- Overview & Prevention
- Profile: Coccidia
- Profile: Giardia
- Profile: Hookworm
- Profile: Roundworm
- Profile: Tapeworm
- Profile: Whipworm
- Additional Resources
The effects intestinal parasites can have on a pet’s health vary greatly depending on a variety of factors; however, puppies and kittens are particularly susceptible to developing serious problems associated with intestinal parasites. And while a wide range of treatment options and preventatives are available; intestinal parasites remain common in both dogs and cats.1
The most common intestinal parasites seen in pets include the protozoan (single-celled) parasites Coccidia and Giardia; and the worm-like parasites (helminths) Hookworms, Roundworms, Tapeworms, and Whipworms. With the exception of Hookworms (which can cause anemia associated with severe blood loss)2 and tapeworms (which often do not cause health complications);34 most intestinal parasites cause diarrhea, although severity of infection can vary depending on the age of the pet and condition of their health.
Most oral Heartworm Preventatives provide protection against Hookworms and Roundworms, although their effectiveness can vary. If your pet has had a previous or recurrent intestinal parasite infection, or there is a risk your pet might acquire one (such as from an infected housemate), your veterinarian might recommend a more comprehensive preventative also effective against tapeworms and/or whipworms.
Overall, practicing good basic hygiene is important in minimizing intestinal parasites’ zoonotic potential. Such practices include regularly washing hands, washing fruits and vegetables before consumption, promptly removing pet feces from the yard and during dog walks, covering sandboxes when not in use, discouraging dogs and cats from roaming (by abiding by leash laws and other pet confinement legislation), and supervising young children to prevent geophagia (consumption of soil).5
Coccidians have a complex life cycle, which incorporates both asexual and sexual reproduction, and which progresses through five (5) life stages.6 Furthermore, coccidians of the genus Cystoisospora, those most commonly found in dogs and cats,7 may utilize a paratenic (intermediate)8 host, such as a mouse or bird, in which larval development is delayed until the animal is eaten by a final host, like a dog or cat.9 Otherwise, coccidiosis is typically transmitted via ingestion of infected feces, soil, or other substrate where oocysts (the initial, single-celled sporont stage of a coccidian’s life cycle) reside.6 In ideal conditions, oocysts can survive up to one (1) year in the environment.10
Dogs are primarily affected by Cystoisospora canis, while cats are primarily affected by Cystoisospora felis. North American prevalence data of coccidiosis in dogs vary widely (between three (3) and 40 percent);10 yet, nearly all cats become infected with Cystoisospora felis during their lifetimes.711
Giardiasis, the disease caused by giardia, is transmitted when cysts shed from an infected animal are ingested from fecal-contaminated water, food, a contaminated surface, or through grooming.12 Giardiasis can cause diarrhea, usually beginning five (5) days post-infection in dogs and seven (7) to 14 days post-infection in cats,13 although dogs and cats may show no symptoms of disease.12 Giardia are present in roughly 15% of the dog population and 10% of the cat population.14 While the understanding of inter-species transmission of Giardia is still developing, it is generally not considered to have significant zoonotic potential.1312
Transmission of hookworm infection in dogs and cats principally occurs via ingestion of the third-stage larvae from a contaminated environment or larval penetration of the skin;151617 although dogs and cats can also become infected by eating an infected vertebrate host or cockroaches containing infective hookworm larvae.1617 Such hosts, in which larvae do not undergo further development, are referred to as paratenic hosts.8
Because all hookworms suck blood to some degree, they can cause anemia due to severe blood loss, which can prove fatal in puppies.217 While severity of hookworm infection can depend on a variety of factors, including the species of hookworm and degree of exposure;19 anemia is of primary concern in an infected pet.1917 Additionally, respiratory disease can occur in puppies or kittens when significant larval populations migrate through the lungs.17
Roundworm infection is primarily transmitted by parasitic worms in the family Toxocaridae, which includes the genera Toxascaris (specifically, the species Toxascaris leonina) and Toxocara. As members of the order Ascaridida, such worms are also collectively, and more appropriately, referred to as ascarids, as the term roundworm (or nematode) refers to a broad range of species totaling over 25,000.20 Ascarids in the genus Toxocara are some of the most common parasites observed in dogs and cats, specifically T. canis and T. cati respectively.21
Like other intestinal parasites, ascarids may utilize paratenic (intermediate)8 hosts, such as a rodent or another small animal, in which larval development is arrested until the animal is eaten by a final host, such as a dog or cat.21 Otherwise, roundworm infection is typically transmitted via ingestion of a substrate in which eggs reside, such as infected feces; or soil, where earthworms have been implicated in its transmission.22
