When they enter through skin they can be seen under skin as pink channels under skin. So no need for poo test, which at this stage, and for many weeks, won't show anything.
Dog's poo, or any other infected animal's, can be on the beach. People not only walk barefoot, but seat and lay down directly on sand.
have to be treated asap.
Even as prevention after holiday in tropics. There are many parasites, including those in food, fruits, salads, sushi, uncooked seafod. They are asymptomatic or symptoms can be after months and years, and more difficult to get rid off