Parasites of the Dog – Core Vocabulary

Key vocabulary covering terminology, major canine parasites, diagnostic methods, and related concepts.

Parasite

An organism that lives on or within a host and benefits at the host’s expense.

Host

The organism that provides nourishment or shelter to a parasite.

Definitive Host

The host in which a parasite reaches sexual maturity and reproduces.

Intermediate Host

A host that harbors immature or asexual stages of a parasite’s life cycle.

Life Cycle (Parasitology)

The sequence of developmental stages a parasite undergoes in the environment and/or hosts.

Endoparasite

A parasite that lives inside its host, producing an infection.

Ectoparasite

A parasite that lives on the surface of its host, producing an infestation.

Helminths

Worm-like parasites including trematodes, cestodes, and nematodes.

Protozoans

Single-celled parasites such as flagellates, amoebae, and apicomplexans.

Arthropod Parasites

Ectoparasites like fleas, ticks, mosquitoes, and lice.

Fecal Flotation

Diagnostic technique that separates parasite eggs/oocysts from feces using solutions of higher specific gravity.

Centrifugal Flotation

A fecal flotation method that uses centrifugation to increase sensitivity.

Sheather’s Sugar Solution

Flotation solution (SG 1.27) ideal for detecting most coccidian oocysts.

Zinc Sulfate Solution

Flotation solution (SG 1.18) commonly used for Giardia cysts and nematode eggs.

Toxocara canis

Canine roundworm (ascarid) inhabiting the small intestine; zoonotic and especially harmful to puppies.

Toxocara Egg

Thick-shelled, 75–90 µm; passed unlarvated and becomes infective after environmental larvation.

Paratenic Host

A transport host in which a parasite survives without further development until eaten by the definitive host.

Ancylostoma caninum

Canine hookworm with three pairs of teeth; causes anemia, bloody diarrhea, and is zoonotic.

Larval Leak

Repopulation of the intestine by hypobiotic Ancylostoma larvae despite prior treatment.

Dirofilaria immitis

Heartworm of dogs residing in the pulmonary artery and right ventricle; transmitted by mosquitoes.

Microfilariae

First-stage larvae of D. immitis circulating in the host’s bloodstream.

Occult Heartworm Infection

Heartworm infection with antigen-positive dogs lacking circulating microfilariae.

Wolbachia pipientis

Endosymbiotic bacteria in D. immitis that exacerbate inflammation; targeted during heartworm therapy.

Cystoisospora spp.

Canine coccidia infecting intestinal epithelial cells; causes diarrhea mainly in young dogs.

Sporulated Oocyst

Environmentally developed, infective stage of Cystoisospora ingested via the fecal-oral route.

Rhipicephalus sanguineus

Brown dog tick; a three-host tick feeding on dogs at every stage and vectoring pathogens like Ehrlichia canis.

Tick Paralysis

Flaccid paralysis caused by neurotoxins in the saliva of some feeding ticks.

Zoonosis

A disease or infection naturally transmissible from vertebrate animals to humans.