Based on a study carried out in 2015, a team led by Dr. Manoj V. Murhekar, Director of the Chennai-based National Institute of Epidemiology, found scrub typhus to be responsible for acute encephalitis syndrome (AES) in 63% of patients admitted to the Baba Raghav Das Medical College Hospital in Gorakhpur. The study was repeated last year by the same team by comparing children with AES and healthy children who are siblings of the patients or living in the same village. It found that AES patients had 35 times greater possibility of having antibodies against scrub typhus compared with healthy children thereby confirming that AES was caused by scrub typhus.
Excerpts from an interview with Dr. Manoj Murhekar:
Have you carried out any studies on children admitted to BRD hospital with AES? How likely is scrub typhus to have caused AES this year as well?
The causation of the disease or etiology will not change from year to year. In 2015 and 2016 we have seen that scrub typhus was responsible for over 60% of AES and Japanese encephalitis virus (JEV) causes less than 10% of AES in children below 15 years. There is vaccination for JE virus but no intervention has been implemented widely for scrub typhus. So the etiology wouldn’t have changed compared with last year.
Besides BRD hospital, is there any other referral hospital in that region? What is the extent of population that BRD hospital caters to?
Except BRD hospital, there is no referral hospital in the Gorakhpur Division in Uttar Pradesh. The hospital caters to people living in Gorakhpur Division (four districts) and Basti division in U.P., Bihar, West Bengal, Assam, Uttarakhand and Himachal Pradesh, and even Nepal.
Why do we see a large number of children with AES each year at BRD hospital?
There is a lot of scrub typhus fever in the community. Between 20-25% of fever in children being attended to at PHCs is caused by scrub typhus. Only a small percentage of these children progress to AES. Most of the cases in the community are sub-clinical with no symptoms or very mild fever. Only some children with fever will progress to AES. About one-fourth of patients with AES are adults. Generally, adults develop immunity against scrub typhus, so only those who have not been exposed to scrub typhus will progress to AES.
Is there any specific reason why scrub typhus is found only in this region?
It is not correct to say it is restricted only to this region. Scrub typhus is found even in Tamil Nadu — Vellore and Thiruvallur districts. About 7-10% of fever in these two districts is caused by scrub typhus. The reason why it is found only in these two districts in Tamil Nadu is because researchers have investigated for scrub typhus in these two districts.
Is it possible to treat scrub typhus and prevent the infection from progressing to AES?
In the beginning of this year, the Indian Council of Medical Research (ICMR) recommended to the Uttar Pradesh government to use doxycycline antibiotic to treat children with fever for five days. If treated early, then children will not progress to AES. This prevention strategy has to be implemented widely and even by doctors in the private sector before we see results. In July, ICMR and doctors from the Christian Medical College, Vellore went to Gorakhpur and conducted awareness campaign for Indian Medical Association (IMA) and Indian Association of Paediatrics (IAP) doctors, chief medical officers and programme officers.
Why is the death rate high at 20% in children with AES?
At BRD hospital, we have observed patients with AES. The mortality is about 20% due to multi-organ involvement. In the case of AES caused by scrub typhus, the mortality is about 15-17% compared with AES caused by JE. This is because treatment started early with azithromycin can treat AES caused by scrub typhus. Azithromycin is in the class of medicines as doxycycline but easy to administer in sick children as it is given intravenously.
What is vaccine coverage for Japanese encephalitis and why don't we see herd immunity with this vaccine?
In 2012, the vaccine coverage for Japanese encephalitis was only 50% but has improved to 75% now. A study we carried out in 2015 found 75% coverage for the first dose and only 42% for the second dose. Three of the four children aged 25-36 months in Gorakhpur region had received at least one dose of the vaccine. We need two doses of the vaccine — during 9-12 months for the first dose and 16-24 months for the second dose — for optimal protection. With just one dose, the efficacy is over 80%. No studies have been done to find the duration of protection. With increasing vaccine coverage the incidence of JE has dropped from about 20% a few years ago to less than 10% now.
In the case of mosquito-borne diseases, herd immunity will not play a major role. So increasing the vaccine coverage should be a priority.