A behaviour change communication intervention trial to reduce the risk of Nipah virus spillover in Bangladesh

INTRODUCTION
Nipah virus infection is a bat-borne zoonosis transmitted to humans through consumption of raw date palm sap contaminated by Pteropus bats. In Bangladesh, raw sap is a delicacy. The objective of this study was to measure the effectiveness of a behaviour change communication intervention to prevent Nipah virus transmission. We also measured the cost of the Nipah virus prevention intervention and estimated the potential cost of scaling it up to districts where spillover has been identified in the past.
METHODS
We developed and implemented a behaviour change communication intervention to reduce the risk of Nipah virus transmission testing two different messages, using community mobilization, interpersonal communication, posters and television as communication channels to reach community residents.
During the 2012-14 sap harvesting seasons, we targeted one district that we denominated as the “no raw sap” area, recommending stopping drinking raw date palm sap. During the 2013-14 sap harvesting season, we targeted a different district denominated as the “only safe sap” area, promoting the use of a traditional method locally called bana, used by sap harvesters (gachhis), to cover the sap with a barrier that interrupts bats' access to sap, recommending drinking only bana-protected sap.
We conducted baseline and endline surveys to measure the proportion of people reached by our intervention and their change of behaviour. Before implementing the intervention during the 2012-13 sap harvesting season, the evaluation team collected baseline survey data from community residents in the “no raw sap” area, and a control area. Before the 2013-14 sap harvesting season, the team collected baseline data among community residents and gachhis in the “only safe sap” area, and the control area again. After the intervention, from March 31 to April 21, 2014, the team collected endline survey data among community residents and gachhis from the two intervention areas and the control. In all areas, the team also observed raw sap consumption and bana usage among gachhis. We calculated the implementation cost of our intervention and also estimated future scaling up cost covering the 30 districts where Nipah virus spillover has been identified.
RESULTS
The evaluation team interviewed a total of 6220 community residents and 665 gachhis during baseline and endline surveys. They also observed 214 gachhis harvesting and selling sap.
Survey data suggest that community residents’ and gachhis’ knowledge about Nipah virus/a disease from raw sap, significantly increased in both intervention areas from baseline to endline. This increase was markedly higher in the intervention areas than the control area.
In the “no raw sap” area, reported raw sap consumption decreased markedly between baseline and endline, from 43% to 18%, and from 57% to 40%, in the control area. The difference in the intervention area was not significantly larger than the control. Our observation data suggest that the proportion of observations of at least one person consuming raw sap at the gachhi’s place declined more in the “no raw sap” area (46% to 22%) than in the control (61% to 53%; difference in difference 95% CI -45%, 15% and p=0.30). In addition, exposure to individual intervention communication elements in the “no raw sap” area was not associated with reported avoidance of raw sap consumption.
In the “only safe sap” area reported overall raw sap consumption decreased markedly, between baseline and endline, from 60% to 44%, and from 49% to 40%, in the control area. The difference in the intervention areas was not significantly larger than the control. Reported consumption of unprotected sap declined in the “only safe sap” (59% to 26%) and the control (36% to 29%) areas. The decline in the intervention area, however, was significantly larger than the control (-26% difference in difference analysis, 95% CI -33%, -18%, p<0.001). Restricting the analysis to residents who consumed sap, reported consumption of bana-protected sap significantly increased in the intervention area (3% to 43%) while it hardly changed in the control (26% to 27%). In the “only safe sap” area respondents with direct exposure to at least one intervention communication element: were more likely to report consuming raw sap from a protected source than those with no exposure (25% vs. 15%, OR 2.0, 95% CI 1.5-2.6, p<0.001).
In the “only safe sap” area, gachhi-reported bana usage increased from 11% to 90% between baseline to endline. In the control, an unexpectedly high proportion of gachhis reported bana use during baseline, though it decreased during endline (66% to 57%). The intervention group’s increase was significantly higher than the change in the control. However, our observation data suggest a higher percentage of gachhis using banas in the control (55%) than in the “only safe sap” area (31%).
In terms of implementation costs, the intervention’s cost was US$30,000 in the “no raw sap” area and US$55,000 in the “only safe sap” area. The highest cost was conducting meetings and interpersonal communication efforts. The lowest cost was broadcasting the public service announcements on local TV channels.
To scale up a similar intervention in 30 districts where Nipah virus spillover has occurred would cost between 2.6 and 3.5 million US$ for one season. Placing the posters would cost US$96,000, and only broadcasting the public service announcement through local channels in the same region would cost US$26,000.
DISCUSSION AND CONCLUSION
The results from the “no raw sap” area suggest that convincing people to abstain from drinking a traditional delicacy are difficult to achieve. Promoting the use of banas, an existing preventive method, in the “only safe sap” area seems to be an effective approach to modify raw sap drinking behaviour. To reduce the risk of Nipah virus transmission, a future “only safe sap” approach intervention should focus on increasing direct exposure to the communication elements to help prevent Nipah virus infection. Broadcasting the TV public service announcement would be a low cost next step to advance Nipah virus prevention, supplemented with posters and targeted interpersonal communication in districts with a high risk of Nipah virus spillover.