Background
Methods
Study area
Study procedures
Longitudinal surveys of indoor mosquito densities
Characterization of the houses and their environments
Survey questionnaires: quantitative assessment of community knowledge, opinions and concerns regarding house designs and environmental characteristics, and how these factors influence malaria transmission
Concepts investigated | Specific questions asked by the interviewer | Relevance of the concepts | |
---|---|---|---|
1 | Knowledge and perception about house characteristics, mosquito entry and malaria transmission risks | Do you know if the house design can influence mosquito entry? | Assessment of knowledge and perception of malaria transmission risks in relation to house characteristics |
Does your house allow mosquito entry? | |||
If your house does not allow mosquito entry, how do you prevent mosquito entry? | |||
Why does your house allow mosquito entry? | |||
How do mosquitoes enter your house? | |||
When was your house constructed? | |||
Why did you decide to construct this kind of house? | |||
What did you consider during construction? | |||
2 | Knowledge and perception about environmental variables influencing mosquito density | Do you know if the environments surrounding your house influence mosquito density? | Assessment of knowledge and perception of malaria transmission risks in relation to environmental characteristics |
How does the environments surrounding your house influence mosquito density? | |||
Mention the common mosquito breeding sites in your area | |||
What do you do to prevent mosquito bites? | |||
3 | Knowledge and perception about settlements, mosquito density and malaria transmission risks | Do you think the number of houses in an area can influence mosquitoes and malaria transmission? | Assessment of knowledge and perception of malaria transmission risks in relation to settlement patterns |
Do you think constructing houses near other houses or far from other houses is an important factor in regard to mosquito biting risk and malaria transmission? | |||
Why do you think close house have many mosquitoes? | |||
What can be done to control mosquitoes in such kind of environment? |
Focus group discussions: qualitative assessment of community knowledge, opinions and concerns regarding house designs and environmental characteristics, and how these factors influence malaria transmission
Data analysis
Analysis of quantitative data
Processing and analysis of qualitative data
Results
Indoor densities of malaria and non-malaria mosquito vectors
Physical characteristics and microclimate of sampled houses
Variables assessed | Category | Percentage (N) |
---|---|---|
Wall type | Plastered brick walls | 1.0% (6) |
Mud walls | 50.5% (315) | |
Un-plastered brick walls | 48.6% (303) | |
Eave space | Closed | 25.3% (158) |
Open | 74.7% (466) | |
Roof type | Corrugated iron sheet | 39.4% (246) |
Grass-thatched | 60.6% (378) | |
Window covers | With netting screen | 25.3% (158) |
Without netting screen | 74.7% (466) | |
Door (observed from 6 pm to 7 pm) | Open | 63.9% (399) |
Tightly closed | 29.5% (184) | |
Partially closed | 6.6% (41) |
Household risk factors associated with indoor mosquito densities
Variables | Category |
Anopheles arabiensis
|
Anopheles funestus
| ||||
---|---|---|---|---|---|---|---|
Mean (CI) | RR (95% CI) | P value | Mean | RR (95% CI) | P value | ||
Wall type | Bricks | 9.3 (6.9–25.5) | 1.0 | 3.8 (2.4–5.2) | 1.0 | ||
Mud | 17.7 (10.1–22.3) | 3.9 (2.7–5.6) | 0.005 | 5.0 (2.6–7.4) | 4.0 (2.4–5.3) | 0.011 | |
Eave space | Closed | 9.3 (4.2–14.4) | 1.0 | 2.8 (1.3–4.2) | 1.0 | ||
Open | 19.2 (12.9–25.6) | 1.9 (1.8–2.0) | < 0.001 | 4.9 (3.2–6.7) | 1.2 (0.9–1.6) | 0.005 | |
Roof type | Iron sheets | 14.4 (6.6–22.2) | 1.0 | 3.3 (1.9–4.8) | 1.0 | ||
Grass | 18.2 (11.8–24.6) | 1.5 (1.4–1.7) | < 0.001 | 5.1 (3.0–7.1) | 2.4 (2.0–3.0) | 0.318 | |
Doors | Closed | 12.6 (0.0–16.8) | 1.0 | 1.6 (0.0–3.0) | 1.0 | ||
Open | 36.0 (9.5–42.5) | 1.4 (0.9–2.1) | < 0.001 | 3.8 (2.4–5.2) | 1.6 (1.3–2.0) | < 0.001 | |
