96 Yearbook of Agriculture 1956 Not all arc free from toxcity herd or flock is directly proportional however. The polymyxins, for ex- to the number of carrier animals and ample, have considerable renal toxic- susceptible animals and to the fre- ity, which definitely limits their use. quency and intimacy of contact be- A disturbing and increasingly dan- tween the two groups. gerous practice of giving antibiotics Many persons have relied too much promiscuously for almost any and all on antibiotics to control diseases. Un- kinds of sickness has become increas- der such circumstances it is natural ingly common in recent years when that there should be concurrent lax- many antibiotics became generally ncss of hygiene and management of an- available. imal patients. Before we can take full Some susceptible strains of disease- advantage of therapy, there producing bacteria, especially staphyl- must be renewed emphasis on isolation ococci, may develop a total resistance of the sick animal, with feeding and because the antibiotics are improperly management measures that decrease used. It has become apparent that the transmission of antibiotic-resistant when an antibiotic is used promiscu- organisms from patient to patient and ously in any given community or hos- from carrier to patient. pital, resistant strains of staphylococcic Antibiotics must be used cautiously, bacteria can be found in a significant or their value will be lost. On the portion of the animal or human popu- other hand, no patient should be de- lation. prived of the benefit of antibiotic The appearance of a disease germ therapy solely because of fear of in- during antibiotic treatment may be a ducing resistance in the disease germ. major tragedy for a patient, but it will have little significance for other ani- L. MEYER JONES is professor of veter^ mals if the patient is properly isolated. inary pharmacology in Iowa State College. Resistant germs, if they are to assume He formerly was a fellow of the Research great significance, must be spread from Council of the American Veterinary Medical a sick animal to other susceptible ani- Association and a Fulbright lecturer in mals. Therefore the population of pharmacology in Tierärztliche Hochschule antibiotic-resistant disease germs in a in Vienna.

