Background
Methods
Study design
Mosquito collection
Satellite-derived variables
Statistical analyses
Results
Descriptive statistics
Sex | Genus | Trap nights | Total | Average per light-trap-night | Standard deviation |
---|---|---|---|---|---|
Female |
Culex
| 1472 | 30,237 | 20.5 | 47.1 |
Anopheles
| 1472 | 4888 | 3.3 | 17.6 | |
Aedes
| 1472 | 156 | 0.1 | 0.9 | |
Male |
Culex
| 1472 | 3526 | 2.4 | 9.7 |
Anopheles
| 1472 | 47 | 0.0 | 0.3 | |
Aedes
| 1472 | 41 | 0.0 | 0.3 |
Sex | Species | Trap nights | Total | Average per light-trap-night | Standard deviation |
---|---|---|---|---|---|
Dry season | |||||
Female |
Anopheles arabiensis
| 845 | 36 | 0.0 | 0.4 |
Anopheles funestus
| 845 | 291 | 0.3 | 2.1 | |
Other Anopheles | 845 | 2 | 0.0 | 0.1 | |
Male |
Anopheles arabiensis
| 861 | 0 | 0.0 | 0.0 |
Anopheles funestus
| 861 | 4 | 0.0 | 0.1 | |
Other Anopheles | 861 | 0 | 0.0 | 0.0 | |
Rainy season | |||||
Female |
Anopheles arabiensis
| 578 | 1134 | 2.0 | 6.5 |
Anopheles funestus
| 578 | 3055 | 5.3 | 22.0 | |
Other Anopheles | 578 | 15 | 0.0 | 0.4 | |
Male |
Anopheles arabiensis
| 611 | 4 | 0.0 | 0.1 |
Anopheles funestus
| 611 | 9 | 0.0 | 0.2 | |
Other Anopheles | 611 | 0 | 0.0 | 0.0 |
Bivariate analysis
An. arabiensis
|
An. funestus
| |||
---|---|---|---|---|
95% CI | P value | 95% CI | P value | |
Demographics | ||||
Number of rooms | 0.8 (0.7, 0.9) | < 0.01 | 0.7 (0.6, 0.8) |
0.0001
|
Number of children under age 5 | 1.9 (1.3, 2.7) | < 0.001 | 1.9 (1.3, 2.8) | < 0.001 |
Number slept in the house | 1.0 (0.8, 1.1) | 0.75 | 0.9 (0.8, 1.1) | 0.42 |
Age of household head (years) | 0.99 (0.98, 1.0) | 0.09 | 0.98 (0.97, 0.99) | < 0.01 |
Male head of household | 1.1 (0.7, 1.7) | 0.78 | 1.3 (0.8, 2.0) | 0.23 |
Highest educational attainment of head of household | < 0.001 |
0.0001
| ||
No formal education | Ref | Ref | ||
Some primary education | 1.3 (0.5, 3.2) | 2.8 (1.2, 6.9) | ||
Some secondary education | 0.5 (0.2, 1.3) | 1.6 (0.6, 4.0) | ||
Some college | 0.4 (0.1, 1.2) | 0.2 (0.1, 0.6) | ||
Malaria prevention practices | ||||
Total number of nets per household | 0.8 (0.6, 0.9) |
0.01
| 0.7 (0.6, 0.9) | < 0.001 |
Respondent used a net night prior to study | 2.5 (1.5, 3.9) |
0.0001
| 2.2 (1.4, 3.4) | < 0.001 |
Other family members used a net night prior to study | 3.2 (2.0, 4.9) |
0.0001
| 2.5 (1.6, 3.9) |
0.0001
|
