A parasite can live on or inside an animal and causes harm. Parasites usually enter the body through the mouth or breaks in the skin.
Swallowed parasites may stay in the intestines or burrow through the intestinal wall and travel to other body organs.
Parasites that enter through the skin may drill directly through the skin or be injected into the skin or blood by insect bites.
Some parasites enter through skin or paws when animals are in contaminated water.
Diagnosing parasitic infections often requires lab tests on blood, feces, or urine. Some parasites can be seen directly on the skin or in droppings, but others require multiple microscopic exams to identify them. In some cases, a biopsy of skin, muscle, or other body organ is needed.
Many parasites reproduce inside the animal host. Others have complex life cycles that include laying eggs or producing young that live in the environment or in insects before becoming infectious to the animal. If egg‑laying parasites live in a pet's intestines, their eggs might be seen in fecal samples under a microscope.
