Any living organism that survives on, in, or among other living things (hosts), while relying on that host for shelter and sustenance, is known as a parasite. There are particular parasites that rely on a host during their whole life, while some parasites only rely on a host for a specific part of their life. The most common parasites that infect horses, dogs, cats, and other animals, are worms. Humans can also become infected by some of these worms. The section below discusses parasitic worms which affect the skin of pets.
Dracunculus insignis refers to a type of roundworm frequently found in the connective tissue underneath the skin of the legs. In North America, they tend to infect minks, raccoons, and other animals such as dogs. The male of the species are small, about 0.6 inches (20 millimetres) long. On the other hand, the female worm can get to a length of 10 feet (3 mqweters). These worms are able to cause ulcers on the skin of their hosts. Any time the ulcers come into contact with water, the worms put their heads out of the wounds so that they can lay elongated, thin-tailed larvae. Another host is then found for the development of the larvae, such as the water flea. Dogs may then get infected if they consume polluted water or ingest another host, like a frog.
Symptoms that indicate infestation by D. insignis worms include red, crater-like ulcers on the surface of the skin and enlarged, snake-like tracks under the skin. Though such infections are unusual, there are cases where dogs get infected because of wading into small lakes and stagnant, shallow water.
The infection can be treated by cautiously and gradually removing the parasites. Miridazole or benzimidazoles are classes of anti-parasitic drugs that may also be helpful.
A recognised parasite that affects humans as well as dogs and other animals is guinea worm (Dracunculus medinensis). It is commonly found in parts of Africa, the Middle East, and Asia.
Pelodera dermatitis is an uncommon, short-term skin condition caused by a skin worm. The infection is caused when roundworm larvae, called Pelodera strongyloides, attack the skin. Pelodera strongyloides are prevalent in rotting raw material (like moist hay) and on the surface of damp soil. They are not usually parasitic in nature. Majority of animals come into contact with the larvae via direct contact with infected materials such as wet, dirty bedding. It is not common to find animals with healthy skin being infected.
It is only the body parts that touch the infested material, for example the abdomen, legs, chest, and groin, which usually develop sores. The parts of the skin that get affected are usually totally hairless and reddish in colour. Other signs may include lumps filled with pus, bumps in the skin, ulcers, or crusts. Though not frequent, there could also be severe itching, forcing the animal to rub, scratch, or bite the infected part. Veterinarians are able to come up with a definitive diagnosis by analysing a skin scraping under a microscope, to confirm the presence of worm larvae. Treatment for affected animals is similar to those of other skin worm infestations. In certain instances, recovery may be as simple as transferring the animal to a dry spot with sanitary bedding.