A mysterious brain disease plaguing children in the Indian city of Muzaffarpur since 1995 is caused by eating lychee fruit on an empty stomach, a new study has proven.
Since 1995, children in Muzaffarpur started suddenly falling ill with an unknown disease. It manifested as seizures, most usually early in the day, and the children would often become comatose. The disease killed roughly 40% of those it affected. Infection also followed an unusual pattern, with outbreaks starting in mid-May and ending in July, year after year. Despite their efforts, researchers struggled to confirm the cause of these illnesses.
A new study has found that lychee fruits could be the cause of this illness. The team analyzed the cases of nearly 400 children who contacted the disease in 2014, and compared them to roughly 100 who didn't. Blood and spinal fluid samples retrieved from the sick kids didn't show any signs of an infection or pesticide poisoning. However, most of these children reported consuming lychee fruits shortly before falling ill. The researchers noticed this, so they asked about the fruit specifically.
Turns out children with the brain illness were almost 10 times more likely to have eaten lychee, and 6 times as likely to have visited a fruit orchard, in the 24 hours before they became ill compared with the healthy kids. Urine samples later showed that two-thirds of the sick children had been exposed to two toxins -- hypoglycin and methylenecyclopropyl glycine. Both of them can be found in high concentrations in lychee seeds, and even higher ones in the unripe fruits.
But a lot of people eat lychee and are just fine. More distressingly, children who had eaten from the same tree weren't all getting sick -- just some of them. The blood tests earlier did reveal that sick children had very low blood sugar levels, and other signs of metabolic problems. The researchers suspected that the other factor dictating whether someone would get sick was an empty stomach.
Their results showed that compared to those who didn't develop the illness, sick kids were twice as likely to have skipped dinner. The researchers said that this causes blood sugar levels to drop in the morning, so the body starts to process fatty acids into glucose. The lychee toxins however disrupted this process, causing blood sugar levels to plummet and causing brain inflammation in the children. This would explain why only some children fell ill, even when everybody was eating the fruits.
"Although [lychee] fruits are ubiquitous in the orchards surrounding the villages in rural Muzaffarpur, typically only one child in an entire village develops this acute illness," the researchers wrote in the Jan. 30 issue of the journal the Lancet Global Health.
"The synergistic combination of [lychee] consumption, a missed evening meal, and other potential factors such as poor nutritional status" and eating a greater number of lychees may be needed to produce the illness, they said.
The researchers recommended that children don't over-indulge on lychees, and that parents make sure they eat an evening meal to prevent new cases.
The full paper "Association of acute toxic encephalopathy with litchi consumption in an outbreak in Muzaffarpur, India, 2014: a case-control study" has been published in the journal The Lancet Global Health.