CONTROL OF HOG CHOLERA. 9 
reduced losses in these counties must have been due in the main to a 
decreasing prevalence of disease. It is clear, then, that although the 
experimental work may have served to keep the number of outbreaks 
lower than it would otherwise have been, it can not be said that the 
reduction in outbreaks in Dallas County, Iowa, was due to that work 
alone. 1 
It is very interesting to compare the records from Montgomery 
County, Ind., with those from Dallas County, Iowa. In the former 
area the disease during the three years of work has shown little 
change in prevalence. It decreased slightly in 1914, only to increase 
in about the same degree in 1915. It is a matter of record that 
throughout the State of Indiana hog cholera showed no indication 
of decreasing in prevalence during the same period. On the con- 
trary there were indications of increased prevalence in the State, 
taken as a whole, particularly in 1915. A personal canvass of four 
Indiana counties adjoining Montgomery County showed that in 
them the percentage of loss from cholera increased steadily during 
the three years. In other words, in these neighboring counties where 
no systematic work was done the disease seems to have pursued about 
the same course with respect to prevalence as in Montgomery County, 
where continued work was carried on. Of course the actual losses 
in Montgomery County were much less than in the surrounding 
counties, due to more general use of serum. 
In Pettis County, Mo., the results were much the same, though it 
may be noted that there was no increase in prevalence there in 1915. 
In counties adjoining Pettis there appeared to be a distinct increase 
in the percentage of hogs lost from cholera. 
It seems unnecessary to consider individually the remaining ex- 
perimental counties where only two years' work has been done as 
against three years' work in those just discussed. 
The fact that the control work did not serve to eradicate the disease 
is self-evident. Considering the records of outbreaks in the three 
original counties in comparison with the losses in neighboring counties 
during the years 1914 and 1915, we must conclude that the reduced 
prevalence in most of the experimental counties is probably a for- 
tuitous circumstance, and at most only partly attributable to the 
experimental control work. It must be borne in mind, however, 
that these conclusions refer only to prevalence of outbreaks of dis- 
ease and not to losses from cholera, for with regard to losses the case 
is entirely different. 
LOSSES FROM CHOLERA. 
It will be remembered that in all of the experimental counties one 
of the duties of the field inspectors was to search out the infected 
farms and apply the serum treatment. This work had a dual pur- 
4571°— 17— Bull. 584 2 
