ANOPHELINES IN THE EPIDEMIOLOGY OF MALARIA 
161 
greatest intensity of the epidemic was 
about stations 17 and 18 and these were 
closest to the known breeding areas of the 
anophelines. For example, house 1125 had 
8 positive blood smears (all the inhabi¬ 
tants) and none of them had positive case 
histories the previous year. Houses 1095 
(8), 1096 (7), 1097 (7), also close to sta¬ 
tion No. 17, showed a hundred per cent 
malaria, except 1096, where 4 out of the 7 
were infected. A similar condition existed 
close to collecting station No. 18. 
From this study it may be inferred that 
given a susceptible population, a “good” 
transmitter in reasonable numbers, and a 
limited source of gametocytes at first there 
is an almost assured epidemic of malaria. 
It is unfortunate that this epidemic was 
not observed through its entire course and 
that no dissections of A. quadrimaculatus 
are recorded. 
It is not possible to give even a cursory 
survey of the West Indies, Mexico and Cen¬ 
tral America in regard to epidemics of 
malaria because we are not certain of the 
species of anophelines present or their dis¬ 
tribution. Malaria is endemic in many 
parts of this area and epidemics occur from 
time to time, as that of St. Croix in 1931 
and Barbados in 1927. In St. Croix only 
15 cases of malaria were recorded from 
1918 to 1930. Yet in 1931 (the wettest year 
on record for the island, 69.81 inches of 
rainfall compared with the average of 45.54 
in.) a severe epidemic occurred, over 900 
cases in a population of about 15,000. In 
Barbados there were reported over 1,000 
cases in 1927, and up to that time no 
anopheline was known from the island. 
However, A. albimanus was found present 
and widely distributed. 
In Jamaica, B. W. I., Washburn (1933) 
records a sudden outbreak of aestivo- 
autumnal malaria in 1931 in Falmouth and 
surrounding area. The town of Falmouth 
and nearby areas have a population of 
about 8,000. During 1931 (July 1931 to 
February 1932) some 4,442 cases of malaria 
developed with 138 deaths. The island 
experienced heavy rainfalls in 1931 after 
two years of low rainfalls (92 inches in 
1931 compared with the normal of 76 
inches; in Falmouth the rainfall was 60 
inches while during the preceding four 
years the average was only 33 inches). 
From 1923 to 1930 only a small number of 
malarial cases were treated at the Falmouth 
public hospital (less than an average of 20 
cases per year; 34 in 1930). Falmouth has 
extensive saline marshes and mangrove 
swamps around it. A road passed through 
this area separating the marsh from the 
mangrove swamp but connected by a 12 
foot channel. In 1928 this channel was 
closed. During the dry seasons of 1929 and 
1930 parts of the mangrove swamp were 
cleared (it lies below sea level). The heavy 
rains of 1931 converted many of the saline 
pools to almost fresh water, especially in 
the mangrove swamp which was now closed 
to its sea connections. Mosquitoes ap¬ 
peared in immense numbers and A. albi- 
manus, A. grabhami, and A. vestitipennis 
were the anophelines. From January to 
June, 1931, only 205 cases of malaria were 
treated at the Public hospital. In July 
505, August 1,455, September 731, October 
401, November 401, December 448, Janu¬ 
ary 211 and February 54 cases of malaria 
were treated in clinics, or a total of 4,442, 
in a population of less .than 8,000. During 
this period anti-mosquito measures were 
carried on, the channel into the mangrove 
swamp was reopened and its waters gradu¬ 
ally became saline. By February 1932 the 
catches per night of A. albimanus (from 
twelve stations) dropped from 1,209 in 
October to 233 in February. However, A. 
grabhami showed an increase from 98 in 
October to 130 in February. In March the 
epidemic had subsided. 
Most epidemics of malaria seem to have 
an almost “explosive” character, develop¬ 
ing with great rapidity in the whole area 
and then subsiding rather rapidly. Such 
results may be explained by the fact that 
there are many strains of each kind of ma¬ 
laria and that a population soon acquires 
a certain immunity to the strain present. 
Probably the anopheline carrier also be¬ 
comes more or less refractory (as indicated 
by many workers demonstrating the fail- 
