Ollulanus tricuspis

Synopsis

CAPC Recommends

• Test cats that chronically vomit, often right after a meal, and not the typical hairball.
• This parasite has a direct lifecycle, so keep infected cats away from other cats in the home until the infected animal is clear of worms.
• Dogs are rarely infected, but should be monitored if living with an infected cat.

Species

Feline

Ollulanus tricuspis (stomach worm of cats)

*Photos courtesy of Dr. Ellis Greiner

Ollulanus tricuspis adult female

Ollulanus tricuspis adult male

Overview of Life Cycle

• Ollulanus tricuspis nematodes are worms found in the gastric mucosa of the cat.
• They have a direct life cycle, and do not require an intermediate host. The egg of O. tricuspis undergoes embryonation and hatches within the uterus of the female (ovoviparous). The female gives birth to third-stage larvae. The third-stage larvae are found within the adult female and free within the lumen of the cat stomach.
• Transmission from cat to cat appears to be direct through the consumption of vomitus containing either third stage, fourth-stage larva, and adult male and females.
• The worms can live in vomitus for up to 12 days. Additionally, these parasites are able to multiply via internal autoinfection which means that larvae can mature to adult worms in the same host. This is especially evident by single cats that build up large number of worms of over one thousand.

Stages

• The egg of O. tricuspis undergoes embryonation within the female and hatches within the uterus of the worm.
• The second- and third-stage larvae develop within the female, and the female gives birth to the third-stage larvae.
• Stage three larvae, fourth-stage larvae, and adult male and females can be found within the stomach of the cat and in vomitus.
• Adult females are characterized by a tail ending with several tubercles.

Disease

• O. tricuspis generally causes chronic vomiting, increased gastric mucous production, weight loss, and anorexia in cats.
• These worms are generally believed to be of low pathogenic potential to cats, but they have caused severe chronic gastritis and carcinogenesis in a few rare cases. In the stomach of infected cats, there is usually a significant increase of mucosal fibrous tissue and mucosal lymphoid aggregates.

Prevalence

• O. tricuspis has been observed worldwide including Canada, the United States, Argentina, Chile, Egypt, Australia, Japan, and throughout Europe and the Middle East.
• These worms most commonly infect domestic cats but have been observed to affect dogs (rarely), tigers, red fox, lions, cheetahs, and pigs.
• It appears this parasite is much more common in feral and multi-cat households. In highly concentrated colonies, there is an increased opportunity for the ingestion of infective vomitus from another animal.

Host Associations and Transmission Between Hosts

• Cats become infected with O. tricuspis by consuming the vomitus of another animal that contains the infected stages.
• The worms can multiply within the cat via internal autoinfection.
• There is no evidence for fecal transmission of this parasite. Most adults and larvae that enter the intestine are usually dead, killed, destroyed, or digested before they are passed in the feces.

Prepatent Period and Environmental Factors

• The prepatent period of O. tricuspis is not well described.
• It takes about 33-37 days for an infection with third-stage larvae to produce the next generation of third-stage larvae.
• The worms can survive in the vomitus for up to 12 days.

Site of Infection and Pathogenesis

• O. tricuspis worms are located in the mucosa of the stomach of the cat.
• In general, they cause increased mucosal fibrous tissue, moderate local erosion of gastric mucosa, increased mucous secretion, and mucosal lymphoid aggregates in the stomach.
• These worms are capable of producing chronic gastritis in cats with severe lesions such as hyperplasia of the stomach epithelium, inflammation, cellular infiltration, and sclerosis of the epithelium.

Diagnosis

• Diagnosis is only rarely made by direct fecal smears or fecal flotation methods because the adults and larvae of O. tricuspis that enter the intestine are usually dead, killed, destroyed, or digested before they are passed in the feces.
• A more reliable diagnosis is made with either induction of vomiting and gastric lavage.
• Emesis in the cat can be induced with xylazine, and examination of the induced vomitus is successful in making a diagnosis in about 70% of infected cats.
• Stomach irrigation may be performed with physiologic saline in anesthetized cats. The collected fluid can be examined after centrifugation or after larvae are collected using a Baermann apparatus.
• The Baermann technique concentrates live larvae and adults, so vomitus or stomach contents should be fresh, and stored at room temperature. Dead worms cannot be collected this way. If material is older or has been refrigerated, a simple sedimentation is effective in recovering worms.
• More recently, gastric biopsy samples during upper gastrointestinal endoscopy have also been utilized to diagnosis this parasite.
• Adult O. tricuspis worms are very small, ranging from 0.7mm to 1.0mm in length. The tail of the female has three major cusps or bumps. The anterior end of the worm usually coils around on itself, and there is a relatively large “cup-shaped” buccal capsule.

Treatment

• Cats have been treated with tetramisole administered at 5mg/kg body weight and has proved efficacious, without side effects.
• Additionally, the use of fenbendazole (50mg/kg daily for 5 days) and oxfendzole (10mg/kg daily for 5 days) has also been shown effective in treating cats with O. tricuspis.

Control and Prevention

• Catteries and multi-cat households should be monitored for signs of increased vomiting in cats. If this occurs, the vomitus should be checked for the presence of O. tricuspis.

Public Health Considerations

• There has been no report of human infections with O. tricuspis.

Selected References

• Bowman, Dwight D., Charles M. Hendrix, David S. Lindsay, and Stephen C. Barr. Feline Clinical Parasitology. 1^st ed. Iowa: Iowa State UP, 2002.
• Cecchi R, Wills SJ, Dean R, Pearson GR. 2006. Demonstration of Ollulanus tricuspis in the stomach of domestic cats by biopsy. Journal of Comparative Pathology 134(4):374-377.
• Kato D, Oishi M, Ohno K, et al. The first report of the ante-mortem diagnosis of Ollulanus tricuspis infection in two dogs. The Journal of Veterinary Medical Science 2015;77(11):1499-1502. doi:10.1292/jvms.15-0158.