Acute encephalitis syndrome (AES) explained: Definition, cause, and its contrary theorieshttps://indianexpress.com/article/explained/explained-what-is-acute-encephalitis-syndrome-bihar-symptoms-causes-treatment-5779371/

Acute encephalitis syndrome (AES) explained: Definition, cause, and its contrary theories

Acute encephalitis syndrome (AES) affects central nervous system, mostly in children and young adults. It starts with high fever, then hampers neurological functions causing mental disorientation, seizure, confusion, delirium, coma.

What is acute encephalitis syndrome?
Acute encephalitis syndrome: According to National Vector Borne Diseases Control Programme (NVBDCP), 10,485 AES cases were diagnosed in 2018 with 632 deaths across 17 states.

Bihar has recorded 188 cases of acute encephalitis syndrome, with 45 deaths, since January. All casualties are children, the maximum in Muzaffarpur— 43 recorded in June. AES outbreaks in Muzaffarpur have been reported since 1995, National Centre for Disease Control officials say. The cause of death in most this year has been attributed to hypoglycaemia (low blood sugar level). What relation does hypoglycaemia have in these deaths and what theories researchers have?

What is acute encephalitis syndrome (AES)?

AES affects central nervous system, mostly in children and young adults. It starts with high fever, then hampers neurological functions causing mental disorientation, seizure, confusion, delirium, coma. The disease outbreak is usually reported during monsoons (June-October). But the incidence is also reported during April-June in Bihar.

What causes AES?

This syndrome is very complex. It can be caused by virus, bacteria, fungi, and a range of agents. Japanese encephalitis (JE) virus is the most common cause of AES in India, with union health ministry estimate attributing 5-35 per cent cases due to JE. But the syndrome is also caused by scrub typhus, dengue, mumps, measles, even Nipah or Zika virus. In several cases though the cause of AES remains clinically unidentified.

Status of AES in India

According to National Vector Borne Diseases Control Programme (NVBDCP), 10,485 AES cases were diagnosed in 2018 with 632 deaths across 17 states. India records fatality rate at 6 per cent in AES, but the fatality rises to 25 per cent amongst children. Bihar, Assam, Jharkhand, Uttar Pradesh, Manipur, Meghalaya, Tamil Nadu, Karnataka, and Tripura are worst affected.

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Relation between hypoglycaemia, children and AES

Bihar government officials claim AES is a syndrome not disease, and cause of death in these children was found to be prolonged hypoglycaemia that witnessed delayed treatment. In 2014 research paper titled ‘Epidemiology of Acute Encephalitis Syndrome in India: Changing Paradigm and Implication for Control’, coauthored by six researchers, a parallel was drawn between Muzaffarpur and Vietnam’s Bac Giang province where undernourished children were suffering from AES and hypoglycaemia that coincided with litchi orchards in neighbourhood. “The possible association with some toxin in litchi or in environment need to be documented. Methylene cyclopropyl glycine (MCPG) which has been known to be a content of litchi fruit has been shown to cause hypoglycaemia in experimental animals,” the study stated. Several children in Muzaffarpur who suffer from AES before 2014 have a history of visit to litchi orchards, the study found. The impact is worse on undernourished children who remain hungry for several hours.

Contrary theories

Dr Ragini Mishra, Bihar state surveillance officer, says if toxins from Litchi were affecting children, then the AES cases should remain consistent each year and affect children of all socio-economic strata. This year’s deaths have all been recorded in lower income groups. “Last year we had very few cases, mortality was less. We believe there is some correlation between high temperature and AES. Last year hot days were followed by rain showers. This year, the heat has been prolonged with no spells of rain,” she told The Indian Express. Government data shows, at least 98 per cent of children with AES getting hospitalised also suffer from hypoglycaemia. Maximum children affected fall under 0-2 age bracket. Mishra adds that an AIIMS Patna study is pointing at presence of enterovirus. “It may have some co-relation. We are yet to study in detail,” Mishra said.

Malnourishment a key

“Association of litchi and deaths due to infectious organism present in it is well documented, but we cannot attribute only this factor as cause of death. There are multiple factors,” says infectious diseases expert Dr Om Srivastava. He added that hypoglycaemia in itself is not a sufficient reason to explain death unless the condition is prolonged and cannot be corrected. “There are other contributing factors that increase risk of death. Under-nutrition is one,” he said. Dr Arun Shah, former Bihar president of Indian Academy of Paediatrics Association, said, “A Centre for Disease Control, Atlanta team, and CMC Vellore’s virologist Dr Jacob John’s findings in past have narrowed down to malnutrition, heat, humidity and poor hygiene as reasons of AES”. AES onset is reported mostly in mornings, especially when a child goes without food the previous night and the sugar level in blood dips further. “A malnourished child has no buffer stock of sugar in liver,” Shah explains. He claims though eating litchi or its seeds has nothing to do with AES, it is possible that malnourished children who eat unripe or rotten litchi may record an aggravated AES because of toxins (MCPG) present in litchi.