Abstract
BackgroundDrinking raw date palm sap is a risk factor for human Nipah virus (NiV) infection. Fruit bats, the natural reservoir of NiV, commonly contaminate raw sap with saliva by licking date palm’s sap producing surface. We evaluated four types of physical barriers that may prevent bats from contacting sap.MethodsDuring 2009, we used a crossover design and randomly selected 20 date palm sap producing trees and observed each tree for 2 nights: one night with a bamboo skirt intervention applied and one night without the intervention. During 2010, we selected 120 trees and randomly assigned four types of interventions to 15 trees each: bamboo, dhoincha (local plant), jute stick and polythene skirts covering the shaved part, sap stream, tap and collection pot. We enrolled the remaining 60 trees as controls. We used motion sensor activated infrared cameras to examine bat contact with sap.ResultsDuring 2009 bats contacted date palm sap in 85% of observation nights when no intervention was used compared with 35% of nights when the intervention was used [p<0.001]. Bats were able to contact the sap when the skirt did not entirely cover the sap producing surface. Therefore, in 2010 we requested the sap harvesters to use larger skirts. During 2010 bats contacted date palm sap [2% vs. 83%, p<0.001] less frequently in trees protected with skirts compared to control trees. No bats contacted sap in trees with bamboo (p<0.001 compared to control), dhoincha skirt (p<0.001) or polythene covering (p<0.001), but bats did contact sap during one night (7%) with the jute stick skirt (p<0.001).ConclusionBamboo, dhoincha, jute stick and polythene skirts covering the sap producing areas of a tree effectively prevented bat-sap contact. Community interventions should promote applying these skirts to prevent occasional Nipah spillovers to human.
Highlights
Nipah virus (NiV) causes seasonal outbreaks in humans in Bangladesh that coincide with the date palm sap harvesting season, November to March [1]
During outbreak investigations, drinking raw date palm sap was identified as a risk factor for NiV infection in humans [8,9,10,11]
Dropped fruit has occasionally been posited as a pathway for transmission, it has never been associated with human NiV infection in outbreak investigations in Bangladesh [2]
Summary
Nipah virus (NiV) causes seasonal outbreaks in humans in Bangladesh that coincide with the date palm sap harvesting season, November to March [1]. During outbreak investigations, drinking raw date palm sap was identified as a risk factor for NiV infection in humans [8,9,10,11]. Dropped fruit has occasionally been posited as a pathway for transmission, it has never been associated with human NiV infection in outbreak investigations in Bangladesh [2]. Preventing the original spillover of Nipah from bats to people through date palm sap can prevent subsequent cases of person-to-person transmission of NiV which has been repeatedly observed in Bangladesh [13,14]. Drinking raw date palm sap is a risk factor for human Nipah virus (NiV) infection. The natural reservoir of NiV, commonly contaminate raw sap with saliva by licking date palm’s sap producing surface. We evaluated four types of physical barriers that may prevent bats from contacting sap
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