Exploiting the Potential of Vector Control for Disease prevention/Exploitation Des Possibilites De la Lutte Antivectorielle Dans la Prevention Des maladies/Aprovechar El Potencial De la Lucha Antivectorial Como Medio De Prevencion De Enfermedades

Article excerpt

Voir page 945 le resume en francais. En la pagina 946 figura un resumen en espanol.

Introduction

Vector-borne diseases account for approximately 17% of the estimated global burden of infectious disease (1) (Table 1). Although well planned vector control can contribute significantly to the reduction of this burden (2), the preventive power of vector control is grossly underutilized in public health. Insecticide-treated bednets (3) and indoor spraying of houses with residual insecticides (4) are highly effective in preventing malaria transmission, and thus in reducing malaria morbidity and mortality. Yet, it was estimated that in 2002, coverage of the target population stood at 31% for malaria treatment, while that for prevention was only 2% (5). To achieve the goal of 50% coverage for prevention by 2007 (5), investment in vector control would need to be significantly increased.

For diseases such as dengue (6) and Chagas disease (7-9), rector control is the only means of protecting populations from infection. For leishmaniasis (10-16) and African trypanosomiasis (17, 18), where current methods of chemotherapy are far from perfect, vector control currently offers the greatest potential for large-scale reduction in the burden of disease. For those vector-borne diseases where preventive chemotherapy is the principal control strategy, such as lymphatic filariasis, vector control can accelerate the reduction in disease transmission, thereby increasing the likelihood that programme goals will be met (19-21), and lessen the risk of drug resistance (22). Furthermore, vector control can add sustainability to strategies of preventive chemotherapy, and may be the most cost-effective option when unit costs of individual case detection and treatment become progressively greater as case numbers drop. For malaria, a reduction in the parasite reservoir cannot be sustained without a reduction in vectorial capacity brought about through vector control (23).

The role of vector control in the major vector-borne diseases is summarized in Box 1.

Box 1. The role of vector control in major vector-borne
diseases (24)

African trypanosomiasis. Imperfect drugs make control of the tsetse
fly vector the main hope for preventing transmission. New long-lasting
treatments may extend the capacity of communities to deploy simple
traps and screens treated with pyrethroid insecticide.

Chagas disease. Vector control, mainly through indoor residual
spraying, remains the only practical option for control of the domestic
triatomine bug vectors.

Dengue. In the absence of an effective vaccine, control of the Aedes
mosquito vectors is the only preventive intervention. This requires
community participation for effective and sustained implementation.

Leishmaniasis. Vector control, through indoor residual spraying,
has proven effective in controlling indoor transmission of visceral
and cutaneous leishmaniasis in Europe, the Middle-East, South Asia
and Africa. Insecticide-treated bednets show promise in experimental
trials but have yet to be deployed in large-scale programmes. They
may be the only means of preventing infection with kala-azar (visceral
leishmaniasis) in rural communities.

Malaria. The uptake of vector control as a preventive strategy lags
far behind the deployment of curative drugs. With the emergence
of resistance to first-line drugs, greater priority needs to be given
to preventive strategies based on vector control. The control of
malaria vectors can also indirectly contribute to control of other
diseases.

Onchocerciasis. Vector control was a major factor in the successful
Onchocerciasis Control Programme in West Africa for more than
25 years. In the later stages of the programme, vector control was
successfully combined with mass drug administration to consolidate
the gains. This success underscores an important historical lesson:
campaigns for the control of vector-borne diseases have the best
chance of success when multiple interventions that target different
points in the disease cycle are implemented concomitantly. …