Quantification of Toxins in Soapberry (Sapindaceae) Arils: Hypoglycin A and Methylenecyclopropylglycine

A sensitive LC-MS/MS method for the quantification of the plant toxins hypoglycin A and methylenecyclopropylglycine and their metabolites in cow's milk and urine and application to farm milk samples from Germany

Hypoglycin A (HGA) and its homologue methylenecyclopropylglycine (MCPrG) are present in ackee and lychee as well as seeds, leaves, and seedlings of some maple (Acer) species. They are toxic to some animal species and humans. The determination of HGA, MCPrG, and their glycine and carnitine metabolites in blood and urine is a useful tool for screening for potential exposure to these toxins. In addition, HGA, MCPrG, and/or their metabolites have been detected in milk. In this work, simple and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) methods without derivatization were developed and validated for the quantification of HGA, MCPrG, and their metabolites in cow's milk and urine. An extraction procedure from milk samples has been developed, whereas a dilute-and-shoot approach was implemented for urine samples. For quantification, the MS/MS analysis was performed in multiple reaction monitoring mode. The methods were validated according to the European Union guidelines using blank raw milk and urine as matrices. The limit of quantification presented here for HGA in milk (1.12 µg/L) is noticeably lower than the lowest published limit of detection (9 µg/L). Acceptable values for recovery (89-106% and 85-104% in milk and urine, respectively) and precision (≤ 20%) were obtained for all the quality control levels. The stability of HGA and MCPrG in frozen milk over a period of 40 weeks has been demonstrated. The method was applied to 68 milk samples from 35 commercial dairy farms and showed the absence of any quantifiable amounts of HGA, MCPrG, and their metabolites.

Characterization of different parts of litchi fruit using UHPLC-QExactive Orbitrap

Litchi fruit is consumed across the globe for its high nutritional value and taste. The qualitative profiling of litchi fruit has been carried out by using ultra-high-performance liquid chromatography with QExactive high-resolution accurate mass spectrometry. Acidified water: methanol: acetonitrile (1:1:1) extracts from individual parts (skin, pulp, and seed) of matured litchi, were subjected to LC-MS analysis with electrospray ionization in full MS-ddMS2 mode as a non-target approach. The data was processed through compound discoverer software by the use of mzCloud and ChemSpider databases, for compound identification. We identified 77 compounds with protonated or deprotonated forms based on the polarity and their characteristic fragments are within ± 4 ppm mass error and retention time ± 0.1 min for parent and fragments. Hypoglycin B is the first time reported in litchi fruit along with hypoglycin A. Further, we verified the distribution of the identified components and differentiation of three different parts of litchi through principal component analysis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05577-z.

Co-Occurrence of Hypoglycin A and Hypoglycin B in Sycamore and Box Elder Maple Proved by LC-MS/MS and LC-HR-MS

Hypoglycin A (HGA) and methylenecyclpropylglycine (MCPrG) are formed by some maple trees (Acer species) and have been associated with incidences of atypical myopathy among horses in pastures. In this work, a simple and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method without derivatization was developed for the quantification of HGA and MCPrG in maple samples and validated according to EU guidelines. The LOQ presented here for HGA (16.4 µg/kg) is considerably lower than the lowest published LOQ (500 µg/kg). This method confirms that sycamore and box elder maple contain considerable amounts of HGA and MCPrG. In addition, the presence of the dipeptides hypoglycin B and γ-glutamyl-MCPrG in these two maple species is shown using high-resolution MS. This is the first report on the presence of these dipeptides in maple since 1973. The presence of HGB and γ-glutamyl-MCPrG could change the way we understand animal intoxication following the ingestion of maple.

