Cysticercus tenuicollis is the larval stage (cysticercoid, metacestode) of Taenia hydatigena, a tapeworm parasite of dogs and other canids (coyotes, wolves, foxes, very occasionally cats, etc.), that has sheep, goats, cattle, deer and other wild ruminants as intermediate hosts, occasionally also horses.

Cysticercus tenuicollis occurs worldwide, mainly in rural areas of countries with large sheep populations. Regional incidence varies a lot. Unexpected outbreaks can happen due to climatic conditions that favor the survival of eggs in pastures or the activity of wild canids that carry the disease.

The disease caused by this and other cysticercoids is called cysticercosis.

Is livestock infected with Cysticercus tenuicollis contagious for humans?

NO. The reason is that  Taenia hydatigena is not a human parasite, and humans do not act as intzermediate hosts of these tapeworms. See the life cycle below.

You can find additional information in this site on the general biology of parasitic worms and/or tapeworms.

Final location of Cysticercus tenuicollis

Cysticercoids of Taenia hydatigena are found mainly in the liver, the omentum and the mesentery, often on the surface of various abdominal organs. The predilection site of adult tapeworms in their final host (dogs and other canids) is the small intestine.

Anatomy of Cysticercus tenuicollis

Cysticercus tenuicollis forms bladders fill of fluid than can be up to 8 cm long, have a long and thin neck, and contain one tapeworm head. Infested animals may have a dozen or more such bladders. Several months after infection the cysts die and scar.

Visit the page on Taenia species for additional information of the anatomy of adult Taenia tapeworms.

Life cycle and biology of Cysticercus tenuicollis

As all tapeworms, Taenia hydatigena has an indirect life cycle, with dogs and other canids (foxes, wolves, coyotes, very occasionally cats) as final hosts, and sheep, goats, cattle, deer, and occasionaly also horses and pigs as intermediate hosts.

The intermediate hosts become infested when ingesting food or water contaminated with eggs or gravid segments of  Taenia hydatigena through herbage or stored feed. A single gravid segment contains thousands of eggs. Contamination of feed can occur through dog feces. The eggs can remain infective for several months.

Once ingested by livestock, horses or other inermediate hosts, the young larvae hatch out of the eggs in the gut, cross the intestinal wall, reach the blood stream and migrate to the liver via the portal vein. Once in the liver the young worms migrate through the liver tissues towards the organ surface (serosa) during about 30 days. There or on the surface or other abdominal organs they build the bladder-like cysts. Cyst development is completed 35 to 55 days after infection. The cysts remain infective for dogs during several months.

Dogs and other canids become infected when scavenging on contaminated carcasses of when fed insufficiently cooked offal contaminated with cysts. Once in the dog's gut, the cysts release the young tapeworms, which attach to the gut's wall and start producing segments. Within 6 to 8 weeks (prepatent period) the tapeworms mature and start shedding eggs.

Harm caused by Cysticercus tenuicollis, symptoms and diagnosis

Cysticercus tebuicollis is usually not seriously pathogenic for infected livestock or horses. Unthriftiness may be observed. But massive infections can cause traumatic hepatitis in livestock when numerous larvae migrate through the liver. Deaths can occasionally follow due to hepatic hemorrage, mainly in young animals. Economic damage is mainly due to condemnation of livers and other organs at slaughter.

So far diagnosis on livestock or horses is only possible post-mortem after carcass examination.

Infection of dogs with  Taenia hydatigena are usually benign as well. They can cause diarrhea and loss of appetite, but they are often asymptomatic.

Prevention and control of Cysticercus tenuicollis

Best prevention consists in preventing livestock feed (fresh pasture as well as hay, silage, and other stored feed) or water from being contaminated with dog feces that may contain tapeworm eggs. It must be considered that the eggs may remain infective in the feed after silage or other processing of hey or fodder (pelletizing, fermentation, etc.).

At the same time, dog scavenging on potentially contamined cadavers or offal has to be avoided as well. If this is not possible, it is is advisable to regularly deworm dogs (particularly working and guard dogs) at least 3 to 4 times a year, especially if Cysticercus tenuicollis has been found in the region. There are numerous dog anthelmintic products that control such infections. They contain active ingredients with broad-spectrum anthelmintic efficacy such as benzimidazoles (e.g. fenbendazole, febantel, mebendazole) or specific taenicides such as praziquantel and epsiprantel, the latter often in combination with nematicides (e.g.levamisole, milbemycin oxime, pyrantel, etc.) to cover a broader spectrum of worms.

Most of these pet dewormers are available in formulations for oral delivery either as solids (tablets, pills, etc.) or as liquids (drenches, suspensions, etc.). There are also a few injectable taenicides in some countries (mainly with praziquantel).

So far there are no antiparasitic medicines for external use (spot-on - squeeze-on - pipettes, shampoos, soaps, sprays, powders, insecticide-impregnated collars, etc.) that control established tapeworm infections on dogs.

The regular use of anthelmintics is not indicated for preventing horse or livestock infections with Cysticercus tenuicollis. There are reports that albendazole and praziquantel are effective, but only at dosis higher than the usual therapeutic ones, and results can be unreliable.

Several classic anthelmintics such as macrocyclic lactones (e.g. ivermectin, doramectin, selamectin, etc.), levamisole, tetrahydropyrimidines (e.g. pyrantel, morantel) and piperazine derivatives are not effective at all against Cysticercus tenuicollis or whatever adult tapeworm or cysticercoid, neither on dogs, nor on horses or livestock.

There are so far no vaccines that would protect sheep or goats, other livestock or horses against Cysticercus tenuicollis. To learn more about vaccines against parasites of livestock, horses and pets click here.

Biological control of Taenia tapeworms respectively Cysticercus tenuicollis (i.e. using its natural enemies) is so far not feasible.

You may be interested in an article in this site on medicinal plants against external and internal parasites.

Resistance of Cysticercus tenuicollis to anthelmintics

So far there are no reports on resistance of Taenia spp, respectively Cysticercus tenuicollis to anthelmintics.

This means that if an anthelmintic fails to achieve the expected efficacy, chance is very high that either the product was unsuited for the control of  Taenia spp or  Cysticercus tenuicollis, or it was used incorrectly.