MALARIA CONTROL BY RESIDUAL INSECTICIDE SPRAYING IN CHINGOLA AND CHILILABOMBWE, COPPERBELT PROVINCE, ZAMBIA AUTHORS: Sharp Brian 1 BSc(Hon), MSc, PhD sharpb@mrc.ac.za Conception, design, implementation of study and drafting of manuscript van Wyk Pieter 2, MBChB, DOH, DCM, DMA vanwyck@nchanga.com Conception, design, implementation of study and revision of manuscript Sikasote Janet B 2, MBChB, MPH bandap@konkola.com.zm Conception and design of study, data analysis and drafting of manuscript Banda Paul 2, HDPH sikasotj@konkola.com.zm Conception and design of study, data analysis and drafting of manuscript Kleinschmidt I 1 BSc, MSc, MSc, PhD: kleinsci@mrc.ac.za Statistical analysis and revision of manuscript Corresponding author: Dr Janet Sikasote 1 Malaria Lead Programme, Medical Research Council, PO Box 17120, Congella, 4013, South Africa. Ph:27 31 2034700, Fax:2034702 2 Konkola Copper Mines Plc, P O Box 2000, Chingola, Zambia. Ph:260 2 350023 Fax:260-2-350021 Key words: Malaria, control, DDT, pyrethroids, residual insecticide house spraying Page 1
ABSTRACT Malaria is endemic in the whole of Zambia and is the leading cause of morbidity and mortality. Prior to 1980, effective malaria control was achieved in the northern mining towns of Chingola and Chililabombwe, by means of annual residual spraying programmes. In the 1970 s incidence rates were as low as 20/1000 p.a. By 2000, the incidence rates had increased to 68/1000 p.a., for Chingola and 158/1000 p.a., for Chililabombwe. Konkola Copper Mines initiated a malaria control programme in which all dwellings in the two towns and within a 10 km radius were sprayed with either Dichlorodiphenyltrichloethane (DDT) or a synthetic pyrethroid (Icon manufactured by ZENECA or Deltamethrin by Aventis). House spraying was done in November and December 2000 and 2001, at the start of the peak transmission period for malaria. There was a statistically significant reduction in malaria incidence recorded at KCM health facilities in the two towns. This represents a protective, incidence rate ratio of 0.65 (95% CI 0.44, 0.97), comparing the post-spraying period with the corresponding period of the previous two years. This reduction followed a single round of house spraying during a year with higher rainfall than the preceding two and in an area where chloroquine was first line treatment. Page 2
This house-spraying programme illustrates private/public sector collaboration in malaria control. Page 3
Introduction Malaria accounts for about 1 million deaths in Africa annuallyand has slowed economic growth in African countries by up to 1.3% per year (The Abuja declaration, 2000). It is endemic in the whole of Zambia and is the leading cause of morbidity and mortality (TDRC 1991). Prior to 1970 malaria in urban areas in Zambia was kept to a minimum due to an effective prevention and control programme. Malaria incidence rates in Zambia have nearly tripled over the past 24 years (1976 2000). In 1976 the incidence rate was 121.5 cases per 1000 population per year, by 1999 the incidence rate had increased to 321.4 per 1000 per year (Anon 2000). Effective malaria control was achieved in Chingola and Chililabombwe prior to 1980, by means of annual residual spraying programmes. In the 1970 s incidence rates were as low as 20/1000/year. In 2000, the incidence rates had increased to 68/1000/year for Chingola and 158/1000/year for Chililabombwe (KCM, 2000). Konkola Copper Mines embarked on a malaria control programme in October 2000. The main thrust of this programme was vector control by means of intra-domiciliary residual insecticide spraying. Page 4
We report here on the malaria incidence rate following the first round of house spraying in comparison to the incidence prior to initiation of this vector control programme. Although this represents a small first step we report on this to highlight the increasing initiative being taken by the private sector to mitigate the effect of malaria on their economic activities. The bigger challenge that lies ahead is the incorporation of such fragmented efforts into the greater framework of National-regional efforts to Roll Back Malaria in Africa Methods Before implementation of the spraying programme, baseline information was collected on: 1. Parasite prevalence rate 2. Knowledge, attitudes and practices (KAP) of the community pertaining to malaria 3. Malaria incidence rates in the previous 6 years, based on blood slide positivity. Intensive publicity preceded the intra-domiciliary spraying campaign, which was conducted in November December 2000/2001. Spraying of the inner walls of houses was done using Hudson Expert spray pumps. The residual insecticides, DDT and the synthetic pyrethroids, Lambda-cyhalothrin and Deltamethrin, were applied at concentrations of 2g/m 2, 0.006g/m 2, and 0.012gm/ m 2 respectively. Spray operators were recruited from the community and trained in spraying techniques. As part of the training Page 5
