I wrote before about some of the newer mosquito trap-and-kill technology–the main brand in the US is called Mosquito Magnet. It attracts biting insects with a combination of CO2 and other odors that mimic human smells.
A new paper out in Malaria Journal compares a couple of brands of these trap-and-kill traps for use in the field to monitor malarial mosquitoes:
“Both types of traps successfully captured mosquitoes with all odour cues used. When the BGS trap was tested against the MM-X trap in a choice assay with foot odour as bait, the BGS trap caught about three times as many mosquitoes as the MM-X trap (P=0.002). Adding CO2 (500ml/min) to foot odour increased the number of mosquitoes caught by 268% for the MM-X (P<0.001) and 34% (P=0.051) for the BGS trap, compared to foot odour alone.
Yes. You read that right. Your stinky feet can attract mosquitoes.
So why were they doing this? Right now, for Anopheles gambiae, a mosquito species that transmits malaria, there is no combination of trapping device and bait available that compares to human landing catch (HLC) as a standard method for population surveillance. If you are trying to assess malarial mosquitoes, that’s a huge risk to put your employees through–they may become infected with malaria as a part of the research!
These traps do a good job of attracting mosquitoes in the US, and CO2 is commonly used as the bait. In rural areas in Africa it’s not practical to burn fuel to produce CO2 (and expensive!). The authors wanted to see if alternative baits would be helpful, and which of the two traps performed better under field conditions.
I love this part from the methods:
“Foot odour was collected on nylon socks, worn for 12 hours by WHS prior to each
experiment (07.00 to 19.00). For each experimental night, a recently-worn sock was
used; a clean sock served as the control.”
Ha! This is actually based on some lab research that found that foot odor is attractive to mosquitoes:
Qiu YT, Smallegange RC, Smid H, Van Loon JJA, Galimard AMS, Posthumus MA, Van Beek TA, Takken W: GC-EAG analysis of human odours that attract the malaria mosquito Anopheles gambiae sensu stricto. Proc Exp Appl Entomol, NEV; Groningen. 2004: 59-64.
So, these earlier smelly feet results are now validated with a field study! Even better, the Authors of the field study did find that smelly socks worked well in the field, and may now have a way to catch and monitor malarial mosquitoes that doesn’t involve risk of infection.