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Chloroquine (CQ) and sulphadoxine/pyrimethamine (SP) are two first-line antimalarials used under the existing Indian National Drug Policy in the north-eastern region of India bordering several countries including Myanmar. Although widespread resistance to antimalarials in Plasmodium falciparum has been reported from western Myanmar, information from the Indian side of the border is scarce. We studied the therapeutic response to CQ and SP at four sites in Changlang and Lohit, two administrative districts of Arunachal Pradesh bordering Myanmar. We monitored uncomplicated falciparum malaria patients after treatment with standard regimens of CQ and SP for 28 days following the revised in-vivo protocol of the World Health Organization. A total of 236 patients, 95 in the CQ group and 141 in the SP group, participated. We recorded 23.8% early treatment failures to CQ and 14.1% to SP; late clinical failures of 14.3 and 12.6%; late parasitological failures of 10.7 and 8.1% and adequate clinical and parasitological responses of 51.2 and 65.2%, respectively. The significantly different treatment failure rates seen in Chowkham (furthest from Indo-Myanmar border) and Jairampur/Nampong (nearest to Indo-Myanmar border) for chloroquine (Cox proportion hazard ratio 9.1, P<0.0001) and SP (Cox proportion hazard ratio 7.35, P=0.001) denote a non-response gradient to the two antimalarials extending from the international border. The gradient is probably indicative of the direction of movement of the drug-resistant P. falciparum parasite. The utility of chloroquine as the first-line drug under the present National Drug Policy in these areas needs reconsideration.

S. shorttii, a common phlebotomine sandfly species of Assam, was tested for susceptibility to commonly used insecticides, D.D.T., malathion and Fenitrothion in Kamrup district, Assam. Tests carried out by WHO test kits showed 100 per cent mortalities against discriminating concentrations of malathion (5 per cent) and Fenitrothion (1 per cent). With D.D.T., in 1 hr. exposure mortalities recorded were 54.5 and 64.4 per cent, whereas in 24 hr. exposure mortalities were 75 per cent and 90 per cent. The area has been under continuous D.D.T. spraying since the beginning of NMEP in 1958, and high selection pressure appears to have precipitated D.D.T. resistance in this partly exophilic species.

In the past Assam was devastated by epidemics of Kala-azar. However, inspite of resurgence of this disease in Bihar and neighbouring areas Assam has remained untouched by this disease since the mid 1950s so far. The study undertaken in Kamrup district, sought to provide an entomological explanation for Assam's present freedom from Kala-azar. Sandfly collections were made in 15 villages. Three different methods were used; namely hand collections by aspirator and torch, sticky traps and examination of soft parts of cattle in the villages for mating swarms. 1049 sandflies were collected which did not include any specimens of P. argentipes. The vector of Indian Kala-azar has either been eliminated by continuous insecticide spraying in this high P. falciparum, and chloroquine resistance area or reduced to such low levels of prevalence that routine sampling methods are unable to reveal its presence. The implications of this finding are discussed in relation to Kala-azar control in India, in general.