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Evidence of an 'invitation' effect in feeding sylvatic Stegomyia albopicta from Cambodia.

Charlwood JD, Tomás EV, Kelly-Hope L, Briët OJ - Parasit Vectors (2014)

Bottom Line: Orientation of haematophagous insects towards a potential host is largely mediated by kairomones that, in some groups or species may include chemicals produced during feeding by the insects themselves, the so called 'invitation' effect.This preference did not vary with collector or pyrethroid.The 'invitation' effect may be due to a semio-chemical produced early in the feeding process.

View Article: PubMed Central - HTML - PubMed

Affiliation: Vector Group, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK. jdcharlwood@gmail.com.

ABSTRACT

Background: Orientation of haematophagous insects towards a potential host is largely mediated by kairomones that, in some groups or species may include chemicals produced during feeding by the insects themselves, the so called 'invitation' effect.

Methods: The 'invitation' effect in blood-feeding diurnally active Stegomyia albopicta was investigated over 33 days in secondary forest in Mondolkiri Province, Cambodia. Two human volunteers sitting inside a shelter collected mosquitoes and noted where and when they landed. A 10% emanator of a synthetic pyrethroid with high vapour action was in use on alternate days.

Results: Overall, 2726 mosquitoes were collected, 1654 of which had the landing site recorded. The heads of the volunteers were the locations with the highest density of landings per surface area whilst the knees and elbows accounted for most of the landings received on the arms and legs. Landings recorded within three minutes of each other on a collector were about 2.5 times more likely to be on the same body part than on a random body part, weighted for landing site preference. This preference did not vary with collector or pyrethroid.

Conclusions: The 'invitation' effect may be due to a semio-chemical produced early in the feeding process. Incorporation of such a chemical into traps designed to control this important vector of dengue and chikungunya viruses might potentially improve their attractiveness.

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Average landing density (dm-2) on body regions.
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Figure 5: Average landing density (dm-2) on body regions.

Mentions: The estimated body surface area of the collectors was similar (1.78 m2 and 1.82 m2 for EVET and JDC, respectively). For each dm2 of body surface, over the 191.5 hours of collecting per person, EVET recorded 5.92 landings compared to 4.70 landings recorded by JDC. Thus, overall more mosquitoes were collected landing on EVET than on JDC (rate ratio =1.26, 95% CI: 1.15 – 1.39, Poisson-test p < 0.001). Stratified by collection period, the difference was significant in the first 16 days of collection when the collectors alternated between sides (rate ratio =1.73, 95% CI: 1.49 – 2.00, Poisson-test p < 0.001) but was not significant during the last 16 days when they did not (when JDC sat slightly closer to the widest part of the opening over which the mosquitoes presumably entered the shelter) (rate ratio =1.00, 95% CI: 0.89 – 1.13, Poisson-test p > 0.05). A total of 1654 St. albopicta were collected with the body part they landed on recorded, while for 252 other St. albopicta collected at the start of the study, the landing site on the body was not recorded (Table 1). These were excluded from subsequent analyses. Also, the 948 engorged mosquitoes collected from the walls were excluded. The distribution of the mosquitoes landing on the body regions were significantly different for both collectors (Pearson's Chi-squared test, p < 0.01, df = 7) with relatively more mosquitoes landing on JDC’s anterior trunk and relatively more mosquitoes landing on EVET’s hands (Table 2).Relative to surface area, most mosquitoes showed a preference for landing on the head (Figure 5). Since the estimation of surface area of the head included the scalp (which accounts for about half of the surface and, with the exception of JDC’s bald patch, was covered by hair preventing mosquitoes from landing) the preference for landing on the head was probably even greater. The cheeks (73 landings) and forehead (52 landings) accounted for 23% and 20%, respectively of the landings recorded on the head and neck, the remainder being on the neck (51 landings; 20%), ear (31 landings; 12%), nose (18 landings; 7%), chin, eye and eyebrow (10, 2 and 16 landings respectively). The knees accounted for most (37%) of the landings on the legs (excluding feet and ankles), and the elbows accounted for most (40%) of the landings on the arms.