Ave. number of nets per person | 0.2 (0.1, 0.5) |
0.0001
| 0.3 (0.2, 0.6) | < 0.001 |
Household environmental characteristics (50 m buffer) | ||||
Within Blantyre city limits | 0.1 (0.1, 0.2) |
0.0001
| 0.02 (0.01, 0.03) |
0.0001
|
Increasing distance from city centre (2.5 km intervals) | 1.5 (1.4, 1.7) |
0.0001
| 1.7 (1.5, 1.9) |
0.0001
|
Section/region | ||||
Lunzu (1) | Ref | Ref | Ref | Ref |
Chileka (2) | 1.1 (0.5, 2.6) | 0.75 | 1.8 (0.9, 3.6) | 0.08 |
Chilomoni (3) | 1.0 (0.4, 2.4) | 0.97 | 1.1 (0.5, 2.1) | 0.87 |
Mpemba (4) | 0.1 (0, 0.3) |
0.0001
| 0.1 (0, 0.1) |
0.0001
|
Chigumula (5) | 0.2 (0.1, 0.4) |
0.0001
| 0.1 (0, 0.1) |
0.0001
|
Mikolongwe (6) | 0.9 (0.4, 2.0) | 0.75 | 0.1 (0.1, 0.2) |
0.0001
|
Kachere (7) | 0.3 (0.1, 0.7) | < 0.01 | 0 (0, 0.1) |
0.0001
|
Machinjiri (8) | 0.5 (0.2, 1.2) | 0.11 | 0.1 (0, 0.2) |
0.0001
|
Rainy (vs. dry) season | 46.1 (29.6, 71.6) |
0.0001
| 15.3 (10.5, 22.4) |
0.0001
|
Elevation (m) | 0.996 (0.995, 0.997) |
0.0001
| 0.992 (0.991, 0.993) |
0.0001
|
Number nearby households | 0.9 (0.9, 1.0) |
0.0001
| 0.9 (0.8, 0.9) |
0.0001
|
Amount of land used for growing crops (%) | 2.3 (1.2, 4.2) | < 0.01 | 1.8 (1.0, 3.1) |
0.04
|
NDVI (rainy season) | 0.4 (0, 6.5) | 0.50 | 2.6 (0.2, 30.4) | 0.44 |
NDVI category (rainy season) | ||||
≤ 0.1 (barren: rock/sand/urban) | Ref | Ref | Ref | Ref |
> 0.1 and ≤ 0.4 (shrub/grassland) | 2.6 (0.1, 94.7) | 0.60 | 0.6 (0, 17.6) | 0.80 |
> 0.4 and ≤ 1 (temperate/tropical rainforest) | 1.8 (0, 69.9) | 0.74 | 0.8 (0, 22.3) | 0.89 |
NDVI (dry season) | 96.5 (0, 212,362.4) | 0.25 | 0.1 (0, 304.7) | 0.53 |
NDVI category (dry season) | ||||
≤ 0.1 (barren: rock/sand/urban) | Ref | Ref | Ref | Ref |
> 0.1 and ≤ 0.4 (shrub/grassland) | 19.4 (5.2, 72.1) | < .0001 | 111.6 (22, 566.7) | < .0001 |
> 0.4 and ≤ 1 (temperate/tropical rainforest) | NA | NA | NA | NA |
Agriculture | 5.8 (3.8, 8.8) |
0.0001
| 4.0 (2.6, 6.1) |
0.0001
|
Fruit trees | 0.9 (0.6, 1.6) | 0.82 | 0.8 (0.5, 1.2) | 0.27 |
Grazing | 0.6 (0.3, 1.0) | 0.06 | 0.5 (0.3, 0.9) |
0.02
|
Forest | 0.4 (0.2, 1.1) | 0.08 | 0.2 (0.1, 0.4) |
0.0001
|
Ownership of goats | 3.1 (1.7, 5.8) | < 0.001 | 3.9 (2.1, 7.0) |
0.0001
|
Ownership of chickens | 1.3 (0.8, 2.1) | 0.25 | 1.7 (1.1, 2.6) |
0.03
|
Housing construction | ||||
Closed (vs. fully/partially open) windows | 0.9 (0.4, 1.8) | 0.72 | 0.5 (0.2, 0.9) |
0.03
|
