Abstract

A project on Integrated Vector Control strategy on malaria was launched at Bharat Heavy Electricals Limited, Hardwar, Uttarakhand, India in 1986. Major components of intervention strategy were source reduction, improving drainage, application of Expanded Polysterene Beads (EPS), biological control, use of larvivorous fishes Poecilia reticulata and Gambusia affinis, bacterial larvicides Bactoculicide (Bacillus thuringiensis israelensis and Spherix (B. sphaericus), limited use of fogging with malathion for the control of Culex mosquitoes, health education and community participation, prompt case detection, proper treatment and follow up of all malaria positive cases. Impact of Integrated Vector Control strategy on malaria incidence with time and estimation of diseases burden in term of Disability Adjusted Life Years (DALY) are presented in this paper.

Implementation of Integrated Vector Control strategy on malaria incidence, at BHEL, Hardwar drastically reduced malaria cases from 2733 in 1986 to 593 in 1987 and constantly decreased up to 1994 with total cases of 96 which implied that there is no indigenous transmission in BHEL area. A slight increase of malaria cases was recorded from 1995 to 1997 with the total cases of 245, 286 and 238 respectively and then decreased constantly till 2011with an overall reduction above 95%. Highest DALY lost was estimated for the age category ≥ 14 in 1986, which showed a sharp decline over the years. However a general decline in DALY was observed in all age groups.

Integrated Vector Control strategy on malaria incidence in industries complex at BHEL Hardwar with limited use of insecticide is highly effective, sustainable in long run, economical and resulted drastic reduction in DALY besides major reduction in malaria cases.

Keywords: Integrated Vector Control strategy on malaria; Disability adjusted life year (DALY); Malaria incidence

Introduction

The control of vector-borne diseases represents one of the greatest global public health challenges of the 21^st century. Malaria and other vector-borne diseases contribute substantially to the global burden of diseases and disproportionately affect poor and under-served populations living in tropical and sub-tropical regions [1]. Today, three billion people- almost half of the world populations are at risk of malaria infection in 109 malarious countries and territories with approximately 250 million cases and one million deaths annually. In the absence of effective control, these diseases have a major impact on public health and socio-economic development [2,3]. Integrated vector control is increasingly being recommended as an option for sustainable malaria control [4].

During pre DDT era, environmental and engineering technologies were used to control vector of malaria. In the early 20^th century larviciding and environmental management were the only tools available to contain malaria. The historical literature and more recent reviews of this approach show that anti-larval mosquito control measures were powerful tools against malaria [5,6]. Larval Source Management (LSM) provides the dual benefits of not only reducing numbers of house-entering mosquitoes, but, importantly, also those that bite outdoors. Large-scale LSM was a highly effective method of malaria control in the first half of the twentieth century, but was largely disbanded in favour of Insecticide Residual Spray (IRS) with DDT. Historically, antimalarial programmes in the US, Europe, the Middle East and some other previously endemic locations had largely succeeded in eliminating malaria even before the use of chemical pesticides. In 1950 and 1960s, the Global Eradication Campaign, superheated by the WHO, integrated the use of the insecticide DDT, into its control programme. The strategy depended on chloroquine for treatment and prevention and DDT for vector control, whereas environmental management activities almost disappeared. Initially, the campaign was very successful but the programme could not be sustained. The cost was high, many communities objected to repeat spraying of their houses, and resistance emerged to chloroquine among malaria parasites and to DDT among Anopheles mosquitoes. Global eradication was abandoned in 1972. Since then, the burden of malaria has increased substantially in many parts of the world and its eradication remains elusive [2,7].

The main tools and strategies currently employed to control malaria are medicines for its prevention and treatment, and chemicals to control the mosquito vectors. Chemical strategies are focused on insecticides treated nets and indoor residual spraying. However, both medical and chemical approaches are posing problems to human health and environment. Pesticides constitute an important element in the current global strategy for the control of major vector-borne diseases such as malaria. Many of these have become ineffective through development of resistance by mosquito vectors to chemicals and by parasites to pharmaceuticals.

