The spread of Japanese Encephalitis is a rising concern in the Philippines and in other Asian countries as it is a fatal disease that mostly affects children and the elderly whose immune system cannot fight the viral infection that targets the brain and causes seizures, paralysis, and death.
This is why Japanese Encephalitis is among the vaccine-preventable diseases highlighted in the World Health Organization’s (WHO) annual World Immunization Week, happening from April 24 to 30 this year. The global public health campaign raises awareness on how immunization saves millions of lives and how it is recognized as the most successful and cost-effective health intervention around the world.
With this year’s theme of “Protected Together, #VaccinesWork”, the World Immunization Week “encourages people at every level—from donors to the general public—to go further in their efforts to increase immunization coverage for the greater good.”
In a recent study released by WHO on the incidence time series of vaccine-preventable diseases in the Philippines, Japanese Encephalitis is shown as the No. 2 vaccine-preventable disease (next to Diphtheria) whose occurrence has shown a steady increase in recent years. It is the third in the number of cases, next to Tetanus and Measles, but the incidences for Measles have significantly decreased while Tetanus cases lowered in 2014 and increased again in 2015 and 2016. From only 24 reported cases of Japanese Encephalitis in the Philippines in 2013, the number has risen to 69 in 2014, 115 in 2015, and 312 cases in 2016.
“Japanese Encephalitis is an endemic disease in the Philippines that is caused by a neurotropic virus that is capable of entering the nervous system. That is why 80 percent of people with Japanese Encephalitis have seizures and convulsions. The virus is carried and transmitted by the Culex tritaeniorhynchus, the biggest mosquito that breeds in rice paddies and is prevalent in rural areas with open irrigation such as in Central Luzon and also in other parts of the Philippines,” explained Dr. May Emmeline B. Montellano, M.D., a pediatric infectious diseases expert who holds the concurrent positions of Philippine Foundation for Vaccination president, International Society for Tropical Pediatrics local chapter vice president, Pediatric Infectious Diseases Society of the Philippines (PIDSP) founding member and adviser for the organization’s Committee on Childhood Immunizations, and Philippine Society for Microbiology and Infectious Diseases (PSMID) Committee on Adult Immunization co-chairman.
According to Dr. Montellano, studies have shown that pigs and birds serve as “reservoir” of the Japanese Encephalitis virus. The Culex mosquito infects pigs and birds with the virus but these vertebrates will show no symptoms of the disease—they merely serve as breeding ground for the completion of the life cycle of the virus. As the virus transmitter, the mosquito infects humans with Japanese Encephalitis by biting infected pigs and birds, and vice versa as the cycle continues.
Dr. Montellano stresses the importance of vaccination as the single most effective way of curbing the spread of Japanese Encephalitis.
“Vector control will not work in stopping the spread of the virus because we cannot kill all the pigs and the birds, and there are just too many mosquitos in various stages of their life cycles. We encourage people to have themselves vaccinated from Japanese Encephalitis, especially very young children as well as the elderly. The Japanese Encephalitis vaccine can be given as early as 9 months of age. Those 9 months to 17 years old will need two doses of the vaccine, to be given with an interval of 20-24 months. Adults 18 years old and above will only need one shot,” the doctor said.
Other Asian countries such as Japan and South Korea have shown significantly lower incidences of Japanese Encephalitis through public administration of the vaccine. In the Philippines, people are encouraged to ask their doctors for the vaccine especially if they live near or travel to rural areas where there are high incidences of the disease.