Elsevier

The Lancet

Volume 353, Issue 9146, 2 January 1999, Pages 22-25
The Lancet

Articles
Impact of fly control on childhood diarrhoea in Pakistan: community-randomised trial

https://doi.org/10.1016/S0140-6736(98)03366-2Get rights and content

Summary

Background

Several million children are killed each year by diarrhoeal diseases; preventive strategies appropriate for developing countries are vital. Despite strong circumstantial evidence that flies are vectors of diarrhoeal diseases, no convincing studies of the impact of fly control on diarrhoea incidence in developing countries have been reported. We undertook a randomised study of the effect of insecticide spraying on diarrhoea incidence.

Methods

Six study villages were randomly assigned to two groups. Flies were controlled through insecticide application in group A in 1995 and in group B in 1996. In 1997 the effectiveness of baited fly traps was tested in group A villages. Diarrhoea episodes were monitored in children under 5 years through mothers' reports during weekly visits by a health visitor. Fly density was monitored by use of sticky fly-papers hung in sentinel compounds.

Findings

During the fly seasons (March–June) of both 1995 and 1996, insecticide application practically eliminated the fly population in the treated villages. The incidence of diarrhoea was lower in the sprayed villages than in the unsprayed villages in both 1995 (mean episodes per child-year 6·3 vs 7·1) and 1996 (4·4 vs 6·5); the reduction in incidence was 23% (95% CI 11–33, p=0·007). At times other than the fly season there was no evidence of a difference in diarrhoea morbidity between sprayed and unsprayed villages. Fly density data for 1997 indicate the ineffectiveness of baited traps in this setting.

Interpretation

Fly control can have an impact on diarrhoea incidence similar to, or greater than, that of the interventions currently recommended by WHO for inclusion in diarrhoeal disease control programmes in developing countries. This important finding needs confirmation in other settings in developing countries. Technologies and practices that interrupt disease transmission by flies need to be developed and promoted.

Introduction

Diarrhoeal diseases are a leading cause of childhood mortality, accounting for 3·3 million deaths worldwide each year.1 Preventive strategies are needed to reduce this mortality and the estimated annual morbidity of 1 billion diarrhoea episodes in children under 5 years of age.2 An effective prevention programme will integrate a selection of proven interventions aimed at specific pathogens (such as rotavirus immunisation) or transmission routes (improved water supply and sanitation). As a step towards defining which interventions should be recommended for inclusion in national programmes, WHO published a series of reviews on the effectiveness of various candidate interventions. Three categories of intervention were defined: ineffective or intervention of limited feasibility unlikely to have a major role in control programmes; intervention for which effectiveness or feasibility remains uncertain and in need of further research; highly effective intervention with strong evidence for its feasibility.3

The third “highly effective” category contained seven interventions that were considered promising for inclusion in diarrhoeal disease control programmes. These were promotion of breastfeeding, improvement of weaning practices, rotavirus immunisation, cholera immunisation (in special circumstances), measles immunisation, improvement of water supply and sanitation, and promotion of personal and domestic hygiene. Of the interventions reviewed, only two reduced diarrhoea incidence by more than 5% (median reduction of many studies) in children under 5 years old.

Fly control was placed in the first “ineffective” category, despite the fact that previous studies indicated a median reduction in diarrhoea incidence of 40%.4 Likely reasons for this decision are that many of the reviewed studies were poorly designed (with the exception of one study carried out in southern USA in the 1940s5) and that the sustainability of fly-control technology was unclear. If these were the reasons, fly control might, more appropriately, have been placed in the second “uncertain” category, pending further investigation.6 Subsequently, Cohen and colleagues found a reduction in diarrhoea incidence among Israeli soldiers after fly control with yeast-baited traps.7 Based on these promising results, and the fact that many previous intervention trials had been poorly designed, we undertook a controlled trial to investigate the impact of fly control on the incidence of childhood diarrhoea in a developing country where diarrhoea is a leading cause of childhood morbidity and mortality.

Section snippets

Location and methods

The study area comprised six study villages and two control villages near the town of Peshawar in North West Frontier Province, Pakistan. Preliminary studies showed that a seasonal peak in diarrhoea incidence between March and June coincided with a peak in fly density.8 The villages consist of 20–40 compounds, each inhabited by two or three related families. Livestock are kept inside the compounds, giving rise to manure heaps throughout the villages, resulting in high fly-breeding potential.

Results

During the study period, 4160 fly catches were done in the eight monitored villages. The number of flies caught per paper per day ranged from 0 to 675; the data on fly density in the three groups of villages over the course of the study is shown in the figure. Data from the control group show three pronounced fly seasons in March to June each year. The fly season of 1996 was less pronounced than the others; this was probably due to climatic factors affecting fly breeding. During the 1995 fly

Discussion

This study suggests that fly control can significantly reduce childhood diarrhoea incidence during periods of high fly densities. This effect compares favourably with some of the WHO recommended diarrhoea interventions such as immunisation. One possible explanation for this finding is reporting bias. However, there was no significant difference in the prevalence of cough or fever, two outcomes that are unlikely to be affected by the intervention.

The results of previous studies have tended to

References (16)

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