
a pilot project for the control of filariasis
in thailand
in a village in kanjanadit district of surat-thani province, south thailand,
where a field station for filariasis studies had been established by the
bangkok school of tropical medicine, blood films were examined from 977 persons
(95.5 per cent. of the total population of 1,023).  two thick films (each of
20 c.mm.) were prepared from each person and stained with giemsa.  it was found
that 21.1 per cent. of the people harboured microfilariae (all brugia malayi).
elephantiasis was found in 5.3 per cent. of the population.
microfilarial periodicity was studied in 25 persons; in every case it was
found to be markedly nocturnal.
the blood of 98 cats, 52 dogs and two monkeys was also examined.  no b. malayi
larvae were recovered.
mosquitoes were caught and identified.  in an initial survey, 4,557 mosquitoes
were examined, of which 568 were mansonia spp.  in 4,136 dissections, b. malayi
larvae in stage ii were found in one m. uniformis and in stage iii in another;
the infection rate for m. uniformis was 0.6 per cent.
spraying with ddt was carried out in all the houses during the last phase of
the investigation.  it resulted in a slight decline in the numbers and
percentage of mansonia mosquitoes caught.
diethylcarbamazine was administered to as many of the villagers as possible,
in a dose of 5 mgm. of the citrate salt per kgm. body weight once weekly for
six weeks.  eight hundred and eighty-eight persons received the drug (86.8
per cent. of the population).  considerable side-effects were observed in
nearly all microfilaria-carriers.  blood examinations were repeated one month
and again one year after cessation of the drug.  it was found that the
proportion of microfilaria-carriers had decreased from 21.1 per cent. to 2.2
and 2.2 per cent. respectively, the filariasis infection rate from 26.1 per
cent. to 8.6 and 8.5 per cent., and the mean microfilarial density of all films
from 4.8 per 20 c.mm. blood to 0.48 and 0.12.  larvae of b. malayi were not
found in mosquitoes dissected one month and one year after the mass therapy.
