Japanese Encephalitis on the wane in Ratnapura district

By Dhaneshi Yatawara
 

Inflammation of the brain

Encephalitis is an inflammation of the brain most commonly due to a viral infection. In nature, the main resevoir of JE infection is not human beings but various animals. Of these the most important is the pig, which is considered to be an amplifier host.

This is because the virus is found at the highest levels for the longest period (3-7 days) in the blood of the pig. Therefore, a mosquito vector biting a pig has the greatest chance of getting infected. The main vector is the culex mosquito. The JE virus does not produce any illness in most of the animals infected, with the exception of encephalitis in horses and abortion in pregnant pigs.

Isolation of Japanese Encephalitis virus

The virus was first isolated in Sri Lanka from a patient by at the Medical Research Institute in 1968. According to historical records the scientists had been Y.L. Hermon, M. Anandarajah as published in the Ceylon Medical Journal (1974) under the topic 'Isolation of Japanese Encephalitis virus from the serum of a child In Ceylon' In reference to the above research Prof.

Tissa Vitharana in his MRI report says, “But its presence was suspected earlier when a child died of encephalitis at the School for the Blind at Mahawewa in June 1960.

One of the serum samples sent to the Virus Research Centre at Poona, India was positive for group B arbovirus, probably Japanese Encephalitis. ”

While Encephalitis occurred sporadically throughout the year in most parts of the country, the first major outbreak occurred in the Kurunegala district in 1971. This mainly affected children and in the course of that year 76 cases were admitted to the children's ward at Kurunegala Hospital. There was a high case fatality of 66 deaths and of the 10 who survived 5 had residual neurological deficits.

Unfortunately, by the time the Medical Research Institute was informed, it was too late to establish the cause of the outbreak. In 1971 a study was made of encephalitis cases admitted to the Children's hospital, Colombo and District Hospital, Gampaha.

Of the 31 cases admitted to D H Gampaha (District Hospital), six were serologically investigated at the MRI and one was found positive for JE. Out of 50 cases at the Children's Hospital, four were serologically investigated but there were no positives.

Source Report done by Prof. Tissa Vitharana when he was MRI Director

Live attenuated vaccines

Live attenuated vaccines are derived from disease-causing viruses or bacteria that have been weakened under laboratory conditions. As it further explains they will grow in a vaccinated individual, but because they are weak, they will cause either no disease or only a mild form. Usually, only one dose of this type of vaccine provides life-long immunity, with the exception of oral polio vaccine, which requires multiple doses.

Inactivated vaccines

Inactivated vaccines are produced by growing viruses or bacteria and then inactivating them with heat or chemicals. Because they are not alive, they cannot grow in a vaccinated individual and therefore cannot cause the disease. They are not as effective as live vaccines, and multiple doses are required for full protection. Booster doses are needed to maintain immunity because protection by these vaccines diminishes over time.

Serological survey

Cases occurred sporadically throughout the island and for the 10 year period 1971 to 1980 there was an average of 1,030 hospital admissions each year for encephalitis with a mean case fatality rate of 38 percent (range of 25 percent - 45 percent). During this period etiological studies done at the MRI on a limited number showed that Japanese Encephalitis is the leading cause, accounting for 413 percent.

A serological survey done by us in 1976 and 1977 in various parts of Sri Lanka indicated that Japanese Encephalitis occurred mainly in certain parts of the country. These were the Western coastal belt extending from Kalutara in the south up to Puttalam in the north and inland for about 10-15 miles to include Gampaha. Domestic pig rearing is common in this area and 83 percent of pigs tested had quite high levels of HI and NT antibodies against JE.

The other areas affected were those with large rice fields and where wild pigs occur such as the districts of Kurugenala, Anuradhapura, Batticaloa and Tissamaharama. There was some JE activity in the Northern Province as well. There was little or no JE in the hill country.

