ingesting guinea noira larvae and noted no development after 

 7 days. 



We know little also of the relation of the reactions of the 

 definitive host to this dissemination of this parasite. If any 

 immunity is produced bj' the presence of worms it must be 

 quickly lost after the completion of development because re- 

 peated infection of the same individual year after year is a 

 common phenomenon. Moorthy (lS32a) recorded that out of 

 a total of 1,363 patients suffering from draeontiasis 83 per- 

 cent gave histories of having suffered in previous years. He 

 also noted that certain individuals seem to be entirely lacking 

 in susceptibility to infection and escape the disease year after 

 year, although they live in the same houses and drink the same 

 water as those who become infected. He suggested from in 

 vitro studies that in such individuals there might be physiologi- 

 cal factors, such as hypo- or hyperchlorhydria, which would 

 prevent the freeing of the infective larvae from the cyclops in 

 the stomach or which would kill them before they could pene- 

 trate into the tissues. 



As suggested above, the character of the water supply is 

 of the greatest importance in the dissemination of draeontiasis. 

 Infected individuals must have access to drinking water that 

 contains suitable species of Cyclops. Absence of this parasite 

 in people who obtain their water supply from rivers or 

 smaller streams can probably be attributed to the absence or 

 scarcity of the proper species of Cyclops (Lindberg, ISS.j). 

 Small open collections of water such as step wells, cisterns, 

 or small pools in which the people frequently wade or bathe 

 are chiefly implicated. For example, in the Gold Coast 

 surface collections of rain water and shallow open wells 

 are considered to be the sources of infection (Leiper, 1907) ; 

 in the upper Volta, village ponds and hollows made by the 

 natives in obtaining mud for building their huts (LeDentu, 

 1024) ; in the Lake Chad basin, temporary cisterns or pools 

 (Roubaud, 1913) ; in southern Sudan, shallow wells or drink- 

 ing pools (Davis, 1931); in Iran, cisterns of rain water 

 (birkehs) or washing basins in the mosques (Lindberg, 1936) ; 

 a,nd in India, the step wells and village pools (Turkhud, 1919; 

 Pradhan, 1930; Moorthy, 1932a: Lindberg, 1936). Such bodies 

 of water only become of considerable danger in spreading the 

 infection when the water is low and the Cyclops are present in 

 large numbers and concentrated near the surface (Turkhud, 

 1912; Pradhan, 1930; Lindberg, 193.i). This explains the sea- 

 sonal cycle of infection in India because the season of great- 

 est infection (March to May) is near the end of the dry sea- 

 son when the water is lowest. It also explains the greater 

 prevalence of guinea worms in those villages with the poorest 

 water supply. The epidemiological data makes clear the diffi- 

 culty that the guinea worm has in finding conditions in human 

 populations suitable for its spread and goes far to explain 

 the discontinuity of the endemic centers, the failure of the 

 disease to spread readily into new territory, and its spotted 

 distribution over the endemic areas. All these facts on epidem- 

 iology suggest obvious methods for control and indicate that 

 any serious attempt to apply control measures should bring 

 rapid and permanent results. 



CONTROL 



It is obvious that prophylaxis and control of draeontiasis in 

 the endemic areas can either deal with habits of the individual 

 or with community relations to the water supply. Boiling, filter- 

 ing, or even straining the drinking water through a cloth would 

 be effective in individual protection. The rapid extraction of 

 the gravid worms from infected individuals and their exclu- 

 sion from the water supply would help in preventing the in- 

 fection of the C3-clops. However, all the workers who have 

 considered the problem are in agreement that permanent con- 

 trol in an infected community can be achieved only by chang- 

 ing the water supply to eliminate sources of infection. Thus 

 Leiper (1907) pointed out that on the Gold Coast the fencing 

 of the pools, the building of parapets or covering the open 

 wells, and the digging of draw wells would permanently elimi- 

 nate the disease. Turkhud (1919) argued that the changing 

 of all step wells in the infected villages in India to draw 

 wells would save many times the cost of the pumps by eliminat- 

 ing the economic losses from the disease. Moorthy (1932b) 

 found that where this was done in the Chitaldrug "district of 

 Mysore great reduction and in some cases entire elimination 

 of the disease resulted. 