Closed (vs. fully/partially open) eaves | 2.0 (1.0, 4.3) | 0.06 | 2.2 (1.1, 4.5) |
0.03
|
Roof type | ||||
Iron sheets | Ref | Ref | Ref | Ref |
Thatched | 3.0 (1.8, 4.9) |
0.0001
| 4.1 (2.5, 6.6) |
0.0001
|
Tile | 0.5 (0, 37.0) | 0.74 | 0.6 (0, 31.2) | 0.80 |
All households | Agriculture absent | Agriculture present | P value (T test or Chi square) | |||||||
---|---|---|---|---|---|---|---|---|---|---|
N | Mean or Freq | SD or % | N | Mean or Freq | SD or % | N | Mean or Freq | SD or % | ||
Demographics | ||||||||||
Number of rooms | 1546 | 3.7 | 1.9 | 726 | 3.8 | 2.1 | 820 | 3.6 | 1.6 | 0.14 |
Number of children under age 5 | 1520 | 0.6 | 0.8 | 700 | 0.5 | 0.7 | 820 | 0.6 | 0.8 | < 0.01 |
Number slept in the house | 1520 | 3.8 | 1.9 | 700 | 3.7 | 2.0 | 820 | 3.9 | 1.7 | 0.13 |
Age of household head (years) | 1520 | 40.5 | 16.8 | 700 | 40.7 | 16.4 | 820 | 40.3 | 17.1 | 0.64 |
Male head of household | 1520 | 621 | 40.9% | 700 | 290 | 41.4% | 820 | 331 | 40.4% | 0.67 |
Highest educational attainment of head of household | 1509 | 692 | 817 | < .0001 | ||||||
No formal education | 95 | 6.3% | 35 | 5.1% | 60 | 7.3% | ||||
Some primary education | 792 | 52.5% | 315 | 45.5% | 477 | 58.4% | ||||
Some secondary education | 487 | 32.3% | 250 | 36.1% | 237 | 29.0% | ||||
Some college | 135 | 8.9% | 92 | 13.3% | 43 | 5.3% | ||||
Malaria prevention practices | ||||||||||
Total number of nets per household | 1546 | 1.6 | 1.3 | 726 | 1.7 | 1.4 | 820 | 1.5 | 1.2 |
0.0001
|
Respondent used a net night prior to study | 1548 | 986 | 63.7% | 728 | 463 | 63.6% | 820 | 523 | 63.8% | 0.94 |
Other family members used a net night prior to study | 1548 | 917 | 59.2% | 728 | 414 | 56.9% | 820 | 503 | 61.3% | 0.07 |
Ave. number of nets per person | 1520 | 0.5 | 0.4 | 700 | 0.5 | 0.4 | 820 | 0.4 | 0.4 | < .0001 |
Household environmental characteristics (50 m buffer) | ||||||||||
Within Blantyre city limits | 1548 | 532 | 34.4% | 728 | 352 | 48.4% | 820 | 180 | 22.0% | < .0001 |
Increasing distance from city centre (2.5 km intervals) | 1548 | 728 | 820 | < .0001 | ||||||
2.5 km | 190 | 12.3% | 143 | 19.6% | 47 | 5.7% | ||||
5 km | 193 | 12.5% | 132 | 18.1% | 61 | 7.4% | ||||
7.5 km | 196 | 12.7% | 115 | 15.8% | 81 | 9.9% | ||||
10 km | 193 | 12.5% | 82 | 11.3% | 111 | 13.5% | ||||
12.5 km | 193 | 12.5% | 81 | 11.1% | 112 | 13.7% | ||||
