Prevalence and Characteristics of Plasmodium vivax Gametocytes in Duffy-Positive and Duffy-Negative Populations across Ethiopia

Ebony Little Department of Biological Sciences, University of North Carolina at Charlotte, North Carolina;

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Tassew T. Shenkutie Department of Microbiology and Immunology, Drexel University, College of Medicine, Philadelphia, Pennsylvania;
Department of Medical Laboratory Sciences, Debre Brehan University, Ethiopia;

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Meshesha Tsigie Negash Ethiopian Public Health Institute, Addis Ababa, Ethiopia;

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Beka R. Abagero Department of Molecular and Cellular Biology and Genetics, Drexel University, College of Medicine, Philadelphia, Pennsylvania;

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Abnet Abebe Ethiopian Public Health Institute, Addis Ababa, Ethiopia;

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Jean Popovici Institute Pasteur in Cambodia, Phnom Penh, Cambodia

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Sindew Mekasha Feleke Ethiopian Public Health Institute, Addis Ababa, Ethiopia;

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Eugenia Lo Department of Biological Sciences, University of North Carolina at Charlotte, North Carolina;
Department of Microbiology and Immunology, Drexel University, College of Medicine, Philadelphia, Pennsylvania;

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Plasmodium parasites replicate asexually in human hosts. The proportion of infections that carries gametocytes is a proxy for human-to-mosquito transmissibility. It is unclear which proportion of Plasmodium vivax infections in Duffy-negative populations carries gametocytes. We determined the prevalence and characteristics of P. vivax gametocytes in Duffy-positive and -negative populations across broad regions of Ethiopia. Finger-prick blood samples were collected for microscopic and molecular screening of Plasmodium parasites and Duffy status of individuals. Molecular screening of Plasmodium species and Duffy blood group genotyping was done using SYBR green and the Taqman quantitative polymerase chain reaction method. Of the 447 febrile patients who were shown to be P. vivax smear positive, 414 (92.6%) were confirmed by molecular screening as P. vivax and 16 (3.9%) of them were from Duffy-negative individuals. Of these, 5 of 16 (31.3%) Duffy-negative P. vivax–infected samples were detected with gametocytes. Of the 398 Duffy-positive P. vivax–infected samples, 150 (37.7%) were detected with gametocytes, slightly greater than that in Duffy-negative samples. This study highlights the presence of P. vivax gametocytes in Duffy-negative infections, suggestive of human-to-mosquito transmissibility. Although P. vivax infections in Duffy-negative individuals were commonly associated with low parasitemia, some of these infections were shown to have relatively high parasitemia and may represent a prominent erythrocyte invasion capability of P. vivax, and hidden reservoirs that can contribute to transmission. A better understanding of P. vivax transmission biology and gametocyte function particularly in Duffy-negative populations would aid future treatment and management of P. vivax malaria in Africa.

Author Notes

Financial support: This research was supported by the NIH (R01 AI162947 and R01 AI173171).

Disclosure: Scientific and ethical clearance was obtained from the institutional scientific and ethical review boards of the Ethiopian Public Health Institute, Ethiopia; and Drexel University, Philadelphia, PA. Written informed consent/assent for study participation was obtained from all participants in the study, and from parents and guardians for minors younger than 18 years old.

Authors’ contributions: T. T. Shenkutie, E. Little, S. M. Feleke, and E. Lo conceptualized and designed the study; T. T. Shenkutie, M. T. Negash, and A. Ababe collected samples and performed preliminary laboratory tests; E. Little, B. R. Abagero and E. Lo performed molecular laboratory tests, analyses, and interpretation; T. T. Shenkutie, E. Little, B. R. Abagero, J. Popovici, and E. Lo wrote and reviewed the paper. All authors read and approved the final manuscript.

Data availability: All data produced in our study are available upon reasonable request made to the corresponding author per institutional and national legal norms and procedures.

Authors’ addresses: Ebony Little, Department of Biological Sciences, University of North Carolina at Charlotte, NC, E-mail: elittle23@charlotte.edu. Tassew T. Shenkutie, Department of Microbiology and Immunology, Drexel University, College of Medicine, Philadelphia, PA, and Department of Medical Laboratory Sciences, Debre Brehan University, Ethiopia, E-mail: ts3576@drexel.edu. Beka R. Abagero, Department of Microbiology and Immunology, Drexel University, College of Medicine, Philadelphia, PA, E-mail: bra38@drexel.edu. Eugenia Lo, Department of Biological Sciences, University of North Carolina at Charlotte, NC, and Department of Microbiology and Immunology, Drexel University, College of Medicine, Philadelphia, PA, E-mail: el855@drexel.edu. Meshesha Tsigie Negash, Abnet Abebe, and Sindew Mekasha Feleke, Ethiopian Public Health Institute, Addis Ababa, Ethiopia, E-mails: meshye21@gmail.com, abnetabas@gmail.com, and mekashasindeaw@yahoo.com. Jean Popovici, Institute Pasteur in Cambodia, Phnom Penh, Cambodia, E-mail: jpopovici@pasteur-kh.org.

Address correspondence to Tassew T. Shenkutie, Department of Microbiology and Immunology, Drexel University, College of Medicine, 3024 West Queen Lane, #A4-D, Philadelphia, PA 19129. E-mail: ts3576@drexel.edu
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