COMPARISON OF 2 SAMPLE SURVEY METHODS FOR HYPERENDEMIC ONCHOCERCIASISAND A NEW FOCUS IN DAKKA, NIGERIA

Most researchers rely only on large samples for the assessment of onch ocerciasis prevalence in communities where it is endemic. However, bec ause of the large population that must be included in the sample and t he cost of surveys, several alternative methods are being explored. On e is the selection of a small ''at risk'' sample of 30 persons from ea ch community to determine the level of onchocercal endemicity. In this study both the Small Sample Survey (SSS) and the Complete Enumeration Survey (CES) techniques were used to determine the prevalence and int ensity of onchocerciasis infection in sixteen communities in Dakka dis trict, Nigeria, using conventional epidemiological procedures. The SSS showed that 82.3% of 390 at risk persons were microfilarial positive with a mean microfilaria density (MFD) of 90.9 microfilaria per skinsn ip (MF/SS) and six communities were classified as hyperendemic (preval ence beyond 59.9%). The CES of 1529 persons produced a count of 78.2% positivity and a MFD of 88.44 MF/SS. For each of the physical symptoms of the disease and the MFD, computed T-test values showed that the SS S gives an estimate that is impressively close to the CES in the estim ation of the prevalence of onchocerciasis in a community despite its l ow cost.