Acer pseudoplatanus: A Potential Risk of Poisoning for Several Herbivore Species

Acer pseudoplatanus is a worldwide-distributed tree which contains toxins, among them hypoglycin A (HGA). This toxin is known to be responsible for poisoning in various species, including humans, equids, Père David's deer and two-humped camels. We hypothesized that any herbivore pasturing with A. pseudoplatanus in their vicinity may be at risk for HGA poisoning. To test this hypothesis, we surveyed the HGA exposure from A. pseudoplatanus in species not yet described as being at risk. Animals in zoological parks were the major focus, as they are at high probability to be exposed to A. pseudoplatanus in enclosures. We also searched for a toxic metabolite of HGA (i.e., methylenecyclopropylacetyl-carnitine; MCPA-carnitine) in blood and an alteration of the acylcarnitines profile in HGA-positive animals to document the potential risk of declaring clinical signs. We describe for the first instance cases of HGA poisoning in Bovidae. Two gnus (Connochaetes taurinus taurinus) exposed to A. pseudoplatanus in their enclosure presented severe clinical signs, serum HGA and MCPA-carnitine and a marked modification of the acylcarnitines profile. In this study, even though all herbivores were exposed to A. pseudoplatanus, proximal fermenters species seemed less susceptible to HGA poisoning. Therefore, a ruminal transformation of HGA is hypothesized. Additionally, we suggest a gradual alteration of the fatty acid metabolism in case of HGA poisoning and thus the existence of subclinical cases.

Phytochemical screening of aqueous leaf extract of Blighia sapida K.D. Koenig (Sapindaceae) and its analgesic property in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Blighia sapida is traditionally used in treating intercostal pain, psychosis, stomach ache, back pain, and skin diseases. However, there is limited information on the scientific basis for its use traditionally in the treatment of pain.

AIM OF STUDY

To identify the major constituents in the aqueous leaf extract of Blighia sapida (AEBS) and to assess its analgesic properties in mice.

MATERIALS AND METHODS

Bioactive compounds were identified and quantified in AEBS by High Performance Liquid Chromatography/Photodiode Array Detector (HPLC/DAD). Analgesic activity of AEBS was assessed at doses of 125, 250, and 500 mg/kg p.o., using animal models.

RESULTS

Chlorogenic acid, saponins, tannins, caffeic acid, quercetin, gallic acid, pyrogallol, quinine, caffeine, and nicotine were identified. At doses 250 mg/kg (p < 0.05) and 500 mg/kg (p < 0.01), AEBS significantly inhibited acetic acid induced writhing in comparison with the control. It also significantly inhibited pain in the inflammatory phase of the formalin induced paw licking test at 250 mg/kg (p < 0.01) and 500 mg/kg (p < 0.05) doses, in comparison with the control. It did not inhibit pain in the neurogenic phase of the formalin paw licking and in the hot plate tests.

CONCLUSION

Blighia sapida leaf extract possesses analgesic activity that is mediated by peripheral mechanisms but not through central mechanisms.

Grazing Mares on Pasture with Sycamore Maples: A Potential Threat to Suckling Foals and Food Safety through Milk Contamination

Simple Summary

Equine atypical myopathy is seasonal poisoning resulting from the ingestion of seeds and seedlings of the sycamore maple that contains toxins. Literature mentions several cases of intoxication among gravid mares and in unweaned foals. The objective of this study was to determine whether the toxins responsible for atypical myopathy could pass to the foal via suckling. Four mares that were pasturing with sycamore in the vicinity were milked. Analysis revealed the presence of toxins in milk. This unprecedented observation could partially explain cases of unweaned foals suffering from atypical myopathy. However, a transplacental transfer of the toxin cannot be excluded for newborn cases. Besides being a source of contamination for offspring, milk contamination by toxins from fruits of trees of the Sapindaceae family might constitute a potential risk for food safety regarding other species’ raw milk or dairy products.

Abstract

Equine atypical myopathy (AM) is seasonal intoxication resulting from the ingestion of seeds and seedlings of the sycamore maple (Acer pseudoplatanus) that contain toxins, among them, hypoglycin A (HGA). Literature mentions several cases of AM among gravid mares and in unweaned foals. The objective of this study was to determine whether HGA and/or its metabolite are present in milk from grazing mares exposed to sycamore maple trees as confirmed by detection of HGA and its metabolite in their blood. Four mare/foal couples were included in the study. Both HGA and its metabolite were detectable in all but one of the milk samples. To our knowledge, this is the first study describing transfer of HGA to the milk. This unprecedented observation could partially explain cases of unweaned foals suffering from AM. However, a transplacental transfer of the toxin cannot be excluded for newborn foals. Besides being a source of contamination for offspring, milk contamination by toxins from fruits of trees of the Sapindaceae family might constitute a potential risk for food safety regarding other species’ raw milk or dairy products.

