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Aedes albopictus Skuse, Culex pipiens form molestus, Culex quinquefasciatus Say, and Culex tritaeniorhynchus Giles mosquitoes from nonendemic JEV regions may be able to efficiently transmit JEV genotype IV in nature. This is the conclusion of an article published on December 10, 2024 in Emerging Microbes & Infections.

Researchers exposed these mosquito species in a laboratory to a JEV genotype IV blood meal that contained virus strain 19CxBA-83-Cv that was collected from domestic pigs on southern Bali Island, Indonesia in 2019.  This JEV genotype IV strain has a ≈ 99% nucleotide similarity to a JEV genotype IV strain collected from pigs on Bali Island in 2017 (reference JEVISN / Epidemiology / Spread of JEV genotype IV for additional information).

Colonies of JEV genotype IV infected mosquito species showed the following 14-day post-exposure salivary transmission efficiency rates:

Mosquito Species	Origin of Mosquito Colony	Transmission Efficiency Rate
Culex tritaeniorhynchus Giles	Japan	≈ 74%
Aedes albopictus Skuse	Japan	≈ 52%
Culex quinguefasciatus Say	Vietnam	≈ 35%
Culex pipiens form molestus	Turkey	≈ 18%

Although researchers measured JEV genotype IV viral loads from collected abdomens and thoraxes (as a measure of infection) and collected heads, wings, and legs (as a measure of dissemination), the presence of JEV genotype IV in saliva demonstrated an ability to transmit the virus when feeding.

Results from this study suggest that increased surveillance for JEV genotype IV in these and other mosquito species in global nonendemic JEV regions should be considered.

In JEV endemic regions, Culex pipiens, Culex quinquefasciatus, and Culex tritaeniorhynchus are highly competent JEV vectors, and Aedes albopictus is a confirmed JEV vector (reference JEVISN / Ecology / Mosquito Vectors for additional information).

The Swine Health Information Center and the Foundation for Food & Agriculture Research have recently funded six new projects to enhance US prevention, preparedness, mitigation and response capabilities for Japanese encephalitis virus (JEV). As a transboundary disease risk for US introduction, JEV is transmitted through the bite of infected mosquitos and can cause reproductive failure, abortions, and stillbirths or weak piglets in swine breeding herds. Recent expansion of JEV into new geographic regions of Australia warrants close investigation to prevent a potential JEV incursion into the US. In the fall of 2024, a total of $1.3M was awarded through the SHIC/FFAR JEV Research Program across six projects now underway. 

Announced in February 2024, the SHIC/FFAR JEV Research Program sought to invest in critical research to prevent JEV incursion, ensure rapid detection of JEV if introduced, inform stakeholder response, mitigate production losses on sow farms, identify effective control measures, and develop clear messaging to consumers on the safety of pork. With a goal to address the emerging threat that JEV poses to US swine health, SHIC and FFAR invited proposal submissions from qualified researchers for funding consideration based on value to US pork producers.  

A total of 26 proposals from 23 different institutions were received by the submission deadline in April 2024. Six proposals were selected for funding after a highly competitive review process conducted by swine industry stakeholders and subject matter experts. Newly funded projects address the SHIC/FFAR JEV Research Program priorities, including transmission and epidemiology, competent vectors, the role of wildlife, diagnostics, challenge models, and vaccine development. 

SHIC/FFAR JEV Research Program projects funded and initiated in response to the RFP include: 

Transmission and epidemiology 

Epidemiology of JEV in Australian intensive piggeries  

Principal Investigator: Brendan Cowled, Ausvet Pty Ltd 

Objectives: 1) Understand the transmission and epidemiology of JEV within farms through a literature review and data analysis of affected farm parameters for model development; 2) Understand and validate the farm-level risk factors for JEV in the Australian outbreak through a qualitative study of expert veterinarians. 

