A Primer on Japanese Encephalitis: What It Is and How to Prevent it

Japanese encephalitis, also known as JE, is a viral infection that most commonly affects humans between the ages of 5 and 20. It is most prevalent between May and September when the virus is most active. The disease has a 30 percent fatality rate.

There are three types of JE. Type I is the most dangerous form of infection, especially for infants, type II causes a more mild form of the disease, and type III is the least severe form.

In its most common form, the virus affects the liver, brain, and spinal cord. Depending on the route of infection, it can travel to the encephalitis centre in the brain or to the intestines.

The disease is spread by mosquitoes and other insects that are carrying the virus.

JE can cause a range of symptoms, including fever, headache, neck stiffness, nausea, vomiting, convulsions, and coma.

The incubation period is usually two to six days, with the disease running its course in 10 to 14 days. A person can be infected only once.

Preventing Japanese encephalitis is best accomplished by using insect repellent and avoiding mosquito-infested areas.

The best way to avoid JE is to vaccinate. The vaccine is an effective way to prevent the disease, even though it is only 95 to 97 percent effective.

Here’s what you need to know about Japanese encephalitis, including how it is contracted and the symptoms to look out for.

What is Japanese Encephalitis?

Japanese encephalitis is a viral infection that affects the central nervous system.

The disease is characterized by inflammation of the brain and the membranes that surround it, specifically the cerebral cortex.

It is caused by infection with one of three types of the Japanese encephalitis virus (JEV), which are:

Type I – Severe infection, occurs most often in children and is usually fatal.

Type II – Intermediate infection, less common than type I and usually milder.

Type III – Mild infection, occurs most often in adults and may also include a few cases of spontaneous recovery.

The disease is highly infectious, with an average of 90 percent of people becoming infected if they are in an area where the virus is endemic. There are currently more than 50 infected piggeries across NSW, QLD, SA and VIC.

JEV is perhaps more harmful to animals, specifically pigs, and horses. The most common clinical symptoms of JE in pigs include reproductive losses such as abortions, mummified fetuses, and stillborn or weakened piglets. Most clinical diseases in horses are mild and may go unnoticed. However, a fever, decreased or no appet­it­e, lethargy, wobbliness, and in-coordination may impact your livestock. Horses in particular can die.

How is Japanese Encephalitis Contracted?

Japanese encephalitis is contracted through the bite of an infected mosquito. The infected mosquito then bites a person and transfers the virus to them.

The majority of mosquito bites are asymptomatic, with the only indication of infection occurring when a person’s body mounts an immune response and produces antibodies capable of flushing out the virus.

Japanese encephalitis is most active between May and September, with infections peaking in July and August.

The adult mosquito that carries the virus is the culex, which is found in India, Pakistan, and many parts of Southeast Asia including Australia.

Symptoms of Japanese Encephalitis

The initial symptoms of Japanese encephalitis are typically a high fever, headache, neck stiffness, nausea, and vomiting.

Over the next few days, the symptoms become more severe and may include convulsions, blindness, coma, paralysis, and mental impairment.

The disease can be fatal in up to 30 percent of cases, usually due to liver failure.

Prevention and control of Japanese Encephalitis

The best method to prevent Japanese encephalitis is to avoid mosquito bites.

Use insect repellent to keep mosquitoes at bay. You can also install screens on doors and windows and keep your house as mosquito-free as possible.

If you are going to be outside for an extended period of time, wear long sleeves and pants.

Stay indoors at dusk and dawn when mosquitoes are most active.

These of course are lower-level control mechanisms and the threat can be almost completely eliminated with a vaccine if you work closely with animals in an endemic area. 

Protecting your property and livestock

Your livestock should be screened from areas where mosquitoes are breeding.

The most effective means of protecting livestock from JE is through vaccination. Horse Rugs and fly masks are useful on horses and stabling during dusk and dawn are beneficial controls.

However, ultimately other than repellents and pest control if your livestock resides in an area conducive to mosquito breeding then it will be difficult to completely eliminate the odds of encountering a JEV case. However, as mentioned above it isn’t the end of the world, JEV is not a food safety concern and in most cases humans and animals are asymptomatic.

Hygiene and Cleaning controls

Daily hygiene practices can help reduce the risk of Japanese encephalitis. Considering how effective preventative measures can be i.e a vaccine and proper PPE, it is unlikely that an outbreak would require special cleaning practices. Good hygiene practices will suffice as the virus is only carried by mosquitos, increasing the number of mosquito coils and other pest management controls would be beneficial. 

You can learn more about biosecurity practices by visiting farmbiosecuity.com.au, especially the guide to controlling mosquitoes near piggeries, and the Australian National Pork Biosecurity Manual which provides in-depth detail on biosecurity practices and management in a piggery.

Conclusion

The Japanese Encephalitis virus is a serious concern for the Australian food industry, particularly pork producers. As the research has shown the best protective action that can be taken currently is to have all of your workers vaccinated against JEV. Use environmental controls to reduce the mosquito load around your property to best protect your livestock, namely by inspecting for bodies of water and areas where collections of water can sit. Doing this alone will reduce mosquito counts. Lastly, just be mindful of any anomalies in your livestock, closely monitoring your animals can give you early signs that something is not right.

Hope you enjoyed this article and if you found it informative or interesting please share it with someone who you think could benefit. It is important to note that this shouldn’t affect the production of pork products as JEV is not a Food safety concern.

Stay safe,

The SGA Team

References & Resources:

Agriculture Victoria – https://agriculture.vic.gov.au/about/media-centre/media-releases/monitoring-continues-for-japanese-encephalitis2

Department of Primary Industries and Regional Development – https://www.agric.wa.gov.au/japanese-encephalitis

National pest & disease Outbreaks – https://www.outbreak.gov.au/current-responses-to-outbreaks/japanese-encephalitis

Australian Government Department of Health – https://www.health.gov.au/health-alerts/japanese-encephalitis-virus-jev/about

NSW Health – https://www.health.nsw.gov.au/Infectious/factsheets/Pages/japanese_encephalitis.aspx

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