PHUKET – An Australian man returned from Thailand has died from the rare but potentially fatal mosquito-borne disease, Japanese encephalitis.
It is understood to be only the 10th case of the disease recorded in Australia since 2001 and one of only a handful of deaths in that time, although Japanese encephalitis is endemic in South-East Asia, where it is most commonly found in rural or farming areas.
The Victorian man in his 60s had visited Phuket for 10 days in early May and became lethargic on day eight.
After returning home he struggled to stay awake and went to hospital a few days later in a confused state.
His conscious state continued to diminish, and he was eventually admitted to the intensive care unit, where he died.
Japanese encephalitis causes a brain infection that is fatal in about 20 to 30 per cent of cases.
But not all mosquitoes carry the virus and the risk of catching it is “vanishingly rare”, according to Steven Tong, who treated the man at Royal Melbourne Hospital.
“We don’t have Japanese encephalitis within Australia itself, so it has to be acquired during travel to areas of risk,” he said.
“That depends on going to those areas and being exposed to mosquitos carrying the virus, being bitten by an infected mosquito, and then developing the disease.
“Most figures suggest that for travellers to endemic areas such as Thailand, the risk is probably in the order of one in a million to one in 500,000 travellers to those areas will get Japanese encephalitis.
Doctors said the man had not been vaccinated and had not sought any pre-travel advice about the virus.
Despite the virus’ potentially fatal nature, Dr Tong said there was no risk the man’s illness could endanger other Australians, because Japanese encephalitis breeds in aquatic birds not found in Australia, or pigs, before they can infect humans.
“People have such a short-lived duration of the virus in them that people are seen as a dead-end host,” Dr Tong said.
It is unclear how the man caught the disease.
There were no reports he had contact with animals or travelled to rural regions in Thailand, but he reported multiple mosquito bites while in Thailand.
The last known case of Japanese encephalitis in Australia was in 2015 when another Victorian man aged 45 returned with the disease after a trip to Bali.
Dr Tong said despite the rare nature of Japanese encephalitis, Australians travelling anywhere in South-East Asia should take precautions, including vaccination and the use of insect repellent.
“Obviously it’s a devastating disease, so any prevention is helpful,” he said.
Japanese Encephalitis Vaccine
Inactivated Vero cell culture-derived Japanese encephalitis (JE) vaccine (manufactured as IXIARO) is the only JE vaccine licensed and available in the United States. This vaccine was approved in March 2009 for use in people aged 17 years and older and in May 2013 for use in children 2 months through 16 years of age. Other JE vaccines are manufactured and used in other countries but are not licensed for use in the United States.
IXIARO is given as a two-dose series, with the doses spaced 28 days apart. The last dose should be given at least 1 week before travel. For persons aged 17 years and older, a booster dose may be given if a person has received the two-dose primary vaccination series one year or more previously and there is a continued risk for JE virus infection or potential for reexposure. Although studies are being conducted on the need for a booster dose for children, data are not yet available.
JE Vaccine Recommendations
JE vaccine is recommended for travelers who plan to spend 1 month or more in endemic areas during the JE virus transmission season. This includes long-term travelers, recurrent travelers, or expatriates who will be based in urban areas but are likely to visit endemic rural or agricultural areas during a high-risk period of JE virus transmission.
Vaccine should also be consideredfor the following:
Short-term (less than1 month) travelers to endemic areas during the transmission season, if they plan to travel outside an urban area and their activities will increase the risk of JE virus exposure. Examples of higher-risk activities or itineraries include:
1) spending substantial time outdoors in rural or agricultural areas, especially during the evening or night;
2) participating in extensive outdoor activities (such as camping, hiking, trekking, biking, fishing, hunting, or farming); and
3) staying in accommodations without air conditioning, screens, or bed nets.
Travelers to an area with an ongoing JE outbreak.
Travelers to endemic areas who are uncertain of specific destinations, activities, or duration of travel.
JE vaccine is not recommended for short-term travelers whose visits will be restricted to urban areas or times outside a well-defined JE virus transmission season.
Precautions and Contraindications
A serious allergic reaction after a previous dose of IXIARO is a contraindication to further doses. The vaccine contains protamine sulfate, a compound known to cause allergic reactions in some people.
No studies of IXIARO in pregnant women have been conducted. Therefore, administration of IXIARO to pregnant women usually should be deferred. However, pregnant women who must travel to an area where risk for infection is high should be vaccinated when the theoretical risk of immunization is outweighed by the risk of infection.
Reactions to JE Vaccine
Reactions to IXIARO are generally mild and include pain and tenderness, mild headaches, myalgia (muscle aches), and low-grade fevers.
By Anne Barker