Threat of Japanese encephalitis outbreak looms in Indonesia

By Mangku Sitepoe

JAKARTA (JP): Malaysia is in the midst of an epidemic of Japanese encephalitis that has already claimed 89 lives, mostly people living in the vicinity of pig farms.

The disease is transmitted to humans from mosquitos, especially insects of the Culex type, which are themselves infected from animal sources (in contrast, dengue fever is spread by the Aedes mosquito).

It is believed that pigs are the source of the disease and mosquitoes are the vectors in the Malaysian case. The Culex mosquito spreads the virus in nine days to 12 days after biting animals infected with the disease. This is the basis for the Malaysian government's move to exterminate three million pigs; The Jakarta Post reported on March 21 that 65,000 pigs were killed daily.

Singapore, which does not have pig farms, has banned the import of pigs from Indonesia and Malaysia. The ban shows the serious approach of the Singapore government in handling contagious diseases posing a risk to humans and animals. It also appears to suspect the epidemic has spread to Indonesia, especially to pigs on Bulan Island in Riau province.

Japanese encephalitis belongs to the group of diseases that are zoonosis in nature, which means they are animal diseases which can be transmitted to humans under natural conditions.

The disease was recorded for the first time in Japan in 1871, and a 1924 outbreak claimed 6,000 lives. The 5,700 Japanese encephalitis cases in Korea in 1958 caused 1,322 deaths. The same year, 519 of 1,800 infected people died in Japan (Harwood R.F., 1969).

Cases are also believed to have occurred in Indonesia in recent years. It was suspected in a 10-year-old Australian boy who died after vacationing in Bali (The Medical Journal of Australia, 1989, vol. 150). In March 1994, there was a report of a woman tourist from Sweden dying after a trip to Bali (The Lancet, April 1995, vol. 345). In January 1995, the disease was suspected in the death of a Dane who had returned from Bali 12 days earlier, according to another report.

Serological surveys have been conducted since 1960 in Bali. They found 52 percent seropositive cases among the Balinese population (Konamitsu, M. et al., 1979). Subsequent serological examinations of encephalitis patients in Indonesia found many were positive for Japanese encephalitis.

Researcher I Komang Kari found startling results in a survey of encephalitis patients from October 1990 to July 1995. Of the 71 patients in Bali, 40, or 56.33 percent, were seropositive for Japanese encephalitis.

The disease's incubation in humans is between five days and 15 days and it occurs in three phases. The early phase is marked by fever and flu-like symptoms, such as painful joints. It progresses to neurological disturbances of tremors, convulsions, stiffening of the nape of the neck, etc. Often, however, an infected person is asymptomatic. Death occurs in from 20 percent to 40 percent of cases.

It also occurs in horses, pigs, cows, buffaloes and birds, but only horses exhibit the neurological effects of the disease. However, it is not mentioned in the annual report of the Directorate General of Husbandry and serological examinations were only carried out after 1997.

The Agency for Animal Disease Control examined pigs in nearly all the provinces and found various degrees of seropositives. The health ministry conducted a serological examination on horses in Jakarta and found 40 percent to 60 percent were infected with Japanese encephalitis.

It also made a serological examination of pigs in Bali, West Nusa Tenggara, Sulawesi and Kalimantan and found they were infected, but infections were not recorded in Irian Jaya and East Nusa Tenggara.

A serological survey of the Jakarta showed high infection. And report that the pig population in the western part of the country is suspected to be infected is among the reasons Singapore banned pig imports from Bulan.

Some experts have dismissed the likelihood of Japanese encephalitis in Indonesia. The weight of evidence, both from research of encephalitis-infected local residents and reports of deaths of foreign tourists in the past decade, appears to show their nonchalance is misplaced.

The writer is a veterinarian and medical doctor.