Jessica Fairley and colleagues are revolutionizing the understanding how leprosy is spread. Also known as Hansen’s Disease, the disease destroys nerves and muscles.
“Leprosy had gone away in many places since multi-drug therapy came on the scene in the ‘80s,” says Fairley, professor in the Emory School of Medicine and Rollins School of Public Health. “But it remained in other places like India and Brazil. My interest was: why does this persist in certain places? What's going on?”
Leprosy was traditionally thought to be transmitted solely through respiratory droplets from the nose and mouth via close human-to-human contact, with the bacteria unable to survive outside the body for long. According to that theory, treating infected individuals should be enough to break the chain.
Traditional health-promotion measures such as handwashing and clean water sources, however useful for other diseases, were irrelevant where leprosy was concerned. Yet even as drug therapy caused total worldwide leprosy cases to shrink dramatically, approximately 200,000 new cases continued to appear each year.
Something else had to be driving disease transmission — but what?
Earlier research by Fairley and others led her to suspect something in the environment also played a role in transmission, especially given bench research showing leprosy bacteria (Mycobacterium leprae) could survive up to several months. A controlled epidemiological study in a region where leprosy was endemic was the next step to confirming their hypothesis.
Jessica Fairley, professor in the Emory School of Medicine and Rollins School of Public Health, is researching leprosy. Photo by Kay Hinton.
That institutional support allowed Fairley to work in leprosy-endemic areas of Ethiopia to discover whether individuals infected with leprosy were more likely to lack access to WASH (water, sanitation and hygiene) resources.
Not having these resources could mean a lack of clean water for cooking, drinking and washing; poor toilet facilities or open defecation; or little access to soap. In Fairley’s study, 319 community members living near a former leprosy hospital were tested for antibodies to the leprosy bacteria.
Surprisingly, more than a third were positive, with many showing chronic infection the following year. At the same time, these participants, along with 54 individuals with leprosy, answered a survey about water and sanitary practices.
Questions included: What was their water source? Did they have a place to wash their hands? Did they have an improved or unimproved toilet?
The URC grant also provided funds for Fairley to collect soil samples from the yards of individuals with leprosy to detect viable bacteria using novel molecular tools. Initially planned in the northern Amahara province, the team pivoted to another study site in Brazil after civil war made study in Ethiopia impossible.
“We found that when there was a lack of sanitary separation from human waste, it was associated with about twice the chances of being infected with the leprosy bacteria,” Fairley says. “Same for living in a house with a dirt floor. The strongest association was not having access to improved bathing water.
“Interestingly, we also found that owning agricultural land was associated with being infected,” Fairley says. “We actually asked that question as a marker of socioeconomic status, thinking that if someone owned land, they'd have a higher socioeconomic status. But it was highly associated with seropositivity.”
These results strongly suggest that unsanitary environments are reservoirs for infection, although the exact mechanism of disease transmission still isn’t understood.
Fairley says the new data has made it feasible for her to apply to other grants, including those from the National Institutes of Health, to launch a planned study in another hot spot later this year. She’s also collaborating on a U.S.-based study of leprosy transmission in armadillos — the only animal known to spread the disease to humans in this country.
“I’ve definitely used the results of the URC-funded study in many grant applications since then,” Fairley says. “It’s still very much the dogma in the leprosy research world that it only transmits person-to-person.
“But there’s no question my work is starting to move the needle on how we think of leprosy transmission. This is where that stagnant number of 200,000 a year is going to start to move.”