Distribution of the population according to their positions from 7:00 pm to 7:00 am
This study looked at the position of household members in selected villages during the harmattan and hot weather seasons. The results of household members’ distribution are shown in Figure 3.
On the one hand, Figure 3 shows that 95% of the village population included in the study stay in their rooms from 7:00 pm to 7:00 am, and only 5% of household members are outdoors during same time intervals during the harmattan season. On the other hand, during hot weather, there are more households outdoors (37%) as shown in Figure 3. Most households, regardless of their position, don't sleep under mosquito nets and are exposed to mosquito bites as shown in Figures 4.
Breakdown of the position of household members by time interval during the harmattan and hot weather seasons
In order to determine the time intervals during which all household members are inside their rooms, the position of each of them household member's location was observed every 30 min, the results of which are illustrated by Figures 5a and 5b.
According to Figure 5a, from 7:00 pm to 7:30 pm, less than 20% of household members are outside their rooms during the harmattan season. This number decreases gradually until 10:00 pm when all of them are inside their rooms. From 5:30 am, household members begin to step out of their rooms until 7:00 am when 10% of the population is outside the rooms. Unlike Figure 5b, the latter shows that during the hot weather season, the majority of household members stay outside from 7:00 pm to 10:00 pm, and begin to enter their rooms gradually only from 10:30 pm. However, during the whole night there are always people outside, carrying out various activities. The latter shows that during the hot weather season, the majority of household members stay outside from 7:00 pm to 10:00 pm, and begin to enter their rooms gradually only from 10:30 pm. However, during the whole night there are always people outside, carrying out various activities.
Influence of the season and the urbanization situation of villages on the position of household members
In this study, the factors determining the position of household members (outside or inside the rooms) of North Benin departments from 7:00 pm to 7:00 am, the time of appearance of malaria Anopheles vectors, were investigated. Thus, an analysis of the two-factor bias variances on the frequency of the position of household members according to the season and their residence areas (peripheral or central village) was carried out (Table 2).
Table 2 shows that there is no significant difference (p> 0.05) between the position frequency of household members and the type of village they live in. However, the analysis of the variances shows a highly significant difference between the period and the position of household members (p <0.001). This analysis shows that the household members being inside or outside their rooms does not depend on the urbanization situation of the village, but rather on the period. Figure 10 shows the results of the Student Newman Keuls test.
Influence of the IRS or non-IRS status of the areas on the position of household members
In this study, the influence of study areas (IRS or non-IRS) on the position (outside or inside the rooms) of household members was verified. An analysis of variances by one factor on the number of household members operating from 7:00 pm to 7:00 am outside or inside their rooms according to IRS or non-IRS status of the areas, made it possible to determine influence of household members fear of mosquito bites. Table 3 illustrates the results of the analysis.
The analysis in Table 3 shows that the effect has a highly significant influence (Prob <0.0001) on the frequency of household members who remain outdoor their rooms from 7:00 pm to 8:00 pm, depending on whether they are in an IRS or non-IRS area. In addition, the analysis of the variances shows no significant difference between the IRS and non-IRS status of the areas and the frequency of household members staying indoor their rooms. From the foregoing, it can be observed that the action of the IRS conditions the choice of the outdoor position in the North Benin villages.
Student-Newman-Keuls (SNK) tests performed on the difference in the frequency of household members staying outdoor their rooms were used to determine the area in which more household members were found outside from 7:00 pm to 7:00 am. The results of these tests are shown in Figure 6.
The analysis in Figure 7 shows that there are more household members spending their time outside their rooms in non-IRS areas than in IRS areas. From this analysis, it can be noted that in villages where indoor spraying is in progress, household members are more likely to protect themselves against mosquito bites by performing their night activities inside their sprayed rooms than in other villages where the spraying action is no longer effective. From all of the above, it can be noted that household members in the North Benin departments recognize the effectiveness of IRS by staying inside their rooms from 7:00 pm to 7:00 am when the effect of spraying is still active.
Variation of household members inside under the net and outside without the bed net as a function of density of An.gambiae measured at different times of the night.
Behavioural activities of humans and An. gambiae, a vector of malaria outside households in the absence of the net, were compared with those of residents inside households with nets at different night time intervals throughout the warm period (Figure 8). At dusk, high mobility activity both outside and inside households showed a low rate of mosquito aggressiveness outside and inside households. The decrease in this mobility from 9pm onwards, characterised by rest, eating, studying, following information on television and radio, sleeping without or with mosquito nets, etc., caused a sudden increase in An. gambiae's aggressiveness. This increase is more noticeable outside households than within households. The aggressiveness of An. gambiae mosquitoes reached its threshold after 1.am in the morning. Despite the low level of outdoor activity at this time of day, aggressiveness is still higher than indoors with an average difference of 0.87 bites per man per hour. Then, this rate of stings gradually decreased as mobility activities were resumed.
From this figure, there is a high level of human activity in households from 7pm to 10.30pm and the resumption of activities from 4am onwards. From 22h30 to 4h in the morning is the period dedicated to rest in the mosquito nets for most of the inhabitants. An gambiae's aggressiveness outside and inside households increased slightly during the first two hours after 7pm and then significantly until 1am when it is at its peak before gradually decreasing until 7am. Throughout the observation period, there was greater aggression outside households without nets than inside.
- During the harmattan season
During the harmattan, the average density of An. gambiae mosquitoes was much higher inside households than outside. This behaviour of malaria-carrying mosquitoes has shown a maximum level of aggressiveness within households. This aggressiveness of An. gambiae in households at dusk is much higher than that observed outside households with a large difference of about 0.55 bites (Figure 9). Then, aggressiveness on the inside first dropped, while on the outside, there is a slight increase for about an hour before it becomes uniform with the inside. At night, rates of aggression inside and outside households oscillate around 0.02 to 0.2 bites with a small increase inside compared to outside. The majority of household members protect themselves under the net from 11pm onwards. From dawn onwards, aggressiveness indoors has increased exponentially inside and slightly outside households.
Causes of outdoor biting exposure
Since exposure to mosquito bites is related to the position of household members in relation to their sprayed rooms, this study investigated the causes of outdoor biting exposure. The results from this study are illustrated in Figure 10.
The analysis of this figure shows that 65% of household members exposed to mosquito bites gave irritation as the main reason for their behavior. 15% of them are exposed to biting because of heat and lack of space.