FIELD STUDIES 
The studies of the disease in the field presents striking opportunities for 
observation of this contagium under natural conditions. Here enter nature’s 
factors such as sunshine, the air, rain, snow, and changeable conditions of 
temperature with a possible range of 100 in midsummer to near or below zero 
in winter. There also exists in the field such conditions of contact as are 
not present in the studies made under artificial infection conditions. 
The influence of nature’s forces of spreading or retarding the spread of 
this disease in the field is problematical. The germicidal effects of the direct 
rays of the sun are undisputed. Many pathogenic organisms are resistant 
to dessication, others have not these powers of resistance. This factor in¬ 
volves the phenomena of sporation which is not common to the group of 
organisms pathogenic to the domestic fowl. The chances of the spread of 
avian typhoid through the air seems remote. Salmon (28) in his original 
studies on fowl cholera in 1880 arrived at the conclusion, after a series of 
experiments, that the chances of the dissemination of this disease through 
the air was negligible. During the artificial infection work at this station, 
birds were left in confinement in the same room in adjacent coops, though 
not in actual contact, with other birds in all stages of avian typhoid. Such 
well birds failed to show any symptoms of the disease. If the air was a 
factor of transmission, it is highly probable that some takes would have 
occurred, the likelihood of infection being enhanced because under condi¬ 
tions of confinement the natural resistance of birds is at a low ebb. 
It is natural to assume that avian typhoid might be transmitted through 
surface washing. Heavy rains will drain infected soil, and with it many 
virulent organisms incorporated with small particles of debris. If the 
topography of the land is favorable, heavy rains are probable factors of dis¬ 
seminating this and other avian diseases. The ability of E. sanguinaria to 
live and retain its virulence in water in the dark for 20 days, and in the 
same medium in the sunlight for less than 24 hours (16) admits of the pos¬ 
sibility of the organism being transmitted from farm to farm through the 
medium of small brooks, and the overflow of the same in rainy season. 
Gwatkin (9) dwells on the spread of avian typhoid in the following: 
“Infection is spread by sick or recently recovered birds introduced into the 
flock. It may also be introduced by the boots, clothing, utensils or on ani¬ 
mals that have been on infected premises. The droppings of affected birds 
contain enormous numbers of the germs which are picked up by the others 
while eating and drinking. In this way the infection spreads very rapidly.” 
Pfeiler and Standfuss (25) maintain that the disease has an acute and a 
subacute stage, and that it is transmitted from bird to bird by cohabitation. 
Curtis (3) stressed the introduction of the disease into the flock through 
the medium of new birds purchased, and advocated the isolation of all new 
birds until the status of their health could be definitely determined. 
d’Herelle (4) in commenting on the spread of avian typhoid says: 
“The establishment of a new focus begins by the importation of the organ¬ 
ism from an infected region either through the agency of a flock of sheep, 
herd of cattle, or by horsemen. The disease rages for a few days on a farm, 
passes to a neighboring farm, and then extends rapidly into the surrounding 
villages.” 
