Pathogenesis 



513 



in the transmission of malaria, its prophylaxis becomes a matter 

 of simplicity when certain measures can be systematically carried 

 out. There are two equally important factors to be considered — 

 the human being and the mosquito. The measures must be di- 

 rected toward preventing each from infecting the other. 



I. The Human Beings. — ^In districts where malarial fever pre- 

 vails, the ^st part of the campaign had perhaps best be directed 

 toward finding and treating all cases of malarial fever, so that the 

 parasites in their blood may be destroyed and the infection of 

 mosquitoes prevented. This is done by the systematic and general 

 use of quinin. 



All cases of malarial fever should be required to sleep in mosquito- 



Fig. 190. — Anopheles maculipennis : Adult male at left, female at right (Howard) 



proof houses under nets, and as the mosquitoes are nocturnal and 

 begin to fly at dusk, the patients should shut themselves in before 

 that time. By thus killing the parasites in the blood, and keeping 

 the mosquitoes from the patientsin the meantime, much can be done. 

 But where malarial fever prevails, the mosquitoes are already largely 

 infected, hence the healthy population should also learn to respect 

 the habits of the insects and not expose themselves to their bites, 

 should screen their houses and their beds, and should take small 

 prophylactic doses of quinin to prevent the development of the 

 parasites when exposure cannot be avoided. 



2. The Mosquitoes. — ^It is not known that the parasites can 

 pass from one generation of mosquitoes to another, hence the 

 mosquitoes to be feared are those that are already infected. By 

 33 



