infection and after a suitable period of time are again ready 

 for further treatment. 



With improved techniques for determining the presence of 

 most parasites and for evaluating the relative degree of in- 

 fection with many of them, mass treatment is no longer justi- 

 fied in the field of medicine. Even in veterinary medicine it 

 can be condoned only in the case of large flocks or herds in 

 which individual diagnosis would be economically unsound. 



The question is frequently raised as to whether an infection 

 with a given number of worms is of clinical importance and 

 thus warrants treatment. No categorical answer can be given 

 to such a question. An infection with a certain number of 

 worms might be injurious to the health of one individual with- 

 out aft'ecting in any appreciable degree the well l)eing of an 

 other individual. No one has been able to define the line of 

 demarcation between a clinical and a sub-clinical infection. 

 In mass treatment such finesse of judgment is not required or 

 at least is not exercised but in medical practice it is best that 

 due cognizance be taken of the relative degree of parasitism. 

 If the patient has only a few worms, such as hookworms, he 

 liad better go without treatment rather than be subjected to 

 the potential hazards of anthelmintic medication. However, 

 with such a circumscribed environmental parasite as Enterobiiis 

 rr.rmicularia, it is necessary from a control standpoint to treat 

 siniultaneou.sly all infected individuals in the household re- 

 gardless of the degree of infection or the presence or absence 

 of clinical symptoms. Otherwise, untreated individuals provide 

 direct avenues of reinfection for treated individuals. 



Methods of Application. Anthelmintics are administered 

 in a great many different ways, depending on the kind of 

 parasite, its location within the host and the species of host 

 animal. In man, palatability is a matter of some importance 

 and it is desirable to administer the drug in a manner least 

 distasteful to the patient. While the esthesia of taste is not 

 usually considered in the case of lower animals, palatable doses 

 of drugs are more apt to be retained by dogs and cats in 

 which the vomiting reflex is acutely sensitive. Many of the 

 anthelmintics now on the market are dispensed in soft gelatin 

 capsules. Hard gelatin capsules are still employed by some 

 practitioners who prefer to fill the capsules at the time they 

 are used. 



For certain parasites located far down in the digestive tract, 

 the use of enteric-coated tablets is an advantage. However, 

 most of the enteric coatings employed become harder with age 

 and are less apt to dissolve in the digestive tract. A new type 

 of water-soluble coating has recently been devised to obviate 

 the disadvantages of the usual enteric coating. The new coat- 

 ing permits timed disintegration of the tablet witliin c^'rtain 

 definite periods after administration and radiographic evidence 

 in support of this has been furnished by Worton, Kempf, Bur- 

 rin and Bibbins (1038). 



For ruminants, certain anthelmintics such as solutions of 

 copper sulphate and nicotine sulphate are given as a drench. 

 In fact, Ortlepp and Miinnig (1936) have shown that the ad- 

 ministration of a dose of copper sulphate solution immediatel.y 

 ))rior to the use of other drugs has the effect of closing the 

 oesophageal groove and permitting the drug to reach the abom- 

 asum directly. This is of marked advantage in connection with 

 some treatments against ruminant parasites. On the other 

 hand, some anthelmintics, such as the sodium arsenite-bhiestoiie 

 mixture for the common sheep stomach worm, are given in 

 j)owdered form. 



The duodenal tube method of administration is an advantage 

 in some instances and is particnl.'irly valuable in stubborn 

 cases of strongyloidosis in man in which ordinary methods of 

 administration fail. 



Somatic helminths, when they can be reached at all, are 

 usually attacked through the intramuscular or intravenous 

 route. Lungworms in domestic animals are susceptible to some 

 extent to anthelmintics introduced intratrachcally and good 

 results have been reported in this connection by certain workers 

 in the Soviet Union. The inhalation method was used by 

 Wehr, Harwood and Schaffer (193S) in the attack against 

 Symgamus trachea in chickens with barium antimonyl tartrate 

 dust. 



Parasites in the lower bowel are subject to attack per rec- 

 timi. The employment of enemas is a common practice against 

 Entcrohins vrrmiciihirix in man. The method has been used by 

 Miinnig in South Africa and by others in removing nodular 

 worms from sheep, while intracecal injections have been advo- 

 cated and employed with some success for the expulsion of 

 whipworms from the dog. In a like manner, HcteraMs galUnae 

 can be reached with anthelmintics injected by way of the 

 cloaca. 



