Background
Methods
Study site
Aquatic stages collection sites
Aquatic stages collection and specimen processing
Geographic information system
Adult mosquito collection and specimen processing
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Adult mosquitoes were collected weekly by two sampling methods:
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Indoor pyrethrum spray catches: two houses (one room per house) per district were sprayed with insecticide early in the morning (between 6:00 and 9:00 am) for the collection of the resting female mosquitoes. Knocked-down female mosquitoes were quickly collected from white sheets laid on the floor and the furniture of sprayed rooms.
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Indoor CDC light-traps (CDC miniature light trap, Model 512, John W. Hock Co., Gainesville, FL): Three other houses (one room per house) close to the indoor pyrethrum sprayed houses were sampled. Light traps were set up at 7:00 pm and mosquitoes were collected at 7:00 am.
PCR identification of the Anopheles gambiae complex
ELISA for the detection of parasite infections in Anopheles gambiae s.l.
Analysis and statistics of the aquatic stage ecology
Results
Aquatic stages survey
Ecological study: anopheles ecological preferences
Ecological study: non parametric test
Anopheles
| Culicinae | |||||
---|---|---|---|---|---|---|
n | Mean | SD | n | Mean | SD | |
Upstream | 936 | 8.43 | 24.99 | 423 | 3.81 | 15.93 |
City | 971 | 3.71 | 12.54 | 3723 | 14.21 | 62.60 |
Downstream | 527 | 2.25 | 4.68 | 1837 | 7.85 | 23.16 |
Anopheles
| Culicinae | |||||
---|---|---|---|---|---|---|
n | Mean | SD | n | Mean | SD | |
<500 m | 802 | 2.247 | 7.429 | 2281 | 6.389 | 23.942 |
500–1500 m | 958 | 7.484 | 22.853 | 1591 | 12.430 | 53.171 |
>1500 m | 674 | 5.525 | 15.427 | 2111 | 17.303 | 71.041 |
Site class |
Anopheles
| Culicinae | ||||
---|---|---|---|---|---|---|
n | Mean | SD | n | Mean | SD | |
Human made | 711 | 3.76 | 10.96 | 3030 | 16.03 | 49.71 |
Kori | 130 | 13.00 | 30.71 | 786 | 78.60 | 234.22 |
Pond | 776 | 11.76 | 31.16 | 233 | 3.53 | 13.59 |
Ricefield | 400 | 3.36 | 9.48 | 692 | 5.82 | 15.80 |
River | 396 | 1.85 | 5.72 | 1196 | 5.59 | 23.93 |
Small temperature | 21 | 2.33 | 3.43 | 46 | 5.11 | 9.69 |
Anopheles
| Culicinae | |||||
---|---|---|---|---|---|---|
n | Mean | SD | n | Mean | SD | |
Dry cool | 737 | 3.96 | 15.69 | 2736 | 14.71 | 71.64 |
Dry hot | 590 | 3.99 | 13.34 | 1121 | 7.57 | 24.98 |
Rainy | 1107 | 4.06 | 13.01 | 2126 | 7.79 | 22.54 |
Ecological study: models
Model parameters | Goodness indices | |||||
---|---|---|---|---|---|---|
Variable type: presence/absence (YN) or count) | Model type | Interaction with season (N = Add/Y = Interact) | Residuals deviance | Null residual | Degrees of freedom | AIC |
Anopheles
| ||||||
YN
|
logreg–binom (Ano1) |
N
|
740.81
|
782.92
|
596
|
762.81
|
YN | logreg–binom | Y | 710.35 | 782.92 | 580 | 764.35 |
Count | glmPoisson | N | 7437.9 | 9536.4 | 596 | 8189.1 |
Count
|
glmPoisson (Ano2) |
Y
|
6831
|
9536.4
|
580
|
7614.1
|
Culex
| ||||||
YN
|
logreg–binom (Culex1) |
N
|
719.22
|
773.65
|
598
|
737.22
|
YN | logreg–binom | Y | 698.48 | 773.65 | 582 | 748.48 |
count | glmPoisson | N | 22.691 | 27.036 | 598 | 23.528 |
count
|
glmPoisson (Culex2) |
Y
|
18,694
|
27,036
|
582
|
19,564
|
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Anopheles ~ Typology + DistRiver + Up/Down + Water surface, with no interaction between factors
-
Anopheles ~ (Typology + DistRiver)*Season + Up/Down + Water surface including the Season interaction with both the typology and Distance to the river.
