Elifaged Hailemeskel1,2,3,4, Surafel K Tebeje1,4, Sinknesh W Behaksra1, Girma Shumie1, Getasew Shitaye5, Migbaru Keffale1, Wakweya Chali1, Abrham Gashaw1, Temesgen Ashine1, Chris Drakeley6, Teun Bousema4,6, Endalamaw Gadisa1, Fitsum G Tadesse7,8,9. 1. Malaria and Neglected Tropical Diseases Directorate, Armauer Hansen Research Institute, PO Box 1005, Addis Ababa, Ethiopia. 2. Department of Biomedical Sciences, College of Natural and Computational Sciences, Addis Ababa University, PO Box 1176, Addis Ababa, Ethiopia. 3. Department of Biology, College of Natural and Computational Sciences, Wollo University, PO Box, 1145, Dessie, Ethiopia. 4. Department of Medical Microbiology, Radboud University Medical Center, 6525 GA, Nijmegen, The Netherlands. 5. Department of Biomedical Sciences, School of Medical Sciences, Bahir Dar University, Bahir Dar, Ethiopia. 6. Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, WC1E 7HT, London, UK. 7. Malaria and Neglected Tropical Diseases Directorate, Armauer Hansen Research Institute, PO Box 1005, Addis Ababa, Ethiopia. fitsum.girma@aau.edu.et. 8. Department of Medical Microbiology, Radboud University Medical Center, 6525 GA, Nijmegen, The Netherlands. fitsum.girma@aau.edu.et. 9. Institute of Biotechnology, Addis Ababa University, PO Box, 1176, Addis Ababa, Ethiopia. fitsum.girma@aau.edu.et.
Abstract
BACKGROUND: As countries move to malaria elimination, detecting and targeting asymptomatic malaria infections might be needed. Here, the epidemiology and detectability of asymptomatic Plasmodium falciparum and Plasmodium vivax infections were investigated in different transmission settings in Ethiopia. METHOD: A total of 1093 dried blood spot (DBS) samples were collected from afebrile and apparently healthy individuals across ten study sites in Ethiopia from 2016 to 2020. Of these, 862 were from community and 231 from school based cross-sectional surveys. Malaria infection status was determined by microscopy or rapid diagnostics tests (RDT) and 18S rRNA-based nested PCR (nPCR). The annual parasite index (API) was used to classify endemicity as low (API > 0 and < 5), moderate (API ≥ 5 and < 100) and high transmission (API ≥ 100) and detectability of infections was assessed in these settings. RESULTS: In community surveys, the overall prevalence of asymptomatic Plasmodium infections by microscopy/RDT, nPCR and all methods combined was 12.2% (105/860), 21.6% (183/846) and 24.1% (208/862), respectively. The proportion of nPCR positive infections that was detectable by microscopy/RDT was 48.7% (73/150) for P. falciparum and 4.6% (2/44) for P. vivax. Compared to low transmission settings, the likelihood of detecting infections by microscopy/RDT was increased in moderate (Adjusted odds ratio [AOR]: 3.4; 95% confidence interval [95% CI] 1.6-7.2, P = 0.002) and high endemic settings (AOR = 5.1; 95% CI 2.6-9.9, P < 0.001). After adjustment for site and correlation between observations from the same survey, the likelihood of detecting asymptomatic infections by microscopy/RDT (AOR per year increase = 0.95, 95% CI 0.9-1.0, P = 0.013) declined with age. CONCLUSIONS: Conventional diagnostics missed nearly half of the asymptomatic Plasmodium reservoir detected by nPCR. The detectability of infections was particularly low in older age groups and low transmission settings. These findings highlight the need for sensitive diagnostic tools to detect the entire parasite reservoir and potential infection transmitters.
BACKGROUND: As countries move to malaria elimination, detecting and targeting asymptomatic malaria infections might be needed. Here, the epidemiology and detectability of asymptomatic Plasmodium falciparum and Plasmodium vivaxinfections were investigated in different transmission settings in Ethiopia. METHOD: A total of 1093 dried blood spot (DBS) samples were collected from afebrile and apparently healthy individuals across ten study sites in Ethiopia from 2016 to 2020. Of these, 862 were from community and 231 from school based cross-sectional surveys. Malaria infection status was determined by microscopy or rapid diagnostics tests (RDT) and 18S rRNA-based nested PCR (nPCR). The annual parasite index (API) was used to classify endemicity as low (API > 0 and < 5), moderate (API ≥ 5 and < 100) and high transmission (API ≥ 100) and detectability of infections was assessed in these settings. RESULTS: In community surveys, the overall prevalence of asymptomatic Plasmodiuminfections by microscopy/RDT, nPCR and all methods combined was 12.2% (105/860), 21.6% (183/846) and 24.1% (208/862), respectively. The proportion of nPCR positive infections that was detectable by microscopy/RDT was 48.7% (73/150) for P. falciparum and 4.6% (2/44) for P. vivax. Compared to low transmission settings, the likelihood of detecting infections by microscopy/RDT was increased in moderate (Adjusted odds ratio [AOR]: 3.4; 95% confidence interval [95% CI] 1.6-7.2, P = 0.002) and high endemic settings (AOR = 5.1; 95% CI 2.6-9.9, P < 0.001). After adjustment for site and correlation between observations from the same survey, the likelihood of detecting asymptomatic infections by microscopy/RDT (AOR per year increase = 0.95, 95% CI 0.9-1.0, P = 0.013) declined with age. CONCLUSIONS: Conventional diagnostics missed nearly half of the asymptomatic Plasmodium reservoir detected by nPCR. The detectability of infections was particularly low in older age groups and low transmission settings. These findings highlight the need for sensitive diagnostic tools to detect the entire parasite reservoir and potential infection transmitters.
Entities:
Keywords:
Asymptomatic; Density distribution; Detectability; Elimination; Plasmodium infection; Transmission; nPCR
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