Search

District filariasis surveys in Tahiti in the years after the Second World War yielded the highest microfilaria rates in the South Pacific area, ranging from 25% to 44%; the mean elephantiasis rate was 5% and microfilaria densities (MfD(50)) ranged from 18 to 31. A co-operative filariasis research programme was begun and a control programme was inaugurated in 1953, using diethylcarbamazine therapy supported by mosquito larvae control measures. By 1959 fifteen districts had received mass treatment. Re-examination after 12 months showed that the mean microfilaria rate had dropped from 31% to 3% and the MfD(50) from 23 to 4. Subsequently, only positives were re-treated and by 1964 the microfilaria rate had risen to 6.8%. The increase caused concern and the significance of this reservoir of infection was investigated.Administration of diethylcarbamazine in periodic mass treatments only in American Samoa began in 1963 and was accompanied by a drop in the microfilaria rate to less than 1%, leading to interruption of transmission in some areas.

Filariasis surveys made during 1962-63 in 5 villages in American Samoa among persons over 5 years of age gave an elephantiasis rate of 3.4%, a microfilarial rate of 26% and a median microfilarial rate (MfD(50)) of 29. These rates were somewhat higher than those found in surveys made in the same villages among villagers of the same ages some 20 years previously. A mass treatment programme with diethylcarbamazine was then decided on.Preliminary treatment with a single total regimen of 72 mg of the drug per kg of body weight, given in 12 doses of 6 mg/kg, was administered in several villages over a period of 6 months. Among villagers of all ages at the end of 3 years, the microfilarial rate was 7.3% and the MfD(50) value was 2. These results appeared to be inadequate for a successful control programme and a periodic mass treatment project of 2 or more regimens of 72 mg/kg to be administered every 2 years was instituted on the Island of Tutuila, to be continued until considered no longer necessary.Surveys made 2 years after the second mass treatment in the villages of Amouli, Amanave, Onenoa, Tula, Alao, Utumea and Alofau, in which 1407 persons were examined, showed that 3 villages were negative for microfilariae, that the average microfilarial rate in all 7 villages was 0.4% and that the MfD(50) was 1. These villages were also negative in intensive mosquito surveys for infective-stage larvae of Wuchereria bancrofti. It is suggested that interruption of transmission has been observed in the 3 villages negative for both microfilariae and infective-stage larvae and that, if favourable surveys continue, eradication programmes should be established.

The infectivity of poliomyelitis virus by the intracutaneous route occurs in certain strains but is not a constant character. The inconsistency of skin infectivity tests indicates that there is some property yet unknown which influences this characteristic. Strains of poliomyelitis virus vary in the degree of immunity produced in experimental monkeys injected with active virus by the intracutaneous route and subsequently tested for resistance by intranasal injections. The variation has no relation to the virulence of the strain. Further investigation on the intranasal route of injection should be carried on so that this method may be used with greater assurance in immunity tests, and also in other procedures of poliomyelitis experimentation.

The data from the first 3 years of the Samoan pilot filariasis control programme were reanalysed using incidence instead of prevalence statistics. With these statistics, failures of diethylcarbamazine treatment can be roughly divided into three groups: primary treatment failures, manifested by persistent microfilaraemia; secondary treatment failures, manifested by microfilaraemia recurring within the prepatent period after apparently successful treatment; and new infections. When cases of persistent and recurrent microfilaraemia are excluded by appropriate statistical manipulations, the incidence of new infections is seen to be many times higher in persons who originally showed microfilaraemia. This suggests that susceptibility or exposure, or both, are not homogeneously distributed in the population, and indicates that proposed mathematical models of filarial epidemiology must be further refined. It also indicates that filariasis control programmes should devote more attention to studies and control methods aimed at this high-risk subgroup of the population.

Although the etiological agent and the vector of filariasis were recognized early in the history of tropical medicine, control programmes were slow in developing, mainly because efficient filaricides were not known. Following the discovery of diethylcarbamazine, however, control projects were inaugurated in many parts of the world, including a number among island populations of the Pacific, in ideal conditions for observation and assessment.This paper reviews the answers to questionnaires sent to twelve areas in the Pacific where control projects have been undertaken. The most rapid and effective results appear to have been obtained in the Society Islands and Niue and Atiue, where mass treatment of the whole population with diethylcarbamazine was employed simultaneously with mosquito control. The authors conclude from the answers received that most control projects support the combined use of diethylcarbamazine and mosquito control, and that, where a control programme has brought the microfilaraemia rate down to 5% or less, the launching of an eradication programme should be considered.

In coccidioidin skin test surveys among persons of high school age in Saugus, Canoga Park, Banning and Palm Springs areas the average incidence of positive reaction was 15 per cent. Although considerably less than the 68 per cent incidence reported among high school students of Kern County, it is high enough to indicate pockets of relatively high endemicity in Southern California below the San Joaquin Valley. Histoplasmin tests were performed on most of the persons tested with coccidioidin in this survey. The over-all incidence of positive reaction in the group was 7.6 per cent. Most of the subjects with positive reaction to histoplasmin gave a history of having previously lived in some area in the central United States where histoplasmosis is known to be endemic.A few subjects who had positive reaction to coccidioidin tests and who had lived in areas known to be endemic for coccidioidomycosis but not for histoplasmosis, also had positive reaction to histoplasmin. However, the induration produced was always smaller than that caused by the coccidioidin reaction, and there was minimal confusion in interpreting the tests.