(6) Lowered efficiency of work animals, such as horses and 
mules. 
(7) Depreciation of capital items--breeder animals, farm 
properties, abandonment of production. 
(8) Inefficient utilization of pastures, barns, and pens 
by unproductive stock. 
(9) Lower resistance of infected stock to other diseases 
and parasites. 
(10) Deaths, sufferings, and anxieties imposed upon man by 
parasites transmitted from domestic animals, or by 
diseases carried by parasites that are primarily animal 
rather than human. 
(11) Expenditures for worthless or inefficient drugs, treat- 
ments, and equipment. 
Control Costs, or Charges Ascribable to Protection Against Parasites 
(1) Expenditures for drugs for treatment, prevention, eradi- 
cation, and control. 
(2) Cost of veterinary and other services, and of labor for 
administering drugs and effecting control. 
(3) Expenditures to prevent parasite introduction. 
(4) Expenditures for research—Federal, State, and private. 
(S) Cost of regulatory services (Federal, State, and other), 
including inspection and quarantine of animals, meat 
inspection, and litigation. 
Recent years have witnessed more and more instances in which 
parasites have been found to be the principal agents in causing 
disease outbreaks characterized by severe morbidity and heavy 
death losses, Yet now, more than at any time heretofore, there 
is also a fuller understanding of the less spectacular ways in 
which these marauders have a significantly greater ecoiomic im- 
pact upon the livestock industry. Because they are ubiquitous 
and unseen, of great variety and abundance, and their effects 
generally inapparent, internal parasites undermine the health 
of countless thousands of food animals and are a constant hazard 
to efficient, profitable production. Vigilance against parasites 
is therefore accepted as an essential aspect of efficient manage- 
ment. There is no way in which the hidden losses can be adequately 
estimated or even fully comprehended, and we have not attempted 
to estimate either the cost of measures directed toward their 
control or the benefit accruing from then. 
eo. 2 
