Short communication Decline in lymphatic filariasis transmission with annual mass drug administration using DEC with and without albendazole over a 10 year period in India I.P. Sunish b , M. Kalimuthu a , R. Rajendran a , A. Munirathinam a , V. Ashok Kumar a , J. Nagaraj a , B.K. Tyagi a, ⁎ a Centre for Research in Medical Entomology (ICMR), No.4 Sarojini Street, Chinna Chokkikulam, Madurai 625 002, India b Regional Medical Research Centre (ICMR), Field Unit, Perka Village, Car Nicobar, Andaman & Nicobar Islands744 301, India abstract article info Article history: Received 17 March 2014 Received in revised form 19 June 2014 Accepted 31 August 2014 Available online 7 September 2014 Keywords: Lymphatic filariasis Transmission indices Tirukoilur South India The National Programme for the Elimination of Lymphatic Filariasis is underway in the endemic districts of Tamil Nadu State, South India, since 2001. Annual mass drug administration (MDA) was carried out by the state health department to all eligible individuals. The impact of MDAs on transmission parameters was evaluated in 2 reve- nue blocks, viz, one with DEC alone and the other with a combination of albendazole. After 10 years with 6 an- nual MDAs, the transmission indices reached low levels in both treatment arms, but still persisted. However, the DEC alone arm showed higher transmission rates, compared to the DEC + ALB arm. Few villages which dem- onstrated persistent transmission need to be targeted with an additional control measure viz, vector control, to achieve LF elimination. It is evident from the 10 year period of the study that inclusion of albendazole along with DEC has significantly reduced the transmission indices to almost nil level, as compared to DEC alone. © 2014 Published by Elsevier Ireland Ltd. 1. Introduction More than 1.2 billion people are estimated to live in areas where they are at risk for lymphatic filariasis (LF) [1]. Of the 120 million actual cases of LF currently thought to occur in 83 endemic countries, 91% are caused by Wuchereria bancrofti, while Brugia malayi and Brugia timori infections account for the other 9% [2]. In 1997, a landmark adoption by the World Health Assembly of Resolution, WHA50.29, called for the elimination of LF as a public health problem globally. As a result, in 2000 the World Health Organization, in collaboration with other inter- national agencies from the public health and private sectors, formed a global alliance and launched a global campaign to eliminate LF by the year 2020 [3]. The Global Programme for Elimination of Lymphatic Filariasis (GPELF) has identified the Indian subcontinent as the region in which the greatest number of people is at risk from LF [4]. The WHO recom- mends a yearly single-dose of diethylcarbamazine (DEC) or ivermectin, combined with albendazole [5], to reduce blood microfilaraemia to levels at which transmission by the vector mosquito cannot be sustained. In India, a pilot scale programme on mass annual single- dose of DEC + ALB was launched in the year 2001. Since then the mass drug administration (MDA) programme in Tamil Nadu is being implemented every year. Monitoring and evaluation of the effect of MDA are important in order to be able to quantify the impact and to make evidence based pro- gramme adjustments. Transmission can be monitored by quantifying the resting and landing vector densities, infection and infectivity rates. This study addresses issues that are important for filariasis elimination efforts, especially with respect to the administration of the combination of DEC with albendazole. Here we report the impact of 6 rounds of MDA carried out over a period of 10 years, on the LF transmission in an area where two drug regimens, viz, DEC with and without albendazole were administered. 2. Materials and methods A longitudinal study was undertaken on an LF elimination pro- gramme in two revenue blocks of Tamil Nadu State, South India, viz,the Tirukoilur block (administered with DEC + ALB), and Mugaiyur block (DEC alone), to assess the effectiveness of these two drug regimens. In each block nine villages were longitudinally monitored for the impact of MDAs on filarial indices. The mosquito Culex quinquefasciatus, which prefers to breed in soakage pits, is the sole vector in this area [6]. Findings on the impact of MDAs on com- munity filarial infection in these villages have already been reported earlier [7,8]. In the 2 blocks of the study site, initial 3 rounds of MDAs were made between 1998 and 2000 with DEC alone, by the Directorate of Public Parasitology International 64 (2015) 1–4 ⁎ Corresponding author at: Centre for Research in Medical Entomology (ICMR), No.4 Sarojini Street, Chinna Chokkikulam, Madurai 625 002, Tamil Nadu State, India. E-mail addresses: sunish67@yahoo.com (I.P. Sunish), crmeicmr@icmr.org.in, abk.tyagi@yahoo.co.in (B.K. Tyagi). http://dx.doi.org/10.1016/j.parint.2014.08.005 1383-5769/© 2014 Published by Elsevier Ireland Ltd. Contents lists available at ScienceDirect Parasitology International journal homepage: www.elsevier.com/locate/parint