A surreal illustration of glowing litchi fruits, symbolizing hidden danger in farmland.

The Litchi Fruit Encephalopathy Mystery: Is a Natural Toxin to Blame?

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Avery Sinclair in Health & Wellness December 2025 • 5 min read.

"Unraveling the truth behind the Muzaffarpur outbreaks and the surprising role of methylenecyclopropyl glycine (MCPG)"


Every year, the recurring outbreaks of hypoglycemic encephalopathy in Muzaffarpur and neighboring areas of Bihar, India, present a serious health challenge. These outbreaks, characterized by acute viral encephalitis that baffled researchers for years, have now been linked to a mysterious cause. For many years, a specific clinical diagnosis eluded medical experts, giving rise to what was known as a mystery disease.

Scientists have considered various explanations for the seasonal disease. Some of these explanations supported the diagnosis of AES, including viruses and contaminations. However, it became clear that the underlying cause was acute hypoglycemic encephalopathy. Researchers then noticed a connection between the disease and Vietnam and Bangladesh outbreaks. This sparked speculation that viruses or pesticides were to blame. Further investigation revealed that the cerebrospinal fluid of affected patients was free of viruses, prompting scientists to investigate pesticides as a probable culprit.

Interestingly, the outbreaks occurred during the litchi harvest season. There was a correlation between case numbers and the amount of litchi harvested in the affected regions. The symptoms of the puzzling Muzaffarpur acute hypoglycemic encephalopathy mirrored Jamaican Vomiting Sickness (JVS), which is also an acute hypoglycemic encephalopathy. Methylenecyclopropyl-alanine (MCPA), or hypoglycin A, is a poisonous chemical present in unripe ackee fruit that causes this disease.

MCPG: The Unexpected Culprit in Litchi Fruit

A surreal illustration of glowing litchi fruits, symbolizing hidden danger in farmland.

Ackee fruit (Blighia sapida, family Sapindaceae) is known to cause acute encephalopathy, also called JVS, according to research. (Tanaka et al., 1976). According to reports, unripe ackee fruit has a higher concentration of MCPA than ripe ackee fruit (Brown et al., 1992). Experts in phytotoxicology have also discovered a lower analog of hypoglycin A known as methylenecyclopropyl-glycine (MCPG) in Asian Litchi seeds (Litchi sinensis, Family Sapindaceae) (Gray and Fowden, 1962).

MCPG and MCPA can both cause hypoglycemia by impairing fatty acid oxidation in the liver mitochondria of test animals, which can result in encephalopathy. (Melde et al., 1989). It was proposed that MCPG in litchi may be the AES causative agent in Muzaffarpur. MCPG was found in litchi seeds, but the question of its existence in edible fruit pulp remained. Recent research has found that MCPG is present not only in litchi seeds but also in significant quantities in both semi-ripe and ripe litchi pulp. (Das et al., 2015). MCPG concentrations were higher in litchi seeds but were four to five times higher in semi-ripe pulp.

To determine whether pesticides or the presence of MCPG were to blame, researchers in Muzaffarpur tested both ripe and semi-ripe litchi fruits. The study discovered:
  • Malathion (0.18–0.19 µg/g) and p'-p'-DDT (0.022–0.023 µg/g) were found on the fruit cover of ripe and semi-ripe litchi.
  • There were no pesticide residues found in the pulp of ripe or semi-ripe litchi.
  • MCPG was discovered in litchi pulp, which could contribute to hypoglycemic encephalopathy.
  • MCPG's hypoglycemic impact was validated in vivo using preliminary weight and glucose measurements.
The study also looked at the amount of MCPG found in ripe and semi-ripe litchi pulp and discovered that it ranged from 0.19 µg/g to 0.57 µg/g. The researchers found that when the human condition was replicated in animals, starvation brought on a decline in glucose and body weight, which caused hypoglycemia in rats fed litchi seeds. These findings imply that eating undernourished semi-ripe and ripe litchi fruits causes hypoglycemic encephalopathy in Muzaffarpur.

A Path Forward in Protecting Vulnerable Populations

The study highlights that litchi fruit containing MCPG has more adverse effects to undernourished children than healthier ones. This situation can deplete the already compromised levels of glucose in the body, leading to the low levels of glucose in the brain. In order to raise awareness among farmers and their families, they must feed youngsters a cooked meal before night. If children start to exhibit symptoms of acute encephalopathy, giving them a 10% dextrose solution may also save the lives of the undernourished (Shah and John 2014). MCPG is the culprit in acute hypoglycemic encephalopathy, not pesticide exposure, as evidenced by dextrose therapy's restoration from the hypoglycemic condition. Raising awareness about the condition and ensuring prompt treatment may help lower morbidity and mortality rates among affected children.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

1

What is the connection between the Muzaffarpur outbreaks and litchi fruit?

The outbreaks of acute encephalopathy in Muzaffarpur, India, have been linked to the consumption of litchi fruit. Specifically, the presence of methylenecyclopropyl-glycine (MCPG), a natural toxin found in litchi, particularly in the seeds and semi-ripe pulp, has been identified as the primary cause of the hypoglycemic encephalopathy. The outbreaks occurred during the litchi harvest season, showing a correlation between case numbers and the amount of litchi harvested.

2

How does methylenecyclopropyl-glycine (MCPG) cause acute hypoglycemic encephalopathy?

MCPG, found in litchi seeds and pulp, causes hypoglycemia by impairing fatty acid oxidation in the liver mitochondria. This metabolic disruption leads to a decrease in glucose levels in the body, especially in undernourished children. The brain, highly dependent on glucose, suffers from this deficiency, resulting in encephalopathy. Studies show that MCPG concentrations are higher in semi-ripe litchi pulp than ripe ones, increasing the risk of the condition.

3

Were pesticides also considered as a cause for the outbreaks in Muzaffarpur, and what was the conclusion?

Yes, pesticides were initially considered a possible cause of the acute encephalopathy outbreaks in Muzaffarpur. Researchers investigated whether pesticides, such as malathion and p'-p'-DDT, found on the fruit cover, were responsible. However, tests on the pulp of ripe and semi-ripe litchi fruit revealed no pesticide residues. The focus then shifted to MCPG, which was discovered in the litchi pulp, making it the primary cause of the hypoglycemic encephalopathy.

4

What is the link between Jamaican Vomiting Sickness (JVS) and the Muzaffarpur outbreaks?

The symptoms of the Muzaffarpur acute hypoglycemic encephalopathy mirrored those of Jamaican Vomiting Sickness (JVS). JVS is also an acute hypoglycemic encephalopathy caused by methylenecyclopropyl-alanine (MCPA), also known as hypoglycin A, a toxin found in unripe ackee fruit. This parallel helped scientists understand the potential role of a natural toxin in litchi, analogous to the role of MCPA in ackee fruit, leading to the discovery of MCPG as the causative agent in the Muzaffarpur cases.

5

What preventative measures can be taken to protect children from the effects of MCPG in litchi fruit?

Preventative measures include ensuring that children, particularly those who are undernourished, are fed a cooked meal before bedtime. Since MCPG affects children more severely when their glucose levels are already compromised due to malnutrition. Furthermore, if a child exhibits symptoms of acute encephalopathy, administering a 10% dextrose solution can be a life-saving treatment. Raising awareness among farmers and their families about the risk of MCPG in litchi fruit is also critical in reducing morbidity and mortality rates.

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