Malaria 619 



in the cortex, and adrenal insufficiency has been considered a possible 

 factor in fatal pernicious malaria. Involvement of the respiratory system 

 may lead to indications of bronchitis or pneumonia. Effects on the uro- 

 genital system may suggest nephritis, orchitis or oophoritis, and haemo- 

 globinuria or haematuria also may develop. 



As complications of pregnancy, the malarias may be blamed for a 

 considerable amount of fetal, neonatal, and maternal mortality. Even 

 benign tertian is important in this respect and malignant tertian is par- 

 ticularly dangerous, both to the mother and to the fetus. The later the 

 falciparum infection occurs in pregnancy, the less is the chance of carry- 

 ing the fetus to term, and if the child is born alive it sometimes lives 

 for only a few days. 



Duration of clinical attacks 



Duration of the vivax attack varies with the strain of parasites, 

 with resistance of the individual, and apparently with the season of the 

 year. Under comparable experimental conditions, July-September cases 

 have shown longer clinical courses than January-March cases (22). Clin- 

 ical symptoms have mostly disappeared in experimental tertian when the 

 parasite density drops to about 100/mm^. In quartan malaria, duration 

 of clinical attacks has averaged 170 days in naturally inoculated whites 

 and 76 days in negroes. After artificial inoculation, the corresponding 

 averages were 81 and 53 days (9). Duration of attacks in experimental 

 falcipariwi malaria has averaged about II days, with a maximum of 36 

 (14). As in benign tertian, the length of the attack may vary with the 

 season, being relatively long during the fall and shorter during the winter 

 months. 



Duration of infections 



The duration of untreated infections is uncertain, in view of the 

 occasional occurrence of prolonged latency. Even in induced malaria it 

 is difficult to determine the end-point because failure to find the parasites 

 does not guaiantee the absence of a latent infection. In uncomplicated 

 vivax malaria, the attacks usually become less and less severe and eventu- 

 ally cease. However, the infection sometimes persists for at least two years 

 after the primary attack. In falciparum malaria, there are grounds for 

 believing that infections usually last no more than six months (12, 56). 

 P. malariae shows greater persistence and latent infections may last for 

 five years or more after the primary attack (106). 



Relapses 



Although the tendency of P. ovale infections to relapse is com- 

 paratively slight (68, 103), relapses are characteristic of the other human 



