Date Published: September 07, 2017
Publisher: The American Society of Tropical Medicine and Hygiene
Author(s): Mohammed Saiful Islam, Ahmad Raihan Sharif, Hossain M. S. Sazzad, A. K. M. Dawlat Khan, Murshid Hasan, Shirina Akter, Mahmudur Rahman, Stephen P. Luby, James D. Heffelfinger, Emily S. Gurley.
Recurrent outbreaks of acute encephalitis syndrome (AES) among children in lychee growing areas in Asia highlight the need to better understand the etiology and the context. We conducted a mixed-methods study to identify risk factors for disease, and behaviors and practices around lychee cultivation in an AES outbreak community in northern Bangladesh in 2012. The outbreak affected 14 children; 13 died. The major symptoms included unconsciousness, convulsion, excessive sweating, and frothy discharge. The median time from illness onset to unconsciousness was 2.5 hours. The outbreak corresponded with lychee harvesting season. Multiple pesticides including some banned in Bangladesh were frequently used in the orchards. Visiting a lychee orchard within 24 hours before onset (age-adjusted odds ratio [aOR] = 11.6 [1.02–109.8]) and 3 days (aOR = 7.2 [1.4–37.6]), and family members working in a lychee orchard (aOR = 7.2 [1.7–29.4]) and visiting any garden while pesticides were being applied (aOR = 4.9 [1.0–19.4]) in 3 days preceding illness onset were associated with illness in nearby village analysis. In neighborhood analysis, visiting an orchard that used pesticides (aOR = 8.4 [1.4–49.9]) within 3 days preceding illness onset was associated with illness. Eating lychees was not associated with illness in the case–control study. The outbreak was linked to lychee orchard exposures where agrochemicals were routinely used, but not to consumption of lychees. Lack of acute specimens was a major limitation. Future studies should target collection of environmental and food samples, acute specimens, and rigorous assessment of community use of pesticides to determine etiology.
Acute encephalitis syndrome (AES) affects approximately 133,000 children each year in Asia.1–3 Several different viruses, bacteria, fungus, parasites, chemicals, and toxins can cause AES.4–6 Although data addressing the cause of AES in Asia are limited, some studies have identified Japanese encephalitis virus (JEV) and herpes viruses as the most common causes in south Asia, though these etiologies explain only a small fraction of illness.7–11 Over the past decades, unusual outbreaks of AES associated with severe illness and death among children have repeatedly been reported from India, Bangladesh, Vietnam, and Thailand.11–14 Based on clinical, laboratory, and environmental findings, investigators have speculated that the cause of some of the illnesses in these AES outbreaks may not be infectious; however, no conclusive evidence about etiology has been published following these investigations.6,15
Fourteen patients met our case definition (Table 1). Thirteen were identified from 13 different villages of four subdistricts in Dinajpur District. One was identified from a village of neighboring subdistrict in Thakurgaon District (Figure 1). The median age of case-patients was 4.6 years (IQR = 2.5–5.0 years). The onset of illness of the case-patients was distributed during the day time and night time. Illness started with a sudden outcry among 43% of the case-patients that awakened the patient and their family members from sleep. Family caregivers reported that 79% of case-patients had convulsions. Fifty-seven percent of case-patients had excessive sweating and 50% had frothy discharge from the mouth. Ninety-three percent of case-patients became unconscious; the median time from onset of symptoms or signs to unconsciousness for the six cases for whom information was available was 2.5 hours (Table 1). In the hospital, we found medical records for nine case-patients; four records mentioned that patients had mid-dilated or fixed pupils and six mentioned that patients had lung crepitations on auscultation. Before seeking care at the tertiary care hospital, 64% of case-patients reportedly sought care from spiritual healers, 57% from village doctors and paramedics, and 29% from subdistrict-level hospitals.
The clinical manifestations in case-patients including sudden onset without a prodromal phase, becoming unconscious within a median of 2.5 hours of illness onset, and the short duration between onset of illness to death all suggest that the outbreak was more likely due to a toxic poisoning than an infection. The outbreak was restricted to the lychee season and to a geographic area in which lychees are grown, which suggests that this outbreak of AES may be linked to exposure to lychees or lychee orchards.12