78 
Joumal of Agricultural Research 
Vol. XXVIII, No. 1 
EPIORNITHOLOGICAL STUDIES 
As to the foci of infection, field studies in cases of well-defined epidemics have 
revealed in each case a starting point, with a definite advance of the disease. 
No conveying agent could be found, as only in rare instances could the inves¬ 
tigators establish such contact between the locations of outbreaks as would be 
a factor in transmitting the disease. The possibility that English sparrows were 
the conveying agent is under investigation at the present time. Figures 1 and 2 
show graphically the history of two typical epidemics of fowl typhoid. The 
progressive advance of the disease may be clearly traced. 
METHOD OF CONTROL 
The most practical method of treating this disease is vaccination, using 
autogenous vaccines when possible, and stock vaccines when the former are not 
procurable. The same principle of desensitization as in making other vaccines 
is used in preparing fowl typhoid vaccine, 24-hour bacillary saline emulsion 
being heated one hour at 60° C., tested for efficiency of desensitization by pig 
inoculation and cultures, and preserved with one-half per cent phenol. The 
dosage used was 1 cc. for adults and one-half cc. for chicks, each weighing 
1 to 2 pounds. 
In 19 epidemics 2,140 birds were vaccinated. Prior to vaccination the loss 
had been 303 birds in these flocks; subsequent to vaccination the loss was 41, 
practically all of the birds lost having well-defined fowl typhoid when vac¬ 
cinated. Of 974 birds prophylactieally vaccinated this year on infected prem¬ 
ises, no losses occurred from this disease. 