Source Report done by Prof. Tissa Vitharana when he was MRI Director

The outbreak of Japanese Encephalitis is reported to further decrease in the Ratnapura district with only one patient suspected to have Japanese Encephalitis, being admitted to the Rathnapura hospital last a week before, according to Consultant Physician of the Rathnapura General Hospital Dr. N. Sritharan.

“Otherwise from March onwards we didn't have any new cases,” said Dr. Sritharan. The outbreak started since last November and in January 2013 it was the peak in getting more and more numbers of patients with symptoms suspected to be Japanese Encephalitis aka JE. “Majority of them were adults from Kuruwita, Pelmedulla, Nivithigala, Kahawaththa areas in the Ratnapura district. But by February the number of patients started to decrease and by March no new JE case was reported,” Dr. Sritharan said.

According to Dr. Sritharan very old patients have died as they were having other medical conditions.

As the Ratnapura General Hospital had all the facilities including a CT scan we were able to treat the patients and manage the illness efficiently. A neurologist was always available. So we were equipped with all the facilities,” said Sritharan.

According to Dr. Sritharan no patient showed residual symptoms – which means symptoms that would remain with the patient life time.

News reported in the recent past quoting the Ministry of Health stated that out of the 52 patients suffering from fever reported from Ratnapura, only eight were confirmed to be infected with Japanese Encephalitis. As the news reported a statement issued by the ministry indicated that the rest of the reported cases were of Viral Encephalitis which is a common condition.

Accordingly seven of the patients who had contracted Japanese Encephalitis were over forty eight years of age while the other patient was a two month old infant.

Around 11 persons died and 48 JE cases detected by February 11 from December last year to January this year, news reports stated quoting Sabaragamuwa Provincial Council Additional Secretary Sunil Leelananda.

Under control

Many of the patients reported with JE had been above 45 years, according to head of the Epidemiology Unit of the Ministry of Health Dr. Paba Palihawadana.

“Vaccinating children at the age of nine months against JE has been happening for a long period under the Expanded Program on Immunisation (EPI),” said Dr. Palihawadana.

According to the data available with the Epidemiology Unit the JE vaccine was introduced to high-risk areas in 1987 - 88. By this time the primary immunisation against JE consists of three doses at an interval of two – four weeks between the first and second doses and one year between the second and third and a booster dose is given every four years after the primary immunization, according to documents published in the Epidemiology Unit website. By then the JE immunisation under the EPI program was given to children below the age of ten years living in identified high-risk areas.

With more effective vaccines coming in to performance in the Medical field the Government took a different option later to adopt the live vaccine for JE which is at present given to children at nine months of age. According to Dr. Palihawadana in the special situation at Ratnapura children up to ten years of age were given the JE vaccine during the recent outbreak. “We didn't have to give to all children as many were vaccinated at nine months. Those who were not vaccinated at that age were given the recommended doses,” she said.

According to Dr. Palihawadana exceptions in the present EPI program are made only in areas that will show signs of high risks of spreading JE. In parts of the country that are not considered as high risk areas these exceptions will not be implemented.

“Still 95 percent of the population depends on the Government initiated National Immunisation program as vaccinating is very costly. And it had been very successful in controlling many diseases that would have crippled the population of the country,” she said.

According to survey done by the Epidemiology unit in Ratnapura to find the nature the disease is spreading they found that many abandoned gem mines and even paddy fields were dried up at that time of the year, though these with collected water are conducive breeding grounds for the vector mosquito. “Even in paddy fields water is not allowed to stagnate for a long time. The farmers let fresh water come in to the paddy fields from time to time. So paddy fields if properly maintained can avoid becoming a breeding ground,” she said.

“The people who ran animal husbandries have vaccinated their pigs except for very few cases where the animals were not vaccinated. But the major part of the pig pens were properly vaccinated,” she said explaining the findings of the Epidemiology unit.

“In general if people try to avoid creating spots where water retains unnecessarily it will reduce breeding grounds for many such diseases,” she said.

