“To stop leprosy in its tracks, you need to find the people who are harboring the infection and get them treated,” says Duthie. “I can’t tell you how hard it was to convince some of the doctors in leprosy clinics I’ve gone to who say, ‘Why do I need a test? I can recognize leprosy walking in the door.’ So I have to ask, ‘Why then for the last couple of years has this patient been treated for fungal infections, acne, and all sorts of things—even cancer!—before getting properly diagnosed?’ It’s mind-boggling.”
One of the places the disease persists is Brazil, the country with the second-most endemic cases after India. The nonprofit IDRI has partnered with a Rio de Janeiro-based diagnostic manufacturer, OrangeLife, to keep down production costs and ensure that price is not a barrier to patients.
“You could say that it took $100 million to create a $1 test,” Reed says. Not that leprosy, as one of the World Health Organization’s official neglected tropical diseases, has ever attracted those kinds of bucks. But because leprosy is a bacterial cousin of tuberculosis, one of the diseases targeted by the Gates Foundation, IDRI has been able to piggyback on an influx of research dollars in recent years. “We’ve been able to apply all we’ve learned in TB to leprosy,” Reed says. “Our profit is in terms of public health, not dollars.”
The test and vaccine come at a critical time for the disease, which has been on the wane thanks to massive public health campaigns to distribute free multidrug therapy. The WHO reports a 90 percent decrease in leprosy prevalence since 1991, but active leprosy cases and leprosy-related disabilities still affect more than 4 million people worldwide. For the past 10 years, the number of new cases reported each year has flatlined at 250,000.
Some experts say that number is too conservative, though, and comes from pressure from WHO and government officials to declare victory. “The easiest way to eradicate a disease is to stop reporting it,” says Duthie, his Scottish brogue tinged with exasperation. “I believe that the problem is as large as 1.5 million to 2 million cases.” Another reason experts believe the actual number of cases may be higher than WHO claims is that the age-old stigma of the disease, long considered a curse, deters people from seeking medical help. Patients who are cured but disfigured often remain ostracized, even from their own families.
Increasing rates of infection, particularly among children and in countries like India with fast-growing populations, have experts worried that, as Duthie puts it, there is a “large reservoir of infection that is ready to pop.”
And multidrug therapy is no panacea. The drugs cannot reverse nerve, muscle, and bone damage. Nor do the drugs confer lifelong immunity, even after a year of taking them—a regimen especially difficult in poor countries with fragmented health care systems. Side effects can be harsh, a fact that leads some patients to slack off their meds and relapse.
The sulfone drug Dapsone was the drug of choice starting in 1947, but increasing resistance is what prompted the WHO to introduce the current regimen, combining Dapsone with two other drugs. Antibiotic resistance to the new drugs may just be a matter of time.
It’s an axiom of epidemiology that the closer you get to wiping out a disease—and, let’s face it, very few scourges have been eliminated from the planet—the harder it is to whack that last mole. That is all the more true with leprosy, as scientists are not sure exactly where it lurks or all the ways it is transmitted.
In 2008, Duthie and his team went to a “hyperendemic” village in remote southwest China and collected blood specimens from leprosy patients and seemingly healthy members of their households. They kept their eye on one girl who had a low antibody count, indicating that she had been exposed to leprosy—her grandfather, with whom she lived, had had a severe case—but she had no visible symptoms. Subsequent monitoring using IDRI’s test indicated that the bacilli in her blood were multiplying. By October 2009, her bacterial index had gone up precipitously, and she had developed suspicious lesions on her back. A clinical exam confirmed the diagnosis.
Duthie notes that the grandfather had died three years earlier, indicating that the disease had been propagating in the child for at least that long. The case showed that a diagnosis based on antibody response could have been made at least eight months earlier, before the onset of dramatic symptoms.
“When I see a 12-year-old girl who gets diagnosed and treated thanks to this test, knowing that even by age 13 she could have been disabled for life,” says Duthie, “I come back re-energized, knowing that is why I do what I do.”