SummaryThis paper reports on DEC distribution and compliance with treatment in a large-scale annual single-dose mass treatment programme to eliminate lymphatic filariasis in the south Indian state of Tamil Nadu. 76.9% of households (82.5% in rural areas and 58.0% in urban areas) were aware of drug distribution for control of filariasis. DEC was given to 70% (= distribution rate) (range 0-92%) of the population and 53.5% (range 12-89%) complied with treatment. The distribution rate was more than 75% in 74% of the villages and compliance was in the range of 51-75% in 76% of the villages. About 5% of the treated population reported side-effects. Distribution and compliance were higher in rural than urban areas and similar between males and females. Qualitative data showed that some socio-economic factors, logistic and drug-related problems and people's poor knowledge and perceived benefits of treatment played a role in a proportion of the population not receiving or taking the drug. The Tamil Nadu programme showed that large-scale repeated annual DEC mass treatment is feasible and that existing health services are capable of delivering the drug to all communities. While even poor to moderate compliance rates can reduce the vector transmission of infection to some extent, improved drug distribution and compliance with treatment are necessary to consolidate the gains of earlier rounds of treatment and achieve the goal of filariasis elimination within a reasonable time frame.

In the mass drug administrations (MDA) that form the principal strategy of the Global Programme to Eliminate Lymphatic Filariasis, treatment coverages of at least 65%-80% will be needed if the programme is to be successful. In the Indian state of Tamil Nadu, where treatment coverages were typically <65%, a comprehensive strategy of advocacy and communication, called the "communication for behavioural impact" (COMBI) campaign, has been developed and implemented, in an attempt to improve treatment coverage. This strategy combined advocacy, aimed at state-, district- and village-level administrations, with communication activities targeted at individual communities. The main aim was to alter the behaviour of many of those included in the rounds of MDA, so that they would be more likely to accept and consume the diethylcarbamazine tablets offered to them. The COMBI campaign had two variants, COMBI(+) and the more intensive COMBI(+ +), each of which has been implemented in six districts. Both the variants included the "personal selling" of treatment, via door-to-door visiting by a total of 113,500 filaria-prevention assistants. These assistants were able to visit 34%-49% of the households in each target community. In the COMBI(+ +) districts, up to 44% and 38% of households received information on lymphatic filariasis and its elimination via television commercials and posters, respectively. Overall, 78% of the villages in the COMBI(+ +) districts and 33% of those in the COMBI(+) districts were considered to have had good exposure to the communication campaign. At the end of this campaign about 30% more people (than pre-campaign) believed that lymphatic filariasis could be eliminated and many of those targeted considered lymphatic filariasis to be a dreadful disease, knew that a particular day had been designated "Filaria Day", and thought that the tablets offered in MDA should be consumed to prevent or eliminate the disease. Apparently as the result of the COMBI campaign, drug consumption increased, from 33% of those living in endemic communities, to 37% in the COMBI(+) districts and to 49% in the COMBI(+ +). Coverages as high as 65%-73% were recorded among those who had had the maximum exposure to the communication campaign. These results indicate that the COMBI campaign favourably changed the perception and behaviour of the people towards the elimination of lymphatic filariasis. The costs of the COMBI(+) and COMBI(+ +) strategies were only U.S.$0.002 and U.S.$0.009 per capita, respectively.

SummaryLymphatic ®lariasis (LF) is targeted for global elimination. Repeated annual single-dose mass treatment with anti®larials has been recommended as the principal strategy to achieve LF elimination. This requires an effective and sustainable strategy to deliver the drug, diethylcarbamazine (DEC), to communities. In this study, a new drug delivery strategy ± community-directed treatment (comDT) ± was developed and implemented and its effectiveness compared with that of the traditional health servicesorganized drug delivery, in rural areas of Tamil Nadu, India. Qualitative and quantitative data showed that the communities and health services were able to distribute the drug in almost all villages. The drug distribution rate and treatment compliance rate of comDT and health services treatment were statistically compared after adjusting them for clustering. Under the comDT 68% (n 20 villages; range: 0±97%) of the population received DEC, compared with 74% (n 20 villages; range: 48±95%) with the health services treatment strategy (P > 0.05). However, only about 53% (range: 0±91%) of comDT recipients and 59% (range: 32±79%) of those who received DEC from the health services consumed the drug (P > 0.05). Although statistically not signi®cant, the distribution and compliance rates were lower under the comDT strategy. Also, the strategy's operationalization appears to be dif®cult because of some social factors, and the tradition of communities' dependence on health services for treatment, whereas health services-organized distribution was much less cumbersome and found to be more acceptable to people. However, the distribution (74%) and compliance rates (59%) achieved by health services were also only moderate and may not be adequate to eliminate LF in a reasonable time frame. Health services manpower alone may not be suf®cient to distribute the drug. We conclude that drug distribution by health services is the best option for India and participation of the community volunteers and village level government staffs in the programme is necessary to effectively distribute the drug and attain the desirable levels of treatment compliance to eliminate LF.keywords lymphatic ®lariasis, drug delivery, elimination, rural areas, India correspondence K. D. Ramaiah, Vector

Antigen-specific hyporesponsiveness to filarial antigens is a phenomenon observed in patent infection with lymph-dwelling filarial parasites of humans. This phenomenon has been attributed to a multitude of factors, one of which is altered monocyte function. To examine the role played by monocytes in filarial infection, we assessed the responses of monocytes obtained from normal and filarial parasite-infected individuals to both crude filarial antigen and purified recombinant filarial antigen WbSXP-1 and attempted to relate these to the altered lymphoproliferative responses seen in filarial infection. Monocytes from microfilaremic (MF) patients demonstrated an inability to respond to lipopolysaccharide compared to monocytes from endemic normal persons or from lymphedema patients. Indeed, interleukin 1␤ (IL-1␤) production was severely limited, a finding that did not extend to monocyte responses to filarial antigens. Serum from MF patients reduced adherence and spreading of normal monocytes, a finding not seen with serum from the other clinical groups. Interestingly, there was a significant correlation between the production of IL-1␤ and adherence. Moreover, the levels of spontaneous production of IL-1␤ correlated with high levels of spontaneous secretion of IL-10. The effects observed were not a result of diminished viability or alteration in the expression of the cell surface markers CD14 and HLA-DR. These data suggest that monocyte function is dampened in MF patients, a finding which could alter lymphoproliferative responses during patent infection.Understanding the induction of differentiated T-cell responses in helminth infections has been a major goal for parasite immunologists. The source of cytokines involved in the skewing of T-cell responses in helminth infections has been of particular interest, as the cytokine microenvironment is considered to be the most important factor influencing the differentiation of naive T cells and the generation of immunoregulatory cells (1,30,31,36,37). Among individuals with human lymphatic filariasis, those with patent infection (microfilaremic or antigenemic) exhibit parasite antigen-specific down-regulation of T-cell proliferation and gamma interferon production. These responses are different from those in patients with lymphedema/elephantiasis (mixed Th1/Th2 response) and infection-free endemic normal (EN) persons (predominant Th1 response to parasite antigen). The occurrence of filarial parasite-associated modulation of the immune response in microfilaremic patients is supported by extensive clinical (35,38,41) and animal (27) data. To date, however, no single mechanism can explain the modulatory effects of filarial infection in patients with patent infection.The induction and maintenance of Th2-type immune responses are based largely on studies with murine models showing that antigen affinity for the T-cell receptor (6), the dose or route by which antigen is administered (11,14), costimulatory molecule interactions (32, 49), the prevailing in vivo cytokine milieu (45),...