Window | Screened | 15.8 (5.4–23.3) | 1.0 | 4.2 (2.7–5.7) | 1.0 | ||
Unscreened | 17.1 (11.5–26.6) | 1.9 (1.7–1.9) | < 0.001 | 4.9 (1.7–8.0) | 2.9 (2.3–2.7) | 0.130 | |
Chicken indoors | No | 15.3 (9.5–21.0) | 1.0 | 4.2 (2.6–5.9) | 1.0 | ||
Yes | 20.4 (10.7–29.9) | 1.8 (1.8–1.9) | 0.343 | 4.8 (2.4–7.1) | 2.0 (1.8 –2.1) | < 0.001 |
Variables | Category |
Culex species
|
Mansonia species
| ||||
---|---|---|---|---|---|---|---|
Mean (CI) | RR (95% CI) | P value | Mean | RR (95% CI) | P value | ||
Wall type | Bricks | 51.7 (45.2 – 86.9) | 1.0 | 0.6 (0.3 – 1.5) | 1.0 | 0.805 | |
Mud | 66.2 (43.9 – 88.5) | 2.3 (2.1– 2.6) | <0.001 | 1.5 (0.4 – 2.5) | 2.5 (1.7 – 3.8) | <0.005 | |
Eave space | Closed | 57.9 (27.7 – 88.1) | 1.0 | 0.3 (0.1 – 0.6) | 1.0 | ||
Open | 67.2 (48.7 – 85.8) | 1.9 (1.8 – 2.0) | <0.001 | 1.5 (0.7 – 2.3) | 1.5 (1.4 –1.8) | <0.001 | |
Roof type | Iron sheet | 56.7 (33.9 – 79.4) | 1.0 | 0.7 (0.1 – 1.4) | 1.0 | ||
Grass | 70.2 (48.7 – 91.7) | 2.6 (2.4 – 2.7) | 0.139 | 1.5 (0.6 – 2.3) | 2.5 (1.8 – 2.4) | 0.705 | |
Doors | Closed | 29.5 (0.0 – 79.9) | 1.0 | 0.2 (0.0 – 0.9) | 1.0 | ||
Open | 56.2 (43.9 – 88.5) | 2.3 (2.1– 2.6) | <0.001 | 1.5 (0.4 – 2.5) | 2.5 (1.7 – 3.8) | <0.005 | |
Window | Screened | 55.4 (23.2 – 86.6) | 1.0 | 0.9 (0.0 – 2.0) | 1.0 | ||
Unscreened | 68.4 (50.3 – 86.5) | 2.5 (2.4 – 2.6) | <0.001 | 1.3 (0.6 – 2.0) | 1.8 (1.7 – 1.9) | <0.001 | |
Chicken indoors | No | 63.8 (46.2 – 81.5) | 1.0 | 1.1 (0.5 –1.8) | 1.0 | ||
Yes | 67.4 (34.6 – 100.0) | 1.2 (1.1– 1.2) | <0.001 | 1.3 (0.0 – 2.7) | 2.6 (2.4 – 2.7) | <0.001 |
Socio-demographic characteristics of survey participants
Variables assessed | Category | Percentage (N) |
---|---|---|
Gender | Males | 40.5 (81) |
Females | 59.5 (119) | |
Age | 18–35 | 48.7 (97) |
36–50 | 26.5 (53) | |
51–65 | 15 (30) | |
> 65 | 20 (10) | |
Marital status | Married | 66 (132) |
Unmarried | 20 (40) | |
Widow/widower | 4.5 (9) | |
Divorced | 9.5 (19) | |
Level of education | No formal education | 11.5 (23) |
Primary school | 67.5 (135) | |
Secondary school | 18 (36) | |
College/university | 2 (4) | |
Other trainings | 1 (2) | |
Occupation | Peasant (self-employed in agriculture) | 68.5 (137) |
Small scale business | 4 (8) | |
Formal employment | 0.5 (1) | |
Unemployed | 0.5 (1) | |
Other | 26.5 (53) |
Results of the questionnaire survey: participants’ knowledge regarding indoor mosquito density and how this relates to housing characteristics and environmental variables
Variables assessed | Response category | Percentage (N) |
---|---|---|
Whether participants believe their house let in mosquitoes | Yes | 98.5% (197) |
No | 1.5% (3) | |
How participants believed mosquitoes entered their houses | Through open doors | 28.5% (57) |
Through windows | 32.5% (65) | |
Through holes in the wall | 3.0% (6) | |
Through the eave space | 19.5% (39) | |
Through both open windows and doors | 13.5% (27) | |
Through open window doors, holes in walls and eaves | 2% (4) | |
Others | 1% (2) | |
Age of house (date of construction) | < 4 years ago | 36.5% (73) |
5–8 years ago | 26.5% (53) | |
> 9 years ago | 37.0% (74) | |
Main reasons for constructing the kind of house | Because it is permanent | 36.5% (73) |
Because it prevents animals from entering the house | 26.5% (53) | |
Because it prevents insects | 17.0% (34) | |
Others | 20.0% (40) | |
Whether people consider mosquito prevention as a key factor when constructing houses | Yes | 58.5% (117) |
No | 40.0% (80) | |
Does not know | 1.5% (3) | |
Specific practices considered by participants (during construction of their houses) for preventing mosquitoes | Netting on the window | 38.0% (76) |
Blocking the eaves | 8.0% (16) | |
Using bricks on the wall | 2.0% (4) | |
Using cement on the wall | 1 (2) | |
Does not know | 38.5% (77) | |
Others | 12.5% (25) | |
Whether participants knew open eave spaces let in mosquitoes | Yes | 96.0% (192) |
No | 4.0% (8) | |
Whether participants knew that surrounding environments influence vector densities in their houses | Yes | 97.0% (194) |
