N L Sitaraman’s scientific contributions

Results of susceptibility tests conducted with Anopheles culcifacies for the period 1973-78 in Karnataka State are presented, showing widespread resistance to both DDT and dieldrin. DDT was in use in many parts of the State for more than 2 decades. HCH was in use in four districts for the past five years. Extensive use of agricultural pesticides might have partially contributed to the development of resistance. The vector was generally susceptible to organo-phosphorus compounds.

Susceptibility status of adult A. stephensi was determined against DDT, dieldrin, malathion and fenitrothion in 13 towns of Tamil Nadu State and in one of Karnataka State. With malathion 5 per cent and fenitrothion 1 per cent, there was 100.0 per cent kill on one hour exposure in all the places. High degree of resistance was noted to DDT and dieldrin in all the towns of Tamil Nadu. Larval tests showed 100.0 per cent kill with 3.125 ppm. of malathion and 0.025 ppm. of chlorpyriphos and 2.5 ppm. dieldrin. With the diagnostic dose of 0.1 ppm. dieldrin the mortality ranged from 72.0 to 97.0 per cent. With DDT 2.5 ppm. it ranged from 80.0 to 100.0 per cent. Highest concentration recommended for temephos (0.624 ppm) was not available but with 0.025 ppm., the mortality ranged from 34.0 per cent in Madras to 96.0 per cent in Tirupattur. With the same concentration, 48 hours exposure killed all the larvae in all the places. The necessity of constant monitoring is stressed and timely detection may be of great help in planning the control operations on a scientific line.

Due to large scale resurgence of malaria in some parts of Karnataka state, it has become difficult to administer radical treatment (RT) to all malaria parasite positive cases. Many cases therefore receive only presumptive treatment (PT) with 600 mg base of chloroquine (adult dose). The result that could be expected from this single dose was investigated on 674 P. vivax and 391 P. falciparum cases which were followed up at an interval of 7-10 days. Persistance of parasites of the respective species was noted in 1.18 and 0.25% of P. vivax and P. falciparum cases respectively for the entire State but in individual localities vivax ranged from 0 to 4.2%. There was only 1 case of falciparum. It was concluded that the purpose of giving presumptive treatment was being served fairly well. It has been suggested that where radical treatment is not possible, another single dose of chloroquine should be given and the younger age group in particular is likely to derive good benefit from this.

A total of 8,329 P. vivax cases in Dharmapuri NMEP division was given 5-day radical treatment. For an adult, the regimen consisted of 600 mg of choloroquine base on the first day and 15 mg. of primaquine base daily from the first to the 5th day. On follow-up 8,305 cases were found to be negative on the 7th day (i.e. on completion of radical treatment). Subsequently, only 6,393 cases could be followed up to the end of one year and only 82 persons were found positive during this period. This gave a breakthrough rate of 1.28 per cent, a rate much less than what was anticipated. The study indicated that 5-day radical treatment is quite efficacious in the particular unit studied.

In response to the suggestion of the World Health Organisation (1973) for continuous monitoring of the sensitivity status of P. falciparum infection to chloroquine therapy, field data were analysed in 2 towns of Tamil Nadu State viz. Salem and Sathyamangalam. Chloroquine base (600 mg.) were administered to 596 cases of P. falciparum infection in Salem town and to 184 cases in Sathyamangalam respectively. All cases were found to be negative on the 7th day of treatment and only one case was found to be positive in Salem on the first monthly follow up. Similar treatment with 1200 mg. base of chloroquine given to 198 and 177 cases in Salem and Sathyamangalam respectively, did not show any positives either on the 7th day or on the first monthly follow up. A few cases found positive on subsequent follow up are considered to be cases of reinfection as transmission could not be interrupted in these towns.