Meiotic recombination, cross-reactivity, and persistence in Plasmodium falciparum

We incorporate a representation of Plasmodium falciparum recombination with in a discrete-event model of malaria transmission. We simulate the introduc tion of a new parasite genotype into a human population in which another ge notype has reached equilibrium prevalence and compare the emergence and per sistence of the novel recombinant forms under differing cross-reactivity re lationships between the genotypes. Cross-reactivity between the parental (i nitial and introduced) genotypes reduces the frequency of appearance of rec ombinants within three years of introduction from 100% to 14%, and delays t heir appearance by more than a year, on average. Cross-reactivity between p arental and recombinant genotypes reduces the frequency of appearance to 36 % and increases the probability of recombinant extinction following appeara nce from 0% to 83%. When a recombinant is cross-reactive with its parental types, its probability of extinction is influenced by cross-reactivity betw een the parental types in the opposite manner; that is, its probability of extinction after appearance decreases. Frequencies of P. falciparum outcros sing are mediated by frequencies of mixed-genotype infections in the host p opulation, which are in turn mediated by the structure of cross-reactivity between parasite genotypes. The three leading hypotheses about how meiosis relates to oocyst production lead to quantitative, but no qualitative, diff erences in these results.