Leishmania is the second-most deadly parasite in the world. According to the Drugs for Neglected Diseases Institute, 20,000-30,000 people die from Leishmaniasis annually. Other estimates put the annual death toll at 50,000. About 350 million people are at risk across an estimated 90 countries, and some scientists have called the parasite the next plague. If you are infected with the visceral variety of Leishmaniasis and don’t treat it, you will likely die within a few months.
With mounting fears about a future increase in U.S. cases, a group of scientists in Georgia is racing to create a vaccine—and their new study shows they may be almost there.
Female sandflies transmit leishmania when they bite people, and the painful disease the parasite causes comes in three varieties. Visceral leishmaniasis, which attacks internal organs, is deadly. With mucosal leishmaniasis, the parasite spreads along the moist surfaces of the body—the linings of the mouth and throat, for example—and can scar these mucus membranes. Cutaneous leishmaniasis, the most common form, produces bumpy and cratered lesions. “People suffer a lot because [leishmaniasis] kills slowly and most of the time it devastates your face,” Alexandre Marques, a parasitology professor at the Universidade Federal de Minas Gerais in Brazil, told Newsweek.
The treatment has problems of its own, largely because the disease is most prevalent in developing nations. The medication for leishmaniasis is fairly effective and affordable, but only for those who can easily access hospitals with trained staff and enough of a supply. And a course of treatment takes four weeks, which can be financially devastating. But if patients discontinue treatment too early, they may relapse.
Scientists at the Georgia Institute of Technology appear on the brink of creating a successful vaccine that could prevent people from being affected with Leishmaniasis in the first place. As described in their study published today in ACS Central science, the researchers injected virus-like particles into 12 mice genetically engineered to have immune systems similar to humans. The approach was designed to attract major immune system forces to attack Leishmania. Another 12 mice were unvaccinated.
After infecting all 24 mice with Leishmania parasites, none of the vaccinated mice developed the disease. All 12 of the unvaccinated ones developed the sickness.
However, mice aren’t people. We don’t know how long it will take before enough tests show that the vaccine is safe and effective in humans. Marques, who was also part of the research team, laments that current funding is not sufficient enough to support further research.
Will this parasite start affecting Americans? People who engage in ecotourism (traveling to pristine areas in an environmentally responsible manner) have already come home with the sickness. The increase in U.S. cases was significant enough to trigger the country's first-ever guidelines for diagnosis and treatment of leishmaniasis.
And some experts are concerned that warming temperatures could expand the habitat of the insect vector. The parasite cannot be transmitted between people, only from certain species of sandflies, and these species live in tropical and subtropical regions. But if the climate warms enough, the flies could extend their range to the southern United States, and bring the deadly, flesh-eating parasite with them.
Recent history shows how readily the disease can spread. Last year, leishmaniasis moved across the Middle East by refugees fleeing Syria. For those who survive the infection, the resulting disfigurement can be devastating.