The individual anthelmintic treatment of farm animals has 

 never appealed to the livestock owner and there has always 

 been keen demand for an anthelmintic which could be given 



with the feed. Other than the tobacco dust or nicotine treat- 

 ment for Ascaridia in poultry, anthelmintics administered in 

 tlie feed are generally ineffective. The method has the disad- 

 vantage that some animals ingest too much and others too little 

 of the drug. More recent tests with phenothiazine seem to in- 

 dicate that for some parasites this drug may be of value when 

 given with the feed. If results are substantiated in further 

 trials, the method will no doubt find widespread use. 



While most anthelmintic therapy is based on the use of single 

 dose treatments, it is sometimes of advantage to employ divided 

 doses. The dose of chenopodium for man is occasionally divided 

 into two or three parts administered at one half to one hour 

 intervals. When given in this way, the efficacy of tlie drug 

 against hookworms is believed by some workers to be slightly 

 enhanced. If toxic symptoms are manifested by individuals 

 having an idiosyncrasy for the drug, dosage can be discontin 

 ued. However, the purgative is usually withheld until the last 

 portion of the dose has been administered and under these 

 conditions increased absorption of the anthelmintic is apt to 

 occur. 



Repeated treatment over a period of time is required for the 

 eradication of such parasitic nematodes as Strongyloides ster- 

 coralis and Enterobiiis vcnnioilaris. Likewise some degree of 

 efficacy can be secured against whipworms by repeated dosing 

 with a drug such as santonin which exerts little or no action 

 against these parasites when given in a single dose. 



The above citations will be sufficient to indicate to the reader 

 that anthelmintic warfare against parasites, whether in man or 

 the lower animals, requires the employment of varied methods 

 of attack based on the nature of the lio,st terrain and the ac- 

 cessibility of the parasite to the range of the weapon or 

 weapons available. Some parasites can be overcome by a 

 single anthelmintic onslaught but others are expelled from 

 their position only after repeated attacks. The method of ap- 

 plying treatment is therefore an important factor in anthel- 

 mintic medication. 



Prelimin.\ky Fasting. It is custoniary usually to fast the 

 jiatient before the oral administration of most anthelmintics 

 with a view of emptying the stomach and reducing the bulk of 

 the intestinal contents. In the treatment of Axcaris and hook- 

 worm infections in man, the patient is usually given a light 

 supper the night before and the anthelmintic administered in 

 the morning, no food being permitted until adequate purgation 

 has ensued. Dogs and cats are usually fasted overnight. Various 

 periods of fasting are prescribed for larger domestic animals. 

 Swine should be fasted for 24, and preferably, 36 hours. For 

 equines it is advisable to withhold feed for 18 hours prior to 

 anthelmintic medication for parasites in the stomach and small 

 intestine and 36 hours for parasites in the large intestine. 

 Conditions are somewhat different in the case of ruminants. 

 Even prolonged fasting will not entirely reduce the bulk of 

 the contents of the rumen. Formerly, it was customary to fast 

 animals for 12 to IS hours but more recently Clunies, Ross and 

 Gordon (1934, 1935) have shown that there is no increase in 

 the efficacy of a number of drugs used for the removal of the 

 common sheep stomach worm in animals fasted for 24 hours as 

 compared to the efficacy of the same drugs in nnsfarved sheep. 

 Consideration op the Patient. Since tlie safety of the pa- 

 tient is of paramount importance, it is the duty of the prac- 

 titioner to satisfy himself that no contraindications for anthel- 

 mintic treatment are present. This calls for an adequate physi- 

 cal examination to rule out general contraindications and a suit- 

 able inquiry to ascertain the possible presence of specific con- 

 traindications for the drug of choice. General contraindications 

 include febrile conditions, extreme youth or old age, chronic 

 debilitating diseases, pregnancy, gastro-intestinal disturbances, 

 chronic constipation and alcoholism. The presence of one or 

 more of these conditions does not necessarily mean that treat- 

 ment should be withheld but it does mean that due regard 

 should be taken with respect to the type of drug and the dosage 

 employed. The practitioner must decide whether the injury 

 from parasitism is sufficient to warrant the risks attendant on 

 treatment and must weigh the advisability of substituting a 

 less specific but safer drug for a more specific but more dan- 

 gerous drug. In patients who are poor risks for adciiuate doses 

 of specific drugs, it is advisable to reduce the dose and remove 

 a few worms at a time rather than hazard injury to the patient. 

 In persons with severe hookworm disease, it is questionable 

 whether anthelmintic treatment should be resorted to until the 

 anemia has been corrected by .suitable doses of iron. 



In particular, doses of anthlemintics for children should be 

 computed very carefully and apparent age rather than chrono- 

 logical age should form the basis of computation. Since the 

 evacuation habits of children are not always regular, the ad- 

 ministration of a high soapsuds enema on the morning of 

 treatment often helps to prevent reactions to such anthelmin- 

 tics as the chlorinated hydrocarbons. 



336 



