362 
MALARIA 
TABLE II 
Expenditures eor Malaria Control 
Year 
Costa Rica 
Cuba* 
El Salvador! 
Panama t 
Puerto Rico § 
1935 
1936 
$34,056 
$2,711 
1,527 
$ 23,000 
23,000 
$ 52,987 
53,883 
1937 
30,097 
692 
110,510 
56,177 
1938 
$ 7,071 
22,115 
390 
99,480 
100,528 
1939 
13,592 
22,490 
1,000 
74,840 
93,887 
* Erom data provided by Dr. H. P. Carr, 
t From data provided by Dr. Y. A. Sutter, 
t From data provided by Dr. Osear Vargas. 
§ From data provided by Dr. Garrido Morales and Engineer L. D. Palacios. 
tive malaria control demonstration by 
drainage was carried on from 1921 to 1925 
in the adjoining towns of La Puebla and 
Rivas. The blood parasite index was re¬ 
duced in 3 years from 64 per cent to less 
than 1 per cent, but when supervision of the 
drainage channels was relaxed, the index 
rose again. Ditches were not at first paved 
with inverts or side slabs and rapidly be¬ 
came choked with Para grass. The per 
capita cost of the entire project was about 
$1.25, though the' annual cost of main¬ 
tenance was very much less. 
In the island of Puerto Rico, the town of 
Salinas was studied for 8 years from 1928 
to 1935. Earle (1937) reported that it was 
necessary to bring all breeding areas under 
control before the mosquito density was 
definitely reduced. The malaria preva¬ 
lence was not affected until this mosquito 
density had been brought down and main¬ 
Fig.~ 6. Maracay, Venezuela. This large collect¬ 
ing ditch was lined with three rows of third rounds 
of pipe 36 inches in diameter, two rows of sixth 
rounds of pipe 36 inches in diameter, two rows of 
flat slabs 16 inches by'24 inches. 
tained at an extremely low figure. Exten¬ 
sive seepages in cane fields near Salinas 
were drained by subsoil tiling. Large 
breeding areas in pools in the bed of the 
Lapa river were not eliminated until a con¬ 
crete pipe had been laid well beneath the 
surface of the river bed itself. During the 
four years from 1935 to 1938 inclusive, 3.9 
per cent of the total expenditures of the 
Health Department of Puerto Rico were for 
malaria control. During this same period 
about 3.5 miles of open ditches, lined with 
precast concrete inverts, were constructed 
and almost 5 miles of subsoil pipe were laid. 
In addition, about 300 acres of swamp land 
were filled and a number of drainage pumps 
were installed. 
Drainage projects for malaria control 
were drawn, up for 5 localities in the Re¬ 
public of Costa Rica, Central America. 
Three of these have been completed and in 
2 others the work is still in progress. 
Fig. 7. The junction of two side drains with a 
main drain in Maracay in the Republic of Vene¬ 
zuela is shown in this cut. A central channel has 
been cut in the main drain to increase the velocity 
of the residual flow. 