No | 3.0% (6) |
Focus group discussions: participants’ knowledge regarding indoor mosquito density and how this relates to housing characteristics and environmental variables
“Many mosquitoes are found in those houses with smaller windows, in which there is less light because mosquitoes like dark places. Then mosquitoes enter the house and won’t leave the area”. (46 years old male, Milola village).
“It is important to make sure that houses are built as far away from the mosquito aquatic habitats as possible. It is good to know the distance that mosquitoes can fly from their aquatic habitats so that we can know where to build houses”. (37 years old male, Minepa village).
“It is necessary to build a house that makes it hard for mosquitoes to get inside. I know that houses that are built lower let mosquitoes in than the houses that have larger height”. (26 years old male Milola village).
“If the environment is dirty mosquitoes increase in number, because they are able to rest in trash. That means if we clean our surroundings then there will be very few mosquitoes. But if our environment is dirty mosquitoes reproduce and increase in numbers” (58 years old male, Minepa village).
“Mosquitoes are found in dirty water around the house, like in water that is in broken containers or cups. They are also found in the ponds, shrubs and in dark places. I believe that is where they accumulate” (34 years old female, Mavimba village).
“When there are many houses together, it means that there is a lot of trash and other things in which mosquitoes can rest. For example, I may keep my surroundings clean, but if my neighbours do not clean their surroundings, and they live close to me, then mosquitoes can easily come from their houses to mine, it will make it easy for mosquitoes to bite me”. (37 years old female, Milola village).
“If there are many houses close together then mosquitoes can move from one house to another. But if houses are few and far apart then the mosquitoes cannot really get from one house to another easily, because there can be many obstacles for them on the way, like the wind and rain” (40 years old female, Milola village).
“When there are a lot of houses together then it is a problem for us because this way many mosquitoes come, because they know that they can get a lot of people in close proximity. It is easy for the mosquitoes to transmit malaria” (23 years old male, Kivukoni village).
“If houses are scattered, then the wind will blow mosquitoes to other places where they cannot easily get people” (51 years old male, Milola village).
“One thing that most of the people in the village can afford is to use bed nets, because everyone has bed nets here. But in order for these nets to be useful they have to be in a good shape. Sadly not everyone has new nets. I sleep with my children in the same bed because we have one net, but our net is not in a very good state, it has a lot of holes that sometime let mosquitoes in. But it still helps; it is not the same as if we did not use anything” (31 years old female, Kivukoni village).
“We make sure that children are protected from mosquito bites by making sure they go to bed early when it gets dark, and then we make sure they are covered by bed nets. Sometimes when they are sitting outside then we use a piece of cloth to chase mosquitoes away” (54 years old male, Milola village).
“Mosquitoes are found here throughout the year. However, their population is the highest during the rainy season because there is a lot of water around, hence many aquatic habitat. During the dry season there are fewer places where mosquitoes accumulate, so their population is lower” (28 years old male, Milola village).
“There are a lot of mosquitoes from February to April because this is the time where there is a lot of water everywhere. There are many pools, ponds and bushes where mosquitoes can accumulate. The mosquito population starts to go down from May and June when the weather starts to get dry and cold” (24 years old male, Minepa village).