Comparison of methods for estimating the frequency of paralytic poliomyelitis in developing countries.

Standard reporting systems have proved to be unreliable in estimating the frequency of paralytic poliomyelitis in many developing countries. The effectiveness of three survey methods for estimating the prevalence of lameness attributable to poliomyelitis were compared in the Danfa Health Project district of rural Ghana. Lameness was studied because it is easily identified by inexpensive survey techniques. A postal survey of school headteachers was the least costly and most accurate method, giving a prevalence of lameness attributable to poliomyelitis of 7.2 per 1000 schoolchildren. This method is recommended for countries with an extensive network of primary schools. Medical examinations in a village health survey yielded a prevalence of 4.6 per 1000 children aged 6-15 years. This method was relatively expensive but could be justified if the survey was multipurpose. A question added to the annual district census showed a prevalence of 2.2 per 1000 children, a rate still many times higher than estimates from national statistics. The inclusion of such a question in a census or other national survey entails little additional cost and with more careful questioning results should improve. Repeated surveys can be used to assess the success of poliomyelitis vaccination programmes.

Outside Europe. Is poliomyelitis a serious problem in developing countries?--the Danfa experience.

Children were examined for lameness in the Danfa Project district of rural Ghana to assess the impact of endemic poliomyelitis and to test a widely held hypothesis that paralytic poliomyelitis is relatively rare in such districts (less than 1 per 1000 children affected). The observed prevalence of lameness attributable to poliomyelitis was 7 per 1000 school-aged children, and the annual incidence is estimated to be at least 28 per 100 000 population. Although no evidence for an epidemic was found, these rates are comparable with those in the USA and Europe during the years of severe epidemics and indicate that a high price is being paid in the Danfa district for the natural acquisition of immunity. As a result, immunisation against poliomyelitis has been given high priority. A teacher questionnaire was also tested for use in postal surveys as a rapid means of estimating the prevalence of lamenes attributable to poliomyelitis in countries with a reasonable network of primary schools.

Is poliomyelitis a serious problem in developing countries?--lameness in Ghanaian schools.

A postal survey of lameness in schools throughout Ghana showed an estimated prevalence of lameness attributable to poliomyetitis of 5-8 per 1000 school-aged children and an estimated mean annual incidence of paralytic poliomyelitis of 23 per 100 000 population. Official reported incidence rates range from 0-1 to 2-1 per 100 000 population, indicating that at least 90% of cases are not reported. No evidence of epidemics was found to account for these high rates. These suggest that mean annual incidence rates in tropical endemic countries have always been as great, if not greater, than those experienced by temperate countries during epidemic periods in the twentieth century and that the total number of cases of paralytic poliomyelitis occurring in the world each year has been reduced by only 25% since the advent of polio vaccine. Immunisation against poliomyelitis must have a high priority in Ghana and other tropical countries where the disease is endemic.