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Preventive effect of permethrin-impregnated long-lasting insecticidal nets on the blood feeding of three major pyrethroid-resistant malaria vectors in western Kenya.

Kawada H, Ohashi K, Dida GO, Sonye G, Njenga SM, Mwandawiro C, Minakawa N - Parasit Vectors (2014)

Bottom Line: ITNs and LLINs are still used as effective self-protection measures, but there have been few studies on the effectiveness of ITNs and LLINs in areas where vector mosquitoes are pyrethroid-resistant.However, during the hours when people were beneath LLINs, these provided protective efficacy as indicated by reduced human blood feeding rates.Such limitation of LLINs will need to be intensively addressed in African countries in the near future.

View Article: PubMed Central - PubMed

Affiliation: Department of Vector Ecology & Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan. vergiss@nagasaki-u.ac.jp.

ABSTRACT

Background: Since the World Health Organization (WHO) adopted the use of long-lasting insecticidal nets (LLINs) as a principal strategy for effective malaria prevention and control, pyrethroids have been the only class of insecticides used for LLINs. The dramatic success of insecticide-treated nets (ITNs) and LLINs in African countries, however, has been threatened by the rapid development of pyrethroid resistance in vector mosquitoes. ITNs and LLINs are still used as effective self-protection measures, but there have been few studies on the effectiveness of ITNs and LLINs in areas where vector mosquitoes are pyrethroid-resistant.

Methods: To investigate the behavioral pattern of mosquitoes in the houses where LLINs were used, indoor mosquito trappings of Anopheles gambiae s.s., An. arabiensis, and An. funestus s.s. were performed with Centers for Disease Control and Prevention (CDC) miniature light trap equipped with a collection bottle rotator at 2-hour intervals between 4:00 pm and 8:00 am. The trapped female mosquitoes were identified and classified as unfed, blood fed, and gravid. The abdominal contents of fed female mosquitoes were used for DNA extractions to identify the blood source.

Results: A large proportion of human blood feeding of An. arabiensis and An. funestus s.s. (but not An. gambiae s.s.) took place during the time people were active outside LLINs. However, during the hours when people were beneath LLINs, these provided protective efficacy as indicated by reduced human blood feeding rates.

Conclusion: LLINs provided effective protection against pyrethroid-resistant malaria vector populations during bedtime hours. However, protection of LLINs was insufficient during the hours when people were active outside of the bed nets. Such limitation of LLINs will need to be intensively addressed in African countries in the near future.

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Related in: MedlinePlus

Photo of the CDC miniature light trap (model 512) equipped with a collection bottle rotator (model 1512) for all-night mosquito collection at 2-hour intervals (4:00 pmto 8:00 am). The trap was hung from the eaves with string and placed at a height of approximately 1.2 m in a corner of the living room away from the place where people slept.
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Fig1: Photo of the CDC miniature light trap (model 512) equipped with a collection bottle rotator (model 1512) for all-night mosquito collection at 2-hour intervals (4:00 pmto 8:00 am). The trap was hung from the eaves with string and placed at a height of approximately 1.2 m in a corner of the living room away from the place where people slept.

Mentions: To investigate the behavioral pattern of mosquitoes, indoor mosquito trapping of An. gambiae s.s., An. arabiensis and An. funestus s.s. was performed with 6 sets of the CDC miniature light trap (model 512) equipped with a collection bottle rotator (model 1512) (John W. Hock Co., FL, USA) (Figure 1). Indoor trapping of An. gambiae s.s. was performed in 6 houses on Mfangano Island from May 16 to June 1, 2011. Indoor trapping of An. arabiensis and An. funestus s.s. was conducted in 6 houses in Nyaroya Village from October 4 to 31, 2011, and July 11 to 18, 2012, and in 6 houses in Ungoe Village from February 21 to March 6, 2012 (Figure 2). The residents of the houses were informed about the study, and their written consent was obtained before mosquito collection. The houses used for indoor mosquito collection were of standard construction for the area; they had mud walls and eaves, traditional opening structures between the roof and the walls, and had 1–2 bedrooms and a living room. Before the start of the study, each house was inspected and untreated bed nets and LLINs were exchanged for new permethrin-incorporated LLINs (Olyset® Nets; Sumitomo Chemical Co., Ltd., Tokyo, Japan). Additional new Olyset® Nets were provided for use in the living room when the residents (most were children >5 years) slept in the living room with no bed nets. Tables 1 and2 show the number of Olyset® Nets, the number of persons who slept in the bedroom(s) and living room, and the approximate number of livestock for each house.Figure 1


Preventive effect of permethrin-impregnated long-lasting insecticidal nets on the blood feeding of three major pyrethroid-resistant malaria vectors in western Kenya.

