Can the Curse of Leprosy Finally Be Lifted?

Health and medicine explained.
Feb. 20 2013 6:59 PM

Can Leprosy Finally Be Eradicated?

A new test and vaccine could stop a disease that has cursed humanity for millennia.

suffering from Leprosy, waits next to a window as a team of unseen doctors from the Bombay Leprosy Project.
Tukaram Maruti (right) suffers from leprosy. He waits for a team of doctors from the Bombay Leprosy Project to arrive for a field visit to Chincvali village, India, in May 2009.

Photo by Pal Pillai/AFP/Getty Images

Inside the headquarters of the Infectious Disease Research Institute, senior scientist Malcolm Duthie dumps a pile of white plastic test cassettes onto a small round conference table. They are the size of flash drives and resemble pregnancy tests but contain a strip of paper infused with four leprosy proteins. I pick one up. “Is that blood?” I ask, pointing to a crimson smear inside a divot.

“Yes!” says Duthie. “With a single drop of blood, we’re now able to determine if someone has leprosy. ”

He snaps the cassette into a cradle hooked up to a smartphone and taps the screen. Two thin blue lines appear, indicating that this particular patient, part of a clinical trial in the Philippines last year, tested positive. “And see those numbers? That gives us a rough quantitative idea of their bacterial burden.”

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Steven Reed, founder and president of IDRI, is pacing around the institute’s Seattle office on this sunny day in January. He is waiting on a phone call from Brazil, where IDRI is preparing to roll out the first rapid diagnostic test to identify people who have leprosy—before they show symptoms.

Leprosy microbes ravage the body slowly and stealthily. Part of what has made early diagnosis difficult is that symptoms vary widely and may take up to 10 years before they become apparent. A recent study in mice shows that leprosy bacteria hijack adult Schwann cells, which normally produce a fatty coating that insulates neurons, and reprogram them into stem cells so they can infiltrate the body’s muscle and nervous systems. An infected person might show zero symptoms or only nebulous ones such as skin rashes, numb patches, and respiratory congestion. The disease is commonly misdiagnosed, and a person with leprosy may squander critical months, even years, getting useless treatments. By the time a clinician clues in, the patient may be disfigured, blind, maimed, or crippled.

Meanwhile, an infected person can unknowingly spread the germ far and wide. One sneeze can spew 100 million bacilli, which can survive for more than a month in the environment, long enough for other people to breathe them in. The organism can remain potent even when dried out, and it can infect someone through the nose or a break in the skin. Although scientists don’t completely understand the mode of transmission, they agree that early detection is crucial to getting ahead of the disease.

IDRI’s test has Reed and colleagues around the world buzzing with optimism that, finally, they “are confronting leprosy in a strong and smart way.”

A few days later, Reed flies to Rio de Janeiro to register the test through ANVISA, Brazil’s regulatory authority, just in time for World Leprosy Day, which fell on Jan. 27. The annual commemoration was started 60 years ago to raise awareness for a disease that at the time infected almost 10 million people a year, was fast outwitting sulfone drugs, and for which a vaccine seemed impossible because leprosy germs cannot be grown in a test tube.

Scientists still can’t cultivate Mycobacterium leprae in vitro. But IDRI has now created the first leprosy vaccine by zippering together four key proteins. When tested on mice, the vaccine reduced the amount and growth of leprosy bacteria in their systems. The researchers are working to produce the fusion protein on a large scale. Clinical trials for humans are scheduled to begin by the end of 2013.

Ideally, the vaccine can be used prophylactically to prevent people from contracting the disease, as well as therapeutically in active cases to thwart bacterial replication. But first you have to know where the cases are. That’s why a quick and easy test is crucial, and IDRI’s can diagnose leprosy in seconds without a microscope.

Besides confirming a diagnosis in patients who already exhibit clear signs, the test can identify hidden cases. Someone with a positive blood test would be a candidate for antibiotic treatment as well as the vaccine. Because long-term exposure to people who have leprosy is the biggest known risk factor for contracting the disease, people who live in close proximity to those who already have leprosy would be candidates for immunization.

The two tools together could finally free humans from the vicious cycle of a disease that has afflicted the population for at least 4,000 years. Leprosy was prevalent in medieval Europe and was considered a serious public health threat in the United States until the 1930s. Most of the cases today are in Asia, Africa, and Latin America. Although leprosy can be cured with a combination of powerful drugs, many people don’t realize they are susceptible until long after they’ve been infected and start exhibiting symptoms.

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