CONTROL OF MALARIA IN PANAMA WITH DRUGS 
283 
days, followed 2 days later by plasmochin 
simplex 0.01 gram twice a day for 5 days. 
These methods of treatment were continued 
from September 1932 to September 1940. 
During the course of these experiments, 
one case of quinine idiosyncrasy was noted. 
Plasmochin simplex, given either following 
quinine or atabrine, gave trouble in many 
instances when administered twice a day 
for 5 days: We found one family the 
members of which cannot take plasmochin 
in any quantity without experiencing ab¬ 
dominal distress. 
4. Blood-film surveys for malarial para¬ 
sites were made monthly throughout the 
entire ten-year period, to measure our re¬ 
sults. The thick-film technique of Barber 
and Komp (1) has been used, and the 
staining and examination of the films have 
been done by experienced technicians. 
5. Administration of treatment during 
the first years was in the hands of a native 
graduate nurse, assisted by the local school 
teachers and civil authorities. One of the 
staff also had charge of the administration 
of the drugs in the Chagres River towns. 
A definite policy was later established of 
employing native girls to give the treat¬ 
ments under the supervision of the river 
supervisor. Thus the administration of 
the drugs was by non-medical personnel; 
visits of inspection were made by a member 
of our staff 4 days a month. 
6. During the later years, large shifts 
of population in our towns interfered seri¬ 
ously with the continuity of our work. The 
population has declined in number steadily 
since about 1938. Many families have 
moved to Madden Highway, where better 
transportation and school facilities are 
available. Greatly increased labor demands 
in the Panama Canal Zone have drawn 
many of our villagers from the river towns. 
A large number of these people had been 
permanent inhabitants of the towns from 
the early years of our work. 
7. The part played by new infections, as 
compared with relapses from previous in¬ 
fections, is believed to be relatively small. 
In the quinine-plasmochin treated group, 
51.6 per cent of all positive for malarial 
parasites were positive from 2 to 7 times 
during a year’s observations. In the ata- 
brine-plasmochin treated group, this per¬ 
centage was 45.6 per cent. A certain por¬ 
tion of the percentage of repeated positives 
is doubtless due to insufficient or incom¬ 
plete treatment, but in the main it is 
the result of low tolerance to the disease. 
Persons repeatedly positive keep up the 
parasite rate, even though given frequent 
complete courses of treatment. These in¬ 
dividuals defeat our efforts to effect a 
further reduction in the parasite rate. We 
believe that they represent cases of relapse, 
in most instances, rather than new infec¬ 
tions. Some confirmation of this view is 
found in the low monthly parasite rates, 
and the low percentages of infections in 
infants, which point to low transmission 
rates. 
8. During the past 10 years, the inci¬ 
dence of the several species of malaria para¬ 
sites among all positives has been as 
follows: P. falciparum, 77.8 per cent; P. 
vivax, 19.3 per cent; P. malariae, 2.9 per 
cent. 
The percentage of crescent-carriers in P. 
falciparum infections has increased rather 
than diminished from year to year; how¬ 
ever, exceedingly few carriers are found 
in any year which are good subjects for 
mosquito infection experiments. The per¬ 
centage of heavy infections found among 
positive individuals has not decreased in 
the treated groups; however, the majority 
of positives in these groups show very few 
parasites in the films, while positives in 
control areas show many parasites, requir¬ 
ing less time to discover them. 
9. Surveys of infants under one year, 
from 1935 to 1940, show positive rates of 
5.9 per cent in the 272 examined in the 
treated areas, as against 20 per cent of 20 
examined in the control areas. 
10. The highest parasite rates were found 
in the age-groups from 5 to 10 years, and 
from 10 to 20 years. The latter group con¬ 
tains the young adults who form a large 