Today, many programmes have reduced the use of pesticides for disease vector control. Several countries have eliminated the use of DDT and in pilot projects; environmental management strategies and biological control are being applied for malaria vector control.

An alternative for reducing the incidence of malaria lies in the development of Integrated Vector Management (IVM) which is systematically based on social and ecological approaches. These operations are designed with the objectives of effectively reducing adult vector populations and pathogen transmission with methods which are ecologically, environmentally, socially, economically and politically acceptable [8].

India is one of the major industrial forces in the world. Most of these industrial complexes are located in areas with a moderate to high risk of malaria. The approach to control malaria adapted in industrial areas is mainly by chemical larvicides, adulticides and chemotherapy [9,10].

The available methods of malaria control which include chemotherapy (antiparasite), insecticides spraying and fogging operations were not producing desired levels of transmission reduction threatening equitable socio-economic development of the area. To contain the disease severity, there was imperative need for alternatives intervention which are operationally feasible, cost effective, community based and sustainable. A study on integrated vector control strategy on malaria was launched in Bharat Heavy Electrical Limited, Hardwar, India in 1986. The aim of the present study was to control malaria by using integrated vector control methods with limited use of insecticide. Impact of integrated vector control strategy on malaria with time and estimation of disease burden in terms of disability adjusted life years (DALY) are presented in this paper. The study was aim to control malaria in cost effective manner, sustainable in long run, free from environmental contamination and provide the opportunity for community participation.

Methods

Study area

A project on integrated vector control strategy on malaria was launched at Bharat Heavy Electricals Limited, Hardwar, Uttarakhand in 1986, It is spread over an area of 25 km2 and is situated south-west of Hardwar between 78°9' and 78°22'E and 29°57' and 30° 18'N. The terrain is composed of foothills of Shivalik range. The average rainfall is 1200 mm per annum (average of 11years), and minimum and maximum temperatures are 2.5-22.7°C (average 11.4°C) and 24.4- 42.0°C (average 35.2°C) respectively with relative humidity 40-90% (average 58%). The area is conducive for mosquito proliferation and longevity. Mosquito fauna of the area is rich and breeding habitats are numerous and diverse [11]. The total population of the area is approximately 70,000.

The campus has innumerable breeding sites, both natural and man made resulting in active malaria transmission and high mosquito nuisance. These include large number of discarded tins, tyres, pots, dissert coolers burrow pits, ditches, low lying areas, community water supply taps in low lying areas of the unauthorized colonies without disposal of waste water, open and blocked drains, over head tanks, seasonal river and stream. The industrial area was highly malarious. Anopheles culicifacies is the primary vector in the area [11,12].

Intervention strategy

Integrated vector control strategy on malaria was started during 1986. The strategy was aimed to utilize the existing infrastructure of BHEL industry by involving the civil maintenance, water supply and sewage, medical and publicity departments as well as volunteer and other government organizations and the local community in vector control programme [13].

Major components of invention strategy were i).Source reduction ii). Improving drainage iii). Application of expanded polysterene beads (EPS) [14] and iv). Biological control, use of Larvivorous fishes Poecilia reticulata and Gambusia affinis [15] v). Bacterial larvicides Bactoculicide (Bacillus thuringiensis israelensis and Spherix (B. sphaericus) [16]. vi). Limited use of Fogging with malathion for the control of Culex mosquitoes, vi). Health education and community partipation [13]. vii). Involvement of Medical department for Prompt case detection, proper treatment and follow up of all malaria positive cases [12].

