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Lychee Fruit Identified As Culprit In Mysterious Illness Plaguing
Indian Children
A frightening and
mysterious outbreak that has plagued Muzaffarpur, India for over 20
years has been attributed to lychee consumption according to a recent
article in Lancet Global Health. Each year between May and
July, hundreds of children who went to bed seemingly healthy would
awake with acute neurological symptoms. Forty percent of them would
die. The illness was unique in that a single child in a village could
be struck leaving
siblings spared. Going back to 1995, the mysterious illness has been
attributed to everything from heat stroke to infection to pesticides.
“They were in a kind of panic,” said
Dr. Rajesh Yadav, an investigator with the India Epidemic
Intelligence Service, speaking to the New York Times. “Their children
were dying, and it was an unknown thing.”
Who
was on the Case?
A joint investigation by India’s National Center for Disease Control
and the India office of the Centers for Disease Control and Prevention
in Atlanta set out to crack the case. The results of the investigation
that carefully tracked the outbreak in the year 2014 were published
last month. Investigators identified consumption of the lychee, also
known as litchi, fruit as the culprit - particularly consumption of
the underripe fruit on an empty stomach. According to the New York
Times, “The Lancet article
walks through a two-year medical detective story, as epidemiologists
like Dr. Yadav closely examined the lives of hundreds of afflicted
children, trying to understand everything they had eaten, drunk and
breathed.” Below are key findings that helped unravel the mystery.
No signs of Infection
The first puzzling result was that these children showed no evidence
of infection. Many outbreaks of this nature are immediately assumed to
be caused by infection. Yet, the sick children were not febrile nor
did they have elevated white blood cell counts, both common indicators
of infection.
Abnormally Low Blood Glucose Levels
Next, investigators assayed for a large number of markers, casting a
wide net for hints. They found one in the form of strikingly low blood
glucose levels, and they found further that children with the lowest
levels were twice as likely to die.
Similarities to a Previous Outbreak
The final piece of the puzzle fell into place when investigators
recognized similarities to a previous outbreak in the West Indies. In
that case, the outbreak had been tied to a toxin found in the ackee
fruit. This toxin, hypoglycin, as well as a similar toxin,
methylenecyclopropyl glycine, are both found in the lychee fruit. The
toxins in the fruit can cause acute hypoglycemia through inhibition of
glucose synthesis. Following the development of a urinalysis test for
hypoglycin, remarkable abnormalities were found in the affected
children, strongly implicating consumption of lychee fruit on an empty
stomach as the cause of extreme hypoglycemia.
Limitations of the Findings
According to the study, “Parents in affected villages report that
during May and June, young children frequently spend their day eating
litchis in the surrounding orchards; many return home in the evening
uninterested in eating a meal.” This common behavioral pattern coupled
with the finding that only a single child from a village might be
affected suggests that more factors than simply lychee consumption and
a missed meal might contribute to susceptibility, including as yet
unidentified genetic differences. The authors also concede that,
“causality is considerably more difficult to establish,” but they
believe their, “findings reflect a plausible, but not necessarily
sufficient, causal pathway between lychee consumption and illness.
Further Implications of the Study
The authors of the study also reference similar outbreaks in other
lychee cultivation regions of India as well as Bangladesh and Vietnam
that have yet to be investigated as exhaustively as the outbreak in
Muzaffarpur. They suggest their findings may shed light on these
similar illnesses. In general, the Muzaffarpur outbreak truly
highlights the need for thorough investigation of unexplained
illnesses in resource-limited settings. The application of similar
systematic approaches has the potential to dramatically improve public
health outcomes.
Lancet Global Health Article
https://tinyurl.com/jdn8wqu
New York Times Coverage
https://tinyurl.com/z5a6nm3
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