Centre’s study to uncover ‘Village of Silence’

The Centre will soon conduct a detailed study in Dhadkai, often called as “The Village of Silence”, to find out the reasons why most babies are born deaf and dumb in this remote hamlet nestled in Jammu & Kashmir’s Doda district.

The decision to order yet another study is baffling because at least three studies conducted by various Ministries of the Government have found a common reason for high incidence of hearing impairment: Flourishing inbreeding or marriage between close relations among families.

A study published in the latest edition of the Indian Journal of Medical Research (IJMR) has pointed out “considerable genetic heterogeneity in the causation of hearing loss in Dhadkai.”

Recessive mutations were observed in the three genes causing hearing loss, the researchers noted after undertaking a genetic study of an extended family of 45 members which included 23 affected and 22 unaffected members.

“Dhadkai clan exemplified a case of genetic heterogeneity underlying hearing loss in a highly endogamous population. Presence of more than one mutation in a family/individual suggested assortative mating,” said the researchers in their study.

The team of researchers comprising Meenakshi Sharma, Anuranjan Anand and Nishtha Pandey from Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru; Tabassum Rashid and Khurshid Iqbal Andrabi from the University of Kashmir, Srinagar; and Rajeev Jalvi and Raghunath Rangasayee from Ali Yavar Jung National Institute for the Hearing Handicapped, Mumbai have suggested genetic screens for neonates and use of suitable audiological tests to aid in early intervention and better management of the disability.

They noted that a majority of individuals in this village belong to the Gujjar tribe, which is an endogamous community. In 2005, 72 cases of hearing-impaired individuals were reported in a survey conducted by the State’s Social Welfare Department.

Another study —Establishing ancestry through pedigree of a village with high prevalence of hearing-impaired — in the latest edition of Journal of Indian Speech Language and Hearing Association said flourishing intermarriage and thereby consanguinity may be the reason behind high number of hearing impaired in this village.

Therefore, population-based genetic counseling may be the key to prevent the same in future, said researchers Sunil Kumar Raina, Ashok Bhardwaj and Munish Saroch from Dr RPGMC, Kangra in Himachal Pradesh and Geetika Yadav from ICMR.

Yet another study published in the Indian Journal of Human Genetics is based on a cross-sectional study among 79 deaf mutes using pedigree analysis, audiometry, imaging and molecular analysis. The researchers said that a high rate of hereditary deafness with 79 individuals diagnosed to be suffering from non-syndrome deafness in a total population of 2,452 individuals residing in the village.

Tracing the village deaf heritage, the researchers noted that it had one common ancestor. And the deafness thought to have originated in the Dadhkai only after immigration to this village by that ancestor. Mixed marriages between deaf and hearing spouses comprised 65 per cent of all deaf marriages in the late 20th century. The last deaf person born into the village is 3 years of age, probably the earliest to pick up the deformity non-medically, said the study.

Sources in the Union Science and Technology Ministry said that the decision to conduct exhaustive study came after Minister Dr Harsh Vardhan’s attention was drawn towards the widespread prevalence of the hearing disorder in the remote village.

According to experts, hearing loss constitutes the most common form of sensory defect, affecting one in 2,000 newborns. Nearly 50 per cent of hearing impairment has a genetic basis to its aetiology, they said.