Urban lymphatic filariasis in central Nigeria

Wuchereria bancrofti and the other mosquito-borne parasites that cause human lymphatic filariasis (LF) infect over 120 million people world-wide. Global efforts are underway to stop transmission of the parasites, using annual, single-dose mass drug administrations (MDA) to all at-risk populations. Although most MDA to date have been in rural settings, they are also recommended in urban areas of transmission. It remains unclear whether there is significant urban transmission in West Africa, however, and the need for urban MDA in this region therefore remains a matter of debate.Clinic-based surveillance, for the clinical manifestations of LF, has now been used to identify areas of urban transmission of W. bancrofti in Jos, the major urban population centre of Plateau state, Nigeria. The eight clinics investigated were all located in slum areas, close to vector breeding sites, and were therefore considered to serve at-risk populations. Over a 1-month period, selected providers in these clinics sought hydrocele, lymphoedema, elephantiasis, or acute adenolymphangitis among the patients seeking treatment. The consenting patients who were suspected clinical cases of LF, and a cohort of patients suspected to be cases of onchocerciasis, were tested for W. bancrofti antigenaemia. All the patients were asked a series of questions in an attempt to determine if those found antigenaemic could only have been infected in an urban area. During the study, 30 suspected clinical cases of LF were detected and 18 of these (including two patients who were found to be antigenaemic) lived in urban areas. Of the 98 patients with exclusively urban exposure who were tested for filarial antigenaemia, six (6.1%) were found antigenaemic. Clinic-based surveillance appears to be a useful tool for determining if there is W. bancrofti transmission in an urban setting.