Mass administration of diethylcarbamazine citrate in preventing transmission of aperiodic human filariasis

An account is given of the follow-up blood survey made 4 years after the mass administration of a double course (total dosage 4.8 grammes) of diethylcarbamazine citrate to a population of about 1700 people in Fiji. The pre-experimental microfilarial infection rate and mean density in 20 c.mm. were 12.2 per cent. and 4.05. The follow-up (4th) survey included 1430 people. The microfilarial infection rate had risen from 2.7 per cent. to 5.5 per cent. in 4 years. The mean microfilarial density had risen from 0.36 to 0.50. For 507 people present at all four blood surveys the corresponding rates rose from 1.2 per cent. to 6.9 per cent. (originally 16.0 per cent.) and from 0.012 to 0.51 (originally 7.08). It is concluded that disease transmission on a significant scale is unlikely to have resumed yet. When known positive cases are considered alone, the proportion not cured by treatment with two courses of drugs appears to have risen from 7 per cent. to 35 per cent. in the 4 years since treatment. It is known, however, that about 40 per cent. of those apparently cured were still harbouring microfilariae in numbers too small for detection by the routine method used, and there has not been any significant increase in the true infection rate. The records of individual subjects show that some had become positive but these were balanced by others who had become negative. The mean mf.d. had, however, increased about 30 times. The pre-treatment mean microfilarial density among those cured by either one or two courses of drug was very highly significantly lower than among those not cured. A high proportion, 74 per cent., of subjects were lost to the experiment through population movement.