Parasites come in many sizes, shapes, and levels of “severity” for our pets. This collection of parasites are those commonly found on dogs and other species, sometimes affecting humans (called a zoonotic disease).
drawing of a flea
 Drawing of a flea in Micrographia. By Robert Hooke (1635-1703) [Public domain], via Wikimedia Commons

Fleas. They make pets’ lives miserable, and humans begin to itch just at the thought of them. Vets are often asked what pill, drop, dip, collar, or shampoo works the best to get rid of these persistent parasites. The answer is that there is no single method or insecticide that will completely eradicate (or at least control) a flea problem. The flea life cycle is fairly complex, and understanding the various stages will make it easier to get rid of them.

Mosquito female
By Mosquito gender en.svg: LadyofHatsderivative work: Anka Friedrich [Public domain], via Wikimedia Commons

Heartworm disease is caused by a parasite that lives mainly in the blood vessels of the lung and in the heart, transmitted by mosquitoes. Heartworm disease has been seen in several species, but dogs are very susceptible. It can be fatal and is difficult to treat, but fortunately heartworm disease is easy to prevent.

Examining a dog's ears
Isa Foltin / Contributor / Getty Images

Ear mites are tiny parasites that live out their life cycle mostly inside the ear canal. They are quite common and can cause severe irritation and itchiness of the ears.

The most common ear mite of cats and dogs is Otodectes cynotis, and therefore an infestation with ear mites is sometimes called “otodectic mange.”

A dog with severe demodectic mange
 A dog with severe demodectic mange. By Julie Knicely – Submitted to OTRS, CC BY 1.0, Link
Demodex mites are microscopic normal inhabitants of dog skin. In a healthy animal, the mites are few in number and do not cause skin problems. In some cases, though, the mites can take over, leading to a condition commonly called “mange” or ​demodicosis. Learn about the types of mange and various treatment options for this skin parasite.
Cheyletiella Mites
Raubmilbe, Cheyletiella
By Kalumet – German Wikipedia, CC BY-SA 3.0, Link

Cheyletiella are mites that live on the skin, causing irritation, dandruff, and itchiness. A distinguishing feature of this mite species are the large, claw-like mouth parts. These mites can be found quite commonly on cats, dogs and rabbits, and other species. Though humans are not a natural host for this parasite, Cheyletiella mites can happily live on humans for a while, causing an itchy rash.

Deer tick, Ixodes dammini, carrier of Lyme disease
 Deer tick, Ixodes dammini, carrier of Lyme disease. Stegerphoto / Getty Images

Babesia infections occur in dogs and other species and are transmitted mainly by ticks. Babesia are protozoal parasites that attack blood cells, though the severity of illness varies considerably depending on the species of Babesia involved, as well as the immune response of the infected dog.

Deer tick, Ixodes scapularis, on a fingernail
 Deer tick, Ixodes scapularis, on a fingernail. Lauree Feldman / Getty Images

There are many ideas about the best way to remove a tick, one of the most common tricks being to put a lit match on the tick to make the tick “angry” enough to back out on its own. The truth is, this can actually make things worse for you and the tick; injecting more foreign material into you (or your pet) from the tick. Early removal of the tick is very important. Find out how to check for and remove ticks safely in this how to.

Cuterebra, a genus of botfly
 First instar larva of Cuterebra, a genus of botfly. Fly, parasite. Image courtesy CDC/Dr. George Healy. Smith Collection / Gado / Contributor / Getty Images

A Cuterebra parasite is an opportunistic parasite found under the skin of small mammals. This parasite is the larval stage of the Cuterebra fly, who uses animal hosts to complete its lifecycle. Learn more about this parasite, most commonly seen in summer and fall, in this FAQ.

Ehrlichia – Tick-bourne Bacterial Disease

Ixodes ricinus
 Ixodes ricinus bloated with food–blood from a dog, in this case. ” Ixodes ricinus” ( CC BY 2.0) by  acidpix

Ehrlichia is a type of bacteria that infect dogs and other species worldwide, causing a disease called ehrlichiosis. Ehrlichiosis has also been called tropical canine pancytopenia (and several other names). Ehrlichia is commonly transmitted by ticks.

Giardia Trophozoites
 Giardia Trophozoites. SuperStock / Getty Images

Giardia is a one-celled protozoan parasite that lives in the intestinal tract of many animals. When this parasite produces a diarrheal disease in animals (including humans), it is called Giardiasis. Learn about this parasite, how it is transmitted, signs of disease, and how it is diagnosed and treated in this FAQ.

” Hookworms” ( CC BY-SA 2.0) by  microbiologybytes

Hookworms are small, thin worms that are less than an inch long. Hookworms are intestinal parasites that are common in dogs. There are three species of hookworms that affect dogs, and some can also affect humans by migrating through the skin.

Whipworm egg
 Whipworm egg. By Joel Mills (Own work) [ GFDL, CC-BY-SA-3.0 or CC BY-SA 2.5-2.0-1.0], via Wikimedia Commons

Whipworms are intestinal parasites that are relatively common in dogs, but only occasionally seen in cats. Whipworms are small worms, reaching a maximum size of 2-3 inches. They have a thin, whip-like front end and a thicker back end. They attach themselves to the walls of the large intestine, feeding on blood.

Dog with ringworm on nose
Sarah Salmela / Getty Image

Technically not a parasite, Ringworm derives its name from the classic red, round “worm-like” lesion seen on human skin that is infected. Ringworm is a fungus that may or may not create clinical signs in animals, but may spread from animals to humans, creating the classic lesion.


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