Significant variable in the model: Yes/No | Interactions | ||||||
---|---|---|---|---|---|---|---|
Typology (reference “human made”) | Distance to river (reference “<500 m”) | Up/down stream (reference “upstream”) | Water surface | Season (reference “Dry cool”) | Typology * season | Distance river * season | |
Ano1 |
Kori (p = 0.0524)
|
Yes (Q—p = 0.0281)
|
(p = 0.0977)
| No | NA | NA | NA |
Ano2 |
Pond (p < 2e−16),
River (p = 0.0217)
|
Yes (Q—p < 2e−16)
|
Yes (L—p < 2e−16)
|
Yes (p = 2e-6)
|
Rainy (p = 0.0003)
| Yes | Yes |
Culex1 |
Pond (p = 0.0028), River (p = 0.0027)
|
Yes (L—p = 0.0139)
| NA | No | NA | NA | NA |
Culex2 |
Kori (p < 2e−16),
Pond (p < 2e−16), Ricefield(p < 2e−16), River (p = 8.7e−11), Small temp(p = 2e-11)
|
Yes (Q—p < 2e−16)
| NA |
Yes p < 2e−16
|
Dryhot (p < 2e−16), Rainy (p < 2e−16)
| Yes |
Yes
|
Typology (reference “Human made”) |
Anopheles
| Culicinae | ||
---|---|---|---|---|
Rainy season | Hot and dry season | Rainy season | Hot and dry season | |
Kori |
Ano2***
|
Culex2***
| ||
Pond |
Ano2***
|
Ano2***
|
Culex2***
| |
Ricefield |
Ano2**
|
Culex2***
|
Culex2***
| |
River |
Ano2***
|
Culex2***
|
Culex2*
| |
Small Temp |
Ano2***
|
Culex2**
| ||
Distance river(L-Linear, Q-Quadratic) |
Ano2*** (Q + L)
|
Ano2***(L)
|
Culex2*** (Q)
|
Culex2*** (Q)
|
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Culicinae ~ Typology + DistRiver + Water surface
-
Culicinae ~ (Typology + DistRiver)*Season + Water surface, including the Season interaction with both the typology and Distance to the river.
Adult mosquito study
Composition of the population and abundance
Districts of Niamey | ||||||||
---|---|---|---|---|---|---|---|---|
Species | Goudel (semi-urban area) | Boukoki 4 (urban area) | Total | |||||
PS | LT | Total | PS | LT | Total | |||
An. gambiae s.l.
| 715 | 1273 | 1988 | 10 | 27 | 37 | 2025 | |
An. funestus
| 2 | 10 | 12 | 0 | 0 | 0 | 12 | |
An. rufipes
| 12 | 21 | 33 | 0 | 3 | 3 | 36 | |
An. ziemanni
| 0 | 36 | 36 | 0 | 0 | 0 | 36 | |
An. pharoensis
| 1 | 29 | 30 | 0 | 0 | 0 | 30 | |
Culex sp.
| 1110 | 2849 | 3959 | 1031 | 4483 | 5514 | 9473 | |
Mansonia sp.
| 1 | 218 | 219 | 1 | 1 | 2 | 221 | |
Aedes sp.
| 1 | 13 | 14 | 0 | 6 | 6 | 20 | |
Phlebotomine | 74 | 16 | 90 | 1 | 13 | 14 | 104 | |
1916 | 4465 | 6381 | 1043 | 4533 | 5576 | 11,957 |