programme, emphasis was placed on avoiding environmental contamination by strict adherence to protocols for the cleaning of equipment as well as the storage, distribution and disposal of insecticides. Representatives from the Zambian Environmental Council audited the programme as independent observers. Due to the urgency to initiate the programme, it was not possible to obtain environmental baseline information on DDT. The programme covered the districts of Chingola and Chililabombwe. All dwellings in the two towns and within a 10 km radius of the furthest built up council area were sprayed, a total geographic area of 2 704 km 2. The type of house determined which insecticide was used. DDT was used in traditional houses, as porous walls do not easily absorb it. Synthetic pyrethroids, which could be sprayed on painted walls and curtains without staining, were used in urban style houses. 14 Days prior to the house spraying, a convenience sample of 1 276 bloods were collected from the community at randomly selected, sentinel sites and tested for malaria parasites using Hrp-2 antigen tests (ICT TM ). Informed consent was a prerequisite to inclusion in the study. All individuals found positive for plasmodium parasites were treated with chloroquine. Malaria cases were recorded at Konkola Mine health facilities, 4 clinics in Chililabombwe and 3 in Chingola and the referral hospital in each town. All malaria cases were definitively diagnosed using Giemsa stained thick blood smears. Malaria case data was available from 1996 as was employee population utilizing these health facilities. Page 6
Chloroquine was used as first line treatment and Sulphadoxine/pyrimethamine as second line treatment. Incidence rates represent symptomatic individuals who report to a mine health facility. Approximate incidence rates per month were calculated by dividing the total number of incident cases for each month by five times the average number of employees for a particular year. This ignored any fluctuation of the population during the year and assumed that each employee has an additional, average of 4 dependents, which also make use of the mine health facilities. Between 1994 and 2001, the annual dependency ratio varied by a maximum of 11% Figure 1 shows the mean, monthly incidence rate after spraying as well as the means for the two years prior to spraying. To determine any association between incidence rates and spraying of DDT, mean incidence rates were calculated for the period after spraying (January 2001 to June 2001, July 2001 to December 2001 and January 2002), and for the corresponding months of the previous six years. Mean incidence rates for the corresponding months during the two years before spraying were also calculated for comparison, since it was believed that these are more comparable, given the long term secular effects of drug resistance and HIV infection. A Student s two-sample t-test was performed to assess the difference in mean incidence before and after spraying. However, this test assumes independent observations for the calculation of standard errors, which is unlikely given the serial nature of the data from the same sites. The incidence rate was Page 7
therefore also modelled using generalized estimating equations (GEE). This method allows for serial correlation in the data and adjusts the standard errors of the incidence rate ratio (comparing incidence rates pre- and post spraying) accordingly. Rainfall data for the two towns were available from the Mines Survey Department as monthly totals from 1990 to date. Results Pre-intervention Parasite Prevalence Study Forty-six of the 1276 blood samples were found to be malaria positive giving an overall parasite prevalence rate of 3.6% (95% CI = 2.7 4.8). Parasite prevalence rate in the under 5 s was 13/260 = 5.0 % and 33/1 003 = 3.3% in the over 5 s. There was no significant difference between the two groups (p<0.2). Knowledge, Attitude and Practices Survey (KAP) 171 questionnaires were completed and the findings were as follows: 83.6% (143) of the respondents were female and 16.4% (28) were male. Page 8
The mean age was 35.5 years with a range of 17 72 years. 82 % of the respondents could define malaria appropriately. 43% thought drinking bad water causes malaria. 27% claimed to use mosquito nets 43% had suffered from a malaria-like illness in the 6 months preceding the survey Residual spraying programme 99% (31 463) of the dwellings within the project area were sprayed. 20.5% (6 438) with a pyrethroid and the remaining 79.5% (25 025) with DDT. Malaria incidence Figure 1 shows comparative incidence rates pre- and post-spraying. The reduction in transmission is more clearly reflected by the line representing the mean of cases reported in the preceding two years. Monthly incidence over the whole 7-year period varied from 1.3 to 18.9 per 1000 per month, with a median of 7.5 per 1000 per month (inter-quartile range 3.6 to 12.0). The Page 9
