Ollulanus tricuspis, the cat stomach worm, is a parasitic roundworm that infects cats and other felids (e.g. lynxes, jaguars, cougars, etc.), foxes, and very occasionally also pigs. It is found worldwide.

Studies in Central Europe have shown that about 40% of stray cats and up to 6% of domestic cats can be infected.

Ollulanus tricuspis belongs to the Trichostrongylidae, a roundworm family with many species that are seriously harmful for cattle, sheep and other livestock. Ollulanus tricuspis is one of the few worms of this family that parasitizes carnivores, and is not very harmful.

The disease caused by Ollulanus tricuspis is called ollulaniasis.

Ollulanus tricuspis does not affect cattle, sheep or poultry.

Are cats infected with Ollulanus tricuspis contagious for humans?

• NO. Neither through contact, nor through the feces or the vomit. The reason is that this worm species is not a human parasite. For additional information read the chapter on the life cycle below.

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

Final location of Ollulanus tricuspis

Predilection site of adult Ollulanus tricuspis is the stomach.

Anatomy of Ollulanus tricuspis

Ollulanus tricuspis is a rather small roundworm, about 0.7 to 1 mm long. Females are larger than males. Females have three (sometimes up to five) specific cusps at the posterior end.

The worm's body is covered with a cuticle, which is flexible but rather tough. The worms have no external signs of segmentation. They have a tubular digestive system with two openings. They also have a nervous system but no excretory organs and no circulatory system, i.e. neither a heart nor blood vessels. Ollulanus tricuspis is viviparous, i.e. the females do not lay eggs but the eggs develop to L2 larvae inside the uterus. Males have chitinous spicules for attaching to the female during copulation.

Life cycle and biology of Ollulanus tricuspis

Ollulanus tricuspis has a direct life cycle but quite particular. After leaving the uterus, L2 larvae develop to L3 and L4 larvae inside the host's stomach. Some larvae leave the hosts through it's vomit Other larvae complete development to adults still in the stomach, i.e. without going through a developmental stage living outside the host in the environment, which is in contrast with most roundworm species. Vomited larvae can infect kittens or other adult cats that eat or lick the vomit.

Adult worms live in the stomach, either in the mucus, or at the openings of the gastric mucosal glands.

Harm caused by Ollulanus tricuspis, symptoms and diagnosis

Infections of domestic cats with Ollulanus tricuspis are mostly benign, cause no clinical signs and recede spontaneously. Massive infections can cause stomach inflammation (gastritis) and vomit. On wild and large cats as well as pigs infections can be more harmful, with loss of appetite, weight loss and frequent vomiting.

Diagnosis is based on the microscopic examination of the vomit or stomach lavage wash, where the larvae can be detected. The presence of larvae or adults in the feces is very rare, because they are mostly digested; therefore fecal examination has usually no diagnostic value. 

Prevention and control of Ollulanus tricuspis

Prevention is based on thorough sanitation, especially removing cat vomits as soon as possible, particularly in catteries.

There is little information on the efficacy of usual anthelmintics (also called wormers or dewormers) against Ollulanus tricuspis. Ivermectin, levamisole, fenbendazole, oxfendazole and pyrantel are effective, but most commercial cat wormers are not approved for this use and therefore dose and treatment regime have to be decided by the veterinary doctor.

There are so far no true vaccines against Ollulanus tricuspis. To learn more about vaccines against parasites of livestock and pets click here.

Biological control of Ollulanus tricuspis (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 Ollulanus tricuspis to anthelmintics

So far there are no reports on resistance of Ollulanus tricuspis 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 Ollulanus tricuspis, or it was used incorrectly.