According to Professor Tissa Vitharana's report based on the research in North Central and North Western provinces following 1985 JE outbreak in Sri Lanka, if the water level in the rice fields is lowered to ground level one day of the week then the mosquito larvae and pupae die. The research was carried out when Professor Vitharana was the Director of the Medical Research Institute. As the report further said, while this is possible to do in large irrigation schemes with sufficient stored water, it is not possible in smaller irrigation schemes. Preliminary studies done at the MRI show that fish such as guppies are good feeders on vector mosquito larvae. At the beginning of 1985 (January and February), 32 cases of Encephalitis were warded at the Anuradhapura Hospital.

“Commencing in November 1985 and extending to February 1986 there was a major outbreak of JE involving the Anuradhapura and Chilaw districts. In Anuradhapura there were 406 cases of Encephalitis with 76 deaths. An unusual feature of this outbreak was that about 50 percent of the cases occurred in the age group 20-50 years and there was a preponderance of male patients. There were 106 cases with 17 deaths in Chilaw, but this followed the classical pattern and mainly affected children,” the report said.

A bigger epidemic of over 600 cases of J E occurred in the Anuradhapura District at the end of 1987 and early 1988.

Dr. Omala Wimalaratne	Dr. Paba Palihawadana

Vaccination is the most effective method to control Japanese Encephalitis and that is how Sri Lanka has been able to control the situation, said, Consultant Virologist and Vaccinologist, Head of the Department of rabies and vaccines of the Medical Research Institute (MRI) Dr. Omala Wimalarathne.

The earlier vaccine type used in Sri Lanka, when it was introduced in 1988, was the purified inactive Nakayama strain vaccine produced in mouse brain - which was first started in the North Western and North Central Provinces and was gradually introduced to the other provinces in a phased manner.

“Then subsequently we changed to the Beijing strain because that was the strain which we found to be similar to the field strains and was found to be more immunogenic,” she said. In 2009 in the government sector, the live attenuated strain of vaccine SA-14-14-2 was introduced for children on completion of one year of age.

The killed JE vaccine was very expensive and the recommendation initially was to give four doses the cost for JE vaccine alone was going beyond the other EPI vaccines which the Ministry of Health recommended for other illnesses, according to Dr. Wimalaratne.

Vaccination compulsory

“With the killed mouse brain Nakayama strain that is used in Sri Lanka 1 millilitre needed to be given to children above three years of age and for those less than three years, 0.5 ml is given. Primary course consists of two doses administered each given two weeks apart and a booster dose given 1 year later,” she said.

“At present the live vaccine is used under the Government vaccination program for children at nine months of age who are given a dose of 0.5ml. No booster doses are recommended at the moment,” she said. “The manufacturer information leaflet recommends giving a booster dose but as for studies conducted in Sri Lanka, suggested that children given one dose were having enough immunity. In Nepal such studies were done and the results showed that even up to five years of age with one dose of JE live vaccine the children have adequate protection against JE,” she said.

According to Dr. Omala Wimalaratne it is only with continuous studies in Sri Lanka that the need for a second dose will be determined.

Killed inactivated vaccine is the one used in the private sector at present. The primary vaccination is given for children above one year. As this is the killed mouse brain vaccine it is not recommended for children less than one year though the live vaccine is given at nine months of age which is given through the EPI program.

“I don’t understand why a lot of people have not vaccinated their children because they are scared of the vaccine. Safety studies are done on the vaccine - with the live vaccine as well as the killed vaccine. And we have had very few minor adverse reactions that were reported. One important thing is if the child has had convulsions during the past one year and is on anticonvulsive treatment we do not recommend JE vaccination.

And if it is a non progressive neurological disease like cerebral palsy then you don't have to worry. It is only acute illnesses and progressive neurological conditions where we do not recommend the JE vaccination -whether it is live or killed. Other than that I don't see any other problems in giving the JE vaccine,” Dr. Wimalarathne said.