15 km | 196 | 12.7% | 61 | 8.4% | 135 | 16.5% | ||||
17.5 km | 194 | 12.5% | 51 | 7.0% | 143 | 17.4% | ||||
20 km | 193 | 12.5% | 63 | 8.7% | 130 | 15.9% | ||||
Section/region | 1548 | 728 | 820 | < .0001 | ||||||
Lunzu (1) | 190 | 12.3% | 113 | 15.5% | 74 | 9.0% | ||||
Chileka (2) | 193 | 12.5% | 106 | 14.6% | 84 | 10.2% | ||||
Chilomoni (3) | 196 | 12.7% | 86 | 11.8% | 104 | 12.7% | ||||
Mpemba (4) | 193 | 12.5% | 120 | 16.5% | 74 | 9.0% | ||||
Chigumula (5) | 193 | 12.5% | 77 | 10.6% | 122 | 14.9% | ||||
Mikolongwe (6) | 196 | 12.7% | 82 | 11.3% | 113 | 13.8% | ||||
Kachere (7) | 194 | 12.5% | 84 | 11.5% | 115 | 14.0% | ||||
Machinjiri (8) | 193 | 12.5% | 60 | 8.2% | 134 | 16.3% | ||||
Rainy season (vs. dry) | 1548 | 618 | 39.9% | 728 | 124 | 17.0% | 820 | 494 | 60.2% | < .0001 |
Elevation (m) | 1548 | 945.0 | 175.9 | 728 | 947.2 | 165.3 | 820 | 943.0 | 184.9 | 0.64 |
Number nearby households | 1548 | 8.3 | 10.4 | 728 | 9.6 | 13.0 | 820 | 7.2 | 7.2 | < .0001 |
Amount of land used for growing crops (%) | 1548 | 25.8 | 40.4 | 728 | 21.4 | 38.7 | 820 | 29.6 | 41.5 | < .0001 |
NDVI (rainy season) | 1548 | 0.3 | 0.1 | 728 | 0.3 | 0.1 | 820 | 0.3 | 0.1 | < .0001 |
NDVI category (rainy season) | 1548 | 728 | 820 | 0.20 | ||||||
≤ 0.1 (barren: rock/sand/urban) | 4 | 0.3% | 2 | 0.3% | 6 | 0.7% | ||||
> 0.1 and ≤ 0.4 (shrub/grassland) | 1291 | 83.4% | 617 | 84.8% | 674 | 82.2% | ||||
> 0.4 and ≤ 1 (temperate/tropical rainforest) | 251 | 16.2% | 107 | 14.7% | 144 | 17.6% | ||||
NDVI (dry season) | 1548 | 0.2 | 0.0 | 728 | 0.2 | 0.0 | 820 | 0.2 | 0.0 | < .0001 |
NDVI category (dry season) | 1548 | 728 | 820 | < .0001 | ||||||
≤ 0.1 (barren: rock/sand/urban) | 92 | 5.9% | 73 | 10.0% | 19 | 2.3% | ||||
> 0.1 and ≤ 0.4 (shrub/grassland) | 1456 | 94.1% | 655 | 90.0% | 801 | 97.7% | ||||
> 0.4 and ≤ 1 (temperate/tropical rainforest) | 0 | 0% | 0 | 0% | 0 | 0% | ||||
Fruit trees | 1548 | 1134 | 73.3% | 728 | 439 | 60.3% | 820 | 695 | 84.8% | < .0001 |
Grazing | 1548 | 275 | 17.8% | 728 | 217 | 8.7% | 820 | 212 | 25.9% | < .0001 |
Forest | 1548 | 108 | 7.0% | 728 | 65 | 8.9% | 820 | 43 | 5.2% | < 0.01 |
Ownership of goats | 1546 | 221 | 14.3% | 726 | 76 | 10.5% | 820 | 145 | 17.7% | < .0001 |
Ownership of chickens | 1546 | 582 | 37.6% | 726 | 248 | 34.2% | 820 | 334 | 40.7% |
0.01
|
Housing construction | ||||||||||
