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Dengue vector control: the effectiveness of community based environmental management and insecticide treated materials

VEERLE VANLERBERGHE UGent (2011) Monografieën van de Vakgroep Maatschappelijke Gezondheidkunde, Universiteit Gent.
abstract
An estimated 40% of the world’s population lives at risk of contracting dengue, a viral disease that inflicts a substantial health, economic and social burden on the populations of endemic areas. The public health importance of dengue is growing rapidly, due to a 30-fold increase in dengue incidence following the geographical expansion of its main vector, the mosquito Aedes aegypti, since the 1960s. Additionally, the accrued co-circulation of multiple dengue serotypes increases the risk of sequential infections and of hemorrhagic fever, a potentially lethal manifestation of the disease. No curative treatment is available and the prevention of a fatal outcome in severe cases depends on early case detection and appropriate supportive treatment. No vaccine is available neither and vector control is the only possible strategy to prevent transmission. Several A. aegypti control methods have proven their efficacy in controlled conditions, but when applied under ‘real world’ conditions, very few were successful in sustainably reducing vector infestation levels and interrupting dengue transmission. The latter is generally measured by proxies, namely entomological parameters, as disease parameters have several operational and conceptual drawbacks. The gap between efficacy and effectiveness of control tools is attributed to “user”- and “implementer”- related factors such as poor acceptance of tools, lack of targeting of control interventions and reactive instead of proactive action. Against this background we conducted research aiming at generating evidence for more rational dengue vector control strategies. We first investigated the effectiveness, cost-effectiveness and sustainability of a participatory approach towards implementing environmental management, a classical control measure against A. aegypti larvae. Subsequently, we assessed the effectiveness and acceptability of insecticide treated materials, a new control tool directed at the adult vector. Environmental management seeks to prevent or minimize vector propagation by destroying, protecting or altering the larval habitats. We developed a community based implementation strategy that hinged on the creation of formal task forces at grassroots level, incorporating formal and informal community leaders and public health workers. These groups were responsible to secure intersectoral support and to actively involve the community in the identification, planning and execution of A. aegypti control activities. Examples of actions set up by the community are the local design of social communication materials and messages, the production of water container covers from recycled material and the mapping of environmental risks. We tested the strategy, over a period of 6 years, in the cities of Santiago and Guantanamo in Eastern Cuba. The strategy was implemented between 2000-2002, in addition to routine control activities, in three health zones (covering 2400 houses) in Santiago de Cuba and we followed up the results in 2003-2004, after withdrawal of external support. In control areas (3 health zones, covering 2600 houses), only the routine vector control programme activities were executed (periodic inspection of houses in cycles of 11 days, larviciding and selective adulticiding). In the intervention area, 87.5% of the water storage containers remained well covered in 2004 and 90.5% of the families continued to correctly use a larvicide, against 21.5% and 63.5%, respectively in the control area. House indices (number of houses positive for at least one container with A. aegypti larvae / total of inspected houses) declined from 1.23% pre-intervention (2000) to 0.17% post-intervention (2004) in the intervention area, in contrast to an increase from 2.08% to 2.25% in the control area (p<0.05). The societal cost for A. aegypti control per inhabitant per year was comparable in both areas at baseline, but reached by the end of follow-up period, US$ 30.6 and US$ 38.3 for the intervention and control area respectively. However, the cost for the community was substantially higher in the intervention areas, reaching US$ 12.2 per inhabitant per year against US$ 6.4 in control areas. By 2004, key elements of the strategy had become integrated into the standard operating practice of the local vertical routine programme. This, together with the developed community capacities indicated that the first steps towards sustainability were taken. Based on these promising results, we set up a cluster randomized trial implementing the “community based environmental management strategy” in order to provide level I evidence. Sixteen intervention and sixteen control clusters of about 500 houses each, were selected in central Guantanamo. After one year of implementation, the provincial health authorities decided on the basis of a crude interim analysis to extend the intervention strategy to the whole city of Guantanamo. At that moment, the adoption of the strategy was fair, but community involvement was not yet homogeneous over the intervention clusters, and entomological indices were significantly lower in the intervention clusters: the rate ratio for house indices was 0.49 (95% CI 0.27-0.88) and for pupae per inhabitant 0.27 (95% CI 0.09-0.76). The trial corroborated fully the results of the Santiago study. In settings with a strong and well-structured routine A. aegypti control programme, complementing its actions with a community based environmental management strategy