Discussion

The results of this survey indicate that xerophthalmia is a public health problem in Gikongoro. The 1.31% prevalence of children with Bitot's spots is well above the WHO threshold of 0.5% denoting significant vitamin A deficiency [4]. In addition, the prevalence of 21.3% of children over one year of age with a retinol level £0.70 µmol/L is comparable to the 20% level used as a further indicator of the presence of a severe public health problem [4]. In addition to Bitot's spots, advanced xerophthalmia was also regularly encountered in the region, as we observed cases of keratomalacia, corneal perforation. and ulcers at the local hospital.

The mean serum retinol level of children with Bitot's spots was significantly lower than that of their matched controls, supporting the use of Bitot's spots as evidence of the presence of vitamin A deficiency.

The anthropometric findings showed a high incidence of poor nutritional status overall, and it would seem that those with Bitot's spots were worse off than controls in regard to protein-energy malnutrition.

The dietary questionnaire shows that Gikongoro children had a very low consumption of vitamin A of animal origin. Carotenes were the main source of vitamin A. The consumption of vegetables was seasonal (two to four months a year) and generally low. The observation that cassava leaves were more frequently consumed by controls than by children with Bitot's spots was not unexpected, since these leaves are a good source of beta-carotenes. Also. the consumption of a greater variety of foods containing beta-carotenes seems to be a protective factor against xerophthalmia.

Two control groups were used to evaluate the scope of vitamin A deficiency in this study. The fact that the mean serum retinol the three groups was low indicates that the entire population was at risk of vitamin A deficiency. If the low serum retinol levels were limited to the children with Bitot's spots, one would expect specific individual risk factors within these communities. Finally, if the mean serum retinol of the representative sample were high and yet both the cases and their controls had low values, the risk factors would be more likely to be related to the communities. In our data, all three groups had low serum retinol levels, indicating a high risk of vitamin A deficiency, but the problem was more acute in children with Bitot's spots. According to the food frequency questionnaire, all three groups seemed to have a very low intake of beta-carotenes, but the intake of the matched control group was significantly lower than that of the representative sample. This might suggest that, in addition to individual risk factors, certain communities are at higher risk. Indeed, the distribution of cases with Bitot's spots tended to cluster in certain higher-altitude areas (data not shown). Poorer food production in these communities might be an explanation. Nonetheless, all children are at risk, and the control programme should target the entire population.