Dry parasites
Fleas do not live in the desert per se. They live on animals as parasites and many times those animals are in the desert.
There are a number of parasites found in the desert, including fleas, ticks, mites, lice and mosquitos.
In the Sahara desert you would only find animals at an oasis.
Of couse, animals can grow in the desert. They would not be able to survive and reproduce if they did not grow.
Animals that need water
Animals in the desert would dig holes in the ground or find a little cave and call it home
All animals potentially carry parasites.
Roundworms can also be parasites to humans.
The animals in the desert are better than the animals in the desert because the desert animals can survive like years without water. The animals in the rainforest get water like everyday so the animals in the rainforest would die if they went like a day without water.
Fleas, ticks and lice are parasites that are found in the desert.
There are a few desert animals in the Americas that would even be capable of eating a human and attacks by these are rare - wolves, jaguars, cougars.
Dogs are not parasites because parasites suck the blood of other animals. Dogs are hosts to various parasites, such as ticks and fleas.