The interrelationship of Plasmodium falciparum and P. vivax in the Punjab.

Analysis of data obtained from Giemsa-stained blood films from patients with mixed Plasmodium vivax and P. falciparum parasitaemias seen in outpatient clinics held over 20 consecutive months in 4 villages in the Pakistani Punjab suggest that infections with P. falciparum and P. vivax were independent of each other. There was no evidence to support the hypothesis that P. falciparum suppressed P. vivax. A likely explanation for the seasonal variation in species parasitaemia rates in the Punjab is that P. vivax was predominant early in the transmission season due to late relapses, while P. falciparum was predominant later in the transmission season because of community-wide development of immunity to P. vivax.