Toxocara cati

Toxocara cati, also known as the feline roundworm, is a parasite of cats and other felids. It is one of the most common nematodes of cats, infecting both wild and domestic felids worldwide. Adult worms are localised in the gut of the host. In adult cats, the infection – which is called toxocariasis – is usually asymptomatic. However, massive infection in juvenile cats can be fatal.

This article is about the organism. For the infection, see Toxocariasis.

Toxocara cati
Cluster of adult worms
Scientific classification
Kingdom: Animalia
Phylum: Nematoda
Class: Chromadorea
Order: Ascaridida
Family: Toxocaridae
Genus: Toxocara
Species:
T. cati
Binomial name
Toxocara cati
Schrank, 1788
Synonyms

Toxocara mystax (Zeder, 1800)

Feline roundworms are brownish-yellow to cream-colored to pink and may be up to 10 cm in length. Adults have short, wide cervical alae giving their anterior ends the distinct appearance of an arrow (hence their name, toxo, meaning arrow, and cara, meaning head). Eggs are pitted ovals with a width of 65 μm and a length of about 75 μm making them invisible to the human eye. The larvae are so small that they are easily transmitted from an adult female to her nursing kittens through her milk.[1][2][3][4]

Transmission

Wild felids can become infected from a variety of sources; the primary source is infected fecal matter. The eggs of the roundworm become infective in three to four weeks after being passed out in fecal matter.[5] Contact with the soil, licking fur near feet, and eating a host animal (such as rodents) can also lead to infection of the felines.[5] The consumption of infected carrion also leads to contraction of the parasites, which is some of the food that members of Felidae consume.[6] The eggs hatch in the intestines and the larvae are then released into the cat's digestive tract.[5] The larvae are capable of migrating through the tissues and are found in the liver, lungs, tracheal washings and muscles as well as in the digestive tract.[7][5] From there, they move up to the trachea where they are swallowed, causing hacking and other problems.[5] The larvae can also move throughout the body and cause more damage to the infected individuals. The worms can even go into the mother's milk and infect the young.[5]

Clinical signs

There are numerous clinical signs when dealing with feline roundworm. Some clinical signs that can be detected easily are vomiting, decreased appetite, and poor growth.[8] Like many diseases, changes in behavior can also be attributed to toxocariasis. Decreased appetite will result in a scrawny, mangy, and sickly appearance. Toxocariasis is exceptionally detrimental to kittens, as appetite loss and poor growth can ultimately lead to mortality. Additional clinical signs that can be identified include a pot bellied appearance, abdominal discomfort, and diarrhea.[8] Those with a small worm burden, however, may not show the clinical signs of being infected with worms,[8] and not receive treatment.

Treatment

Treatment for Toxocara cati infections in cats is rather simple. There are a number of anthelmintics that will kill the adult worms, including Ivermectin, emodepside, fenbendazole, milbemycin, and moxidectin. However, most drugs are ineffective against the immature parasites. Consequently, infected cats will usually need multiple doses administered in two or three week intervals in order to fully eradicate the worms.[8][9]

T. cati infection in humans
Main article: Toxocariasis

It is possible for Toxocara cati to be transmitted to humans, usually as a consequence of humans consuming the larval stage of the parasite, resulting in a condition known as toxocariasis.[2] Typically, this happens when an individual pets an infected cat, picks up the parasite off of the fur and touches their face before washing their hands. The larvae migrate through the viscera in humans. Depending on the location and number of the larva in the human host, the disease can either be asymptomatic or cause conditions such as fever, cough, pneumonia, and vision loss.[3][4]

The two more severe forms of the disease are visceral toxocariasis and ocular toxocariasis. Visceral toxocariasis typically occurs in children, but can infect persons of any age. Signs and symptoms can include fever, wheezing, hepatomegaly, abdominal pain, anorexia, or skin reaction. Rarely, the migrating larvae can cause eosinophilic meningitis or encephalitis, myelitis, optic neuritis, radiculitis, cranial nerve palsy, or myocarditis. In lab findings, there is almost always a marked peripheral eosinophilia and often, anemia and a hypergammaglobulinemia.[10]

Ocular toxocariasis typically occurs in 5 to 10-year-olds resulting in significant damage to the eye.[11] Usually only one eye is affected, and manifestations can include strabismus, decreased vision, and leukocoria. Eye exam may show a subretinal granulomatous mass or posterior pole granuloma.[10] Even in relatively healthy people, the roundworm larvae infect organs such as the liver, lungs, eyes or brain and cause severe symptoms, such as:

  • fatigue
  • loss of appetite or weight loss
  • skin rashes
  • wheezing or breathing difficulties
  • seizures (fits)
  • blurred or cloudy vision, usually only affecting one eye
  • a very red and painful eye[12]

See also

References
  1. Bowman, Dwight D.; Hendrix, Charles M.; Lindsay, David S.; Barr, Steven C. (2002). Feline clinical parasitology (First ed.). Ames, Iowa: Iowa State University. p. 275. ISBN 978-0-8138-0333-3.
  2. "Toxocara cati". American Association of Veterinary Parasitologists. 17 June 2014. Archived from the original on 9 May 2017. Retrieved 21 April 2017.
  3. "Parasites - Toxocariasis (also known as Roundworm Infection)". Centers for Disease Control and Prevention. Retrieved 21 April 2017.
  4. Saravanan, M.; Sarma, K.; Mondal, D. B.; Ranjith Kumar, M.; Vijayakumar, H. (1 March 2016). "Concomitant infestation of Toxocara cati and Ancylostoma tubaeforme in a mongrel cat". Journal of Parasitic Diseases. 40 (1): 205–207. doi:10.1007/s12639-014-0451-5. PMC 4815833. PMID 27065627.
  5. "Roundworm in Cats". WebMD. Retrieved 23 October 2013.
  6. "Roundworms". Michigan Department of Natural Resources. Retrieved 24 October 2013.
  7. "CAB Direct".
  8. Ward, Ernest (2 December 2008). "Roundworm Infection in Cats". VCA Hospitals. Retrieved 29 July 2017.
  9. "IVERMECTIN DOSE for HORSES & LIVESTOCK".
  10. "Neglected Parasitic Infections: Toxocariasis". www2c.cdc.gov. Retrieved 27 August 2017. This article incorporates text from this source, which is in the public domain.
  11. Sabrosa, N. A.; de Souza, E. C. (1 December 2001). "Nematode infections of the eye: toxocariasis and diffuse unilateral subacute neuroretinitis". Current Opinion in Ophthalmology. 12 (6): 450–454. doi:10.1097/00055735-200112000-00010. PMID 11734685. S2CID 8046622.
  12. Choices, NHS. "Toxocariasis - NHS Choices". www.nhs.uk. Retrieved 27 August 2017.
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