Methylenecyclopropylglycine and hypoglycin A intoxication in three Pére David's Deers (Elaphurus davidianus) with atypical myopathy

BACKGROUND

Hypoglycin A (HGA) and methylenecyclopropylglycine (MCPrG) from seeds/seedlings of Sycamore maple (SM, Acer pseudoplatanus) causes atypical myopathy (AM) in horses. AM was not known to occur in wild ruminants until several fatalities in milus (Elaphurus davidianus) following the ingestion of HGA in SM seeds. However, a role for MCPrG has not previously been evaluated.

OBJECTIVES

To test the hypothesis that MCPrG is also a major factor in AM in milus, three milus (M1, M2, M3) from the Zoo Dresden (aged 7-11 years, 2 females and 1 male, in good nutritional condition) that developed AM were studied.

METHODS

Serum, urine and methanol extracts from the liver, kidney, rumen digesta and faeces were analysed by ultrahigh-performance liquid chromatography-tandem mass spectrometry for HGA, MCPrG and for conjugates of carnitine (C) and glycine (G): Methylenecyclopropylacetyl (MCPA)-G, MCPA-C, Methylenecyclopropylformyl (MCPF)-G, MCPF-C, butyryl-C and isobutyryl-C.

RESULTS

HGA in serum was high (M2 480 nmol/L; M3 460 nmol/L), but MCPrG was not. HGA and MCPrG were found in rumen and faeces extracts, and MCPrG was also identified in the liver. Metabolites of HGA and MCPrG were high in serum, urine and liver, but not in the rumen or faeces.

CONCLUSIONS

This study shows that MCPrG is involved in the pathophysiology of AM in milus. The metabolism of MCPrG is considered to be faster because, after ingestion, the specific metabolites appear highly concentrated in the serum. The high toxin concentration in the liver suggests that a possible transfer into products for human consumption may pose a risk.

Study on the Metabolic Effects of Repeated Consumption of Canned Ackee

Ackee fruits (Blighia sapida), an important food source in some tropical countries, can be the cause of serious poisoning. Ackees contain hypoglycin A and methylenecyclopropylglycine. Experiments were undertaken by a volunteer to elucidate the metabolic details of poisoning. Rapid intestinal absorption of the toxins was followed by their slow degradation to methylenecyclopropylacetyl and methylenecyclopropylformyl conjugates. Impairment of the metabolism of branched chain amino acids and ß-oxidation of fatty acids was found. Reduced enzyme activities were observed for several days after ingestion. A defined dose of fruit material caused significantly higher concentrations of metabolites when consumed 24 h after a previous ingestion than when consumed only once. The accumulation of toxins, toxin metabolites, and products of the intermediate metabolism after repeated consumption may, at least partly, explain the high frequency of fatal cases observed during harvesting. No inhibition of enzymes that degrade long-chain acyl compounds was observed in the experiments.

Detection of toxic methylenecyclopropylglycine and hypoglycin A in litchi aril of three Chinese cultivars

As a subtropical fruit with high commercial values, litchi is also a source of methylenecyclcopropylglycine (MCPG) and hypoglycin A (HGA), which could cause hypoglycemia and fatal encephalopathy in human. In this work, a quantitative method was developed well to detect MCPG and HGA present in litchi aril of different cultivars. Method validation was evaluated well by linearity, recovery, precision and sensitivity. Among three cultivars, 'Feizixiao' contained the highest toxin level with 0.60-0.83 mg kg^-1 of MCPG and 10.66-14.46 mg kg^-1 of HGA, followed by 'Huaizhi' with 0.08-0.12 mg kg^-1 of MCPG and 0.63-1.54 mg kg^-1 of HGA, and 'Nuomici' with 0.09-0.11 mg kg^-1 of MCPG and 0.35-0.91 mg kg^-1 of HGA. The toxin levels were highly associated with litchi cultivar and storage time. These findings can provide new knowledge to help to recommend the safe consumption of fresh litchi based on human health.