is a good investment for decreasing dengue vector infestation levels. Besides reducing vector population densities by larval control, one can also target adult mosquitoes to decrease their longevity and the risk of virus transmission. We tested this alternative control option by deploying long lasting insecticide treated materials (ITM), window curtains and jar covers, recently developed tools directed at the adult stages of A. aegypti. The research was conducted over a period of 4 years in Valera, Venezuela and Laem Chabang, Thailand. In addition to routine control activities we set up community trials to evaluate the effectiveness, household uptake and continued use of ITM. In Thailand, 22 urban clusters of 80-110 houses were selected. Health volunteers distributed the ITM curtains and reached a coverage of 92.3%. In Venezuela, 5 urban and 5 suburban clusters of each 300-600 houses were selected. ITM curtains and jar covers were distributed through the routine A. aegypti control programme and health committees and coverage reached 76.7% for curtains and 21.5% for jar covers. The use of ITM curtains declined rapidly and steadily over time to 59.7% and 38.4% after 18 and 22 months in Thailand and Venezuela respectively. We found that the continued use of ITM curtains was mainly determined by the perceived effectiveness of the tool. For the ITM jar covers, distribution coverage was essentially determined by the presence of uncovered jars in the household. No data were available on the residual insecticidal activity of ITM curtains used under field conditions and we performed standard WHO bio-assays on used curtains in Thailand. A. aegypti mortality was 100% for unused curtains before distribution and 98.2% (95%CI 97.9-98.5) at 12 months of use. Sunlight, hand-washing and detergent use had no effect on the residual insecticidal activity. The Breteau Index (number of containers positive for immature stages of A. aegypti per 100 inspected houses) was 8.5 in urban and 42.4 in suburban areas at baseline in the Venezuelan intervention area. In a before - after comparison, the Breteau Index showed a decrease of 63% for urban and 67% for suburban clusters. At the corresponding municipal levels, the observed patterns were less pronounced and reductions were 35% and 26% respectively. After control for confounding the percentage ITM curtain coverage was significantly associated with the Breteau index and the pupae per inhabitant index (rate ratio of 0.98 per percentage point; 95% CI 0.97-0.99). In other words, each 1% coverage increase with ITM curtains reduced the entomological indices by 2%. ITM jar cover coverage had no influence. In conclusion, we showed that adding a supplementary A. aegypti control measure on top of routine control programmes can lead to substantial reductions of mosquito infestation levels. However, cost and sustainability are key issues. Involving the communities to identify an array of culturally acceptable tools and to promote their sustainable use can be a way forward but participation does not come as a free ride and careful targeting of interventions, based on a surveillance system that includes epidemiological, entomological and environmental information will be essential.
Please use this url to cite or link to this publication:
author
promoter
UGent
organization
year
type
dissertation (monograph)
subject
keyword
community-based, insecticide treated materials, Aedes, Dengue, disease control
in
Monografieën van de Vakgroep Maatschappelijke Gezondheidkunde, Universiteit Gent
pages
142 pages
publisher
Ghent University. Faculty of Medicine and Health Sciences
place of publication
Ghent, Belgium
defense location
Gent : Het Pand (zaal rector Blancquaert)
defense date
2011-11-29 17:30
ISBN
9789078344209
language
English
UGent publication?
yes
classification
D1
additional info
dissertation consists of copyrighted material
copyright statement
I have transferred the copyright for this publication to the publisher
id
2006167
handle
http://hdl.handle.net/1854/LU-2006167
date created
2012-01-27 11:59:48
date last changed
2012-01-30 09:22:24
@phdthesis{2006167,
  abstract     = {An estimated 40\% of the world{\textquoteright}s population lives at risk of contracting dengue, a viral disease that inflicts a substantial health, economic and social burden on the populations of endemic areas. The public health importance of dengue is growing rapidly, due to a 30-fold increase in dengue incidence following the geographical expansion of its main vector, the mosquito Aedes aegypti, since the 1960s. Additionally, the accrued co-circulation of multiple dengue serotypes increases the risk of sequential infections and of hemorrhagic fever, a potentially lethal manifestation of the disease. No curative treatment is available and the prevention of a fatal outcome in severe cases depends on early case detection and appropriate supportive treatment. No vaccine is available neither and vector control is the only possible strategy to prevent transmission. Several A. aegypti control methods have proven their efficacy in controlled conditions, but when applied under {\textquoteleft}real world{\textquoteright} conditions, very few were successful in sustainably reducing vector infestation levels and interrupting dengue transmission. The latter is generally measured by proxies, namely entomological parameters, as disease parameters have several operational and conceptual drawbacks. The gap between efficacy and effectiveness of control tools is attributed to {\textquotedblleft}user{\textquotedblright}- and {\textquotedblleft}implementer{\textquotedblright}- related factors such as poor acceptance of tools, lack of targeting of control interventions and reactive instead of proactive action.   
