''Toxocara cati'', also known as the feline roundworm, is a

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson h ...

cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

s and other

felids Felidae () is the family of mammals in the order Carnivora colloquially referred to as cats, and constitutes a clade. A member of this family is also called a felid (). The term "cat" refers both to felids in general and specifically to the dom ...

. It is one of the most common

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant- parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a bro ...

s 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 Toxocariasis is an illness of humans caused by the dog roundworm (''Toxocara canis'') and, less frequently, the cat roundworm ('' Toxocara cati'').https://academic.oup.com/ajcp/article/142/suppl_1/A104/1771175 Eosinophilic Pseudoleukemia Due to T ...

– is usually asymptomatic. However, massive infection in juvenile cats can be fatal. 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 The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer ( American spelling), also commonly known as a micron, is a unit of length in the International System of Uni ...

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.

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. Contact with the soil, licking fur near feet, and eating a host animal (such as rodents) can also lead to infection of the felines. The consumption of infected carrion also leads to contraction of the parasites, which is some of the food that members of Felidae consume. The eggs hatch in the intestines and the larvae are then released into the cat's digestive tract. 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. From there, they move up to the trachea where they are swallowed, causing hacking and other problems. 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.

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. 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. Those with a small worm burden, however, may not show the clinical signs of being infected with worms, and not receive treatment.

Treatment

Treatment for ''Toxocara cati'' infections in cats is rather simple. There are a number of

anthelmintics Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms (helminths) and other internal parasites from the body by either stunning or killing them and without causing significant damage to the host. They may ...

that will kill the adult worms, including

Ivermectin Ivermectin (, '' EYE-vər-MEK-tin'') is an antiparasitic drug. After its discovery in 1975, its first uses were in veterinary medicine to prevent and treat heartworm and acariasis. Approved for human use in 1987, today it is used to treat i ...

emodepside Emodepside is an anthelmintic drug that is effective against a number of gastrointestinal nematodes, is licensed for use in cats and belongs to the class of drugs known as the ''octadepsipeptides'', a relatively new class of anthelmintic (research ...

fenbendazole Fenbendazole is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including: giardia, roundworms, hookworms, whipworms, the tapeworm genus '' Taenia'' (but not effective against '' Dipylidium caninum'', a comm ...

milbemycin The milbemycins are a group of macrolides chemically related to the avermectins and were first isolated in 1972 from '' Streptomyces hygroscopicus''. They are used in veterinary medicine as antiparasitic agents against worms, ticks and fleas.

, 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.

''T. cati'' infection in humans

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

. 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. 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. Ocular toxocariasis typically occurs in 5 to 10-year-olds resulting in significant damage to the eye. 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. 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

References

* Dare, O.K. and Watkins, W.G. “First Record of Parasites in Cougars (Puma Concolor) in Manitoba, Canada” The Canadian Field-Naturalist. 24 Oct. 2013. http://www.canadianfieldnaturalist.ca/index.php/cfn/article/view/1378/1373

External links