24 September 2024

3 minute read

By: USDA APHIS

North America

What is it?

Japanese encephalitis virus (JEV) is a virus that mainly affects pigs, horses, waterbirds (e.g., herons and egrets) and people. JEV can produce disease in people, neurological disease in pigs and horses and reproductive failure in breeding swine. There is no specific treatment for Japanese encephalitis (JE) in pigs. JEV is not a food safety concern.

How does JEV spread?

JEV is an arbovirus which means that it is transmitted via bites from infected mosquitoes. The natural lifecycle of JEV is between waterbirds and mosquitoes. On occasion spillover to other animals, such as pigs, may occur. Waterbirds and pigs act as amplifying hosts, which means that they develop a level of virus in their blood that is high enough to infect more mosquitoes after feeding on infected animals.

What are the signs in pigs?

Many pigs infected with the virus do not show any signs of illness. Swine that are not pregnant do not typically show signs of infection or experience only mild transient fever. However reproductive losses can reach up to 50-70%.

Piglets

• Increase in stillborn, mummified or weak piglets (most common)
• Convulsions
• Shaky, wobbly or shivering
• Increase in pre-weaning deaths

Sows

• Increased return rates after mating
• Delayed farrowing—more than 118 days
• Increase in abortions

Boars

• Inflamed or swollen testicles
• Semen abnormalities
• Infertility

How can I minimize the risk of JEV to my pigs?

Is there a vaccine?

There is currently not a vaccine available in the United States.

Control mosquitoes on your property

Monitoring for mosquitoes at the various stages of their lifecycle helps to determine the most effective control methods. Key measures that will help reduce mosquito numbers on your property include:

• Inspecting bodies of water and containers for larvae, as well as areas where adult mosquitoes rest, like ceilings and walls
• Removing anything in the open that is filled with water or has the potential to hold water
• Filling in potholes or other areas that collect water
• Clearing debris from gutters, downspouts, and drains around buildings so that water doesn’t pool
• Trimming overhanging tree branches where mosquitoes may rest
• Ensuring effluent drainage is free flowing, flushed regularly and does not pool
• Sealing tanks, wells or other large water containers, or screening with 1mm mesh
• Installing insect screens
• Using fans inside buildings where pigs are housed to disrupt mosquito activity

What do I do if I suspect my pigs have JE?

JE is a notifiable disease in the United States.

If you suspect JE (or any other notifiable disease) in your pigs, please call your private veterinarian or State Animal Health Official.

How does JEV affect people?

Humans can also be infected with JEV. Most infections in people cause no symptoms. Some people experience a fever and headache, but severe cases may result in convulsions, disorientation, and coma. If you experience any worrisome symptoms, you should seek medical advice from a healthcare provider
immediately.

You can protect yourself by preventing mosquito bites.

• Use Repellents: Protection against Mosquitoes, Ticks and Other Arthropods | US EPA
• Wear loose-fitting long-sleeved shirts and pants when outdoors, especially between dawn and dusk