Parasitological survey

Weekly active surveillance of malaria cases was carried in BHEL, Hardwar by project staff to detect all fever cases through house to house visit. Passive surveillance of malaria at BHEL Hospital was maintained by the BHEL hospital staff. Thin and thick blood smears were prepared. All blood slides were brought to the malaria clinic, and stained with JSB-1 and JSB-11 (Jaswant Singh and Bhattacharjee stain). Blood slides collection and examination was made by the same team uniform over all the years. The blood slides were examined at malaria clinic on the same day with the project staff. All the blood slides examined and found positive for malaria cases were recorded. Radical treatment was provided to all malaria cases within 24 hours by the project staff. Surveillance in the control area was not possible due to practical limitations.

Entomological survey

Indoor resting adult mosquito densities were monitored by searches with flashlight and aspirator in experimental and control area at fortnightly interval. Man hour density of mosquito was recorded. Weekly peridomestic and intradomestic larval surveys were conducted and positive larval habitats were subjected to intervention measures in the experimental area [12].

Estimation of diseases burden

The Disability-Adjusted Life Year (DALY) is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death. DALYs for a disease or health condition are calculated as the sum of the Years of Life Lost (YLL) due to premature mortality in the population and the Years Lost due to Disability (YLD) for people living with the health condition or its consequences, numerically it is calculated as [17,18].

DALY = YLL + YLD

Since there was no death due to malaria, the factor YLL is not taken into consideration. YLD is calculated as follows:

Life time lost due to morbidity: According to the Population Reference Bureau's 2000 World Data Sheets, life expectancy at birth for Indians was between 60 and 61 years. Only 4% of our population is over the age of 65. Malaria data was available in four age groups namely 0 - <4, 5 - 8, 9 - 14 >14, age at onset of disease in each group was taken as the average age of each group i.e. 2.5, 7, 12 and 37 average expected life was taken as 60 years. Duration of morbidity in two types of infections namely, P. vivax and P. falciparum is taken as 7 and 9 days respectively,, however since the data of two type of infection was not available separately, duration of illness was taken as average of two i.e.8 days [12].

Disability weights : A group of independent experts established weights for two disability classes associated with P. vivax and P. falciparum infection as 0.70 and 0.75 respectively falling within (0,1). For the reason given above average weight was 0.725 [12].

Age-weights: These are used to indicate relative importance of healthy life at different ages. The age weights used in the World Bank report rise from birth until age 25 and decline slowly thereafter. The formula to calculate age weights is defined as follows [12].

Age weighting function = C x e- ^{β x} ...(2)

Where C - Constant (= 0.16243), Β - Constant (= 0.04), x - Age and e - Constant (= 2.71).

Age discounting function: It indicates the value of health gains today compared to the value attached to health gains in the future, also discounted if they are spread over more than one year to determine cost-effectiveness. The discount rate used in the DALY formula is 3 percent. The formula to discount for time preferences [12].

Discounting function = e^{- r ( x - a)} ...(3)

Where r - Discount rate (= 0.03), x - Age, e - Constant (= 2.71), a - disease onset year.

Sum across individuals: It is generally added linearly but to give priority to fewer people suffering for long intervals over more people suffering for shorter intervals is weighed non-linearly. In the present study individuals are added linearly.

Results and Discussion

Malaria cases during study period i.e. from 1983 - 2011 are given in Table 1. Data revealed that the implementation of Integrated Vector Control strategy on malaria, at BHEL, Hardwar drastically reduced malaria cases from 2733 in 1986 to 593 in 1987 and constantly decreased up to 1994 with total cases of 96. Moreover, P.falciparum also declined from 207 in 1986 to 9 in 1994 which implied that there is no indigenous transmission in BHEL area. A slight increase of malaria cases was recorded from 1995 to 1997 with the total cases of 245, 286 and 238 respectively and then decreased constantly till 2011with an overall reduction above 95%. Follow up of malaria cases revealed that more than 30% cases were either imported from other part of the Country or from nearby areas where no interventions work by the project staff was carried out [12]. It is to point out that P.vivax cases were followed for relapsed rate and 10. 2% cases were relapsed in spite of 5 day radical treatment with primaquine each time as per National Drug policy [19,20].