Plasmodium vivax Infections in Duffy-Negative Individuals: A Paradigm Shift in Indian Malaria Epidemiology

To investigate the occurrence of Plasmodium vivax infections in Duffy-negative individuals, challenging the long-held belief that P. vivax requires the Duffy antigen receptor for chemokines to infect human erythrocytes.

In the present study, 365 samples were screened using serological techniques, PCR-RFLP analysis, and DNA sequencing of the ACKR1 gene promoter region mutation to identify Duffy-negative individuals. P. vivax infection was detected using PCR targeting the 18S rRNA gene and microscopic examination of Giemsa-stained blood smears.

Five individuals (1.36%) were confirmed Duffy-negative (Fy^(a-b-)). Surprisingly, 3 out of these 5 Duffy-negative subjects (60%) were infected with P. vivax, as confirmed by both microscopy and PCR. Various parasite stages were observed in infected Duffy-negative samples, with parasitaemia ranging from 0.01% to 0.5%.

Our findings provide compelling evidence that P. vivax can infect Duffy-negative individuals, suggesting the existence of alternative invasion pathways or adaptations. This has profound implications for P. vivax biology, evolution, and global distribution. The burden of vivax malaria may be underestimated, particularly in regions with a high prevalence of Duffy negativity. This study highlights the need to reevaluate P. vivax epidemiology, diagnostic approaches, and control strategies, especially in areas previously considered at low risk. Further research is needed to elucidate the mechanisms enabling P. vivax invasion of Duffy-negative erythrocytes and to assess the clinical and epidemiological consequences of these infections.