Repellent Research Focusing on Mosquito Blood-sucking Behavior

Hippopotamus Secretion (red sweat) Has the Same Properties

An example in nature, the red sweat of a hippopotamus has also been shown to be effective in suppressing mosquito accretion.

Mosquito repellent by the red sweat of the hippopotamus

As we proceeded with our research, we thought that there might be examples in the natural world that use the wetting phenomenon to repel mosquitoes. There are several animals known to produce sweat and secretions, but among them, the “red sweat” that the hippopotamus secretes on their skin has ultraviolet protection (sunscreen) effects, as well as a moisturizing effect, and we speculated that it might also protect against mosquito bites.

Therefore, we obtained hippopotamus secretions from Adventure World in Wakayama Prefecture and conducted an experiment to determine if mosquitoes on this substrate and on silicone oil, which has similar physical characteristics to this secretion, have a comparative reaction. As a result, it was determined that both liquids suppress mosquito accretion (Fig. Y).

Video: Adventure World hippo secretion collection and mosquito accretion experiment

Figure: Leg contact time with the substrate coated with hippo secretion (from Kao news release)

(reference: modified from Iikura et al., Sci Rep 10, 14480 [2020])

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