Detection of hypoglycin A and MCPA-carnitine in equine serum and muscle tissue: Optimisation and validation of a LC-MS-based method without derivatisation

BACKGROUND

Measurement of hypoglycin A (HGA) and its toxic metabolite, methylenecyclopropylacetic acid (MCPA), in equine serum confirms a diagnosis of atypical myopathy (AM), a pasture-associated toxic rhabdomyolysis with high mortality linked to the ingestion of Acer trees plant material. Supportive diagnostic tests include plasma acyl-carnitine profiling and urine organic acid testing, but these are not specific for AM. Previously reported HGA and MCPA analytical techniques used liquid chromatography-mass spectrometry (LC-MS) with a derivatising step, but the latter prolongs testing and increases costs.

OBJECTIVES

To develop a rapid LCMS method for detection of serum and tissue HGA and MCPA that enables expedited diagnosis for horses with AM.

STUDY DESIGN

Analytical test validation.

METHODS

Validation parameters to industry standards using as criteria precision, accuracy, linearity, reproducibility and stability in analyte-spiked samples were calculated on 9-calibration points and 3 different validation concentrations in both serum and muscle tissue.

RESULTS

The test was successfully validated for the detection of HGA and MCPA-carnitine in equine serum and muscle. Test linearity was excellent (r²  = .999), accuracy was very good for both analytes (93%-108%), precision did not exceed 10% coefficient of variation and reproducibility met the requirements of the Horwitz equation. Stability was unaffected by storage at a range of temperatures.

MAIN LIMITATIONS

The spectrum of the tested analytes was limited to only two relevant analytes in favour of a quick and easy analysis. Linearity of the muscle method was not evaluated as calibration curves were not produced in this matrix.

CONCLUSION

We report an optimised, simplified and validated method for detection of HGA and MCPA-carnitine in equine serum and muscle suitable for rapid diagnosis of suspected AM cases. The serum-based test should also enable risk assessment of toxin exposure in cograzing horses and assessment of horses with undiagnosed myopathies, while the tissue detection test should help to confirm cases post-mortem and to determine toxin distribution, metabolism and clearance across different tissues.

Acute encephalopathy in children in Muzaffarpur, India: a review of aetiopathogenesis

The acute encephalopathy occurring in children in Muzaffarpur, India, also recognised in other litchi-cultivating areas of India, Bangladesh, Vietnam and China, had previously been linked to litchi consumption. Recently, it has been identified as hypoglycaemic encephalopathy of an unusual aetiology with three key factors: undernutrition, prolonged fasting and litchi consumption. A second set of investigators has independently reconfirmed the diagnosis and the three-factor aetiology. Skipping the evening meal with an intake of large amounts of litchi in undernourished children is causative. Early-morning hypoglycaemia with an inadequate glycogen store leads to initiation of gluconeogenesis and fatty acid β-oxidation, but methylene cyclopropyl alanine and glycine present in the litchi aril block the fatty acid β-oxidation cycle. The outcomes are uncorrected hypoglycaemia and encephalopathy due to the entry of metabolic intermediates that cross the blood-brain barrier and affect neuronal function. Suggested measures include early 10% dextrose infusion. Awareness about the disease is of prime importance. The diagnosis and aetiopathogenesis are still under question from a part of the scientific community. This review was undertaken to present a comprehensive view of hypoglycaemic encephalopathy and to remove some of the lingering doubts.

A new method for quantifying causative and diagnostic markers of methylenecyclopropylglycine poisoning

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Quantification of methylenecyclopropylglycine by tandem mass spectrometry.

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Combined measurement of acyl compounds and toxins of Sapindaceae.

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Rapid diagnosis of soapberry poisoning by serum and urine analysis.

