SEASONAL AND ENVIRONMENTAL FACTORS INFLUENCING INDOOR RESTING DENSITY OF ANOPHELES SPECIES AND MALARIA PARASITAEMIA AMONGST UNDER-FIVE CHILDREN IN ELELE COMMUNITY, RIVERS STATE, NIGERIA

Abstract

Weather is known to influence the ecology of malaria vectors, which in turn affects malaria transmission. There are gaps in knowledge on the effects of changing weather conditions on vector density in relation to malaria parasitaemia in Nigeria. This study was designed to assess malaria parasitaemia and indoor Resting Densities (IRD) of Anopheles species across two seasons in Elele community. A Comparative Cross sectional study was carried out in the Dry Season (DS) of December 2008 to March 2009 and Rainy season (RS) of April to July 2009 A 5-stage random sampling technique was used to select 180 under-five children and their mothers as respondents. A semi-structured questionnaire which included a 22-point knowledge scale was used to assess respondents' knowledge on environmental predisposing factors to malaria as well as malaria prevention practices. An observation checklist was used to obtain information on environmental sanitation activities. Levels of parasiteamia of 180 Children selected by systematic random sampling of households were determined by microscopy. Mosquitoes were collected for a period of 4 months from 10 specific houses in each season and I RILE or Anopheles species calculated using standard methods Quantitative data were analyzed using descriptive statistics, Chi-square and t-test, Spearman correlation and logistic regression, at 5% level of significance. The mean age of the under-five children studied was 29± 0.89 months and 68.9% of them were females. The mean age of the mothers of under-fives was 32.1 ± 4.60 years and 56.4% of them had at most secondary education and their mean knowledge score was 12.7 ± 1.5. Proportion of participants' houses observed with stagnant pool of water in the DS and RS were 71.0% and 69.6% respectively, with no significant difference (p>0.05). The IRD of Anopheles funestus (highly predominant species) in the DS and RS were 3.1±0.2 and 2.6± 0.3 respectively. The proportion of IRD of Anopheles funestus was significantly higher in the DS, thereby posing a higher risk to under-fives to malaria. There was no significant difference between median parasite densities in the DS (750 parasites/microlitre) and RS (732 parasites/microlitre). Malaria parasite prevalence was higher in the DS (87.2%) than in the DS (62.8%). Presence of stagnant pools of water was significantly associated with increased malaria prevalence in the DS (OR= 12.9, CI = 2.8 - 81.7) and RS (OR 2.8. CI- 1.2- 6.3). Respondents' practice of indoor residual spraying was significantly higher in the RS(67.4%) than in the DS(44.4%), (p<0.05). Indoor residual spraying was significantly associated with, reduced malaria prevalence in the RS(OR- 1.4, CI =0.12- 0.60). Respondents' practice of environmental sanitation was also higher in the RS (52.5%) than in the DS(27.8%) and was significantly associated with reduced malaria parasite prevalence (OR=4.0, CI= 1.4-9.7). There was an unusually higher malaria parasite prevalence in the dry season than in the rainy season. This may be attributed to the higher indoor resting density of Anopheles flinestus in the dry season. There is a need to design perennial interventions which focus on the reduction of indoor resting density of Anopheles finestus in the area.