Kawada H, Ohashi K, Dida GO, Sonye G, Njenga SM, Mwandawiro C, Minakawa N - Parasit Vectors (2014)

Photo of the CDC miniature light trap (model 512) equipped with a collection bottle rotator (model 1512) for all-night mosquito collection at 2-hour intervals (4:00 pmto 8:00 am). The trap was hung from the eaves with string and placed at a height of approximately 1.2 m in a corner of the living room away from the place where people slept.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4150967&req=5

Fig1: Photo of the CDC miniature light trap (model 512) equipped with a collection bottle rotator (model 1512) for all-night mosquito collection at 2-hour intervals (4:00 pmto 8:00 am). The trap was hung from the eaves with string and placed at a height of approximately 1.2 m in a corner of the living room away from the place where people slept.
Mentions: To investigate the behavioral pattern of mosquitoes, indoor mosquito trapping of An. gambiae s.s., An. arabiensis and An. funestus s.s. was performed with 6 sets of the CDC miniature light trap (model 512) equipped with a collection bottle rotator (model 1512) (John W. Hock Co., FL, USA) (Figure 1). Indoor trapping of An. gambiae s.s. was performed in 6 houses on Mfangano Island from May 16 to June 1, 2011. Indoor trapping of An. arabiensis and An. funestus s.s. was conducted in 6 houses in Nyaroya Village from October 4 to 31, 2011, and July 11 to 18, 2012, and in 6 houses in Ungoe Village from February 21 to March 6, 2012 (Figure 2). The residents of the houses were informed about the study, and their written consent was obtained before mosquito collection. The houses used for indoor mosquito collection were of standard construction for the area; they had mud walls and eaves, traditional opening structures between the roof and the walls, and had 1–2 bedrooms and a living room. Before the start of the study, each house was inspected and untreated bed nets and LLINs were exchanged for new permethrin-incorporated LLINs (Olyset® Nets; Sumitomo Chemical Co., Ltd., Tokyo, Japan). Additional new Olyset® Nets were provided for use in the living room when the residents (most were children >5 years) slept in the living room with no bed nets. Tables 1 and2 show the number of Olyset® Nets, the number of persons who slept in the bedroom(s) and living room, and the approximate number of livestock for each house.Figure 1

Bottom Line: ITNs and LLINs are still used as effective self-protection measures, but there have been few studies on the effectiveness of ITNs and LLINs in areas where vector mosquitoes are pyrethroid-resistant.However, during the hours when people were beneath LLINs, these provided protective efficacy as indicated by reduced human blood feeding rates.Such limitation of LLINs will need to be intensively addressed in African countries in the near future.

View Article: PubMed Central - PubMed

Affiliation: Department of Vector Ecology & Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan. vergiss@nagasaki-u.ac.jp.

ABSTRACT

Background: Since the World Health Organization (WHO) adopted the use of long-lasting insecticidal nets (LLINs) as a principal strategy for effective malaria prevention and control, pyrethroids have been the only class of insecticides used for LLINs. The dramatic success of insecticide-treated nets (ITNs) and LLINs in African countries, however, has been threatened by the rapid development of pyrethroid resistance in vector mosquitoes. ITNs and LLINs are still used as effective self-protection measures, but there have been few studies on the effectiveness of ITNs and LLINs in areas where vector mosquitoes are pyrethroid-resistant.

Methods: To investigate the behavioral pattern of mosquitoes in the houses where LLINs were used, indoor mosquito trappings of Anopheles gambiae s.s., An. arabiensis, and An. funestus s.s. were performed with Centers for Disease Control and Prevention (CDC) miniature light trap equipped with a collection bottle rotator at 2-hour intervals between 4:00 pm and 8:00 am. The trapped female mosquitoes were identified and classified as unfed, blood fed, and gravid. The abdominal contents of fed female mosquitoes were used for DNA extractions to identify the blood source.

Results: A large proportion of human blood feeding of An. arabiensis and An. funestus s.s. (but not An. gambiae s.s.) took place during the time people were active outside LLINs. However, during the hours when people were beneath LLINs, these provided protective efficacy as indicated by reduced human blood feeding rates.

Conclusion: LLINs provided effective protection against pyrethroid-resistant malaria vector populations during bedtime hours. However, protection of LLINs was insufficient during the hours when people were active outside of the bed nets. Such limitation of LLINs will need to be intensively addressed in African countries in the near future.

Show MeSH
Related in: MedlinePlus