Efficacy of a single dose treatment of Wuchereria bancrofti microfilaria carriers with diethylcarbamazine in Matara, Sri Lanka.

OBJECTIVE: To test the efficacy of diethylcarbamazine DEC single dose regimen of 6 mg/kg body weight (bw) on a sample of Wuchereria bancrofti microfilaria (mf) carriers in Matara. DESIGN: 6 mg/kg bw DEC dose in 50 mg tablets given under direct observation to the subjects at 23.00 hours after pre-treatment blood collection for mf counts. Post-treatment mf counts were at 1, 2 weeks and 1, 3, 6, 12 months. SUBJECTS: 31 asymptomatic mf carriers, 14 males, age range 6 to 62 years. RESULTS: Treatment resulted in 89 to 97% success rate, 19 to 28% cure rates and 74 to 80% reduction in mf density. There was no difference statistically in the success rate and cure rate at 6 and 12 months. The effect of DEC treatment at 6 and 12 months compared by sex, age group and pre-treatment mf level showed no difference. 64.5% of the carriers treated had at least one mild adverse reaction. Rates of the common reactions were 41.9% fever, 22.6% headache and 16.1% joint pains. CONCLUSION: A new mass treatment program has been initiated by the national Antifilariasis Campaign using the single dose DEC 6 mg/kg bw regimen. The satisfactory reduction in mf density at 6 and 12 months following DEC single dose treatment we observed provides support for this program.

Microfilarial periodicity of Wuchereria bancrofti and man landing periodicity of the vector Culex quinquefasciatus say in Matara, Sri Lanka.

OBJECTIVE: To compare the microfilarial periodicity of Wuchereria bancrofti, with the man landing periodicity of the vector Culex quinquefasciatus in Matara, Sri Lanka. DESIGN: Periodicity was estimated using a statistical method. 60 microliters finger prick (FP) blood was smeared from a single subject every 2 hours for 24 hours of the day to make 12 samples. Smears were stained with Giemsa and the microfilariae (mff) counted. Man landing catches of mosquitoes were made inside a bedroom of a house in the same area on a sleeping volunteer during the night, between 18.00 and 06.00 hours. Each hourly catch was placed in separate paper cups. Hourly C. quinquefasciatus taken were counted. SUBJECTS: 10 asymptomatic microfilaria (mf) carriers. RESULTS: The individual mf peaks in the 10 carriers varied from 22.00 to 04.00 hours. Using the statistical method the parameter k showing the mf peak hour was 1.19 estimating the peak mf density at 01.11 hours. The influence of different times of blood collection on false negatives among the very low density carriers was estimated by the periodicity curve. It would be desirable to collect blood during the estimated time interval when the mf count was 80% of the peak count, between 21.55 and 04.27 hours in Matara. The results of 25 all-night mosquito landing catches gave a peak activity hours of k as 7.78, corresponding to 01.47 hours. CONCLUSION: The close agreement in the peak hours of mf density and vector activity suggests a perfect adaptation between parasite and vector for optimum transmission.