The Sulfa Drugs

L. MEYER JONES

THE SULFONAMIDES were dis- low economic value and must be treat- covered in 1935. They have been as ed as members of a herd or flock. Mass important in controlling bacterial dis- treatment in most instances involves eases in animals as in man. giving the drug in water or ground Despite the subsequent introduction feed. The sulfonamides possess greater of the more efifective and less toxic physical and chemical stability than do antibiotics, the sulfonamides continue the antibiotics and are more adaptable to be widely used in the treatment of to mass treatment in the control of dis- certain animal diseases because many eases in animals. domestic animals individually are of The sulfonamides are produced by The Suífa Drugs 97 chemical synthesis, and are stable white Chronic toxicity from sulfonamides powders, which may be mixed in ani- is more important than acute toxicity. mal feeds or compressed readily into The most significant form is kidney tablets for administration by mouth. toxicity, which occurs after several days They are sparingly soluble in water of therapy because the kidneys fail to and in the fluids of the body. The low excrete the sulfonamides properly. solubility sometimes leads to difficulty The sulfonamides have a low solubil- in eliminating the drug in the urine. ity in the body fluids. After filtering out was the first of the of the blood into the urinary fluid of sulfa drugs to be synthesized. It w^as the kidney, the sulfonamides normally followed by , sulfathia- are concentrated five times or more zole, , sulfamerazine, and through the reabsorption of water from sulfamethazine. Other sulfonamides— the filtrate by the kidneys. The sulfon- phthalylsulfathiazole and phthalylsul- amides may exceed their solubility facetamide—have been synthesized for and precipitate in the urinary system. slow release in the digestive tract to The tendency for crystallization to oc- control infections. Sulfasoxizole is ad- cur is increased by the normal reab- mirably adapted to treatment of uri- sorption of the alkali ions by the kid- nary infections because of a broad neys, which lowers the acidity of the antibacterial activity and a high solu- urine and the solubility of the sulfas. bility in the urinary system. The needlelike crystals of a precipi- The sulfonamides inhibit bacterial tated puncture and tear multiplication during the growth phase. the lining of the kidneys. The crystals A therapeutic dose of sulfonamide does may become numerous enough to con- not kill the micro-organisms but pre- glomerate and to form stones, which vents further bacterial multiplication obstruct the urinary tract. After the until the body defenses can destroy the obstruction, waste products that nor- invading organisms. Early treatment mally are eliminated in the urine ac- of an infected animal is therefore neces- cumulate in the body. The accumula- sary if the sulfas are to be effective. tion of wastes is progressive until it The sulfonamides have little value in leads to the death of the animal. treating prolonged sickness, because Other toxic reactions are noted. In the body defenses already have been poultry, for example, sulfanilamide exhausted by the chronic infection and causes a hen to lay eggs with soft shells cannot dispose of the invading disease or without shells. Other sulfonamides germs. Prolonged use of sulfonamides may not interfere with the formation of in a chronic infection tends to make shells but will lower egg laying. Large the disease germs more resistant to the amounts of sulfonamides cause a mark- drugs. ed interference with the structure and The sulfonamides must be adminis- the function of the nerves to the legs so tered at regular intervals throughout that walking becomes difficult or im- the 24 hours for greatest effectiveness. possible. The continuous use of sulfon- The objective in sulfonamide therapy amides at therapeutic levels sup- is to maintain an antibacterial concen- presses the bacteria in the digestive tration of sulfonamide continuously in tract that the animal needs to synthe- all tissues of the body where the dis- size certain nutrients. ease germs might multiply. Sulfonamides may be prescribed for The sulfonamides are excreted pri- any generalizing disease that is caused marily by way of the urine. Large by a susceptible organism, if there is no amounts of the poorly absorbed sulfon- impairment of kidney function that amides are excreted in the feces. They handicaps excretion. are excreted also in milk and in bile in Virus infections are not susceptible concentrations approaching that of the to sulfonamides, although secondary blood stream. bacterial invaders may be. 300304°—56 8 98 Yearbook of Agriculture 1956 Water must be available at all times The maximum period is 4 days. The to the patient receiving sulfonamide. dose should be decreased soon after the If necessary, forced intake of water is patient shows improvement. Therapy indicated to insure a nearly normal should be stopped 24 to 36 hours after consumption. Water is the vehicle for the patient appears vigorous or after excreting sulfonamides, which will pre- the 4-day maximum. cipitate and block the kidney if there is too little fluid. L. MEYEK JoNE^, prof essor of veterinary Signs of sulfonamide toxicity, espe- pharmacology in Iowa State College, holds cially bloody and frequent urination, degrees of doctor of veterinary medicine from must be recognized promptly and the Iowa State College and doctor of philosophy treatment stopped immediately. from the University of Minnesota, He is Sulfonamides should be administered author of a textbook^ Veterinary Phar- no longer than absolutely necessary. macology and Therapeutics.

Disinfection

W. U MALUMANN

A FARMER can do much for the tact with the skin. The surfaces should health of his animals by keeping his be treated with the alkaline solution barns and sheds absolutely clean. and allowed to react for a few minutes The initial step in sanitation is to before brushing. The surfaces should know (and to have workers who know) be thoroughly flushed with clean water what proper cleaning is, why it is to remove all traces of the detergent. important, and how to do it. Lye tends to destroy most micro- Disinfection—destroying the disease organisms; it kills as it cleans. It germs—is possible only after thorough corrodes metals and so cannot be cleaning. Disinfectants spread over used as a general cleaner. unclean surfaces kill only the micro- The value of good cleaning before organisms on the surface; the em- disinfection was shown in a test made bedded organisms are untouched; the in a meatpacking plant. On a badly disinfectant is wasted. contaminated concrete wall, 28 million Effective cleaning begins with the bacteria were counted per 2-inch removal of all gross waste, such as square. A section of the wall was manure and bedding. Then the sur- sprayed with a good germicidal solu- faces arc scrubbed with brushes and a tion. The bacterial population was good detergent solution until they are reduced to 11 million, which demon- visibly clean. The surfaces then can be strated the disinfectant had failed. flushed with clean water and a dis- Another section was washed with an infectant applied. alkaline detergent solution. Before rins- Any good alkaline detergent in warm ing, the bacterial count was 380,000. water is satisfactory, but lye (caustic After rinsing with clean water, the soda) alone may be used. Because lye count was 53,000. The wash operation is very caustic, rubber boots should be removed the visible soil and 99.8 per- worn and the solution should be cent of the bacteria. The same disin- handled carefully lest it come in con- fecting solution applied to the clean-