Closed (vs. fully/partially open) windows | 1527 | 175 | 11.5% | 719 | 93 | 12.9% | 808 | 82 | 10.2% | 0.09 |
Closed (vs. fully/partially open) eaves | 1537 | 146 | 9.5% | 720 | 76 | 10.6% | 817 | 70 | 8.6% | 0.19 |
Roof type | 1512 | 694 | 818 | < .0001 | ||||||
Iron sheets | 1129 | 74.7% | 565 | 81.4% | 564 | 68.9% | ||||
Thatched | 379 | 25.1% | 126 | 18.2% | 253 | 30.9% | ||||
Tile | 4 | 0.3% | 3 | 0.4% | 1 | 0.1% |
Multivariate analysis
An. arabiensis
|
An. funestus
| |||
---|---|---|---|---|
95% CI | P value | 95% CI | P value | |
Model 1a | ||||
Agriculture | 5.2 (3.4, 7.9) | < .0001 | 2.7 (1.8, 4.0) | < .0001 |
Within city limits | 0.2 (0.1, 0.3) | < .0001 | 0.02 (0.01, 0.04) | < .0001 |
Model 2a | ||||
Agriculture | 5.6 (3.7, 8.6) | < .0001 | 3.4 (2.3, 5.1) | < .0001 |
Increasing distance | 1.4 (1.3, 1.6) | < .0001 | 1.6 (1.4, 1.7) | < .0001 |
Model 3a | ||||
Agriculture | 5.5 (3.6, 8.4) | < .0001 | 3.7 (2.4, 5.6) | < .0001 |
House densitya | 0.5 (0.4, 0.8) |
0.001
| 0.3 (0.2, 0.4) | < .0001 |
An. arabiensis
|
An. funestus
| |||
---|---|---|---|---|
95% CI | P value | 95% CI | P value | |
Model 1b | ||||
Agriculture | 1.4 (0.8, 2.2) | 0.21 | 0.6 (0.4, 0.9) |
0.01
|
Within city limits | 0.2 (0.1, 0.2) | < .0001 | 0.02 (0.01, 0.04) | < .0001 |
Model 2b | ||||
Agriculture | 1.6 (1.0, 2.5) | 0.07 | 0.7 (0.4, 1.2) | 0.19 |
Increasing distance | 1.3 (1.2, 1.5) | < .0001 | 1.4 (1.3, 1.6) | < .0001 |
Model 3b | ||||
Agriculture | 1.5 (1.0, 2.5) | 0.08 | 0.7 (0.5, 1.2) | 0.21 |
House densitya | 0.5 (0.4, 0.7) | < 0.001 | 0.2 (0.1, 0.3) | < .0001 |
An. arabiensis
|
An. funestus
| |||
---|---|---|---|---|
95% CI | P value | 95% CI | P value | |
Model 1c | ||||
Agriculture | 3.8 (2.3, 6.2) | < .0001 | 2.7 (1.7, 4.2) | < .0001 |
Within city limits | 0.1 (0, 0.2) | < .0001 | 0.02 (0.01, 0.05) | < .0001 |
Agriculturea within city limits | 3.4 (1.2, 9.6) |
0.02
| 1.0 (0.4, 2.8) | 1.00 |
Model 2c | ||||
Agriculture | 15.6 (5.4, 45.2) | < .0001 | 8.2 (2.9, 23.8) | < .0001 |
Increasing distance | 1.6 (1.4, 1.8) | < .0001 | 1.7 (1.5, 2.0) | < .0001 |
Agriculturea increasing distance | 0.8 (0.7, 1.0) |
0.04
| 0.8 (0.7, 1.0) | 0.07 |
Model 3c | ||||
Agriculture | 5.3 (2.7, 10.5) | <.0001 | 4.2 (2.0, 8.9) |
0.0001
|
Housing density | 0.5 (0.3, 0.9) |
0.02
| 0.3 (0.2, 0.6) | < 0.001 |
Agriculturea house densitya | 1.0 (0.5, 2.2) | 0.91 | 0.8 (0.3, 2.0) | 0.65 |