Evidence of an 'invitation' effect in feeding sylvatic Stegomyia albopicta from Cambodia.

Charlwood JD, Tomás EV, Kelly-Hope L, Briët OJ - Parasit Vectors (2014)

Average landing density (dm-2) on body regions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230241&req=5

Figure 5: Average landing density (dm-2) on body regions.
Mentions: The estimated body surface area of the collectors was similar (1.78 m2 and 1.82 m2 for EVET and JDC, respectively). For each dm2 of body surface, over the 191.5 hours of collecting per person, EVET recorded 5.92 landings compared to 4.70 landings recorded by JDC. Thus, overall more mosquitoes were collected landing on EVET than on JDC (rate ratio =1.26, 95% CI: 1.15 – 1.39, Poisson-test p < 0.001). Stratified by collection period, the difference was significant in the first 16 days of collection when the collectors alternated between sides (rate ratio =1.73, 95% CI: 1.49 – 2.00, Poisson-test p < 0.001) but was not significant during the last 16 days when they did not (when JDC sat slightly closer to the widest part of the opening over which the mosquitoes presumably entered the shelter) (rate ratio =1.00, 95% CI: 0.89 – 1.13, Poisson-test p > 0.05). A total of 1654 St. albopicta were collected with the body part they landed on recorded, while for 252 other St. albopicta collected at the start of the study, the landing site on the body was not recorded (Table 1). These were excluded from subsequent analyses. Also, the 948 engorged mosquitoes collected from the walls were excluded. The distribution of the mosquitoes landing on the body regions were significantly different for both collectors (Pearson's Chi-squared test, p < 0.01, df = 7) with relatively more mosquitoes landing on JDC’s anterior trunk and relatively more mosquitoes landing on EVET’s hands (Table 2).Relative to surface area, most mosquitoes showed a preference for landing on the head (Figure 5). Since the estimation of surface area of the head included the scalp (which accounts for about half of the surface and, with the exception of JDC’s bald patch, was covered by hair preventing mosquitoes from landing) the preference for landing on the head was probably even greater. The cheeks (73 landings) and forehead (52 landings) accounted for 23% and 20%, respectively of the landings recorded on the head and neck, the remainder being on the neck (51 landings; 20%), ear (31 landings; 12%), nose (18 landings; 7%), chin, eye and eyebrow (10, 2 and 16 landings respectively). The knees accounted for most (37%) of the landings on the legs (excluding feet and ankles), and the elbows accounted for most (40%) of the landings on the arms.

Bottom Line: Orientation of haematophagous insects towards a potential host is largely mediated by kairomones that, in some groups or species may include chemicals produced during feeding by the insects themselves, the so called 'invitation' effect.This preference did not vary with collector or pyrethroid.The 'invitation' effect may be due to a semio-chemical produced early in the feeding process.

View Article: PubMed Central - HTML - PubMed

Affiliation: Vector Group, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK. jdcharlwood@gmail.com.

ABSTRACT

Background: Orientation of haematophagous insects towards a potential host is largely mediated by kairomones that, in some groups or species may include chemicals produced during feeding by the insects themselves, the so called 'invitation' effect.

Methods: The 'invitation' effect in blood-feeding diurnally active Stegomyia albopicta was investigated over 33 days in secondary forest in Mondolkiri Province, Cambodia. Two human volunteers sitting inside a shelter collected mosquitoes and noted where and when they landed. A 10% emanator of a synthetic pyrethroid with high vapour action was in use on alternate days.

Results: Overall, 2726 mosquitoes were collected, 1654 of which had the landing site recorded. The heads of the volunteers were the locations with the highest density of landings per surface area whilst the knees and elbows accounted for most of the landings received on the arms and legs. Landings recorded within three minutes of each other on a collector were about 2.5 times more likely to be on the same body part than on a random body part, weighted for landing site preference. This preference did not vary with collector or pyrethroid.

Conclusions: The 'invitation' effect may be due to a semio-chemical produced early in the feeding process. Incorporation of such a chemical into traps designed to control this important vector of dengue and chikungunya viruses might potentially improve their attractiveness.

Show MeSH
Related in: MedlinePlus