Furthermore; in dogs, transplacental transmission of ascarid larvae from an infected mother to her puppies is the primary route of infection for T. canis.922 For this reason, and due to the resiliency of T. canis eggs in the environment, which can remain infective for years;2322 nearly all puppies become infected with T. canis.2224 On the other hand, transplacental transmission has not been shown to occur in cats affected by T. cati or Toxascaris leonina, or in dogs affected by Toxascaris leonina,22 where transmammary transmission can occur.22 Transmammary transmission of T. cati can occur, yet only in cats infected acutely during the final stage of pregnancy.23
An ascarid infection can result in mild diarrhea; with vomiting sometimes associated with migration of adult ascarids from the small intestine to the stomach.225 Additionally, significant numbers of immature and adult worms may appear in the feces or vomitus of infected animals.2326 Furthermore, abdominal distension (pot-bellied appearance) may develop in severely infected animals.5
Toxocara and Toxascaris eggs are particularly resilient to environmental extremes.23 Consequently, there are no reasonable means for eliminating or killing these ascarid eggs in the environment; although completely removing topsoil and replacing it with gravel, or paving the contaminated area, may be effective.23
Furthermore, of intestinal parasites commonly found in dogs and cats; ascarids carry the greatest zoonotic potential, where eggs containing infective larvae of Toxocara species are commonly found in soil samples from public areas, such as parks and playgrounds.5 Consequently, Toxocariasis, the disease caused by the larvae of T. canis or T. cati, ranks among the most common of all zoonotic infections associated with pets in the United States,27 and has been targeted by the Centers for Disease Control (CDC) as a Neglected Parasitic Infection (NPI) worthy of receiving priority for public health action.28
Fleas are the primary intermediate host for the most common type of tapeworm, Dipylidium caninum; with the dog louse, Trichodectes canis, also serving the same role.2930 Transmission occurs when flea larvae ingest D. caninum eggs along with other organic matter.29 The newly-hatched tapeworm larvae are able to survive the flea’s metamorphosis to the adult stage, where the flea may be ingested when nipped or licked out of the fur of a dog or cat.29 Although rare; people can become infected with D. caninum in the same way, by accidentally ingesting an infected flea, with children most commonly affected.3132 While tapeworms in children are easily cleared with a physician-prescribed anthelmintic (a drug which expels helminths);33 the experience can be stressful for parents.
Ultimately, Flea Prevention serves as an important method of preventing tapeworm infections in dogs and cats and minimizing the parasite’s zoonotic potential.
Trichuriasis, the disease caused by whipworms (members of the genus Trichuris), is transmitted in dogs by Trichuris vulpis, which is also prevalent in wild canids,34 such as the fox and coyote.3536 Transmission occurs through ingestion of infected feces, soil, or other substrates; where eggs can survive a number of years,3436 due to their strong resistance to environmental extremes.37383436 An infective first-stage larva develops within the egg, but does not hatch until ingested.3834 Once ingested, whipworm larvae hatch within the small intestine.34 After roughly two (2) weeks, larvae colonize the cecum and large intestine.39
We recommend testing for intestinal parasites via fecal flotation be performed yearly in all animals, as no product is available that prevents all of the most common intestinal parasites seen in pets. Furthermore, while many products have efficacy against various intestinal parasites, none guarantee 100% prevention; therefore, intestinal parasites remain common in both dogs,41 and cats.11
All kittens and puppies are treated for hookworms and roundworms with an oral suspension at their first visit irrespective of fecal test result, as they could have an occult (hidden) infection.
Treatment options for other intestinal parasites varies, but is often in the form of an oral suspension, powder, or tablet.
Follow-up Diagnostics may be required to verify treatment effectiveness.
- Blagburn BL. Prevalence of canine and feline parasites in the United States. Comp Cont Edu Pract. 2001; 23(6A): 5-10.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 182.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 151.
- Cestodes. Companion Animal Parasite Council. https://capcvet.org/guidelines/cestodes. Updated November 1, 2016.
- Little SE. Controlling canine and feline gastrointestinal helminths. Advanstar Communications Inc. http://veterinarymedicine.dvm360.com/controlling-canine-and-feline-gastrointestinal-helminths. Published May 1, 2005.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 93.
- Constable PD, ed. Coccidiosis of Cats and Dogs. Merck & Co. http://www.merckvetmanual.com/mvm/digestive_system/coccidiosis/coccidiosis_of_cats_and_dogs.html. Updated March 2012.
