Molecular detection of P. vivax and P. ovale foci of infection in asymptomatic and symptomatic children in Northern Namibia

Abstract

Background Knowledge of the foci of Plasmodium species infections is critical for a country with an elimination agenda. Namibia is targeting malaria elimination by 2020. To support decision making regarding targeted intervention, we examined for the first time, the foci of Plasmodium species infections and regional prevalence in northern Namibia, using nested and quantitative polymerase chain reaction (PCR) methods. Methods We used cross-sectional multi-staged sampling to select 952 children below 9 years old from schools and clinics in seven districts in northern Namibia, to assess the presence of Plasmodium species. Results The median participant age was 6 years (25–75%ile 4–8 y). Participants had a median hemoglobin of 12.0 g/dL (25–75%ile 11.1–12.7 g/dL), although 21% of the cohort was anemic, with anemia being severer in the younger population (p<0.002). Most of children with Plasmodium infection were asymptomatic (63.4%), presenting a challenge for elimination. The respective parasite prevalence for Plasmodium falciparum ( Pf) , Plasmodium vivax (Pv) and Plasmodium ovale curtisi ( Po) were (4.41%, 0.84% and 0.31%); with Kavango East and West (10.4%, 6.19%) and Ohangwena (4.5%) having the most prevalence. Pv was localized in Ohangwena, Omusati and Oshana, while Po was found in Kavango. All children with Pv/Pf coinfections in Ohangwena, had previously visited Angola, affirming that perennial migrations are risks for importation of Plasmodium species. The mean hemoglobin was lower in those with Plasmodium infection compared to those without (0.96 g/dL less, 95%CI 0.40–1.52 g/dL less, p = 0.0009) indicating that quasi-endemicity exists in the low transmission setting. Conclusions We conclude that Pv and Po species are present in northern Namibia. Additionally, the higher number of asymptomatic infections present challenges to the efforts at elimination for the country. Careful planning, coordination with neighboring Angola and execution of targeted active intervention, will be required for a successful elimination agenda.

Comparison of Plasmodium ovale curtisi and Plasmodium ovale wallikeri infections by a meta-analysis approach

“…by Sutherland et al 25 , and 2020. The majority of included studies (14/36, 38.9%) were conducted in African countries (1 in Angola 9 , 1 in Equatorial Guinea 26 , 2 in Ethiopia 5 , 8 , 2 in Gabon 43 , 51 , 1 in Ghana 15 , 1 in Kenya 46 , 1 in Namibia 44 , 2 in the Republic of Congo/Congo 26 , 42 , 2 in Senegal 6 , 7 and 1 in Uganda 26 ), Asian countries (9 in China 12 , 14 , 32 , 35 , 39 , 49 , 50 , 52 , 53 , 2 in India 10 , 11 , 1 in Bangladesh 41 , 1 in Myanmar 12 and 1 in Thailand 13 ), Europe (3 in Italy 29 – 31 , 2 in France 23 , 45 , 2 in Spain 47 , 48 , 2 in the United Kingdom 25 , 34 and 1 in Germany 40 ) and Northern America (1 in Canada 28 ). Most of the included studies 23 , 25 , 28 , 30 – 32 , 34 , 35 , 39 , 40 , 45 , 47 – 50 , 52 , 53 (19/36, 52.8%) reported indigenous cases of malaria caused by P. ovale curtisi or P. ovale wallikeri , and the remaining studies (17/36, 47.2%) reported imported cases.…”

“…The first identification of the species P. ovale wallikeri and P. ovale curtisi was reported by Sutherland et al 25 . Since then, differences in morphology, clinical characteristics, laboratory parameters and genetic differences between the two species have been observed in Africa 5 – 9 , 15 , 26 , 42 – 44 , 46 , 51 , Asia 10 – 14 , 32 , 35 , 39 , 41 , 49 , 50 , 52 , 53 , Europe 23 , 25 , 29 – 31 , 34 , 40 , 45 , 47 , 48 , and North America 28 . This widespread distribution of P. ovale spp.…”

Past and current biological factors affecting malaria in the low transmission setting of Botswana: A review

“…Of the five species of Plasmodia generally accepted to exploit humans for schizogony (Antinori et al, 2012), the three most predominant in Africa have been found in Botswana: P. falciparum, P. vivax and P. malariae (Motshoge et al, 2016). Given the presence of P. vivax, a small reservoir of P. ovale is also likely, and has been found in surrounding countries (Amanfo et al, 2016;Haiyambo et al, 2019;Ukpe, 1998;Wolfe, 1968). Here we discuss two of these species, P. falciparum and P. vivax, due to their prevalence, prognosis, and inclusion in malaria treatment guidelines in Botswana (Republic of Botswana, 2015).…”

Recent Molecular Assessment of Plasmodium vivax and Plasmodium falciparum Asymptomatic Infections in Botswana

“…Details of the amplification reactions and cycling parameters for qPCR and nested PCR have been published previously. 25 …”

“…Details of the amplification reactions and cycling parameters for qPCR and nested PCR have been published previously. 25 Statistical analysis. Data were entered in an Excel (Microsoft, Redmond, WA) data sheet.…”