Abstract:

Objective  To understand the allelotype characteristics of the merozoite surface protein 1（MSP1） in imported Plasmodium falciparum.  Methods  Blood samples were collected from P. falciparum-infected patients returning from African malaria endemic areas. Nested PCR was used to amplify gene fragments of MSP1 coding for block 2 and block 3 motifs of MSP1 of P. falciparum by using the MSP1-specific primers. Then the allelotype of MSP1 was analyzed.  Results  The  MSP1 allelotype was detected in 117 of 135 blood samples, with a detection rate of 86.7%. In the 117 cases with successful PCR amplification, the detection rates for MAD20, K1, RO33, MAD20+K1, MAD20+RO33, K1+RO33 and MAD20+K1+RO33 were 6.0%（7/117）, 36.8%（43/117）, 20.5%（24/117）, 6.8%（8/117）, 3.4%（4/117）, 17.1%（20/117） and 9.4%（11/117）, respectively, wherein the mixed infection accounted for 36.8%（43/135）. The mean multiplicity of infection（MOI） of MSP1 allelotype was 1.46. There was no significant difference in the proportion of patients with major severity of illness among the MAD20, K1 and RO33 genotypes. The proportions of patients with major severity of illness were 25.7%（19/74） and 32.6%（14/43） in 74 cases of singular infection and 43 cases of mixed infection, respectively. The two infection types of patients had 241±176 days and 285±216 days of stay abroad, with no significant difference between them.  Conclusion  The three genotypes of MSP1 and their four types of combination exist in imported cases of P. falciparum malaria from Africa. K1 and RO33 are the dominant genotypes.

Key words: Plasmodium falciparum, MSP1, Genotype, Imported case