Adorable animal families that will make you aww. A parasitologist is a scientist that studies parasites, and the relationship between the parasites and their hosts. While parasites can be found in any form of animal or plant life, parasitology is usually confined to the study of protozoan and metazoan parasites.onsidered a major pest to pets such as dogs, fleas bite and suck the blood of humans and animals. Parasites can spread diseases among crops. A parasitic infection may cause skin changes, such as a rash. Some parasitologists work with livestock in rural communities.