You can cause harm by deworming a horse when they don't need it because we can actually cause resistance against the medications that we use to deworm horses in those parasites that do exist in the environment.
Professor James Logan from the London School of Hygiene and Tropical Medicine explains that DEET, the chemical used in many repellents, confuses the insects' sense of smell, making it difficult to recognise humans.
The best way to prevent infections is using insect repellant with DEET, wearing thick long sleeve shirts and long pants and staying inside, in screened, air-conditioned areas as much as possible.
The most effective and easiest measure you can take are simply using the right insect repellent and wearing long sleeve shirts and pants, especially during dusk and dawn, when mosquitoes are most active.
" So these odors, which, before, would strongly activate the olfactory system, essentially now didn't do anything." Meaning repellents like DEET actually act like an invisibility cloak against mosquitoes.
The fishing expedition will go forward tomorrow as planned, and for those of you who have not brought suitable rain gear and insect repellent, these are available for a nominal charge at the Registration Desk.
Many of the plant molecules that humans have adopted as drugs, medicines, and seasonings evolved as part of plants' immune systems because they're antimicrobial or insecticidal.