Background

Up to now quantification of hypoglycin A in serum and urine in the range of nmols to μmols per liter plus the measurement of accumulated acyl conjugates have been used for the diagnosis of poisoning by fruits or seeds ofSapindaceae in humans and animals. A second poison, methylenecyclopropylglycine, however, is known to occur in this material. The objective of our study was to develop and evaluate a method for the quantification of this compound suitable for test materials obtained from animals and man.

Method

Methylenecyclopropylglycine was extracted from serum and urine of a volunteer by a methanolic solution containing labeled methylenecyclopropylglycine as internal standard. UPLC-MS/MS analysis was performed after butylation.

Results

Lower limits of detection and quantification were found at 0.5 and 2.5 nmol/L respectively in both urine and serum for each of two isomers, linearity of results (r² > 0.998) was demonstrated for the range of 0.5–500 nmol/L in urine and serum.

The method was applied to urine and serum of horses poisoned by Acer seeds, methylenecyclopropylglycine was found in addition to hypoglycin A. Methylenecyclopropylformyl glycine, a metabolite of methylenecyclopropylglycine, however, was present in much higher concentrations than methylenecyclopropylglycine in all but one samples.

Conclusions

Quantification of methylenecyclopropylglycine can be successfully integrated into our established analytical procedure used for clinical diagnosis of Sapindaceae poisoning. The extended method will improve disease evaluation in humans and animals.

Hypoglycemic Toxins and Enteroviruses as Causes of Outbreaks of Acute Encephalitis-Like Syndrome in Children, Bac Giang Province, Northern Vietnam

We investigated the cause of seasonal outbreaks of pediatric acute encephalitis-like syndrome associated with litchi harvests (May–July) in northern Vietnam since 2008. Nineteen cerebrospinal fluid samples were positive for human enterovirus B, and 8 blood samples were positive for hypoglycemic toxins present in litchi fruits. Patients who were positive for hypoglycemic toxins had shorter median times between disease onset and admission, more reports of seizures, more reports of hypoglycemia (glucose level <3 mmol/L), lower median numbers of leukocytes in cerebrospinal fluid, and higher median serum levels of alanine aminotransferase and aspartate transaminase than did patients who were positive for enteroviruses. We suggest that children with rapidly progressing acute encephalitis-like syndrome at the time of the litchi harvest have intoxication caused by hypoglycemic toxins, rather than viral encephalitis, as previously suspected. These children should be urgently treated for life-threatening hypoglycemia.

Detection of MCPG metabolites in horses with atypical myopathy

Atypical myopathy (AM) in horses is caused by ingestion of seeds of the Acer species (Sapindaceae family). Methylenecyclopropylacetyl-CoA (MCPA-CoA), derived from hypoglycin A (HGA), is currently the only active toxin in Acer pseudoplatanus or Acer negundo seeds related to AM outbreaks. However, seeds or arils of various Sapindaceae (e.g., ackee, lychee, mamoncillo, longan fruit) also contain methylenecyclopropylglycine (MCPG), which is a structural analogue of HGA that can cause hypoglycaemic encephalopathy in humans. The active poison formed from MCPG is methylenecyclopropylformyl-CoA (MCPF-CoA). MCPF-CoA and MCPA-CoA strongly inhibit enzymes that participate in β-oxidation and energy production from fat. The aim of our study was to investigate if MCPG is involved in Acer seed poisoning in horses. MCPG, as well as glycine and carnitine conjugates (MCPF-glycine, MCPF-carnitine), were quantified using high-performance liquid chromatography-tandem mass spectrometry of serum and urine from horses that had ingested Acer pseudoplatanus seeds and developed typical AM symptoms. The results were compared to those of healthy control horses. For comparison, HGA and its glycine and carnitine derivatives were also measured. Additionally, to assess the degree of enzyme inhibition of β-oxidation, several acyl glycines and acyl carnitines were included in the analysis. In addition to HGA and the specific toxic metabolites (MCPA-carnitine and MCPA-glycine), MCPG, MCPF-glycine and MCPF-carnitine were detected in the serum and urine of affected horses. Strong inhibition of β-oxidation was demonstrated by elevated concentrations of all acyl glycines and carnitines, but the highest correlations were observed between MCPF-carnitine and isobutyryl-carnitine (r = 0.93) as well as between MCPA- (and MCPF-) glycine and valeryl-glycine with r = 0.96 (and r = 0.87). As shown here, for biochemical analysis of atypical myopathy of horses, it is necessary to take MCPG and the corresponding metabolites into consideration.

