In the context of this study the ethnic origin of the patients revealed no noteworthy difference in the clinical reaction to the parasite; neither did age or sex of the patients. Any minor differences whcih appeared in length of history before seeking treatment and frequency of repeat attacks were more a reflection of the cultural pattern of response to illness (i.e. resort to traditional medicines) and the distance between the patient's home and the doctor rather than any altered response on the part of the host to the parasite. However, the fact that about 35 per cent of all the episodes had a history of eight or more days (about 10 per cent more than 30 days) suggest that more "malaria consciousness" is called for in what is after all an endemic malaria area. The value (and necessity) of repeated examination of the blood to detect the parasite is confirmed but it is also encouraging to note that in 84% of cases a single careful examination of the blood revealed the parasite. Since in 49% of our malaria episodes the patient was afebrile when the parasite was discovered, it is obvious that in outpatient practice especially blood should be examined when the patient presents for treatment, irrespective of the presence or absence of pyrexia. As always, a prerequisite to the diagnosis of malaria is an awareness of its possible presence.
Chloroquine pressure was applied over a 22 month period on a somewhat isolated, malarious rubber estate by examination of residents at 4-week intervals and treatment of parasitaemias with chloroquine. During this time the monthly attack rate for P. falciparum rose four-fold to an average of nearly 18% per month, while that of P. vivax remained relatively constant at about 8%. Eight in vivo chloroquine resistance studies, which allowed both detection of late recrudescing R-I resistance and estimation of the risk of reinfection, showed an apparent rise in the drug resistance rate, from 12% to 20% prior to the study to the range of 40-50%. Virtually all resistance encountered was R-I in nature. There was no convincing evidence of chloroquine resistance among 148 tested P. vivax infections.