It turns out that donkeys are exceptionally good at repelling deer ticks. Now, researchers at the University of Massachusetts Amherst (UMA) have harnessed that ability to create a natural bug repellent that proved as effective as DEET at fighting the pests.
While they’re most famous for spreading the debilitating and painful Lyme Disease, deer ticks also spread several other bacterial and parasitic infections including anaplasmosis and babesiosis.
The repellents DEET and permethrin are effective at repelling the pests, but they are fairly heavy-duty chemicals that can cause skin irritation and other side effects, although they are generally considered safe to use. Natural tick repellents such as oil of lemon eucalyptus do exist, but they are not usually as effective as DEET in keeping ticks away and tend not to last as long.
Enter the donkey.
The sebaceous glands of donkeys secrete a compound known as (E)-2-octenal from their skin. A small field study last year showed that volunteers wearing a slow-release device that emitted the compound as they walked through a tick-infested area in Brazil had significantly fewer of the bugs attach themselves to leg guards. Another study has shown that in tick-rich areas where there are horses and donkeys present, the ticks will attach to the horses but not the donkeys.
Seeking to further investigate donkeys’ tick-repelling superpower, the UMA researchers applied a 20% solution of octenal to a filter paper and then let the ticks crawl across it for 10 minutes. They also tested the ticks’ movements using a 20% solution of DEET and a control paper with ethanol. The movement of the ticks was observed using tracking software.
Once again, the research showed that the octenal was in all cases at least as effective as DEET in repelling the ticks and in the case of male ticks, it was actually more effective than DEET. They also observed that the octenal was able to repel ticks at a further distance than the DEET.
The researchers say that more work is warranted into finding out exactly how the compound fights off the pests so that an effective green repellent can be developed that doesn’t rely on harsh chemicals. The team also says that in addition to being applied to human skin, such a compound could also be leveraged as a natural pesticide to control deer ticks in the wild.
The findings have been reported in the journal PLOS One.