Need for a differential criteria to stop mass drug administration, based on an epidemiological perspective of lymphatic filariasis in Thiruvananthapuram, Kerala, India

ObjectiveTo determine the prevalence of any of the clinical manifestations of lymphatic filariasis, parasitological and entomological indices in Thiruvananthapuram district, Kerala, India, prior to launching mass drug administration (MDA) in the district in 2005.MethodsA cross sectional survey was conducted in 7 endemic wards of the district, in a sample of 2 472 individuals above the age of one year. The study consisted of data collection using questionnaire, night blood smear examination and mosquito collection followed by identification and dissection.ResultsThe prevalence of any of the clinical manifestations of filariasis in this endemic area was 3% (73/2 472) (95% CI between 2.3% to 3.7%). The microfilaria rate was found to be 0.38%. Culex quinquefasciatus formed the predominant mosquito species. The vector infection rate was 1.4% and infectivity rate was 0.47%. Half of the population had satisfactory knowledge regarding the disease. In almost an equal number, the knowledge was poor and only about 10% had good knowledge. Most of the people had not heard about the MDA program.ConclusionsThe prevalence of filariasis even in an area considered to be endemic in Kerala, was low. Microfilaraemia was much lower than the clinical manifestations. However, the potential risk of transmission of disease continues. For such areas which had a pre-MDA mf rate less than 1%, there needs to be more stringent criteria for evaluating the effectiveness of the programme, doing transmission assessment surveys and stopping MDA.