The key determinants for epidemiology of vector-borne disease are the variation in vulnerability level of the specific population. Living conditions are the key factors that determine the malaria vulnerability of a given population. In the current study, characteristics of living conditions such as housing quality (types of walls, roof, floor); location of kitchen (outdoor, indoor with or without separation); energy source; drinking water source; spending night with livestock and socio-demographic variables were tested. The argument is whether above indicated living conditions could increase the probability of asymptomatic malaria infection through increasing mosquito vector entry, indoor resting, bite and contribute for malaria transmission. This research findings revealed that living conditions such as wall type of the house, spending night with livestock in the same house and the location of kitchen were significantly associated with prevalence of asymptomatic malaria infection.
As per the findings of this research, the association between asymptomatic malaria prevalence and housing structure showed that better housing was associated with reduced odds of asymptomatic malaria and it’s an effective addition to vector control strategies. The prevalence of asymptomatic malaria infection among occupants living in houses built with traditional floor/wall/roof ranges from 8.1% to 8.4% while it ranges from 2.0% to 4.6% among those living in modern floor/wall/roof houses. It was 4.3 times higher in occupants residing in a house built with traditional wall materials (natural or rudimentary) compared with occupants residing in a house built with modern (finished- cement or brick) wall materials.
Previous findings on the association between malaria infection and housing quality indicated the prevalence of malaria among occupants residing in houses built in traditional materials was 8.8% while it ranges from 1.4 to 1.6% among occupants living in houses built with modern materials, supported the result of the current study [27, 28]. Significant association between housing quality and asymptomatic malaria infection found in this study was supported by studies conducted in Southern Zambia, Uganda, Swaziland, Northern Botswana, and a working paper series on quality of homes in Africa [16, 27,28,29,30].
In the current study, spending nights with cattle in the same house was significantly associated with increased asymptomatic malaria infection. The occurrence of asymptomatic malaria infection was 5.6 times higher in individuals who spent their nights with their cattle compared with those who did not. This may be due to the attractive nature of livestock for zoophilic and opportunistic mosquito vectors to households and once they get into the households, the opportunistic mosquito prefers to bite human skin as it is easy for their proboscis. Previous study findings conducted in southern Ethiopia and Indonesia on the association of malaria infection and keeping medium sized animals in the same house with family members supported the findings of this study and showed a 3 times higher risk of contracting malaria infection [17, 19].
The location of the kitchen was classified as outside the main house, separate rooms in the main house and in the main house with no separation and analyzed for association with asymptomatic malaria infection. In logistic regression model analysis, the odds of kitchen location in the main house with no separation was more than two times compared with households who kept their kitchen outside the main house. This association may be due to the kitchen location serving as proxies for indoor resting of the households during non-smoky hours. This finding was supported by a study conducted among children in the Ethiopian highlands .
Strength and limitation of the study
The strength of the study includes generalizability to similar lowland areas in the continent Africa and representativeness of study area (selection of districts from three different regions which have similar characteristics (altitude, weather condition, water bodies and malaria burden). In addition to its large sample size, systematic and simple random sampling techniques were used for household (household registration logbook) and study subject selection respectively. Adjustments for confounders also applied during data analysis.
Though this is one of a few studies that tried to determine the association between asymptomatic malaria infection and comprehensive living conditions, it should be interpreted cautiously as there are some limitations. For instance, it applied observational studies, limiting causality implications between asymptomatic malaria carriages, and living conditions. In addition, we couldn’t directly show the association of asymptomatic malaria infection and number holes, cracks, open doorways, or eaves, as we didn’t collected information. We recommend future studies to include the association of number of holes and crack with prevalence of asymptomatic malaria.