Rare Disease Mystery: Nodding Syndrome May Be Linked to Parasitic Worm

Rural Uganda village gathering

Caption: Village in the East Africa nation of Uganda
Credit: Centers for Disease Control and Prevention

In the early 1960s, reports began to surface that some children living in remote villages in East Africa were suffering mysterious episodes of “head nodding.” The condition, now named nodding syndrome, is recognized as a rare and devastating form of epilepsy. There were hints that the syndrome might be caused by a parasitic worm called Onchocerca volvulus, which is transmitted through the bites of blackflies. But no one had been able to tie the parasitic infection directly to the nodding heads.

Now, NIH researchers and their international colleagues think they’ve found the missing link. The human immune system turns out to be a central player. After analyzing blood and cerebrospinal fluid of kids with nodding syndrome, they detected a particular antibody at unusually high levels [1]. Further studies suggest the immune system ramps up production of that antibody to fight off the parasite. The trouble is those antibodies also react against a protein in healthy brain tissue, apparently leading to progressive cognitive dysfunction, neurological deterioration, head nodding, and potentially life-threatening seizures.

The findings, published in Science Translational Medicine, have important implications for the treatment and prevention of not only nodding syndrome, but perhaps other autoimmune-related forms of epilepsy. As people in the United States and around the globe today observe the 10th anniversary of international Rare Disease Day, this work provides yet another example of how rare disease research can shed light on more common diseases and fundamental aspects of human biology.

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Creative Minds: Interrogating a Master of Disguise

Monica Mugnier

Monica Mugnier

When I volunteered several years ago as a physician in a small hospital in West Africa, one of the most frustrating and frightening diseases I saw was sleeping sickness. Now, an investigator supported by the NIH Common Fund aims to figure out how this disease pathogen manages to evade the human immune system.

Monica Mugnier’s fascination with parasites started in college when she picked up the book Parasite Rex, a riveting, firsthand account of how “sneaky” parasites can be. The next year, while studying abroad in England, Mugnier met a researcher who had studied one of the most devious of parasites—a protozoan, spread by blood-sucking tsetse flies, that causes sleeping sickness in humans and livestock across sub-Saharan Africa.

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Mouse Study Finds Microbe Might Protect against Food Poisoning

T mu in a mouse colon

Caption: Scanning electron microscopy image of T. mu in the mouse colon.
Credit: Aleksey Chudnovskiy and Miriam Merad, Icahn School of Medicine at Mount Sinai

Recently, we humans have started to pay a lot more attention to the legions of bacteria that live on and in our bodies because of research that’s shown us the many important roles they play in everything from how we efficiently metabolize food to how well we fend off disease. And, as it turns out, bacteria may not be the only interior bugs with the power to influence our biology positively—a new study suggests that an entirely different kingdom of primarily single-celled microbes, called protists, may be in on the act.

In a study published in the journal Cell, an NIH-funded research team reports that it has identified a new protozoan, called Tritrichomonas musculis (T. mu), living inside the gut of laboratory mice. That sounds bad—but actually this little wriggler was potentially providing a positive benefit to the mice. Not only did T. mu appear to boost the animals’ immune systems, it spared them from the severe intestinal infection that typically occurs after eating food contaminated with toxic Salmonella bacteria. While it’s not yet clear if protists exist that can produce similar beneficial effects in humans, there is evidence that a close relative of T. mu frequently resides in the intestines of people around the world.

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Gene Drive Research Takes Aim at Malaria

Mosquitoes and a Double HelixMalaria has afflicted humans for millennia. Even today, the mosquito-borne, parasitic disease claims more than a half-million lives annually [1]. Now, in a study that has raised both hope and concern, researchers have taken aim at this ancient scourge by using one of modern science’s most powerful new technologies—the CRISPR/Cas9 gene-editing tool—to turn mosquitoes from dangerous malaria vectors into allies against infection [2].

The secret behind this new strategy is the “gene drive,” which involves engineering an organism’s genome in a way that intentionally spreads, or drives, a trait through its population much faster than is possible by normal Mendelian inheritance. The concept of gene drive has been around since the late 1960s [3]; but until the recent arrival of highly precise gene editing tools like CRISPR/Cas9, the approach was largely theoretical. In the new work, researchers inserted into a precise location in the mosquito chromosome, a recombinant DNA segment designed to block transmission of malaria parasites. Importantly, this segment also contained a gene drive designed to ensure the trait was inherited with extreme efficiency. And efficient it was! When the gene-drive engineered mosquitoes were mated with normal mosquitoes in the lab, they passed on the malaria-blocking trait to 99.5 percent of their offspring (as opposed to 50 percent for Mendelian inheritance).

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Enlisting mHealth in the Fight Against River Blindness

CellScope Loa

When it comes to devising new ways to provide state-of-the art medical care to people living in remote areas of the world, smartphones truly are helping scientists get smarter. For example, an NIH-supported team working in Central Africa recently turned an iPhone into a low-cost video microscope capable of quickly testing to see if people infected with a parasitic worm called Loa loa can safely receive a drug intended to protect them from a different, potentially blinding parasitic disease.

As shown in the video above, the iPhone’s camera scans a drop of a person’s blood for the movement of L. loa worms. Customized software then processes the motion to count the worms (see the dark circles) in the blood sample and arrive at an estimate of the body’s total worm load. The higher the worm load, the greater the risk of developing serious side effects from a drug treatment for river blindness, also known as onchocerciasis.

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