Prevalence and characteristics ofPlasmodium vivaxGametocytes in Duffy-positive and Duffy-negative populations across Ethiopia

Abstract

Plasmodiumparasites replicate asexually in the human host. The proportion of infections that carries gametocytes is a proxy for human-to-mosquito transmissibility. It is unclear what proportion ofP. vivaxinfections in Duffy-negatives carries gametocytes. This study aims to determine the prevalence ofP. vivaxin Duffy-negatives across broad regions of Ethiopia and characterize parasite stages. Finger-prick blood samples were collected for microscopic and molecular screening ofPlasmodiumparasites and Duffy status of individuals. Molecular screening of plasmodium species and Duffy blood group genotyping was done using SYBR green and Taqman qPCR method. Among the total 447 samples, 414 (92.6%) wereP.vivaxconfirmed and, 16 (3.9%) of them were from Duffy-negatives. Of these, 5/16 (31.3%) Duffy-negativeP.vivax-infected samples were detected with gametocytes. Of the 398 Duffy-positiveP.vivax-infected samples, 150 (37.7%) were detected with gametocytes, slightly higher than that in Duffy-negatives. This study highlights the presence ofP. vivaxgametocytes in Duffy-negative infections, suggestive of human-to-mosquito transmissibility. AlthoughP. vivaxinfections in Duffy-negatives are commonly associated with low parasitemia, some of these infections were shown with relatively high parasitemia and may represent better erythrocyte invasion capability ofP. vivaxand hidden reservoirs that can contribute to transmission. A better understanding ofP. vivaxtransmission biology and gametocyte function particularly in Duffy-negative populations would aid future treatment and management of vivax malaria in Africa