Against this background we conducted research aiming at generating evidence for more rational dengue vector control strategies. We first investigated the effectiveness, cost-effectiveness and sustainability of a participatory approach towards implementing environmental management, a classical control measure against A. aegypti larvae. Subsequently, we assessed the effectiveness and acceptability of insecticide treated materials, a new control tool directed at the adult vector.   
Environmental management seeks to prevent or minimize vector propagation by destroying, protecting or altering the larval habitats. We developed a community based implementation strategy that hinged on the creation of formal task forces at grassroots level, incorporating formal and informal community leaders and public health workers. These groups were responsible to secure intersectoral support and to actively involve the community in the identification, planning and execution of A. aegypti control activities. Examples of actions set up by the community are the local design of social communication materials and messages, the production of water container covers from recycled material and the mapping of environmental risks. We tested the strategy, over a period of 6 years, in the cities of Santiago and Guantanamo in Eastern Cuba. 
The strategy was implemented between 2000-2002, in addition to routine control activities, in three health zones (covering 2400 houses) in Santiago de Cuba and we followed up the results in 2003-2004, after withdrawal of external support. In control areas (3 health zones, covering 2600 houses), only the routine vector control programme activities were executed (periodic inspection of houses in cycles of 11 days, larviciding and selective adulticiding). In the intervention area, 87.5\% of the water storage containers remained well covered in 2004 and 90.5\% of the families continued to correctly use a larvicide, against 21.5\% and 63.5\%, respectively in the control area. House indices (number of houses positive for at least one container with A. aegypti larvae / total of inspected houses) declined from 1.23\% pre-intervention (2000) to 0.17\% post-intervention (2004) in the intervention area, in contrast to an increase from 2.08\% to 2.25\% in the control area (p{\textlangle}0.05). The societal cost for A. aegypti control per inhabitant per year was comparable in both areas at baseline, but reached by the end of follow-up period, US\$ 30.6 and US\$ 38.3 for the intervention and control area respectively.  However, the cost for the community was substantially higher in the intervention areas, reaching US\$ 12.2 per inhabitant per year against US\$ 6.4 in control areas. By 2004, key elements of the strategy had become integrated into the standard operating practice of the local vertical routine programme. This, together with the developed community capacities indicated that the first steps towards sustainability were taken. 
Based on these promising results, we set up a cluster randomized trial implementing the {\textquotedblleft}community based environmental management strategy{\textquotedblright} in order to provide level I evidence. Sixteen intervention and sixteen control clusters of about 500 houses each, were selected in central Guantanamo. After one year of implementation, the provincial health authorities decided on the basis of a crude interim analysis to extend the intervention strategy to the whole city of Guantanamo. At that moment, the adoption of the strategy was fair, but community involvement was not yet homogeneous over the intervention clusters, and entomological indices were significantly lower in the intervention clusters: the rate ratio for house indices was 0.49 (95\% CI 0.27-0.88) and for pupae per inhabitant 0.27 (95\% CI 0.09-0.76). The trial corroborated fully the results of the Santiago study. In settings with a strong and well-structured routine A. aegypti control programme, complementing its actions with a community based environmental management strategy is a good investment for decreasing dengue vector infestation levels. 
Besides reducing vector population densities by larval control, one can also target adult mosquitoes to decrease their longevity and the risk of virus transmission. We tested this alternative control option by deploying long lasting insecticide treated materials (ITM), window curtains and jar covers, recently developed tools directed at the adult stages of A. aegypti. The research was conducted over a period of 4 years in Valera, Venezuela and Laem Chabang, Thailand. In addition to routine control activities we set up community trials to evaluate the effectiveness, household uptake and continued use of ITM. 
