Using key informants to estimate prevalence of severe visual impairment and blindness in children in Cross River State, Nigeria.

PURPOSE: To assess the prevalence and causes of childhood blindness in Cross River State, Nigeria, using the key informant (KI) method. METHODS: KIs were selected and trained and requested to bring children to identified facilities 2 weeks after training for examination by a specialist team. Visual acuity and cause of impaired acuity were assessed. Children at a Cross River State school for the blind were also assessed. An estimated prevalence of childhood blindness and severe visual impairment (BL/SVI) in the Cross River State was calculated. RESULTS: A total of 742 KIs were included. The prevalence of BL/SVI in Cross River State was estimated to be 0.09-0.22 per 1,000 children. The three most common anatomic causes are lens related (35%), whole globe (19.4%), and corneal (15.7%), most of which are avoidable. CONCLUSIONS: The prevalence of childhood BL/SVI in Cross River State was somewhat lower than expected but similar to other recent reports from Africa. Lens-related causes were the most common. KIs performed well, ensuring that many children in need of eye services were examined.

Status of forest onchocerciasis in the Lower Cross River basin, Nigeria: entomologic profile after five years of ivermectin intervention.

In the Lower Cross River basin in Nigeria, no pre-control entomologic profile of Onchocerca volvulus infection in the local Simulium damnosum population was available prior to the initiation of an ivermectin control program in 1995. A longitudinal entomologic study was therefore carried out over a 12-month period (January-December 2001) at the Agbokim waterfalls and Afi River, which are breeding sites of S. damnosum in the river basin. A total of 9,287 adult S. damnosum were caught on human bait; 9,048 (97.43%) were dissected, of which 313 (3.46%) were infected. Annual biting rates (ABRs) of 42,419 and 28,346 bites per persons per year were recorded at the Agbokim Waterfalls and Afi River, respectively. The annual transmission potential (ATP) was 419 infective larvae per person per year at the Agbokim Waterfalls and 427 at the Afi River. Monthly biting rate and monthly transmission potential varied significantly (P < 0.05) at the two sites. Transmission was highly seasonal from April to September, corresponding to the peak biting period of the vector. The high ATP and ABR values are a measure of the mesoendemicity of onchocerciasis in the river basin. There was a significant F(0).05 (1, 10) (P < 0.05) variation in the relative fly abundance from both sites. It was observed that human activities such as farming, fishing, timber cutting, and hunting are done in the early morning and late afternoon, which corresponds to the peak diurnal biting period of the vector. Changes in these practices and attitudes may markedly affect the disease intensity and transmission.