SCREENIXC; 205 



and construction gangs organized, the work should be carried on 

 systematically, street by street, or block by block. Careful cost 

 records should be made. 



5. A system of monthly inspection should be organized to see 

 that the screening is maintained in good condition. 



VALUE OF SCREENING 



That screening, if properly done, is very effective in reducing 

 morbidity and annoyance occasioned bj r mosquitoes is certain. 

 Shaw 1 reports that at Lake Charles, La., the malaria rate of 

 screened houses, as ascertained by history index, was 50 per cent 

 lower than in unscreened houses. 



The St. Louis & Southwestern Railway in 1917 began screen- 

 ing the box cars in which its bridge and building gangs sleep. 

 The following table 2 shows the remarkable falling off in the rate 

 of hospital admissions for malaria following the screening: 



1915 1916 1917 1918 



Hospital admissions for malaria 87 74 37 11 



An interesting demonstration involving screening was carried 

 out on a number of plantations near Lake Village, Ark., in 1916 

 by the U. S. Public Health Service and the International Health 

 Board. Thirty-three houses were screened at a cost of $14.59 

 per house or SI. 76 per capita. The incidence of malaria, as 

 revealed in blood examinations in May and December, 1916, 

 both of the screened group and of a control unscreened group, is 

 shown in the following table. 3 



COST OF SCREENING 



While the cost of screening varies, of course, with the size of 

 the house and the number of doors, windows, porches and chim- 



1 Transactions of the First Annual Conference of Sanitary Engineers, 

 U. S. Public Health Service, 1919. 



2 Transactions of the First Annual Conference of Sanitary Engineers, 

 U. S. Public Health Sendee, 1919. 



'"Malaria Control, A Report of Demonstration Studies," U. S. Public 

 Health Service, 1917. 



