Human scent guides mosquito thermotaxis and host selection under naturalistic conditions.

The African malaria mosquito Anopheles gambiae exhibits a strong innate drive to seek out humans in its sensory environment, classically entering homes to land on human skin in the hours flanking midnight. To gain insight into the role that olfactory cues emanating from the human body play in generating this epidemiologically important behavior, we developed a large-scale multi-choice preference assay in Zambia with infrared motion vision under semi-field conditions. We determined that An. gambiae prefers to land on arrayed visual targets warmed to human skin temperature during the nighttime when they are baited with carbon dioxide (CO2) emissions reflective of a large human over background air, body odor from one human over CO2, and the scent of one sleeping human over another. Applying integrative whole body volatilomics to multiple humans tested simultaneously in competition in a six-choice assay, we reveal high attractiveness is associated with whole body odor profiles from humans with increased relative abundances of the volatile carboxylic acids butyric acid, isobutryic acid, and isovaleric acid, and the skin microbe-generated methyl ketone acetoin. Conversely, those least preferred had whole body odor that was depleted of carboxylic acids among other compounds and enriched with the monoterpenoid eucalyptol. Across expansive spatial scales, heated targets without CO2 or whole body odor were minimally or not attractive at all to An. gambiae. These results indicate that human scent acts critically to guide thermotaxis and host selection by this prolific malaria vector as it navigates towards humans, yielding intrinsic heterogeneity in human biting risk.

Unna boot central gauze technique for chronic venous leg ulcers.

BACKGROUND: Venous leg ulcers generally take manyweeks to heal. Novel therapies that shorten healingtime and require less complex care are needed. PURPOSE: The purpose of this report is to presenta pilot study for a new method that can result ina faster healing time for venous leg ulcers usinginexpensive materials. METHODS: A central-gauzeprotocol was developed as described here. A three-ply gauze sponge was placed in the center of theulcer, allowing a peripheral 3-5 mm rim of ulcer toremain exposed. Saline solution was applied to thegauze sponge. A 3-layer Unna boot was applied overthe ulcer with short-stretch compression. This noveltechnique exposed only a peripheral rim of the ulcerto the zinc oxide paste, allowing the central portionof the ulcer to drain through the saline-soaked gauze.The ulcer was photographed at each clinic visit andthe wound area was estimated by finding the bestfitellipse for the ulcer area and computing the areaof the ellipse by a standard formula. RESULTS: Threepatients with small venous leg ulcers treated with thezinc rim technique showed an average healing rate of46.1% per week (range 27.8% - 50.7%). All ulcers werenearly healed by three weeks. After the ulcer size wasreduced sufficiently, patients were discharged withinstructions to apply pieces of Unna dressing to theulcer, under a conventional self-adhesive bandage,maintaining compression, without any saline-gauzein the center. CONCLUSIONS: The three patients in thispilot study showed rapid healing for venous leg ulcerswith the central gauze modification of Unna boottherapy.