the last decade. The state has one of the highest rates of infection in the United States, according to data from 2020.
- Leprosy is most commonly caused by the bacterium Mycobacterium leprae and, more rarely, by Mycobacterium lepromatosis. People may become infected from other people with untreated leprosy or from the nine-banded armadillo, a natural host of M. leprae.
- There is a risk that armadillos may contaminate soil with the leprosy bacteria by burrowing and defecating, infecting humans who later handle soil. Researchers are studying this possibility.
- Leprosy can be cured. Treatment with antibiotics is highly effective, but early diagnosis is key to a smooth recovery.
One of the world’s oldest diseases is garnering more attention in the United States, with Florida among the hardest hit states. Leprosy, also known as Hansen’s disease, attacks the skin and nerves and is most commonly caused by bacteria called Mycobacterium leprae. While leprosy can be cured, the unusual new cases have caught the attention of medical experts.
The World Health Organization (WHO) reports that each year, there are 200,000 new cases in 120 countries. There have also been reports of people getting leprosy after coming in direct contact with nine-banded armadillos, which can carry the bacteria that causes leprosy. Many recent cases of leprosy in Florida, however, follow neither of these typical transmission routes.
One of the scientists working to understand what may be happening is Norman Beatty, M.D., an assistant professor at the University of Florida College of Medicine.
“We need a better understanding of who’s at risk of leprosy in Florida. That’s why we have a team here at the University of Florida, which is in collaboration with several other universities, ready to dive into these questions,” Beatty said.
Data from the National Hansen’s Disease Program shows the disease is still relatively uncommon in the United States, with 159 new cases in 2020. Most people in the country are unlikely to get leprosy, but the rareness of this disease can be a double-edged sword. Those who do develop leprosy may take longer to receive a diagnosis and begin treatment, since few people are looking out for it.
The most obvious symptoms of leprosy are skin lesions and manifestations. Manifestations include, but are not limited to, thickened skin, nodules and lesions that are reddish or lighter in color than the rest of the skin.
Because leprosy also attacks the peripheral nervous system, which includes nerves outside of the brain and spinal cord, there can also be a loss of sensation that begins with tingling (or pins and needles) before eventually becoming numb and painless. The attacked nerves also become enlarged and palpable.
Beatty urged residents of the Sunshine State in particular to pay attention to any symptoms like these. According to a research letter published by the Emerging Infectious Diseases Journal, which is run by the Centers for Disease Control and Prevention, Central Florida accounted for nearly one fifth of the leprosy cases in the United States.
“It is important to be aware that we have leprosy being locally transmitted here in our state, so people know to report any symptoms to their doctor,” Beatty said.
The medical response to leprosy in Florida
Leprosy can be particularly challenging to diagnose because the disease has a long incubation period. This means several years can pass between initial exposure and the first appearance of symptoms. The rash it produces is also non-specific, meaning there aren’t enough characteristics to identify its cause. According to Nicole Iovine, M.D., a clinical professor at the University of Florida College of Medicine, leprosy can often be misdiagnosed.
“Sometimes a patient will come in who tested negative for Lyme disease but was given antibiotics anyway. They’re the wrong kind of antibiotics for treating leprosy, so the lesions continued to get worse,” she said.
To handle this tricky diagnosis, Iovine typically begins by taking an in-depth history from the patient. She calls it the most powerful tool she has as an infectious disease doctor.
“We would ask questions about travel, hobbies, and employment,” Iovine explained. “So, for someone coming in with a rash we would really want to know what kind of outdoor activities they do. We can unearth a lot of clues this way.”
A major hint that someone might have leprosy is if they handle soil or otherwise work in areas where they are likely to encounter a nine-banded armadillo. This nocturnal animal, the only mammal other than humans that is known to get leprosy, is a common sight in Florida. Papers estimate that, in some areas, 15 – 20% of armadillos carry the M. leprae bacteria.
The nine-armadillo often looks for insects to eat by digging in flowerbeds, then rests in a burrow below patios. While there have been reports of people becoming infected with leprosy after coming into contact with armadillos, the details of these encounters are unclear. Juan Manuel Campos Krauer, Ph.D., an assistant professor at the University of Florida College of Veterinary Medicine, seeks to better understand this route of transmission.
“Where the armadillo eats, lives, and reproduces, everything could affect the chance of a human being exposed to leprosy. That’s because the bacteria that causes leprosy can remain for a while in the soil,” Campos Krauer said.
When startled, the armadillo’s natural instinct is to jump several feet into the air, which is often a deadly choice during encounters with cars and trucks. As a result, armadillos often become roadkill.
“Imagine if an armadillo was carrying leprosy and got hit by a big truck. How risky is that bacteria being sprayed across the pavement? We don’t know yet, but it’s important to evaluate,” Campos Krauer said.
As scientists work to understand the potential risks of human and armadillo encounters, Campos Krauer recommends that people avoid close contact with armadillos. To be safe, he adds that anyone who works with soil should wear gloves and clothing to prevent contamination.
Leprosy has also traditionally been thought to transmit from person to person as respiratory droplets and nasal secretions carry the bacteria. This, however, requires two people to be in prolonged contact over months because M. leprae replicates slowly, dividing every two weeks.
Early diagnosis of leprosy aids in a smooth recovery
The slow reproduction rate of the bacteria that causes leprosy means that the disease itself also progresses relatively slowly. Still, complications can arise the longer the disease goes without treatment.
That’s why Kartik Cherabuddi, M.D., a professor at the University of Florida College of Medicine, says it’s important to diagnose leprosy as early as possible by keeping an eye out for a few key symptoms.
“Good clues for leprosy include a patch of skin that is lighter in color or numb to the touch. There aren’t many things that cause these symptoms,” Cherabuddi explained.
Lesions caused by leprosy also tend to be on cooler parts of the bodies such as the nose, eyebrows, and ears. Anyone with these symptoms, he said, should seek out a medical expert who can do a biopsy to determine if the bacteria are present.
Left untreated, the symptoms of leprosy continue to worsen and can lead to disabilities. An arm that was numb could become paralyzed and the bone could get reabsorbed on the inside. Lesions in the feet could become nonhealing.
“Fortunately, someone with leprosy can be cured. There’s no need to panic because leprosy is easier to treat than many things in medicine. It’s a simple infection of the skin and peripheral nerves, and an early diagnosis can lead to a straightforward recovery.”
The WHO recommends a treatment regimen of dapsone, rifampicin and clofazimine—three antibiotics that, together, form the first line of treatment. For those who cannot tolerate any of these, the National Hansen’s Disease Program is studying alternative antibiotics that could also work in treating leprosy.
“Typically though, there isn’t a lot of resistance to antibiotics. There also isn’t a lot of recurrence,” said Jessica Fairley, M.D., MPH, an associate professor at the Emory University School of Medicine.
In many countries, leprosy treatment lasts between six months to a year. Doctors in the United States, however, often recommend an even longer treatment time of one to two years.
“Even with the delay in diagnosis we see in the United States, we still see many good outcomes compared to other countries where leprosy is more common,” Fairley said. She attributes this not only to access to quality medical care, but also reduced stigma. “In areas where leprosy is more common, it is more stigmatized. So, people who receive a diagnosis might leave care because of the stigma, or they might recognize what they have and purposely avoid seeking care at all.”
As scientists work to answer the research questions surrounding leprosy in Florida, early recognition of its symptoms will be key to keeping people healthy. Treatment for leprosy is highly effective, and greater awareness of how the disease is transmitted and treated can help make medical care more accessible to patients.
Written by: Jiayu Liang