Spirometra mansonoides is a tapeworm parasite that commonly infects bobcats, domestic cats and dogs.
Unlike the more common tapeworm of dogs and cats, Dipylidium caninum, which uses the flea as its intermediate host, Spirometra have two intermediate hosts.
The life cycle begins with an infected animal (bobcat, dog, cat, racoon, and other mammals) passing eggs in worm segments called proglottids. Eggs mature into a larval stage that infects a copepod, which is a tiny aquatic animal. In the ocean, copepods are a major component of the food source known as plankton. Copepods are equally numerous in fresh water, and may be swallowed by a rodent, frog, snake or bird drinking contaminated water. Thus, the copepod is the first intermediate host and the rodent, frog, snake or bird, is the second intermediate host.
The definitive host becomes infected by eating the second intermediate host. The bobcat is Spirometra’s preferred host, but it can reproduce satisfactorily in your house pet, hunting dog or outdoor cat.
Most people are unaware of their pet’s infestation with Spirometra until we perform a routine fecal flotation. We see the characteristic eggs of the parasite, which appear on the microscope, to me, like a folded omelet. Attentive pet owners may notice proglottids of Spirometra in their pet’s stool or attached to the hair of the perineum.
Spirometra infestation rarely causes overt disease in pets, although vomiting, diarrhea and weight loss are possible when the parasite is present in large numbers.
The risk to humans is discussed in this article.