Quantitative HPLC-MS/MS analysis of toxins in soapberry seeds: Methylenecyclopropylglycine and hypoglycin A

Methylenecyclcopropylglycine (MCPG) and hypoglycin A (HGA) are naturally occurring amino acids found in various soapberry (Sapindaceae) fruits. These toxins have been linked to illnesses worldwide and were recently implicated in Asian outbreaks of acute hypoglycemic encephalopathy. In a previous joint agricultural and public health investigation, we developed an analytical method capable of evaluating MCPG and HGA concentrations in soapberry fruit arils as well as a clinical method for the urinary metabolites of the toxins. Since the initial soapberry method only analyzed the aril portion of the fruit, we present here the extension of the method to include the fruit seed matrix. This work is the first method to quantitate both MCPG and HGA concentrations in the seeds of soapberry fruit, including those collected during a public health investigation. Further, this is the first quantitation of HGA in litchi seeds as well as both toxins in mamoncillo and longan seeds.

Quantification of hypoglycin A and methylenecyclopropylglycine in human plasma by HPLC-MS/MS

Hypoglycin A (HGA) and methylenecyclopropylglycine (MCPG) are naturally-occurring amino acids known to cause hypoglycemia and encephalopathy. Exposure to one or both toxins through the ingestion of common soapberry (Sapindaceae) fruits are documented in illness outbreaks throughout the world. Jamaican Vomiting Sickness (JVS) and seasonal pasture myopathy (SPM, horses) are linked to HGA exposure from unripe ackee fruit and box elder seeds, respectively. Acute toxic encephalopathy is linked to HGA and MCPG exposures from litchi fruit. HGA and MCPG are found in several fruits within the soapberry family and are known to cause severe hypoglycemia, seizures, and death. HGA has been directly quantified in horse blood in SPM cases and in human gastric juice in JVS cases. This work presents a new diagnostic assay capable of simultaneous quantification of HGA and MCPG in human plasma, and it can be used to detect patients with toxicity from soapberry fruits. The assay presented herein is the first quantitative method for MCPG in blood matrices.

Detection of equine atypical myopathy-associated hypoglycin A in plant material: Optimisation and validation of a novel LC-MS based method without derivatisation

Hypoglycin A (HGA) toxicity, following ingestion of material from certain plants, is linked to an acquired multiple acyl-CoA dehydrogenase deficiency known as atypical myopathy, a commonly fatal form of equine rhabdomyolysis seen worldwide. Whilst some plants are known to contain this toxin, little is known about its function or the mechanisms that lead to varied HGA concentrations between plants. Consequently, reliable tools to detect this amino acid in plant samples are needed. Analytical methods for HGA detection have previously been validated for the food industry, however, these techniques rely on chemical derivatisation to obtain accurate results at low HGA concentrations. In this work, we describe and validate a novel method, without need for chemical derivatisation (accuracy = 84-94%; precision = 3-16%; reproducibility = 3-6%; mean linear range R2 = 0.999). The current limit of quantitation for HGA in plant material was halved (from 1μg/g in previous studies) to 0.5μg/g. The method was tested in Acer pseudoplatanus material and other tree and plant species. We confirm that A. pseudoplatanus is most likely the only source of HGA in trees found within European pastures.

