596 



SCIENCE 



[N. S. Vol. LIV. No. 1407. 



late the larvse from considerable quantities 

 of soil. Botli field and laboratory studies 

 ■were included in the program. The field 

 investigations consisted of intensive epidemi- 

 ologic studies of the factors involved in the 

 spread of hookworm disease in two limited 

 areas, one on a sugar estate and the other on 

 a cacao estate. The laboratory investigations 

 included a study of the following points, viz. : 

 (1) the relation of the chicken and pig to the 

 spread of hookworm disease, (2) some of the 

 factors influencing the hatching of the eggs, 

 (3) the migrations both vertical and lateral 

 of the infective hookworm larvae and (4) the 

 length of life of the infective hookworm 

 larvse. 



A summary of the most important results 

 obtained will be given here.- 



1. SOURCES OF HUMAN INFESTATION 



In the two field areas studied a comparison 

 of the distribution of soil infestation and the 

 habits of the people revealed that almost the 

 exclusive sources of human infestation in 

 these two areas were the places in a cane 

 field and a cacao grove which were constantly 

 visited for the purpose of defecation. 



2. REDUCTION OF SOIL POLLUTION BY THE INTRO- 

 DUCTION OF LATRINES AND AN EDUCA- 

 TIONAL CAMPAIGN 



It was found by a study of the distribu- 

 tion of soil pollution in the cane area that 

 the building of an adequate number of la- 



2 These results are taken from the work of all 

 the members of the expedition. The epidemiologic 

 studies in the field were made by Doctors Cort and 

 G. C. Payne. The work on the relations of the 

 chickens and pigs to the spread of hookworm dis- 

 ease and on the conditions influencing the hatching 

 of hookworm eggs was done by Dr. Aekert. Drs. 

 Florence K. Payne and Aekert collaborated on 

 the work on the new species of pig hookworm from 

 Trinidad, and Dr. Florence K. Payne made the 

 studies on vertical migrations of the infective 

 hookworm larvsB. The laboratory experiments on 

 the horizontal migrations and length of life of the 

 infective hookworm larvae were made by Mr. Augus- 

 tine. 



trines and the carrying through of the regular 

 educational campaign against hookworm dis- 

 ease resulted in a very great reduction of soil 

 pollution in a period of about three weeks. 



3. RELATION BETWEEN THE DISTRIBUTION OF 

 SOIL POLLUTION AND SOIL INFESTATION 



In both the cane and cacao areas gross 

 soil pollution by infested individuals did not 

 always produce soil infestation, especially in 

 unprotected places near houses, latrines or 

 at the edge of the cane field. The conclusion 

 was drawn that in the heavy clay loam soil 

 of these areas the conditions are unfavorable 

 for the development or continued life of the 

 hookworm larvse, unless there is protection 

 by shade and vegetation. 



4. THE RELATION OP CHICIiENS TO THE SPREAD 



OF HOOKWORM DISEASE 



When chickens ingested human feces con- 

 taining hookworm eggs only a very small 

 percentage of such eggs produced infective 

 hookworm larvse. Chickens fed on human 

 feces containing hookworm eggs were found 

 to produce limited areas of soil infestation 

 at their drinking places, or under their roosts. 

 The conclusion is drawn, however, that in 

 view of the great reduction of infective larvse 

 produced by passage through the chickens, 

 they are, under the conditions in Trinidad, 

 a factor favorable rather than unfavorable to 

 hookworm control. 



5. THE RELATION OF THE PIG TO THE SPREAD OF 



HOOKWORM LARV^ 



Eggs of tlie human hookworm which had 

 passed through the digestive tract of the pig 

 developed as readily in pig as in human 

 feces, thus making pigs a factor in the dis- 

 semination of hookworm larvse whenever they 

 have the opportunity of ingesting human 

 feces containing hookworm eggs. In connec- 

 tion with this work a new species of Necafor 

 closely resembling Necator americanus was 

 found to be prevalent in the pigs in Trinidad, 

 and its morphology and distribution studied. 



