Wageningen researchers lured malaria mosquitoes with Limburger cheese

Malaria-vector surveillance and control in sub-Saharan Africa depends on trapping Anopheles gambiae mosquitoes, the species primarily responsible for transmitting the disease, and the traps work best when baited with something that mimics what actually draws the mosquitoes to bite humans in the first place: human body odor, particularly the smell of human feet and the bacteria that produce it.

The obvious source for that lure is human odor itself — sweat, skin bacteria byproducts, worn clothing — but producing or standardizing that signal for traps deployed by the thousand across a large region is expensive and impractical; a lure requiring a live human volunteer, or synthesized replication of dozens of specific odor compounds, doesn't scale to the level a real vector-control or surveillance program needs.

Entomologists Bart Knols and Ruurd de Jong at Wageningen Agricultural University tested whether Limburger cheese, whose bacterial ripening process produces isovaleric acid and other compounds chemically similar to those responsible for human foot odor, could substitute for human odor as a mosquito attractant.

Substituted Limburger cheese, whose ripening bacteria emit the same fatty acids as human feet, attracting Anopheles gambiae as well as real odor at far lower cost.

Anopheles gambiae mosquitoes are attracted to specific fatty acids in human foot odor, not to humans per se.

Limburger cheese's ripening bacteria produce isovaleric acid and similar compounds, matching the mosquito's chemical trigger.

Cheese is mass-produced, shelf-stable, and cheap, making it scalable for thousands of traps.

The chemical similarity triggers the same host-seeking behavior, so the substitute works without human volunteers.

When a needed signal is costly or perishable, find a mass-produced analog that shares the specific chemical trigger.

The finding, published in The Lancet and Parasitology Today in 1996, earned Knols and de Jong the 2006 Ig Nobel Prize in Biology and became a foundational reference point for subsequent odor-bait trap research.