THE DISTRIBUTION OF MALARIA IN NORTH 
AMERICA, MEXICO, CENTRAL AMERICA 
AND THE WEST INDIES 
By ERNEST CARROLL FAUST 
DEPARTMENT OF TROPICAL MEDICINE, TULANE UNIVERSITY OF LOUISIANA, NEW ORLEANS 
At the present time, as in past decades, 
all three cosmopolitan species of human 
malaria plasmodia, Plasmodium vivax, P. 
malariae and P. falciparum, occur as etio¬ 
logical agents of human malaria in the 
Western Hemisphere. In North America 
P. falciparum and P. malariae are not nor¬ 
mally indigepous north of the Ohio River 
Valley in the region east of the Mississippi 
River, while their distribution west of the 
Mississippi probably extends northward 
only into southern Missouri and to the 
northern boundary of Oklahoma. Never¬ 
theless, under favorable circumstances spo¬ 
radic cases of estivo-autumnal malaria de¬ 
velop from time to time in regions as far 
north as New York State, central Ohio, 
central Indiana and central Illinois, due 
most probably to the infection of anopheline 
mosquitoes from human cases imported 
from the south, and the transfer of the para¬ 
site by the infected mosquitoes to a few 
individuals of the indigenous population in 
these more northerly climates. Typically, 
the infection is not transferred again to 
mosquitoes and dies out at this point. An 
exception to the limitation of the estivo- 
autumnal parasite to a warm climate appar¬ 
ently exists in New York City, where this 
species has become artificially established 
in drug addicts as a result of the use of a 
common hypodermic needle (Most 1940b). 
'Even in areas most favorable for its propa¬ 
gation the quartan malaria plasmodium has 
an unexplained “spotty” distribution. 
Thus, the tertian parasite has a wide¬ 
spread distribution in many of the cooler 
portions of the United States, where the 
other two species of malaria plasmodia are 
not indigenous, while in the warmer cli¬ 
mates it shares responsibility for human 
malaria primarily with the estivo-autumnal 
parasite. 
The incidence of malaria in a given area 
may be judged either from morbidity or 
mortality data. Since clinical diagnosis of 
“chills and fever” cannot be relied on as 
a diagnostic criterion, a true estimate of the 
distribution and amount of malaria or the 
species of malaria plasmodia in a particular 
district depends on the identification of the 
plasmodium in stained films made from the 
bloods of a representative cross section of 
the population (i.e., surveys to detect the 
parasite), or on malaria spleen surveys. 
Unfortunately, there are several reasons 
why malaria incidence statistics are usu¬ 
ally unreliable. These include the paucity 
of adequate malaria parasite or malaria 
spleen surveys, the inability of many phy¬ 
sicians to suspect or diagnose malaria in a 
sick population, the danger of using clini¬ 
cal laboratory records as representative of 
a population as a whole, the common prac¬ 
tice of self-diagnosis and self-treatment 
with proprietary drugs, and prescription of 
antimalarials by the physician without ade¬ 
quate diagnosis. 
Mortality data on malaria are, on the 
whole, more likely to be dependable than 
are morbidity data, and are relatively reli¬ 
able as an index of malaria endemicity in 
the Southern United States and to a lesser 
extent in countries of Tropical America 
where vital statistics have been compiled. 
However, since malaria deaths in warm 
climates result primarily from infection 
with the estivo-autumnal parasite, mor¬ 
tality statistics fail to provide information 
on the distribution or intensity of infection 
8 