Competent vectors 

Vector competence and JEV pathogenesis and immunity in domestic pigs 

Principal Investigator: Angela Bosco-Lauth, Colorado State University 

Objectives: 1) Evaluate vector competence of JEV in the primary West Nile virus mosquito vectors in the US; 2) Determine susceptibility and pathogenesis of JEV in domestic swine; 3) Assess protective efficacy of WNV vaccination and JEV vaccination against JEV infection in domestic swine; 4) Evaluate cross-neutralization of porcine antibodies against JEV, WNV, and St. Louis encephalitis virus. 

Role of wildlife 

Understanding the threat of wild pigs and mosquitoes for JEV transmission to domestic swine farms  

Principal Investigator: Daniel Peach, University of Georgia 

Objectives: 1) Establish whether wild pigs increase the habitat available to JEV vectors by identifying the mosquito species that breed in wild pig wallows; 2) Determine the extent of access and which mosquito species commonly try to enter sow and wean-to-finish farms; 3) Assess exposure of domestic swine herds to mosquito-borne pathogens associated with wild pigs. 

Diagnostics 

Building diagnostic capability for Japanese encephalitis virus in the United States  

Principal Investigator: Katharine Bossart, Integrated Research Associates, LLC 

Objectives: 1) Assess assay performance using recombinant and inactivated viral antigens from multiple JEV genotypes to build serologic diagnostic capabilities; 2) Create a prototype JEV IgM ELISA kit with all reagents and instructions and create a prototype JEV IgM dot enzyme immunoassay; 3) Develop secondary JEV IgM ELISAs and dot enzyme immunoassays using JEV nonstructural proteins. 

Challenge models 

Development of a pregnant sow model to study the pathogenesis of the emergent Japanese encephalitis virus genotype IV   

Principal Investigator: Juergen Richt, Kansas State University 

Objectives: 1) Develop robust and harmonized in vivo and in vitro methods for comparative analysis of infected pregnant sows across two study centers; 2) Conduct JEV infection trials at three gestational timepoints at each site; 3) Determine the pathobiological features of in utero infection and compare across the two study centers. 

Vaccine development 

Translation of the highly safe, pure and potent IMOJEV® live, attenuated chimeric vaccine against JE in humans for prevention of JEV infection and disease in swine  

Principal Investigator: Thomas Monath; Substipharm Biologics SA 

Objectives: 1) Demonstrate safety and immunogenicity of IMOJEV in swine; 2) Demonstrate efficacy of IMOJEV in protecting pigs from challenge with JEV; 3) Determine minimum effective dose for immunization with IMOJEV; 4) Provide quality assurance and quality control; 5) Develop a product development plan to meet product licensing requirements. 

Awarded projects are nine to 24 months in duration; research results will be shared as soon as they become available. In partnership with FFAR, this effort helps SHIC fulfill its mission to generate new intelligence for preventing, preparing for, and responding to emerging swine disease threats. Understanding the potential impacts of JEV on pork production is critical to protecting the health of the US swine herd as well as mitigating the risk of this emerging disease. 

Foundation for Food & Agriculture Research 

The Foundation for Food & Agriculture Research (FFAR) builds public-private partnerships to fund bold research addressing big food and agriculture challenges. FFAR was established in the 2014 Farm Bill to increase public agriculture research investments, fill knowledge gaps and complement the U.S. Department Agriculture’s research agenda. FFAR’s model matches federal funding from Congress with private funding, delivering a powerful return on taxpayer investment. Through collaboration and partnerships, FFAR advances actionable science benefiting farmers, consumers and the environment. 

Swine Health Information Center 

The Swine Health Information Center, launched in 2015 with Pork Checkoff funding, protects and enhances the health of the US swine herd by minimizing the impact of emerging disease threats through preparedness, coordinated communications, global disease monitoring, analysis of swine health data, and targeted research investments. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Megan Niederwerder at mniederwerder@swinehealth.org or Dr. Lisa Becton at lbecton@swinehealth.org.

On August 5, USDA APHIS Veterinary Services published an updated Foreign Animal Disease Preparedness & Response Plan for Japanese Encephalitis (JE) in the event of a Japanese encephalitis virus (JEV) outbreak in the United States.

