August 09, 2017
2 min read

Encephalitis outbreak in Bangladesh linked to pesticide use in orchards

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Mohammed Saiful Islam

A 2012 outbreak of acute encephalitis syndrome in Bangladesh has been linked to the use of pesticides — some of which are banned in the country — in lychee orchards, according to a study published in the American Journal of Tropical Medicine and Hygiene.

The researchers point out that proximity to the orchards, not consumption of the fruit, was responsible for the onset of illness.

“A conventional epidemiological study focuses on identifying the proximate, individual-level risk factors of the outbreak that often ignores the context in which the outbreak occurred,” Mohammed Saiful Islam, MSS, MPH, associate scientist at the International Center for Diarrheal Disease Research in Bangladesh, and colleagues wrote. “To understand an outbreak thoroughly enough to devise prevention strategies, we often require individual-level risk factors that contributed the outbreak to occur.”

To describe clinical presentation of the cases and to examine individual-level risk factors, including behaviors and practices concerning lychee cultivation in communities, the researchers conducted a mixed-methods study. The outbreak of acute encephalitis syndrome affected 14 children, 13 of whom died. Unconsciousness, convulsion, excessive sweating and frothy discharge were the main symptoms witnessed, and the time of onset of unconsciousness from illness was a median 2.5 hours.

Researchers observed through village analysis that visiting a lychee orchard between 24 hours (adjusted OR = 11.6 [1.02-109.8]) and 3 days before onset (aOR = 7.2 [1.4-37.6]), as well as having family members who worked in a lychee orchard (aOR = 7.2 [1.7-29.4]) were risk factors associated with illness. Additionally, visiting any garden while pesticides were being applied up to 3 days before illness (aOR = 4.9 [1.0-19.4]) was correlated with acute encephalitis syndrome.

When neighborhoods were analyzed, researchers noted that the visitation of orchards that implemented pesticide in 3 days before onset of symptoms (aOR = 8.4 [1.4-49.9]) was connected to the outbreak; however, eating lychees was not related to the same outbreak.

“This study makes a strong case for the value of solid detective work and community engagement when investigating the causes of a dangerous and tragic public health crisis,” Patricia F. Walker, MD, DTM&H, FASTMH, said in a release regarding the study. “By working closely with the affected communities and earning their trust, researchers were able to identify the potential role of agricultural chemicals in this outbreak. Community education and improved oversight of pesticide use will be needed to help reduce the risk of future tragedy.” — by Katherine Bortz

Disclosure: The researchers provide no relevant financial disclosures.