Abstract:
Background: Recent studies from different malaria-endemic regions including western Africa have now shown that
Plasmodium vivax can infect red blood cells (RBCs) and cause clinical disease in Duffy-negative people, though the
Duffy-negative phenotype was thought to confer complete refractoriness against blood invasion with P. vivax. The
actual prevalence of P. vivax in local populations in Ghana is unknown and little information is available about the
distribution of Duffy genotypes. The aim of this study was to assess the prevalence of P. vivax in both asymptomatic
and symptomatic outpatients and the distribution of Duffy genotypes in Ghana.
Methods: DNA was extracted from dried blood spots (DBS) collected from 952 subjects (845 malaria patients and
107 asymptomatic persons) from nine locations in Ghana. Plasmodium species identification was carried out by
nested polymerase chain reaction (PCR) amplification of the small-subunit (SSU) rRNA genes. For P. vivax detection, a
second PCR of the central region of the Pvcsp gene was carried out. Duffy blood group genotyping was performed by
allele-specific PCR to detect the presence of the FYES allele.
Results: No cases of P. vivax were detected in any of the samples by both PCR methods used. Majority of infections
(542, 94.8%) in the malaria patient samples were due to P. falciparum with only 1 infection (0.0017%) due to Plasmodium
malariae, and 2 infections (0.0034%) due to Plasmodium ovale. No case of mixed infection was identified. Of
the samples tested for the FYES allele from all the sites, 90.5% (862/952) had the FYES allele. All positive samples were
genotyped as FY*B-33/FY*B-33 (Duffy-negative homozygous) and therefore classified as Fy(a−b−).
Conclusions: No cases of P. vivax were detected by both PCRs and majority of the subjects tested carried the FYES
allele. The lack of P. vivax infections observed can be attributed to the high frequency of the FYES allele that silences
erythroid expression of the Duffy. These results provide insights on the host susceptibility for P. vivax infections that
had not been investigated in Ghana before.
