[Phenotypic variability in P. vivax with short- and long-term incubation period]

The combined transmission of P. vivax phenotypes was studied. The phenotypes were determined by the duration of a latent parasitic development stage by comparing the intervals from first manifestations of malaria with short- and long-term incubations to its relapse. The study used data on 2493 patients treated with chloroquine (900 mg base for adults) alone at follow-ups in the North-Eastern Delhi (India) in 1988-1992. The combined transmission of P. vivax phenotypes was shown to differ in malaria with short- and long-term incubation. The P. vivax phenotype with manifestations on an average a year following infection in patients with mainly short-term incubation malaria and that with manifestations on an average year and a half after infection in a group of patients with primary long-term incubation malaria were significantly more frequently. Long-term incubation malaria shows simultaneously a larger number of phenotypes than does short-term incubation one. Patients with long-term incubation malaria display a combination of 2 phenotypes (6%) significantly less frequently than that of 3 different phenotypes or more (17%). The similar combinations were observed in the equal number of patients with short-term incubation malaria (7%).