In Thailand, 22 urban clusters of 80-110 houses were selected. Health volunteers distributed the ITM curtains and reached a coverage of 92.3\%. In Venezuela, 5 urban and 5 suburban clusters of each 300-600 houses were selected. ITM curtains and jar covers were distributed through the routine A. aegypti control programme and health committees and coverage reached 76.7\% for curtains and 21.5\% for jar covers. The use of ITM curtains declined rapidly and steadily over time to 59.7\% and 38.4\% after 18 and 22 months in Thailand and Venezuela respectively. We found that the continued use of ITM curtains was mainly determined by the perceived effectiveness of the tool. For the ITM jar covers, distribution coverage was essentially determined by the presence of uncovered jars in the household. No data were available on the residual insecticidal activity of ITM curtains used under field conditions and we performed standard WHO bio-assays on used curtains in Thailand. A. aegypti mortality was 100\% for unused curtains before distribution and 98.2\% (95\%CI 97.9-98.5) at 12 months of use. Sunlight, hand-washing and detergent use had no effect on the residual insecticidal activity.  
The Breteau Index (number of containers positive for immature stages of A. aegypti per 100 inspected houses) was 8.5 in urban and 42.4 in suburban areas at baseline in the Venezuelan intervention area. In a before - after comparison, the Breteau Index showed a decrease of 63\% for urban and 67\% for suburban clusters. At the corresponding municipal levels, the observed patterns were less pronounced and reductions were 35\% and 26\% respectively. After control for confounding the percentage ITM curtain coverage was significantly associated with the Breteau index and the pupae per inhabitant index (rate ratio of 0.98 per percentage point; 95\% CI 0.97-0.99).  In other words, each 1\% coverage increase with ITM curtains reduced the entomological indices by 2\%. ITM jar cover coverage had no influence.
In conclusion, we showed that adding a supplementary A. aegypti control measure on top of routine control programmes can lead to substantial reductions of mosquito infestation levels. However, cost and sustainability are key issues. Involving the communities to identify an array of culturally acceptable tools and to promote their sustainable use can be a way forward but participation does not come as a free ride and careful targeting of interventions, based on a surveillance system that includes epidemiological, entomological and environmental information will be essential.},
  author       = {VANLERBERGHE, VEERLE},
  isbn         = {9789078344209},
  keyword      = {community-based,insecticide treated materials,Aedes,Dengue,disease control},
  language     = {eng},
  pages        = {142},
  publisher    = {Ghent University. Faculty of Medicine and Health Sciences},
  school       = {Ghent University},
  series       = {Monografie{\"e}n van de Vakgroep Maatschappelijke Gezondheidkunde, Universiteit Gent},
  title        = {Dengue vector control: the effectiveness of community based environmental management and insecticide treated materials},
  year         = {2011},
}

Chicago
Vanlerberghe, Veerle. 2011. “Dengue Vector Control: The Effectiveness of Community Based Environmental Management and Insecticide Treated Materials.” Monografieën Van De Vakgroep Maatschappelijke Gezondheidkunde, Universiteit Gent. Ghent, Belgium: Ghent University. Faculty of Medicine and Health Sciences.
APA
Vanlerberghe, Veerle. (2011). Dengue vector control: the effectiveness of community based environmental management and insecticide treated materials. Monografieën van de Vakgroep Maatschappelijke Gezondheidkunde, Universiteit Gent. Ghent University. Faculty of Medicine and Health Sciences, Ghent, Belgium.
Vancouver
1.
Vanlerberghe V. Dengue vector control: the effectiveness of community based environmental management and insecticide treated materials. Monografieën van de Vakgroep Maatschappelijke Gezondheidkunde, Universiteit Gent. [Ghent, Belgium]: Ghent University. Faculty of Medicine and Health Sciences; 2011.
MLA
Vanlerberghe, Veerle. “Dengue Vector Control: The Effectiveness of Community Based Environmental Management and Insecticide Treated Materials.” Monografieën van de Vakgroep Maatschappelijke Gezondheidkunde, Universiteit Gent 2011 : n. pag. Print.