Quantification of Methylenecyclopropyl Compounds and Acyl Conjugates by UPLC-MS/MS in the Study of the Biochemical Effects of the Ingestion of Canned Ackee (Blighia sapida) and Lychee (Litchi chinensis)

Consumption of ackee (Blighia sapida) and lychee (Litchi chinensis) fruit has led to severe poisoning. Considering their expanded agricultural production, toxicological evaluation has become important. Therefore, the biochemical effects of eating 1 g/kg canned ackee, containing 99.2 μmol/kg hypoglycin A, and 5 g/kg canned lychee, containing 1.3 μmol/kg hypoglycin A, were quantified in a self-experiment. Using ultra-high-performance liquid chromatography/mass spectrometry, hypoglycin A, methylenecyclopropylacetyl-glycine, and methylenecyclopropylformyl-glycine, as well as the respective carnitine conjugates, were found in urine after ingesting ackee. Hypoglycin A and its glycine derivative were also present in urine after eating lychee. Excretion of physiological acyl conjugates was significantly increased in the ackee experiment. Ingestion of ackee led to up to 15.1 nmol/L methylenecyclopropylacetyl-glycine and traces of methylenecyclopropylformyl-carnitine in the serum. These compounds were not found in the serum after eating lychee. Hypoglycin A accumulated in the serum in both experiments.

Association of acute toxic encephalopathy with litchi consumption in an outbreak in Muzaffarpur, India, 2014: a case-control study

BACKGROUND

Outbreaks of unexplained illness frequently remain under-investigated. In India, outbreaks of an acute neurological illness with high mortality among children occur annually in Muzaffarpur, the country's largest litchi cultivation region. In 2014, we aimed to investigate the cause and risk factors for this illness.

METHODS

In this hospital-based surveillance and nested age-matched case-control study, we did laboratory investigations to assess potential infectious and non-infectious causes of this acute neurological illness. Cases were children aged 15 years or younger who were admitted to two hospitals in Muzaffarpur with new-onset seizures or altered sensorium. Age-matched controls were residents of Muzaffarpur who were admitted to the same two hospitals for a non-neurologic illness within seven days of the date of admission of the case. Clinical specimens (blood, cerebrospinal fluid, and urine) and environmental specimens (litchis) were tested for evidence of infectious pathogens, pesticides, toxic metals, and other non-infectious causes, including presence of hypoglycin A or methylenecyclopropylglycine (MCPG), naturally-occurring fruit-based toxins that cause hypoglycaemia and metabolic derangement. Matched and unmatched (controlling for age) bivariate analyses were done and risk factors for illness were expressed as matched odds ratios and odds ratios (unmatched analyses).

FINDINGS

Between May 26, and July 17, 2014, 390 patients meeting the case definition were admitted to the two referral hospitals in Muzaffarpur, of whom 122 (31%) died. On admission, 204 (62%) of 327 had blood glucose concentration of 70 mg/dL or less. 104 cases were compared with 104 age-matched hospital controls. Litchi consumption (matched odds ratio [mOR] 9·6 [95% CI 3·6 - 24]) and absence of an evening meal (2·2 [1·2-4·3]) in the 24 h preceding illness onset were associated with illness. The absence of an evening meal significantly modified the effect of eating litchis on illness (odds ratio [OR] 7·8 [95% CI 3·3-18·8], without evening meal; OR 3·6 [1·1-11·1] with an evening meal). Tests for infectious agents and pesticides were negative. Metabolites of hypoglycin A, MCPG, or both were detected in 48 [66%] of 73 urine specimens from case-patients and none from 15 controls; 72 (90%) of 80 case-patient specimens had abnormal plasma acylcarnitine profiles, consistent with severe disruption of fatty acid metabolism. In 36 litchi arils tested from Muzaffarpur, hypoglycin A concentrations ranged from 12·4 μg/g to 152·0 μg/g and MCPG ranged from 44·9 μg/g to 220·0 μg/g.

INTERPRETATION

Our investigation suggests an outbreak of acute encephalopathy in Muzaffarpur associated with both hypoglycin A and MCPG toxicity. To prevent illness and reduce mortality in the region, we recommended minimising litchi consumption, ensuring receipt of an evening meal and implementing rapid glucose correction for suspected illness. A comprehensive investigative approach in Muzaffarpur led to timely public health recommendations, underscoring the importance of using systematic methods in other unexplained illness outbreaks.

FUNDING

US Centers for Disease Control and Prevention.