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Disease Information






A parasite is a living organism which lives in another living organism, known as the host. The parasite gains an advantage from the host, usually without providing any compensation to the host.

Endoparasites live within a host and must obtain nutrients from that animal in order to survive and reproduce. The host's ability to thrive, or even survive, is often decreased as a result of the parasite's presence. Many parasites are specific to a species of animal. For example, Trichuris vulpis, the whipworm, infects only dogs and foxes, whereas another species of the same genus, Trichuris ovis, infects sheep. Other parasites, such as Ancylostoma braziliense, a hookworm, may infect several species, including dog, cat and fox. Each species of parasite has a predilection for a specific location within the host animal. The common names of many worms reflect the location of the adult parasites. Two examples are the bladder worm (Capillaria plica) and the heartworm (Dirofilaria immitis).

Parasites that feed or live on the body surface of a host animal are called ectoparasites. Most of them are arthropods, that is, invertebrates with jointed legs and hard external skeletons. Arthropod ectoparasites fall into two classes, arachnids and insects.

Ectoparasite infectation affects the health of the host animal in several ways. Dogs may be so preoccupied with the itching and irritation caused by ectoparasites that feeding is irregular and, consequently, the host dog may lose weight or grow slowly. Such "parasite worry" is a problem in almost all infestations. Animals may become emaciated and susceptible to various other sicknesses, such as bacterial and viral diseases. Heavy infestations can cause serious blood loss. Perhaps the most serious aspect of ectoparasite infestation is the ability of some ectoparasites (particularly ticks) to transmit other serious diseases, including canine thrombocytopenia, canine babesiosis and Rocky Mountain spotted fever.

Various canine parasites are found worldwide. The incidence of parasites in dogs and their importance are greatly influenced by geographic location, season of the year and climatic conditions.

The effects of both endo and ectoparasites acting together on dogs are greater than the damage caused by either type of parasite by itself. For example, a dog that is heavily infested with lice will be more severely affected by a sudden build-up in roundworm parasites than would an animal that is free of ectoparasites.

Because of the compound effect of two or more classes of parasites, the use of a broad-spectrum parasiticide will provide more effective treatment than the use of a product that kills only one group of parasites.

Roundworms, hookworms, and heartworms are important internal parasites of dogs. These parasites are widespread and can cause death in heavily infected puppies.

Most parasites have complex life cycle coordinated with climatic conditions. The seasonal incidence of each parasite species varies in different regions. This seasonal incidence of parasites is a very important factor to consider when planning a total parasite control program.

Parasite Groups