Table 4 Risk ratios (lower 95% CL, upper 95% CL) from the adjusted (multivariate) regression models of the association of environmental factors with anopheline occurrence. Statistically significant (P < 0.05) outcomes are indicated with an “*”. In the case of three-level variables, statistically significant differences between the two non-reference categories are indicated with different letters within the same column. For the continuous variable “Distance to nearest hut” we report the risk ratio and the significance level (P < 0.05)

Distance to nearest hut

0.99672*

1.00026

1.0004

1.00288*

0.9998

0.9993

0.997*

 No

0.22 (0.06–0.81)*

1.25 (0.58–2.70)

None

0.10 (0.02–0.46)*

12.08 (4.84–30.14)*

0.90 (0.33–2.41)

0.08 (0.02–0.26)*

 Yes

Ref.

Ref.

All

Ref.

Ref.

Ref.

Ref.

 Permanent

2.83 (0.82–9.71)

0.66 (0.40–1.09)

19.25 (1.43–259.15)*

0.10 (0.03–0.33)*

0.55 (0.27–1.13)

0.74 (0.34–1.59)

1.93 (0.52–7.19)

 Seasonal

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

 Shaded

0.006 (0.001–0.03)*^a

0.36 (0.15–0.90)*^a

None

0.01 (0.004–0.06)*^a

1.33 (0.57–3.10)

12.11 (1.06–138.21)*^a

1.80 (0.19–17.12)

 Partially exposed

0.15 (0.06–0.37)*^b

1.40 (0.66–2.95)^b

3.01 (0.53–17.16)

0.10 (0.04–0.27)*^b

1

6.83 (0.67–69.17)^a

0.55 (0.04–8.02)

 Mostly exposed

Ref.

Ref.

Ref.

Ref.

None

Ref.

Ref.

 Clear

5.34 (1.92–14.88)*^a

0.29 (0.15–0.57)*^a

0.43 (0.09–1.94)^a

3.55 (1.15–10.95)*^a

0.97 (0.14–6.50)^a

1.18 (0.36–3.86)^a

All

 Semi-turbid

2.35 (1.02–5.45)*^a

0.66 (0.33–1.30)^b

0.32 (0.06–1.71)^a

2.23 (0.9–5.48)^a

0.21(0.03–1.65)^b

2.29 (0.61–8.55)^a

None

 Turbid

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

None

 Yes

0.36 (0.08–1.59)

0.70 (0.24–2.03)

None

5.91 (0.58–59.93)

0.52 (0.23–1.15)

0.42 (0.17–1.03)

200.3 (55.7–720.0)*

 No

Ref.

Ref.

All

Ref.

Ref.

Ref.

Ref.

 Absent

0.96 (0.14–6.81)

1.74 (0.75–4.05)

0.02 (0.01–0.07)*

4.15 (1.01–17.05)*

1.01 (0.16–6.63)

All

All

 Present

Ref.

Ref.

Ref.

Ref.

Ref.

None

None