Japanese Encephalitis
Japanese Encephalitis is prohibited matter and zoonotic disease. If you suspect JE you must immediately notify the EAD hotline on 1800 675 888 (24hrs) or your Local Land Services Veterinarian on 1300 795 299 (business hours).
NSW Health has confirmed the detection of Japanese Encephalitis virus in mosquitos caught near Griffith and Moree in NSW. There have been two detections of Japanese Encephalitis virus in pigs, near Tamworth and Cowra. Ongoing surveillance in feral pigs has detected the virus in multiple locations across regional NSW. The Agriculture and Biosecurity branch are advising producers to implement their mosquito management plan. Producers can visit farm biosecurity website for tools to assist development of their management plans.
Japanese Encephalitis (JE) is a mosquito born vial disease that can result and reproductive losses and nervous signs in susceptible horses. Other animals can be infected however they do not typically show clinical signs.
What does Japanese Encephalitis look like?
Clinical signs in pigs
- Pregnant sows and gilts may abort, produce mummified or stillborn foetuses, farrow stillborn of weak piglets.
- Weak piglets or piglets infected afterbirth can show neurological signs, paddling, tremors and convulsions.
- Boars may experience infertility with poor semen quality and enlarged testes
Post mortem:
- Subcutaneous oedema
- Hydrocephalus
- Cerebella hypoplasia
- Lack of myelin in spinal cords may be observed.
Clinical signs in Horses
Most clinical cases in horses are mild, however more severe disease can occur.
Clinical signs may include:
- Incoordination
- Difficulty swallowing
- Vision disturbances
- Hyperexcitability
- Fever
- Lethargy
- Anorexia
- Neck pain
Post mortem:
- Post mortem examinations should not be undertaken on horses due to the risk of Hendra virus.
If a post mortem is conducted general nonspecific neurological signs may be observed.
What should I do if I suspect Japanese Encephalitis?
If you suspect Japanese Encephalitis in animals, contact your veterinarian, Local Land Services on 1300 795 299 or the Emergency animal disease hotline on 1800 675 888.
If you suspect Japanese Encephalitis in humans, contact your GP or local hospital for advice.
Whilst waiting for results or a farm visit, you should continue to monitor your pigs for unusual signs of disease. If possible, undertaking mosquito control can be beneficial. Refer to Controlling mosquitoes around piggeries - Farm Biosecurity or Mosquito Management for Horses - Farm Biosecurity.
Minimise your exposure to mosquito bites by following these tips Bite prevention - Mosquito borne diseases.
How is it diagnosed?
Japanese Encephalitis is diagnosed based on laboratory diagnosis. Samples are to be submitted to the Animal and Plant Health Laboratories at the Elizabeth Macarthur Agricultural Institute. Blood and unpreserved samples should be chilled to 4oC and submitted on ice. Do not freeze samples.
Samples to take:
Live Pigs:
- 10mL of clotted blood (Red Top) from the dam of affected litters.
- 10mL of clotted blood (red top) from up to 10 animals in the same unit that the affected litters are in
- Fresh semen from boars with sperm abnormalities or azoospermia.
Live Horses
- 10mL of clotted blood (red top) per animal. A convalescent sample should be taken 2-4 weeks apart. A single positive sample will only confirm pervious exposure. A convalescent sample may provide an indication of the time of infection.
Post Mortem from deceased (12hrs) and euthanised animals
Due to the similarity in clinical signs to Hendra virus, equids showing these signs should not have a post mortem or CSF collection performed until Hendra virus has been excluded as the cause of disease.
- Fresh brain, spleen, thoracic fluid, liver, CSF and any other fluid available.
- Brain, spleen, liver, kidney, heart and lung in 10% neutral buffered formalin.
- Whole aborted, stillborn or mummified foetuses are also able to be submitted.
- These foetuses should be placed in a sealed plastic bag and stored at 4oC until submission.
How is Japanese Encephalitis (JE) spread
JE is a virus that is primarily spread by mosquitos. The virus does not generally spread directly from animal to animal. Australia has many mosquito species that are capable to transmitting the virus, however Culex spp. is the most common vector of the virus.
The major reservoir is wading waterbirds, such as herons and egrets. These birds and pigs are amplifying hosts, meaning these species can be an ongoing source to infect the local mosquito population.
A mosquito biting one of these infected animals will become infected themselves. These mosquitos then bite a naive host, transmitting infection.
Horses generally do not have a sufficient level of virus in the blood to contribute to the spread of the disease. I.e., they are dead end hosts.
Does Japanese Encephalitis (JE) affect people?
JE can affect people. Infection occurs through mosquito bites. Humans are not infected by contact with infected animals, or consuming animal products infected with JE.
NSW Health has more information here: Japanese encephalitis fact sheet - Fact sheets (nsw.gov.au).
