A medical investigation into the deaths of 13 children in Bangladesh in 2012 has now revealed that they were most probably caused by insecticides and not by litchi seeds.

The children, who were from a rural community in the Dinajpur District in northern Bangladesh, had all experienced acute encephalitis syndrome or AES – a condition associated with fatal inflammation of the brain. Fourteen children took ill between May 31 and June 30, 2012 and only one survived. All the deaths occurred within 20 hours of the onset of symptoms and were linked to exposure to the litchi fruit, which is cultivated across South Asia.

Similar deaths were recorded in Muzaffarpur, a district in Bihar, India. Analyses of those cases indicated that toxic compounds in the litchi fruit trigger low blood glucose levels in malnourished children who skipped evening meals leading to death.

However, a team of researchers from the International Centre for Diarrhoeal Disease Research and the Institute of Epidemiology Disease Control and Research in Bangladesh, and from the Centers for Disease Control and Prevention and Center for Innovation in Global Health in the United States have looked into the Bangladesh litchi deaths and found that the AES was probably triggered by excessive and improper applications of insecticides and other agriculture chemicals in local fruit orchards.

The researchers pointed out that the litchi the seeds were not eaten and if the seeds were the cause, then there would have been cases scattered across the country and not just in a certain small area.

The scientists discovered that the 2012 outbreak occurred during harvest time and growers were applying endosulfan in the orchards, a highly toxic insecticide that has been banned in more than 80 countries. In 2016, Bangladesh was one of several countries, including India and the United States, that still allowed restricted use of endosulfan.

Local residents told the investigators that it was common for children to play in the orchards and to eat fruit that had fallen on the ground without washing it, using their teeth to peel the tough skin. Moreover, several of the victims had family members who worked in the orchards and this could have increased exposures to insecticides through residues on clothing worn into the home.

The research team collected physical evidence from the orchards, which included discarded containers of insecticides and other chemicals. They interviewed residents t find that multiple chemicals were applied to the fruit and in amounts far greater than are normally used by other lychee producers. The study also found evidence that the lychee growers were applying an insecticide that had been approved only for use in cotton, not food crops.

The findings were published in the American Journal of Tropical Medicine and Hygiene. The scientists plan to conduct follow-up studies to get more biological evidence liver and brain biopsies of the victims.