The updated response strategy is available here. A USDA APHIS Veterinary Services press release stated the following:

JE is not currently found in the United States. This document is intended to provide strategic guidance for USDA, APHIS, and responders at all levels in the event of a JE outbreak, should it enter the United States. If JE is introduced into the United States, Veterinary Services will provide additional policy guidance on specific response operation activities, tailored to the conditions of the outbreak.

The 2024 Strategy updates and expands the scope of the 2013 version. VS incorporated current science and research, shifted away from eradication as a response strategy, and updated considerations for control and vaccination. The updated version also includes more elements of the response than were previously addressed, such as a recognizing a one health approach, increasing collaboration with public health authorities, and enhancing communication plans. VS included feedback from industry and Federal One Health partners in this update.

Barbara Campbell Determan, SHIC, at barb@teamhmg.com or 515-249-8460
Michelle Olgers, FFAR, at molgers@foundationfar.org or 804-304-4200

Manhattan, KS (February 12, 2024) – The Swine Health Information Center and the Foundation for Food & Agriculture Research (FFAR) have partnered to fund a $1 million research program to enhance US prevention, preparedness, and response capabilities for Japanese encephalitis virus, a transboundary disease risk for US introduction.

SHIC’s strategic mission to identify risks to swine health includes global and domestic disease monitoring to maintain an acute awareness of emerging swine diseases around the world. Japanese encephalitis is an emerging zoonotic disease identified through global monitoring as a priority for North American prevention and preparedness activities. JEV is transmitted through the bite of infected Culex mosquitoes and biosecurity practices focused on mosquito control are key to reducing risk. The US is currently negative for this mosquito-borne virus which has waterbirds as a natural reservoir but is capable of infecting pigs, humans, and horses.

In 2022, an outbreak of JEV genotype IV spread rapidly across new geographic regions of Australia affecting breeding swine herds and causing reproductive failure, delayed farrowing, stillbirths, mummified fetuses, abortions, and weak piglets. This recent incursion of a new JEV genotype into areas previously free from disease warrants the need for a close investigation of this virus and its potential for incursion and establishment in the US. Understanding the potential impacts of JEV on pork production in the US is critical to protecting the health of the US swine herd as well as mitigating the risk of this emerging disease.

In response to this emerging disease, SHIC and FFAR have partnered to invite proposal submissions from qualified researchers for funding consideration to address identified research priorities for JEV, including topic areas of 1) transmission and epidemiology, 2) mosquito control, 3) diagnostics, 4) communication, 5) surveillance, 6) compatible cases, 7) challenge models, 8) vaccines, 9) cross-protection, 10) competent vectors, 11) role of wildlife, 12) novel hosts, and 13) viral sequencing. Proposal information and a detailed list of research priorities can be found here.

Proposals should clearly state which of the identified SHIC/FFAR JEV research priorities will be addressed through the project. Collaborative projects that include the pork industry, international organizations, allied industry, academic institutions, and/or public/private partnerships are highly encouraged. Projects demonstrating the most urgent, timely completion, providing the greatest value to pork producers, and showing efficient use of funds will be prioritized for funding. Projects are requested to be completed within a 12-to-18-month period with sufficient justification required for extended project duration. The JEV research proposal template can be found here.

Total funding available for the SHIC/FFAR JEV Research Priorities is $1 million. Individual awards are capped at $250,000 but proposals may exceed the cap if sufficient justification is provided. Matching funds are encouraged but not required; the $250,000 cap applies to only those funds requested from SHIC/FFAR. All projects should strive to be unique, have a high impact, show value to pork producers, and have industry-wide benefit.

The deadline for proposal submission is 5:00 pm CDT on April 15, 2024. SHIC and FFAR are co-hosting an informational webinar on February 22, 2024, at 3:00 pm CST to provide additional details about the application criteria. Attendees must register to attend the webinar here. Additional information can be found at www.swinehealth.org. For questions, please contact Dr. Megan Niederwerder at mniederwerder@swinehealth.org or (785)452-8270 or Dr. Lisa Becton at lbecton@swinehealth.org or (515)724-9491.

