Globalization and urbanization with their inherent developmental activities and ecological transformations impact on malaria epidemiology. Entomological factors involved in malaria transmission in periurban Lusaka were assessed prior to vector control reintroduction. Data was collected through standard entomological and epidemiological protocols and a pretested structured questionnaire. Larval habitats were characterized as transient (43%), semipermanent (36%), and permanent (21%).
Malaria remains a serious global health problem, killing more than one million people per year. The global community has recently had many successes in malaria control. The number of malaria cases has fallen by more than 50% in 43 countries over the past decade [
Malaria transmission is driven by a complex interaction of the vector, parasite, human host, and the environment, and is governed by different ecological and social determinants [
Transmission patterns and severity of malaria are influenced by the geographic attributes and the socioeconomic environment that vary significantly by city, season, and age group [
Malaria transmission in peri-urban areas is mostly ascribed to increased vector breeding created by the agricultural and construction activities, lack of drainage of surface water [
Owing to malaria cases resurgence and paucity of entomological data, specific local investigations to appraise and confirm malaria transmission in peri-urban Lusaka were required before approaches to malaria vector control could be considered. We report here on malaria vectors, parasite prevalence rates in febrile patients and knowledge and attitudes of the community pertaining to malaria, precedent to the implementation of the integrated vector management (IVM) strategy.
Zambia is a landlocked country in southern Africa with an estimated population of 13 million people, 45% are children below 15 years of age [
Map of greater Lusaka showing the periurban study site locations.
Mosquito larvae were collected from breeding sites using WHO-standard 250 mL dippers [
Mosquito breeding sites were characterized into three different categories: transient, semipermanent, and permanent. Transient breeding site refers to temporal water collections, semi-permanent ones are those that would persist for a considerable period of time. Permanent breeding site refers to water bodies available throughout the year.
Adult mosquitoes were collected by the pyrethrum spray catch (PSC) between 06:00 hrs and 08:00 hrs in randomly selected households [
A pretested structured questionnaire was administered to 150 randomly selected respondents, tested for malaria, to determine community knowledge and attitudes as regards malaria, family demographic data, and possibility of malaria importation from rural areas.
Randomization was calculated for both study sites. Data was collected and entered in Excel spread sheets (Microsoft Corporation) and statistically analyzed by employing Epi Info version 3.2.2. The Chi-square (
Ethical approval for the research was granted by the University of Zambia Research Ethics Committee (Assurance number. FWA00000338 IRB00001131 of IOR G0000774). A freely administered informed consent was given to respondents and householders for participation in the study.
Of 1840 larvae collected, 66% (95% CI: 65.7–68.1) were from transient (gardens and abandoned building foundations), 28% (95% CI: 25.6–29.6) semipermanent (abandoned shallow wells and ditches that followed in the wake excavations for building sand or quarrying) and 6% (95% CI: 5.4–7.7) permanent water bodies (perennial streams and dams) (Figure
Entomological survey data.
Breeding sites, larval densities and ratios | ||||
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Habitat type | Transient | Semipermanent | Permanent | Total |
Abundance | 6 (43%) | 5 (36%) | 3 (21%) | 14 |
Larvae collected | 1213 (66%) | 508 (28%) | 119 (6%) | 1840 |
Anophelenes | 212 (17.5%) | 161 (31.7%) | 30 (25%) | 403 |
Culicines | 1001 (82.5%) | 347 (68.3%) | 89 (75%) | 1437 |
An-Cul ratio | 0.21 | 0.46 | 0.34 | |
Larvae/250 mL | 70 | 45 | 20 | |
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Vector molecular identification | ||||
Kalikiliki | Chazanga | |||
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11 (58%) | 7 (37%) | ||
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0 | 1 (5%) |
Abundance of breeding sites, collected larvae, and
Anophelines constituted 12.83% (95% CI: 8.7–17.9) of the 203 adult mosquitoes collected (Table
DNA bands produced by ribosomal DNA-polymerase chain reaction (PCR) amplification from the different species in the
DNA bands produced by ribosomal DNA-polymerase chain reaction (PCR) amplification from the different species in the
A total of 297 randomly selected febrile patients were recruited into the study (Table
Parasitological survey data.