- Roberts LS, Janovy J Jr. Foundations in Parasitology 8th ed. New York, NY: McGraw-Hill; 2010: 4.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 203.
- Coccidia. Companion Animal Parasite Council. https://capcvet.org/guidelines/coccidia. Updated October 1, 2016.
- Gastrointestinal Parasites of Cats. Cornell University. http://www.vet.cornell.edu/fhc/health_information/brochure_parasite.cfm.
- Giardia. Companion Animal Parasite Council. https://capcvet.org/guidelines/giardia. Updated September 1, 2016.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 89.
- Carlin EP, Bowman DD, Scarlett JM, Garrett J, Lorentzen L. Prevalence of Giardia in symptomatic dogs and cats throughout the United States as determined by the IDEXX SNAP Giardia test. Vet Ther. 2006; 7(3): 199-206.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 180.
- Hookworms. Companion Animal Parasite Council. https://capcvet.org/guidelines/hookworms. Updated October 1, 2016.
- Bowman DD. The nuances of hookworm biology in dogs and cats. Paper presented at CVC; April 1, 2009; Washington, DC. http://veterinarycalendar.dvm360.com/nuances-hookworm-biology-dogs-and-cats-proceedings.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 181-182.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 182-183.
- Zhang Z-Q. Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013). Zootaxa. 2013; 3703(1): 4. doi:10.11646/zootaxa.3703.1.3.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 201.
- Ascarid (also Roundworm, also Toxocara) Companion Animal Parasite Council. https://capcvet.org/guidelines/ascarid. Updated November 1, 2016.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 205.
- Barriga OO. A critical look at the importance, prevalence and control of toxocariasis and the possibilities of immunological control. Vet Parasitol. September 1988; 29(2-3): 195-234.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 206.
- Urquhart GM, Armour J, Duncan JL, Dunn AM, Jennings FW. Veterinary Parasitology 2nd ed. Oxford, ENG: Blackwell; 1996.
- Schantz PM. Toxocara larva migrans now. Am J Trop Med Hyg. 1989; 41(3) Supplmental: 21-34.
- Parasites – Toxocariasis (also known as Roundworm Infection). Centers for Disease Control. http://www.cdc.gov/parasites/toxocariasis. Updated January 10, 2013.
- Roberts LS, Janovy J Jr. Foundations in Parasitology 8th ed. New York, NY: McGraw-Hill; 2010: 358.
- Macpherson CNL, Torgenson PR. Dogs and Cestode Zoonoses. In: Macpherson CNL, Meslin F-X, Wandeler AI, eds. Dogs, Zoonoses and Public Health 2nd ed. Boston, MA: CAB International; 2013.
- Roberts LS, Janovy J Jr. Foundations in Parasitology 8th ed. New York, NY: McGraw-Hill; 2010: 359.
- Parasites – Dipylidium Infection. Centers for Disease Control. http://www.cdc.gov/parasites/dipylidium. Updated January 10, 2012.
- Molina CP, Ogburn J, Adegboyega P. Infection by Dipylidium caninum in an infant. Arch Pathol Lab Med. March 2003; 127(3): e157-9.
- Blagburn B. The elusive whipworm, Trichuris vulpis. Supplement to NAVC Clinician’s Brief. Gainesville, FL: NAVC; September 2008: 1.
- Roberts LS, Janovy J Jr. Foundations in Parasitology 8th ed. New York, NY: McGraw-Hill; 2010: 401.
- Trichuris vulpis. Companion Animal Parasite Council. https://capcvet.org/guidelines/trichuris-vulpis. Updated October 1, 2016.
- Bowman DD. Georgis’ Parasitology for Veterinarians 9th ed. St. Louis, MO: Elsevier; 2009: 182.
- Roberts LS, Janovy J Jr. Foundations in Parasitology 8th ed. New York, NY: McGraw-Hill; 2010: 400.
- Kirkova Z, Dinev I. Morphological changes in the intestine of dogs experimentally infected with Trichuris vulpis. Bulg J Vet Med. 2005; 8(4): 239-43.
- Peregrine AS, ed. Whipworms in Small Animals. Merck & Co. http://www.merckvetmanual.com/mvm/digestive_system/gastrointestinal_parasites_of_small_animals/whipworms_in_small_animals.html. Updated September 2014.
- Blagburn BL, Lindsay DS, Vaughn JL, et al. Prevalence of canine parasites based on fecal flotation. Comp Cont Educ Pract. 1996; 18: 483–509.