1. Japanese Encephalitis Risk Assessment Using Novel Environmental Sampling Techniques
Maj Timothy Davis PhD, MS, MPH
This Briefing is UNCLASSIFIED

2. DISCLAIMER
The views expressed in this presentation are those of the author and do not reflect the official policy or position of the United States (U.S.) Air Force, U.S. Department of Defense, or the U.S. Government.

3. Overview Japanese Encephalitis (JE) Virus Biology JE in Okinawa, Japan
JE and Mosquito Surveillance Study
Results

4. Japanese Encephalitis
Military Significance: >50,000 US military members in the Western Pacific
Causative agent is a flavivirus
Life history: enzootic cycle in Ardeid birds, swine are the amplification host, humans are a dead-end host
JE can result in severe and acute encephalitis in humans with a high-case fatality rate and a high case-disability rate
Prevention: vaccination, evening and night time mosquito biting precautions
According to Department of Defense Immunization instruction dated 29 September 2006, JE vaccine is to be administered to all personnel deployed for more than 30 days to areas where there is a substantial risk of exposure, especially those involved in prolonged field operations at night.

5. Japanese Encephalitis
Ardeola bacchus
Dead-end Host
Reservoir Host
Culex tritaeniorhynchus
Vector
Cx. vishnui
Cx. tritaeniorhynchus
Cx. fuscocephala
Cx. gelidus
Cx. annulus
Amplification Host

6. Japanese Encephalitis

7. JE in Okinawa Japan JE epidemics in Okinawa, Japan prior to 1960s
3 JE diagnosed cases from in Okinawan population
1 JE diagnosed case in 1987, 3 in 1991; all in US Marines in Okinawa

8. JE in Okinawa Japan
Japanese JE vaccination policy is to provide free vaccine
2008 immunization rates show ~ 40% of the Japanese population is immunized
US DoD policy is to vaccinate all personnel deployed for more than 30 days to areas where there is a substantial risk of exposure

9. What is the JE risk in Okinawa?
Okinawa Prefectural Government routinely tests swine for JE
When over 50% of the swine test positive a caution status in announced
JE caution status occurred in , and 2012; but no human cases diagnosed in those years
In 2011 a JE case occurred with no JE caution status announced
Farming practices in Okinawa continue to change

10. JE Surveillance in Mosquitoes Study
Mosquito surveillance performed weekly June thru Aug 2015
Compare Passive Box Trap and the Mosquito Magnet Pro Trap
Mosquitoes and nucleic acid preserving cards screened for flavivirus using SYBR Green I-based real-time PCR

11. JE Surveillance in Mosquitoes Study

12. Results
11 weeks of trapping

13. Results

14. Results

15. Results
No positive flavivirus mosquitoes or nucleic acid preserving cards
Minimum infection rates of 1/200 Cx. tritaeniorhynchus have been reported
1806 Cx. tritaeniorhynchus were tested in this study
JE risk at study site from Jun-Aug 2015 is very low

16. Questions?