Clear vision
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| Trachoma causes blindness |
Latest research reveals that it is possible to control
the spread of trachoma — a disease that results in blindness — by adopting
sustainable sanitation measures. Trachoma — a conjunctival infection — is caused
by Chlamydia trachomatis and is responsible for 15 per cent of all blindness worldwide.
Trachoma epidemics are associated with vastly increasing number of eye-seeking flies (
Muska sorbens) that breed in faeces. Paul Emerson, researcher at the School of Biological
and Biomedical Sciences, Durham, the UK, and his team targeted these flies for their
study. The underlying idea was to prove that trachoma could be controlled by a sanitation
drive. They carried out the study in 1999-2001 in high trachoma-endemic areas of Gambia,
Africa. They conducted cluster-randomised control trials in three groups, each comprising
seven clusters.
Two of the groups were divided on the basis of two
different intervention strategies — using insecticide (permethrin) spray and pit
latrines (non-ventilated) — and one group was treated as control (no intervention).
After six months, the clusters were compared on the basis of trachoma screening, and the
number of eye-seeking flies from the eyes of the volunteer children younger than five
years was calculated.
| About six million people in Asia
and Africa currently suffer from irreversible blindness due to trachoma. In India alone,
an estimated 865,000 people have turned blind due to trachoma |
Insecticide spray reduced the fly population by 88 per
cent and led to a 56 per cent reduction in the incidence of trachoma. On the other hand,
pit latrine reduced both fly population and trachoma incidence by mere 30 per cent.
The fact that the result was in favour of insecticide
spray has a wider positive implication in the context of developing countries. But the
sanitation drive has other collateral benefits that are not evident with insecticide
spray. Pit latrine is economi-cally viable, can be constructed in remote villages with
locally available tools and is culturally acceptable. It needs very little water. Further,
this latrine can control all kinds of waterborne dis-eases.
The study mentioned active community participa-tion in
the sanitation drive, which gave a sense of owner-ship to the beneficiaries.
Permethrin, on the other hand, can cause neurological
damage, breast cancer, hormonal changes and childhood cancers in addition to ecological
damage (for instance, it adversely affects fish, honey bee and waterborne arthropods).
Moreover, regular insecticide operation is expensive and needs trained manpower and proper
planning, which is difficult to implement in developing countries. There are reports of
permethrin resistance in eye-seeking flies and also in Aedes aegypti (vector for dengue
fever), which may cause further devastation to the community.
According to recent estimates, about six million people
in Asia and Africa currently suffer from irreversible blindness due to trachoma. In India
alone, an estimated 865,000 people have turned blind due to trachoma. It is mostly
prevalent in the poor (particularly children) living in unhygienic condition. The current
strategy of trachoma control comprises mass antibiotic eye ointment treatment, surgical
correction of eyelid deformity caused by infection, insecticide spray to control fly and
personal hygiene. But since these measures are expensive, donor dependent, manpower
oriented and also hazardous, only a sustainable sanitation programme can save the eyesight
of hundreds of people every year in India and other developing countries.
References:
1.
Paul M Emerson et al 2004, Role of flies and provision of latrines in trachoma
control: cluster-ran-domised controlled trial, in The Lancet, The Lancet Publishing
House, the UK, Vol 363, No 9415, pp 1093-1098.
2.
Park K 2003, Park's textbook of preventive and social medicine, Banarasidas Bhanot
publishers, Jabalpur, India, pp 236-238. |
