Japanese Encephalitis is a mosquito-borne disease of the central nervous system that occurs chiefly in three areas of Asia: (1) China and Korea, (2) the Indian sub-continent consisting of India, parts of Bangladesh, southern Nepal, Sri Lanka, and probably in the Indus Valley in Pakistan and (3) the Southeast Asian countries of Myanmar (Burma), Thailand, Cambodia, Laos, Vietnam, Malaysia, Indonesia and the Philippines.
Japanese Encephalitis is primarily a rural disease and transmission is usually seasonal, following the prevalence of mosquitoes. The chance that a traveller to Asia will develop Japanese Encephalitis is probably very small; the risk is proportional to exposure to the mosquitoes that breed chiefly in rural rice-growing and pig farming regions. Only 5 cases among Americans travelling or working in Asia are known to have occurred since 1981. Among persons who are infected by a mosquito bite, only 1 in 50 to 1 in 1,000 persons will develop an illness.
It is spread mostly in rural areas where conditions favour breeding of the mosquito that carries the virus. They are most likely to bite during the cooler hours of the evening, and at dusk and dawn when they are out feeding.
The incubation period following mosquito bites varies from 5-15 days.
This is based on the typical illness and confirmed by special blood tests or post-mortem tests in fatal cases.
The course of the disease is divided into three stages:
Sudden onset of high fever is common. Also: malaise, vomiting, nausea and headache. Duration: 1-6 days.
The acute brain, or encephalitic, stage with: continuous fever, neck stiffness, alteration of consciousness and convulsions. Paralysis may also be noted. Stage 1 and 2 may take up to 2 weeks.
The late stage at which point the fever subsides and neurologic signs become stationary. At this stage intellectual impairment is common.
The majority of infected persons develop mild symptoms or no symptoms at all. However, among persons who develop the disease, the consequences of the illness may be grave with a variety of signs developing. Japanese Encephalitis begins clinically as a flu-like illness with headache, fever, and often gastrointestinal symptoms. The illness may progress to a serious infection of the brain i.e. encephalitis, and in one third of cases, the illness may be fatal. Another one third of cases survive with serious brain after effects such as paralysis or other forms of brain damage, and the remaining one third of cases recover without further problems. If the outcome is fatal this is usually within the first 10 days.
There is no specific treatment. After the onset of the infection, and until the illness has run its course, only supportive treatment is available. Cases recover spontaneously, die, or develop permanent brain damage.
This is by avoidance of mosquito bites, however an effective vaccine is available (see below).
Mosquito coils burnt in the immediate area will help repel mosquitoes. Care is suggested here because breathing problems, even asthma, may rarely develop.
Avoid perfumes; mosquitoes are attracted to scents.
Wear long sleeves and pants, avoid dark coloured clothes.
Avoid JE mosquito prone areas like pig farms.
A portable mosquito net for sleeping under is suggested. It should have been previously soaked in permethrin, which is an insecticide.
Protection using DEET mosquito repellent and protective clothing with permethrin. DEET should not be applied to babies and only sparingly, (quick sprays, 2-3 in 24 hours) to children 6-24 months of age, because of the potential toxic effects.
Children and pregnant women are recommended to use our natural insect repellent products
An effective vaccine is available. It is not generally recommended for all travellers to Asia, but is recommended for persons who plan to live for a month or more, during the transmission season, in areas where Japanese Encephalitis is present. It is also suggested for persons whose outdoor activities in rural areas place them at high risk for exposure.
travellers visiting areas where an epidemic is present
long tern travellers or residents living in endemic areas
travellers spending greater than one month continuously in rice growing areas endemic for the disease.
The vaccine series is three doses of 1.0 ml each, subcutaneously on days 0, 7 and 30. It is about 90% effective. Time to immunity is 10 days and duration of cover is about 3 years; however, the full duration of protection is unknown. A booster dose may be required two years after the primary vaccination if the traveller is still at risk for infection.JEV and Rabies can be given on the same day/s: 0, 7, 28.
A rapid schedule can be used when the longer schedule is impractical because of time constraints. The last dose should be administered at least 10 days before the start of travel to ensure an adequate immune response, and access to medical care in the event of delayed adverse reactions. A 3-dose schedule on days 0, 7 and 14 will need boosting after 1 year. Two doses administered one week apart will confer short-term immunity among 80% of vaccines.
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