Children exposed to indoor cooking fire at greater risk for severe trachoma

Children who sleep in unventilated rooms with cooking fires are at greater risk for severe trachoma, a leading cause of preventable blindness in developing countries, according to the findings of a recent study conducted in Tanzania. The study was supported by the National Eye Institute, part of the National Institutes of Health.

Trachoma is an infectious eye disease caused by the bacterium Chlamydia trachomatis. The bacteria are spread through direct contact with an infected eye, nose or throat fluids. Recurrent infections over a lifetime lead to scarring of the conjunctiva, the lining of the inside of the eyelids.

Children in trachoma-endemic communities are more likely than adults to be infected. Identifying factors that increase the risk of trachoma in children is therefore vital to the World Health Organization's (WHO) goal to eradicate trachoma by 2020. "Understanding the factors that may increase the risk of severe trachoma in children is key to developing effective ways of preventing the eye disease," said the study's lead investigator, Sheila West, Ph.D., of the Wilmer Eye Institute at Johns Hopkins Hospital in Baltimore.

For the study, Dr. West and her colleagues examined the eyes of 5240 children in 4311 households in Kongwa, Tanzania, and found that children who slept in a room with a cooking fire were almost twice as likely to have active trachoma, and four times as likely to have severe trachoma, compared to children who slept in a room with ventilation and without a cooking fire. Trachoma is considered active when there are five or more visible follicles on the undersurface of the eyelid and when the conjunctiva is thick and swollen. Severe trachoma involves ingrown eyelashes turning inward causing scaring on the cornea and clouding of the eye.

Cooking fires, fueled by wood or charcoal, were common in the homes where the children lived; 99 percent of the homes had them, sometimes in rooms where people slept, but more commonly in another room in the house. No increased risk was observed for children who spent time around cook fires in rooms that were properly ventilated and not used for sleeping.

"Cooking fires can release air pollutants that trigger inflammation in the eye, which appears to increase the severity of the disease, and may contribute to its transmission in the household" said Andrea Zambrano, M.D., the study's first author who is also at the Wilmer Eye Institute. "Without ventilation, pollutants accumulate in the air, contributing to inflammation and the likelihood of spreading infection."

Dr. Zambrano hopes this study will "improve the construction of houses to include sources of ventilation in the sleeping rooms and keep cooking fires in rooms outside the house." The good news is that only three percent of the children in the study slept in a room with a cooking fire, down from 60 percent of children according to data from the same district from nearly 30 years ago.

The goal is to continue education efforts so children are no longer sleeping in the same room as a cooking fire, and all have adequate ventilation while they sleep.