Parasitemia in febrile patients by age and sex | ||||
---|---|---|---|---|
Age group | 0–4 yrs | 5–15 yrs | >15 yrs | Total |
Number surveyed |
52* | 14* | 63* | 129 |
38† | 21† | 109† | 168 | |
Frequency (age) | 27 (30%) | 9 (25.7%) | 40 (23.3%) | 76 |
Frequency (sex) | 15* | 4* | 26* | 45 |
12† | 5† | 14† | 31 | |
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Parasite densities by age | ||||
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1–10/100 O.I | 25 (62.5%) | 3 (33.3%) | 15 (55.6%) | 43 |
11–100/100 O.I | 9 (19.0%) | 2 (22.2%) | 4 (17.4%) | 15 |
10/O.I | 3 (7.5%) | 1 (11.1%) | 3 (7.5%) | 7 |
>10/O.I | 3 (7.5%) | 1 (11.1%) | 5 (18.5%) | 11 |
O.I: oil immersion field, †female, and *male.
Of the 150 respondents 18% (95% CI: 12.4–24.6) were male and 82% (95% CI: 75.4–87.3) were female. The mean age was 29.9 with a range of 18 to 53 years. Forty-eight percent exhibited good knowledge of malaria as a disease. Sixty-three percent were knowledgeable about malaria transmission. Seventy-nine per cent were conversant with causes, signs and symptoms. Sixty-two per cent showed awareness of what to do when they suspected malaria and only forty-six per cent were knowledgeable about vector control interventions. Family demographic data showed an average of seven residents with at least one child under five years per household. Eighty-one per cent of respondents had no history of travel outside Lusaka. There was positive association between knowledge and malaria prevalence in peri-urban Lusaka (
The malaria vectorial system in Zambia comprises of
Urban areas are perceived not to support significant levels of malaria transmission [
While formal urban development typically reduces mosquito densities, informal urbanization has been shown to alter the vector species composition within the
The presence of
Malaria had been known to be hyperendemic in hot riverine valleys with perennial transmission, meso-to hypoendemic on plateaus, and hypo-endemic in urban areas of Zambia [
The prevalence rate of malaria in children under five years is dependent on the intensity of transmission and declines with age as immunity develops and is thus a good indicator of a recent transmission of malaria [
The knowledge and attitudes survey indicated the need for intensified information, education and communication (IEC) on malaria and its prevention. The 46% knowledge level on vector control interventions indicated a weakness in individual efforts to prevent the disease. Population expansion and its health impact has been epitomized by sub-Saharan Africa. In many malaria endemic countries, including Zambia, the population has doubled in the past two decades, thus greatly increasing the absolute numbers of those at risk [
It has equally been established that human migration contributes markedly to malaria transmission [
The pragmatic data reported on here was an essential prerequisite of evidence-based and effective vector control efforts. The high malaria infection rates in peri-urban Lusaka could be ascribed to the definitively demonstrated local transmission. This necessitated the institution of appropriate control strategies based on the prevailing transmission paradigm. The presence of
Clearly, the malaria epidemiology in peri-urban Lusaka required an integrated approach involving IRS and ITNs against the adults and larval source management (LSM) against the aquatic stages. Information education and communication (IEC) to increase awareness and knowledge about malaria vector control needed to be intensified. Following this study, IVM was introduced in Lusaka with IRS and ITNs as main thrust interventions and IEC has been strengthened [
The authors declare that they have no conflict interests.
E. Chanda: codesigned the study, collected and analysed the data, and drafted the paper. K. S. Baboo: critically reviewed the manuscript. C. J. Shinondo codesigned the study, guided in data analysis and interpretation and contributed to the drafting of the paper and critically evaluated it. All authors read and approved the final paper.
The aurhors thank all Ministry of Health staff from the Health Centres and National Malaria Control Centre who participated in the study. They thank Dr. John Govere and the two anonymous reviewers for their useful comments on the paper. They also thank the Lusaka District Health Office for authority to work in Health facilities and the National Institute for Communicable Diseases, South Africa, for analyzing the malaria vector samples. The work was supported by the United States Agency for International Development (USAID).