mean incidence rate for the 6 months after house spraying (the high incidence season) was 8.3 cases per 1000 per month. The mean incidence rate during the corresponding six months of the six years before spraying (1995 to 2000) was 11.4 compared to a mean of 13.0 per 1000 per month for the corresponding months during the two preceding years (1999 and 2000). This represents an incidence rate ratio of 0.65 (95% CI 0.44, 0.97), comparing the post-spraying period with corresponding months of the previous two years. During the low incidence season (July-December) mean incidence per month was 2.8 cases per 1000 per month in 2001 (after spraying), compared to a mean of 5.0 cases per 1000 per month for the corresponding months during 1999 and 2000 (before spraying). This represents an incidence rate ratio of 0.5 (95% CI 0.18, 1.46), comparing the low incidence season of 2002 with that for 1999/2000. Incidence during January declined from a mean of 17.8 during the two years before spraying to 13.9 and 10.8 cases per 1000 per month in 2001 and 2002 respectively. Annual rainfall ranged from 864mm to 1775mm from 1990 to July 2001 at Chililabombwe and from 984mm to 1743mm at Chingola. Discussion The malaria incidence data from Chililabombwe and Chingola show tremendous inter annual variation from 1994 to present, with a distinct malaria transmission Page 10
season. Malaria cases generally increase in December, peak in February and May and decline rapidly thereafter. The Malaria transmission season follows the very distinct rainfall pattern for the area with rains starting in October/November and stopping in April, with the rainfall peak extending from December to March. House spraying should therefore ideally be done during October and November, preceding the peak seasonal increase in transmission. The fact that there was no significant difference in the parasite prevalence ratio of the two age categories (Under and over 5 s) suggests a non-immune population and an area of low transmission. There was a statistically significant reduction in incidence of malaria in the two towns after spraying in comparison to the previous two seasons. This is considered particularly significant when considering that the rainfall in the 2000/2001 season was the second highest recorded in 10 years and 40% and 20% higher than the preceding two years in the two towns. The success of the programme can be attributed to a number of factors, which include: The high spray coverage (approaching 100%) Co-operation from the community due to the intensive communication exercise preceding the spraying campaign and the involvement of community members in the actual spraying. Factors that are believed to directly have facilitated such a high coverage rate. The use of insecticides with proven efficacy. Page 11
The KAP survey indicates the need for further health education on malaria and it s prevention. The 43% (cf. confirmed incidence) report of malaria type symptoms indicates the weakness of self reported clinical diagnosis and/or time compression by individuals. The statistically significant reduction in malaria incidence following one house spraying round compares well with the results of similar programmes in the 1950 s and 1960 s (Curtis and Lines 2000, Bradley 1991, Fontaine et al 1978) for which data is available. More recently, South Africa has reverted to the use of DDT following the detection of pyrethroid resistance in Anopheles funestus (Hargreaves et al 2000) a change that has resulted in dramatic case reductions (Sharp et al 2000). Based on these data, further reductions in malaria incidence following the next round of spraying in Zambia can be expected. The incidence rates for January 2002 are lower than that for this month in the two years prior to spraying and also lower than the January data post spraying in year one, indicating such a downward trend. It should be borne in mind that chloroquine was first line treatment in the study area; Plasmodium falciparum is chloroquine resistant in this area, indicating the efficacy of malaria control by house spraying in the presence of a partially effective drug. The overall unit cost of the residual spraying programme was US$ 6 per dwelling which on average, consist of 5 or more people. Following the United Nations Environmental Programmes Persistent Organic Pollution convention the use of DDT was restricted to disease vector control and the exemption required that countries notify WHO if they use DDT. Zambia in accord with these outcomes has registered to use DDT for indoor residual spraying. Page 12
The malaria control programme initiated and reported on here is an example of how collaboration between the Private and Public sector can benefit both the community and business. All structures were sprayed in the two towns, irrespective of whether the inhabitants were employed by KCM mines or not. Page 13
Acknowledgements We are indebted to the following for their kind support and advice, without which this project would not have been possible: Konkola Copper Mines, who funded the project, The Ministry of Health, Central Board of Health, The Malaria Technical Commission, Medical Research Council of South Africa, Department of Health Mpumalanga Province, South Africa, District Health Management Teams and Municipal Councils of both Chililabombwe and Chingola, National Malaria Control Centre, Zambia, Zambia Information Services, DAPP Child Aid and Tropical Disease Research Centre, Zambia. Dr D le Sueur for critical comments on the manuscript Page 14
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Figure1: Pre- and post-spraying comparisons of mean monthly malaria incidence 20 2001 (high season) 2001 ( low season) 1999/2000 (high season) 1999/2000 (low season) 1999/2000 Cases per 1000 per month 2001 2002 0 Jan month Dec Page 16