Determinants of malaria transmission and bed net utilization among households around Lake Tana, northwest Ethiopia
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Date
2020-06
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Addis Ababa University
Abstract
Background: Malaria still attacks millions of people predominantly in sub Saharan Africa,
including Ethiopia. The contribution of house proximity to water bodies, the role of migration,
malaria information and child age on malaria transmission dynamics have not yet been examined
in detail in northwest Ethiopia. Identification of malaria vectors in meso-endemic settings with a
high potential of introduced malaria has not also been done in the study setting. The ownership
and use of LLINs is one of the primary prevention strategies for malaria transmission control and
elimination. In Ethiopia, evidences showed the presence of major gaps between LLIN ownership
and compliance. However, the reasons that influenced consistent utilization of LLINs have not
yet explored qualitatively in Amhara region, particularly in the study area. Identifying factors for
imported and locally acquired malaria, malaria vectors, and exploring barriers of consistent
utilization of LLINs are useful to facilitating the effort for malaria elimination.
Objectives: This study aimed at investigating the contribution of house proximity to a water
body, individual and household-level drivers of imported and locally acquired malaria, malaria
vector species and barriers of consistent LLINs utilization in meso-endemic villages around Lake
Tana, northwest Ethiopia.
Methods: A combination of approaches, including matched case-control study designs,
entomological survey and phenomenological qualitative method were undertaken in 12 kebeles
around Lake Tana, northwestern Ethiopia. Health facility-based matched case-control studies
involving 303 and 81 matched pairs among all age groups and under-five children were
conducted from October 10, 2016, to June 30, 2017, respectively. Anopheles mosquito larvae
sampling was done from April 30, 2017, to June 24, 2017, from 7 potential breeding sites in the
study area using the standard dipping method. A phenomenological qualitative approach
comprising 23 community interviewees and 38 key informants was conducted from April to June
2017. Households for cases and controls, household proximate water bodies, health centers and
larvae survey sites were geo-referenced. A semi-structured questionnaire was used to collect data
from households. Collected larvae were reared to adulthood at an insectary. Each adult was
individually identified at the species and species complex levels using standard adult mosquito
morphological identification keys. In-depth interviews were carried out to explore the local
contexts and reasons that influenced consistent use of LLINs. Quantitative data were entered and
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cleaned in EpiData Version 3.1 software. Qualitative data were managed and analyzed using
NVivo Version 10 software. Principal component analysis was performed to estimate household
wealth. Stratified analyses were used to confirm confounding and effect modification.
Multivariable conditional logistic regression models were fitted to identify independent
predictors of malaria occurrence. Thematic analysis was used for the interview data to code and
identify themes. Statistical analyses were performed using Excel®
, SPSS statistical software
version 22 and STATA version 14.0. The maps were plotted using ArcGIS 10.5.
Results: Of 303 malaria cases, 59 (19.5%) were imported malaria whereas 244 (80.5%) were
locally acquired. Travel to malarious lowlands in the preceding month (adjusted mOR = 7.23;
95% CI: 2.38-22.00), household member‘s travel to malarious lowlands (adjusted mOR = 3.04;
95% CI: 1.14-8.08), and inadequate malaria information (adjusted mOR = 1.56; 95% CI: 1.02-
2.37) were observed as independent predictors of malaria occurrence in the study area. Stratified
analyses confirmed that travel to malarious lowlands had a confounding effect on malaria
occurrence in the study area.
Children aged 36-59 months (adjusted mOR = 3.88; 95% CI: 1.55-9.74) were at increased risk of
locally acquired malaria among under-five children. Presence of water body within a 500m
radius from a house was not a statistically significant predictor of local malaria. The malaria
vectors, Anopheles gambiae complex, An. pharoensis and An. funestus group were identified in
malaria meso-endemic villages around Lake Tana.
The qualitative investigation explored wrong perceptions about LLINs, malaria and mosquitoes;
bedbug infestation; structural inconvenience; unintended uses; weather conditions; problem in
distribution of nets; and socio-cultural and economic factors as critical barriers for consistent
utilization of LLINs. Killing ability of nets against arthropods other than mosquitoes reportedly
made use of LLINs a favored malaria prevention method despite their ineffectiveness after 3
months. Circular-shaped nets were preferred due to their compatibility with varied sleeping
structures. Unintended uses were often associated with local needs and seldom linked with social
issues and deficiencies in information about malaria and LLINs. Collateral benefits were
considered equally important, principally in terms of short-term disinfestations of bedbugs.
Conclusions: In this study, travel to malarious lowlands and inadequate malaria information
determined the occurrence of malaria infection in villages around Lake Tana. Children aged 36-
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59 months old continued to be at increased risk of local malaria in these villages where An.
gambiae complex is present. Non-consistent bed net use in villages around Lake Tana was
associated with inconvenient bed net design and early damage; non-potency of the insecticide
against other arthropods; facilitation of bedbug infestation; unintended uses; wrong perceptions
about malaria, mosquitoes, and LLINs; and inadequate follow-up regarding LLINs utilization.
Recommendations: National malaria control & elimination programmers and health authorities
should design improved effective and integrated interventions that consider imported malaria
cases. Malaria information that involves IEC and SBCC should be given to optimize coverage
and adequacy of information by considering the educational status of the community. Increment
of long-acting insecticide spraying coverage and frequency, use of repellents until sleep under
nets and equal management of both child age groups while applying LLINs utilization should be
considered to reduce local malaria in children aged 36-59 months. Vector control interventions
should be designed in accordance with malaria vector species present in a locality. The provision
of nets that are structurally compatible with sleeping spaces and the delivery of adequate
information about malaria and its vectors, and the properties and proper uses of LLINs to the
community indicate substantial accumulation of knowledge that may guide effective LLIN
programs in the study area.
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Keywords
Locally acquired malaria, Malaria information, Travel, Matched analysis, Under-five children, Malaria vectors, LLINs, Consistent use, Circular nets, Bedbug infestation, Ethiopia