Serological evidence for a decline in malaria transmission following major scale-up of control efforts in a setting selected for Plasmodium vivax and Plasmodium falciparum malaria elimination in Babile district, Oromia, Ethiopia

Abstract

Background Following successful malaria control during the last decade, Ethiopia instituted a stepwise malaria elimination strategy in selected low-transmission areas. Methods Cross-sectional surveys were conducted in Babile district, Oromia, Ethiopia from July to November 2017 to evaluate malaria infection status using microscopy and nested polymerase chain reaction (nPCR) and serological markers of exposure targeting Plasmodium falciparum and Plasmodium vivax apical membrane antigen-1 (AMA-1). Results Parasite prevalence was 1.2% (14/1135) and 5.1% (58/1143) for P. falciparum and 0.4% (5/1135) and 3.6% (41/1143) for P. vivax by microscopy and nPCR, respectively. Antibody prevalence was associated with current infection by nPCR for both P. falciparum (p<0.001) and P. vivax (p=0.014) and showed an age-dependent increase (p<0.001, for both species). Seroconversion curves indicated a decline in malaria exposure 15 y prior to sampling for P. falciparum and 11.5 y prior to sampling for P. vivax , broadly following malaria incidence data from district health offices, with higher antibody titres in adults than children for both species. Conclusions Malaria transmission declined substantially in the region with continuing heterogeneous but measurable local transmission, arguing in favour of continued and tailored control efforts to accelerate the progress towards elimination efforts.

Prevalence of Plasmodium falciparum Pfcrt and Pfmdr1 alleles in settings with different levels of Plasmodium vivax co-endemicity in Ethiopia

“…Overall, the wild type Pfcrt -K76 haplotype was detected in 23.7% (40/169) and the mutant Pfcrt -76T in 76.3% (129/169) of samples across sites. We observed a statistically significant difference in the prevalence of Pfcrt -76 codons among the study sites (P < 0.001): mutant ( Pfcrt -76T) type was virtually fixed in Babile (100%, 31/31) and with near fixation at Adama (98.4%, 61/62) districts of Oromia region where P. vivax is highly endemic (41.4% and 62.2% of cases, respectively) (Keffale et al, 2019; Tadesse et al, 2018). On the other hand, a higher prevalence of the wild type ( Pfcrt -K76) codon was found in Abobo and Lare districts of Gambella (58.5%, 31/53) and in Mao-Komo and Menge districts of Benishangul-Gumuz (34.8%, 8/23) (Table 1).…”

“…Benishangul-Gumuz region, with Mao-Komo and Menge districts, is also P. falciparum dominated with relatively higher prevalence of P. vivax (10.1%) (Geleta and Ketema, 2016) and more seasonal transmission. The Oromia region study site districts of Babile and Adama are characterized by seasonal malaria transmission with co-endemicity for P. falciparum and P. vivax where P. vivax infections attributed to be 41.4% (Keffale et al, 2019) in the first and 62.2% (Tadesse et al, 2018) in the later district, respectively (Fig. 1 and Table 1).…”

Antibodies Against the Plasmodium vivax Apical Membrane Antigen 1 From the Belem Strain Share Common Epitopes Among Other Worldwide Variants

“…Most of these individuals (328/611) presented anti-PvAMA1 binding IgG, corresponding to 53.68% of the entire cohort. Among infected and non-infected individuals, the percentage of positive sera for anti-PvAMA1 binding IgG was significantly higher during the patent infection (80.77%) than in non-infected counterparts (49.72%) (p < 0.0001 -Figure 3A), confirming the immunogenicity of the PvAMA-1 protein during natural infections (Rodrigues et al, 2005;Morais et al, 2006;Wickramarachchi et al, 2006;Mufalo et al, 2008;Vicentin et al, 2014;Xia et al, 2015;Rosas-Aguirre et al, 2015;Salavatifar et al, 2015;Sańchez-Arcila et al, 2015;Kale et al, 2019;Keffale et al, 2019;Surendra et al, 2019). The prevalence of these antibodies significantly increased with age for either infected or noninfected individuals, ranging from 68.8%/38.5% in children and youngsters (0-20 years old) to 83.3%/56.3% in young adults (21-40 years old), respectively (noninfected 0-20 years old vs noninfected 21-40 years oldp < 0.05; infected 0-20 years old vs infected 21-40 years oldp < 0.05; infected 0-20 years old vs infected > 40 years oldp < 0.05 -Figure 3B).…”

“…Several studies characterizing the naturally acquired human immune responses to the PvAMA-1 ectodomain were performed in malaria endemic areas from Brazil ( Rodrigues et al., 2005 ; Morais et al., 2006 ; Múfalo et al., 2008 ; Vicentin et al., 2014 ; Sánchez-Arcila et al., 2015 ; Pires et al., 2018 ; Soares et al., 2020 ), Peru ( Rosas-Aguirre et al., 2015 ), Sri Lanka ( Wickramarachchi et al., 2006 ), India ( Kale et al., 2019 ), Ethiopia ( Keffale et al., 2019 ; Assefa et al., 2020 ), Indonesia ( Surendra et al., 2019 ), Iran ( Salavatifar et al., 2015 ) and other regions around the world ( Kim et al., 2003 ; Cook et al., 2010 ; Xia et al., 2015 ). These studies confirmed the high immunogenicity of this protein during infections, especially in regions with higher levels of disease transmission and in individuals with recent infections.…”

Serological Markers of Exposure to Plasmodium falciparum and Plasmodium vivax Infection in Southwestern Ethiopia

“…Two residents in Arjo consented to participating but did not complete the questionnaire or provide blood samples and were thus excluded from the study. The median age of participants was 27 years (interquartile range [IQR] 20-36) in Arjo and 28 years (IQR [23][24][25][26][27][28][29][30][31][32][33][34][35][36] in Gambella. The study population in Arjo was female biased (60.5%), whereas the inverse sex ratio was reported among participants in Gambella (60.1% male).…”