Population characteristics
A total of 229 children aged 3-59 months were included in the analysis: 71 from Zinder, 77 from Dosso, and 81 from Gaya (Fig1). The number of samples categorized by mean age and sex was comparable between districts and difference was seen in RDTs results (Table 1).
Figure 1: Characteristics of samples collected.
Table 1. Characteristics of children included in the survey
Characteristic
|
ZINDER (N=71)
|
DOSSO (N=77)
|
GAYA (N=81)
|
|
AGE (months)
|
|
|
|
Mean age
|
30.2 ± 17.5
|
25.4 ±14.5
|
25.0 ±15.4
|
|
SEX (%)
|
|
|
|
|
M
|
53
|
50
|
63
|
|
F
|
47
|
50
|
37
|
|
RDTs results (%)
|
|
|
|
|
Positive
|
60.3
|
66.2
|
44.44
|
|
Negative
|
39.7
|
33.8
|
55.56
|
|
|
|
|
|
|
|
Zinder district (SMC since 2014), Dosso district (No SMC) and Gaya district (SMC 2016).
Anti-CSP and GLURP-R2 IgG antibodies medians levels measured by districts
The Ig G antibody levels to CSP and GLURP-R2 were compared between the three (3) districts, are presented on Table 2. The medians of anti-CSP Ig G level were higher than anti-GLURP-R2 Ig G in all districts (CSP=17.5; 4.5 and 7.7 µg/ml) vs (GLURP-R2=14.3; 3.6 and 6.5 µg/ml). In Zinder where SMC was implemented since 2014 Ig G antibody levels to CSP and GLURP-R2 observed were higher than Gaya (SMC+ 2016) and Dosso (Never received SMC). A low level of Ig G antibody CSP=4.5 µg/ml and GLURP-R2=3.6 µg/ml was observed in the district that never received SMC. The medians levels of IgG anti-CSP and anti-GLURP-R2 by districts were significantly different (p<0.0001 and p=0.0004) (Table 2).
In Zinder with SMC since 2014 (CSP=17.5 µg/ml and GLURP-R2=14.3 µg/ml) and Dosso with no SMC (CSP=4.5 µg/ml and GLURP-R2=3.6 µg/ml), median level of Ig G antibody responses was significantly different for the two antigens (figure 2 and 3). No significant difference in median levels of all antibodies was showed between Dosso (CSP=4.5 µg/ml and GLURP-R2=3.6 µg/ml) and Gaya (CSP=7.7 µg/ml and GLURP-R2=6.5 µg/ml) (p=0.05 and p=0.05).
Analysis of the differences between the median levels of anti-CSP Ig G and anti-GLURP-R2 in Zinder and Gaya showed significant difference (CSP: p=0.008 and GLURP-R2: p=0.017).
Table 2. Anti-CSP and GLURP-R2 IgG antibodies levels compared between the districts.
Antibodies levels
|
Zinder (N=71)
|
Dosso (N=77)
|
Gaya (N=81)
|
P
|
CSP
|
|
|
|
Medians
|
17.5 (IQR : 33.9)
|
4.5 (IQR : 9.8)
|
7.7 (IQR : 21.26) 0.0001
|
GLURP-R2
|
|
|
|
|
Medians
|
14.3 (IQR : 37.6)
|
3.6 (IQR : 19.5)
|
6.5 (IQR : 23.5)
|
0.0004
|
D1: Zinder district, SMC+ since 2014, D2: Dosso district, No SMC and D3: Gaya district, SMC+ 2016. IQR: Interquartile range. Comparison was performed by Mann-Whitney test. The significance level was 0.05.
Figure 2: Comparison of anti-CSP IgG antibody medians levels. D1: Zinder district (SMC since 2014), D2: Dosso district (No SMC) and D3 Gaya district (SMC since 2016). Comparison of the three districts simultaneous was performed by Median test and two by two with Mann-Whitney test. The significance limit was p<0.05.
Figure 3: Comparison of anti-GLURP-R2 IgG antibody medians levels. D1: Zinder district (SMC since 2014), D2: Dosso district (No SMC) and D3 Gaya district (SMC since 2016). Comparison of the three districts simultaneous was performed by Median test and two by two with Mann-Whitney test. The significance limit was p<0.05.
Anti-CSP and GLURP-R2 IgG median levels measured by RDTs results
The median concentrations of anti-CSP and GLURP-R2 IgG antibodies by RDTs results are showed in table 3. When subdividing the groups into those that were RDTs positive or negative and compared the differences between the median levels of antibodies responses against CSP and GLURP-R2 in each groups, no significant differences were observed (p=0.093 and p=0.539).
Table 3. Anti-CSP and GLURP-R2 IgG antibodies levels compared between RDT positive and negative
Antibodies levels
|
RDT+
|
RDT-
|
P
|
CSP
|
|
0.093
|
Median
|
9.4 (IQR : 29.9)
|
6.5 (IQR : 16.4)
|
|
GLURP-R2
|
|
|
0.539
|
Median
|
8.3 (IQR : 35.4)
|
6.0 (IQR : 20.1)
|
|
RDT+= Positive rapid diagnostic test and RDT-= Negative rapid diagnostic test. IQR: Interquartile range. Comparison was performed by Mann-Whitney test. The significance limit was p<0.05.