Though little known outside the developing world, the disease called lymphatic filariasis wreaks havoc on millions of people by causing their limbs and genitals to fill with fluid and swell monstrously — the symptom commonly known as elephantiasis.
Now, a new review of existing research suggests that enriching a community’s salt with a drug could treat and prevent the condition without any adverse effects.
But it remains a challenge to get governments to enrich their salt with the drug, diethylcarbamazine, or DEC.
“Biologically and medically, it’s a great tool. Operationally and socially, it’s a challenge to put it into place,” said Eric Ottesen, M.D., director of the Lymphatic Filariasis Support Center in Decatur, Ga. Ottesen was not involved with the research but is familiar with the review’s findings.
To gauge the effectiveness of enriching salt with DEC, researcher Srividya Adinarayanan of the Vector Control Research Center in Pondicherry, India, and her colleagues examined 21 studies in a new systematic review.
The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews like this one draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
With filariasis affecting an estimated 120 million people in more than 83 countries, a proven treatment can have a big impact. The condition is caused by parasitic worms that are deposited in the body by mosquitoes and then grow, mate and release tiny baby worms. Those worms are picked up by mosquitoes, mature into the infective form and are then transmitted to other community members through mosquito bites.
“Essentially, it is a disease of poverty,” said Charles Mackenzie, a pathology professor who studies filariasis at Michigan State University. But he added that filariasis is also connected to poor hygiene and warm temperatures.
While people with filariasis typically don’t die of the disease, their limbs and genitals can become hugely swollen. In men, the scrotum is especially susceptible.
“It makes these people recluses,” said Ottesen. “They are unable to perform their work. It is an enormous drain economically on a population and just destroys their lives. That’s a common thing with most of these neglected tropical diseases. They don’t really kill, they just sap the energy and make the productivity of the communities far lower than it ought to be.”
Drug treatments are fairly effective at getting rid of adult worms and very good at killing off the baby worms, which transmit the disease to other people through mosquitoes. But when tens of millions of people are infected, it can be difficult to provide care to individuals.
Enter the drug DEC, which kills the baby worms, known as microfilariae. Since the drug only works if people take it repeatedly, some health officials have put it in salt supplies so people could get a regular dose.
According to the reviewers, the studies suggest that DEC-medicated salt is effective at reducing transmission of the disease if maintained for at least six months. They added that the salt treatment can eliminate transmission entirely if used over a long period of time.
The reviewers also suggest that a very low dose of DEC over an extended period — perhaps six months — is better than bigger doses given at once.
A couple of caveats exist. For one, the reviewers say that widespread use of DEC could lead to resistance to the drug, although there’s been little research into this possibility. The reviewers add that “political and administrative commitment and community motivation is a necessity for community programs to be successful.”
Indeed, while China has eliminated filariasis with the help of DEC, regulatory hurdles have prevented many countries from enriching their salt despite research suggesting that DEC is effective, Ottesen said.
Still, the drug “is very effective in treating people without their really being aware that they need to be undergoing treatment,” he said. “It’s not tricking them, but letting them treat themselves without having to remember anything.”
The salt itself “comes in bags, and people just use it,” he said. “It’s tasteless, and no one knows they’re taking it. As the review indicates, there are no side effects and no negative reasons for not giving it.”
If the drug works as expected, the benefits could be huge. “My own crude calculations [suggest] something like one in 60 people living on the earth are affected by the disease, and around one in 15 are either infected or at risk,” said Michigan State’s Mackenzie.
Pharmaceutical companies and the Gates Foundation are helping in the long run, providing money for medicines to treat clusters of devastating tropical diseases like filariasis, Ottesen said. “It’s so cheap to get rid of all these things, but nobody knows about them. If you put them in a package, it makes it more effective.”
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