183 
YELLOW FEVEK 
August 1956 ] 
Virus isolations were undertaken by Dr. 
Enid de Rodaniche. Yellow fever virus has 
been recovered from six such batches of 
Haemagogus mesodentatus , and from two of H. 
equinus , and one of Sabethes chloropterus. 
3. Transmission experiments had pre¬ 
viously been conducted at the Gorgas 
Memorial Laboratory with Central Ameri¬ 
can species of Haemagogus and with Sabe¬ 
thes chloropterus. It was shown that H. 
equinus , H. mesodentatus and a related but 
as yet undescribed species from the Pacific 
side of Guatemala are experimental vectors. 
One transmission by bite was also obtained 
with S. chloropterus. A report of these ex¬ 
periments is shortly to be submitted for 
publication (Galindo, Rodaniche and Tra- 
pido. “ Experimental transmission of yellow 
fever by Central American species of Haema¬ 
gogus and Sabethes chloropterus”) 
4. Field work by Drs. Pedro Galindo and 
Harold Trapido in Panama, Central Amer¬ 
ica, Mexico and Texas has furnished exten¬ 
sive data on the distribution of the above 
mosquitoes. Haemagogus mesodentatus oc¬ 
curs from the Atlantic side rain forest of 
Panama near the Costa Rican border north 
along the Atlantic versant of Middle Amer¬ 
ica to the end of the neotropical faunal zone 
near Tamazunchale, San Luis Potosi, 
Mexico. The northernmost specimens were 
collected in a coffee plantation at Ciudad 
Santos (formerly known as Tancanhuitz), 
82 miles southwest of Tampico. The rapid 
drop in precipitation north of this point 
limits the range of this forest-inhabiting 
species. This point is also the northern limit 
of the continuous distribution of monkeys. 
Field experience has shown that H. meso¬ 
dentatus is much more abundant in Mexico 
and Guatemala than it is to the south. It 
has been taken from near sea-level in Mexico 
to an elevation of 4,200 feet in Panama. 
The other closely related but as yet unde¬ 
scribed species which has been shown to 
transmit yellow fever in the laboratory has 
been found on the Pacific side from El Salva¬ 
dor north to the southern border of the Mexi¬ 
can state of Sinaloa. This species, or a rac 
of it, occurs from near sea-level to 5,000 feet 
in Chiapas. Haemagogus equinus has the 
most extensive range of any Middle Ameri¬ 
can species of this genus. It has been found 
to be abundant on both the Atlantic and 
Pacific slopes. On the Pacific slope it has 
been taken as far north as San Bias, Naya- 
rit, Mexico. The extreme limit of its distri¬ 
bution on the Pacific side has not yet been 
determined. On the Atlantic side it extends 
beyond the limits of the neotropical zone to 
the vicinity of Brownsville, Texas, (See 
Trapido and Galindo, Science , 1956, Vol. 
123, p. 634). This species is the least dis¬ 
criminating of any Middle American Haema¬ 
gogus in its choice of habitat. It has been 
found biting man not only in tropical rain 
forest and tropical deciduous forest, but 
also in areas of semi-arid scrub vegetation, 
coastal mangrove, and even in peridomestic 
situations. It occurs from sea-level to about 
4,500 feet. Sabethes chloropterus occurs on 
both the Atlantic and Pacific slopes and 
has been taken at a maximum altitude of 
of 4,500 feet in western Panama. Its northern 
limit approximates that of H. mesodentatus 
near Tamazunchale. 
The neotropical forests extend north 
from the present area of virus activity in 
Guatemala, across the Peten of Guatemala 
and the Mexican versant as far as the south¬ 
eastern comer of the Mexican state of San 
Luis Potosi, except where it is broken by 
cultivation and limited areas of savannah 
and pine woods. This forest carries with it 
the monkeys and mosquitoes ( Haemagogus 
mesodentatus and H. equinus , and possibly 
Sabethes chloropterus ) which are capable of 
sustaining yellow fever in nature. Barring 
the intervention of some climatic factor 
which cannot be predicted, it is possible 
that this yellow fever wave which has passed 
from Panama to Guatemala will continue to 
the limits of the tropical forests. While one 
of the vectors, H. equinus , is present beyond 
this point, monkeys are absent. It would 
be necessary to determine the potential 
role of other animals as reservoirs before 
judging the possibility of sustained trans¬ 
mission farther to the north. 
