Threat of Japanese encephalitis outbreak looms in Indonesia

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.