The Foundation for Food & Agriculture Research (FFAR) is a non-profit organization established in the 2014 Farm Bill to build public-private partnerships that fund bold research addressing food and agriculture challenges. SHIC and FFAR collaborated with the Pork Checkoff to fund the Wean-to-Harvest Biosecurity Program research project now underway.

The Swine Health Information Center, launched in 2015 with Pork Checkoff funding, protects and enhances the health of the US swine herd by minimizing the impact of emerging disease threats through preparedness, coordinated communications, global disease monitoring, analysis of swine health data, and targeted research investments. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Megan Niederwerder at mniederwerder@swinehealth.org or Dr. Lisa Becton at lbecton@swinehealth.org.  

Reprinted verbatim from a USDA APHIS email 12/27/2023 (source – Swine Health Information Center)

APHIS Veterinary Services (VS) is updating the Japanese Encephalitis (JE) Response Strategy and invites feedback from key stakeholders.  

JE is not currently found in the United States. The primary purpose of this document is to provide strategic guidance to those government officials responding to an outbreak if it were to be introduced into the United States. This revision updates and expands the scope of the 2013 JE Disease Response Strategy. We have incorporated current science and research, shifted away from eradication as a response strategy, and updated considerations for control and vaccination. We also included more elements of the response than were previously addressed, such as recognizing a one health approach, increasing collaboration with public health authorities, and enhancing communication plans.  

Please provide feedback or comments, such as technical information, assessment of operational feasibility, and resource constraints, regarding the response strategy, using this form: https://forms.office.com/g/kwus5M8c5D. The form will be open until Wednesday, January 26, 2024.  

If you have any questions, please reach out to the APHIS Veterinary Services Emerging Diseases Coordinator, Dr. Sarah Speth, at sarah.speth@usda.gov.

The US swine industry, including the Swine Health Information Center (SHIC), continues to prepare for the possible incursion of Japanese encephalitis virus (JEV) in pigs. The threat of JEV has prompted the USDA APHIS Veterinary Services division to issue a statement regarding related testing and preparedness. The statement also addresses the diagnostic submission process and USDA plans for further preparedness activities.  

Diagnostic testing for any animals with clinical signs suggesting of Japanese encephalitis virus (JEV) is available at no cost to animal owners and producers at the National Veterinary Services Laboratories (NVSL) in Ames, Iowa. Veterinarians and producers must first notify their State or Federal Animal health officials if JEV is on a differential list, and these officials will assist in the submission and sampling as needed. NVSL uses both PCR and sequencing to identify and confirm the virus. While serology has proven useful in the surveillance and diagnosis of JEV in endemic countries, it is of limited use in JEV free countries and will not be offered as an on-demand diagnostic test at NVSL at this time. USDA scientists are actively collaborating with partners to develop and characterize additional diagnostics, and in the future USDA will expand their active JEV research program to the National Bio and Agro-Defense Facility, once the facility is fully operational, to better understand the pathogenesis, evolution and epidemiology of JEV. 

The US is considered a geographic region at risk for the introduction of Japanese encephalitis, a disease capable of affecting humans as well as pigs. JE is transmitted primarily by Culex mosquitoes infected with the virus. Environmental conditions similar to JEV endemic countries, as well as the availability of susceptible hosts and vectors, create concern for the US pork industry and public health officials. Clinical signs of JEV in the breeding herd includes reproductive failure, delayed farrowing, stillbirths, mummified fetuses, abortions, and weak or shaker piglets.

Additional information regarding animal JEV diagnostic testing is available from NVSL (515-337-7551; NVSL.DVL.TeamLeads@usda.gov).

Through a Cooperative Research Agreement with the United States Department of Agriculture National Agro Bio-Defense Facility, Dr. Natalia Cernicchiaro of the College of Veterinary Medicine, Kansas State University and Dr. John Drake, Director of the Center for the Ecology of Infectious Diseases at the University of Georgia, have begun a collaboration to 1) develop a spatial interaction model of the 2022 Australian JEV genotype IV outbreak and 2) build a JEV spatial interaction model for the United States using results from the Australian model. 

As research advances, periodic updates will be published on the JEVISN website and JEVISN listerv.