incitants in the expression of disease, including tumors, as stress factors, and as agents 
in nutritional interference. We know less about the way parasites live, their physiology, 
special enzymes, nutritional requirements, and hormones, If we intend to confront the 
real enemy on a rational basis, we cannot long neglect such knowledge or serious study 
of the fundamental processes of life as they obtain in this common and complex phe- 
nomenon. Only upon a backlog of solid knowledge along these lines can we effectively 
expand the use of chemicals in parasite control. Serendipity will undoubtedly play its 
continued role in this area as it proverbially has in all science through all time, but this 
moment may well mark the last when we want for even a single example in all chemo- 
therapy of an agent that was rationally developed. Selectively toxic chemicals are 
destined increasingly to be ‘‘made-to-order,"’ 
The design of acceptable and effective control measures requires more than the 
selective, physiologic, basic approach. If we trust reason, observation, and experience, 
effective control is predicated on a certain fullness of knowledge of total problems, 
This means, as it meant for cattle fever and screwworms, knowledge about speciation, 
life-cycle, parasite-host relationships, bionomics, immunity, geographical distribution, 
epizootiology, sources of infection, and means of transmission, In short, the design of 
any attack on parasitic or other disease can ill afford to leave any stone unturned in the 
development of all facets of the problem, 
A third, significant aspect of need concerns development of knowledge of the place 
of chemicals in parasite control. It is a paradox that those who are closest to problems 
of chemical control seem most commonly obliged to emphasize that this approach is 
never the whole solution, and rarely the best, to any problem. A primary urgency in 
parasite control is thorough inquiry into potential means of minimizing or circumventing 
reliance on foreign chemicals. At the very minimum, there should be full exploration of 
efficient means of doing the job with the least amount of chemical and of measures that 
obviate the direct use of chemicals inoron food animals. Any true evaluation of the place 
of chemicals in parasite control must scientifically depend upon a weighing of all 
approaches, including alternatives to chemical measures, If today’s guess is of signifi- 
cance, it can only stress that total problem knowledge is the cornerstone of the best 
control measure, There is usually only one best solution to a problem. To this end, there 
must be extensive investigation of immunological phenomena, of parasite pathogens, 
predators, and hyperparasites, of the delicate associations and adjustments of parasites 
at all stages of their development and in their varied environments. This want of knowl- 
edge of parasitism and parasitic diseases clearly means that parasitology is today a 
discipline of dimensions and depth undreamed a decade ago. 
We have emphasized basic biology of parasitism as the foundation for rational 
development and expanded use of antiparasitic chemicals, reconnaissance of total 
problems as the foundation for best usage, and intensive inquiry into alternatives to 
chemical measures as the foundation for properly evaluating the place of chemicals in 
parasite control, Without these things, further effort toward improved chemical controls 
is indefensible if not doomed to failure, 
One other problem must be mentioned, It is the question of unbiased evaluation of 
new agents. During recent years, industry has become especially active in the develop- 
ment of antiparasitics, It has done what appears to have been a notable service, 
Medicated feeds have unquestionably proved to be the key to prevention of many 
devastating diseases of food animals, especially poultry. Many products are competitively 
marketed and, for some purposes, the number of products has mushroomed ona scale 
which seems quite unwarranted by the experimental background, 
The grower has traditionally looked to the Department for advice on the product that 
is best for him. Today, he is confused by the bombardment. Is he not entitled to the one 
best answer to his question? 
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