Project Lead(s): Emily Gurley
Issue
Japanese encephalitis virus (JE) is transmitted to humans by mosquitoes that have fed on infected wading birds and pigs.
Approximately 1% of human infections result in encephalitis; approximately 30% of these patients will die and another 30% will suffer from permanent neurologic deficits. It is the most common cause of encephalitis in Asia, including Bangladesh.
Research findings suggest that pigs may be an important environmental reservoir for JE in northwestern Bangladesh and, by vaccinating pigs against JE, it is likely that this could reduce the risk of JE to humans.
In Bangladesh, pig-raising communities are impoverished, socially marginalized and receive minimal veterinary health services.
Solution
The research team used anthropological approaches to better understand the willingness of pig-raising communities to participate in a JE vaccination program.
The team sought to show that they can import and deliver pig vaccines against JE, which could reduce the JE transmission among pigs and thus reduce human transmission.
The process included:
• Identifying and importing a low-cost, effective vaccine
• Engaging with local pig-raising communities for support for the program
• Identifying a non-governmental organization (NGO) partner to deliver the vaccine to these communities
• Delivering the vaccine to a large proportion of the pig population
• Demonstrating the vaccine produces antibody titers sufficient to protect the animals.
A low-cost vaccine shown to be safe and effective, and manufactured in South Korea, was used.
The team conducted surveillance of reproductive outcomes among pigs, and collected blood from vaccinated and unvaccinated pigs to estimate sero-conversion risk and to measure JE antibody titer.
A total of 185 pig serum samples from piglets aged 4–6 months were collected and tested for antibodies against JE virus.
Deworming medications were also distributed to pig raisers, as an added benefit of participation.
Outcome
The project found culturally acceptable approaches to vaccinating pigs against JE, which will likely reduce human JE incidence in the study areas.
The approach enabled the team to fully vaccinate 3,065 pigs against JE.
Of 180 samples, 175 were negative for IgG antibodies against JE virus samples and five were found to be borderline positive for IgG antibodies against JE virus, suggesting that they had not been exposed during the first six months of life.
The target (vaccinate >95% of ~11,000 pigs) was not reached, for three reasons:
1. During the field work, the team found only ~7,000 pigs, compared to the 10,000 expected, based on the last census. Villagers reported that epidemic disease killed many of the pigs during the past few years.
2. The team encountered more reluctance to vaccinate than expected.
3. The team was unable to deliver a second dose to all pigs, because they were sold or eaten during the study.
The next phase of the project will involve continuation of vaccination campaigns in the initial study area, and scaling up to other endemic JE regions of Bangladesh.
The project team also plans to demonstrate the health and economic impact of vaccination on people in other endemic areas where the vaccine has been introduced.