Where for some reason it is not possible to change the coii- 

 struction of the wells or pools the employment of methods to 

 kill the Cyclops have been suggested. Such measures have to 

 be used repeatedly since they serve only to eliminate the Cy- 

 clops temporarily. A number of authors have experimented on 

 the use of chemicals to kill cyclops. Davis (1931) recom- 

 mended lime, either unslaeked or slacked, in proportions of 1 

 to 1,000. In fact in the previous year Pradhan (1930) had 



already reported an extensive lield experiment in which the 

 use of lime (about 1 drachm per gallon of water) in 27 in- 

 fected step wells had reduced the incidence of guinea worm in 

 the people using them 21 to -l-j percent. Moorthy (1932b) re- 

 ported that when perchloron (3 lbs. per 100,000 gallons) in 

 combination with copper sulphate (1 lb. per 200,000 gallons) 

 was used in wells they could be rendered completely free of cy- 

 clops for about a month. He advocated the use of this method 

 during the infection period (March to June) as a good method 

 of reducing the number of cases in areas where permanent con- 

 trol methods could not be undertaken. 



Several authors have suggested the "biological control" of 

 guinea worm infection by the introduction into the wells or 

 ponds of fish that feed on cyclops, but Moorthy and Sweet 

 (193fic) appear to have been the first to report on the success- 

 ful use of this method. They found a number of cases in 

 which people using wells containing certain species of small fish, 

 particularly of the genus Barbus, were entirely free from guinea 

 worm infection. This led to the development of methods for 

 raising and introducing fish into the step wells. Use of this 

 control method in 3.") infected villages in 1934 and 193-5 caused 

 complete elimination of draeontiasis in six and a marked reduc- 

 tion in four. Their results led to the conclusion that the use 

 of fish was not only cheaper but much more effective than chemi- 

 cal methods. 



Finally it seems clear from all the evidence in the literature 

 that prospects for the control of draeontiasis are excellent in 

 any endemic area where a systematic effort can be made. It 

 is very encouraging that Moorthy and Sweet (1936b) were able 

 to report that from 1S29 to 1936, by the introduction of draw 

 wells, the use of chemicals, and the introduction of fish, dra- 

 eontiasis was entirely eliminated from all but 25 of 112 in- 

 fected villages in the Chitaldrug district of Mysore, India. 



Enterobius vermicularis 

 E. B. C. 



The human pinworm or seatworm, Enterobius rermiciilaris 

 (Linn., 17."iS) Leach, in Baird, 18.13, was one of the first of 

 the intestinal helminths to be described from man, a fact easily 

 understood since it comes to the exterior and there produces 

 local sj-mptoms which would lead to its discovery. According 

 to Schmidt, it was discussed by Hippocrates, Aristotle, Galen 

 and others under the name Ascaris, before Linnaeus gave it its 

 specific name. 



E. vermicularis is apparently restricted to man. In view of 

 Cameron's (1929) study indicating that in primates one species 

 of Enterobius is restricted to hosts of one genus, reports of E. 

 vermiculari.<i from primates other than man must be regarded 

 with suspicion unless supported by unimpeachable evidence. 

 This parasite occurs in the intestine but is not limited in loca- 

 tion as are many other intestinal nematodes. It occurs, in va- 

 rious stages of development, from the lower ileum through the 

 rectum and gravid females migrate through the anus to the 

 perianal region to lay eggs. 



SYMPTOMATOLOGY AND PATHOLOGY 



Symptoms are extremely variable in nature and degree being 

 apparentlj' absent in some cases and severe in others. There is 

 mechanical stimulation and irritation of the gastrointestinal 

 tract, occasionally with nausea and vomiting, and of the ex- 

 ternal surfaces during migration, producing pruritus ani and 

 vulvae, in some cases apparently allergic in nature (Brady and 

 Wright, 1939). By transporting organisms during migrations, 

 the parasites may induce vaginitis and even peritonitis and may 

 cause the formation of cysts in the female genital tubes or in 

 the peritoneal cavity, with resulting irritation (summarized by 

 Africa, 1938). Probably there is slight eosinophilia. The role 

 in appendicitis is debatable (Bachman, 193.5; Driiner, 1921; 

 Penso, 1939; and others) but worms apparently may give rise 

 to the .syndrome of appendicitis without characteristic histo- 

 logical changes (Botsford, Hudson and Chamberlain, 1939). 

 Restlessness and others secondary effects in behaviorism, in- 

 cluding scholastic difficulties, feeling of shame and poor social 

 attitude, may be pronounced. 



DIAGNOSIS 



The most reliable method of diagnosis is by the microscopic 

 detection of eggs in scrapings made from the perianal region. 

 This technique has been standardized by the use of a cellophane- 

 tipped swab (Hall, 1937; Folan, 193"9), known as the NIH 

 (National Institute of Health) swab (Fig. 201) ; the cellophane 

 is detachable for mounting and examination under the micro- 

 scope. Swabs should be made during the night or first thing 

 in the morning, preferable on at least 7 days if first results 

 are negative. 



322 



