Can Cat Worms Infect People?

A disease which can be transmitted from animals to humans is known as a zoonotic disease. There are several external and internal cat parasites which are zoonotic, some of which can be more serious to humans than to their pets.

This is because humans are an abnormal host for feline parasites, so the parasites become lost and confused in a human body and do some unusual things when they cannot find their way to a target feline organ.

External parasites like fleas and mites (such as Notoedres mites and Cheyletiella mites) can sometimes hop on to humans and cause a lot of itching of the skin, sometimes accompanied by a rash. However these little critters only remain on humans for a short time.

While cats are not as commonly affected by ticks as dogs, both cats and humans are susceptible to attack by ticks. However humans don't catch ticks from cats but are more likely to be preyed upon by a hungry tick waiting in the environment, which leaps onto a passing human in search of a meal of blood. Ticks can transmit diseases such as Lyme Disease and Rocky Mountain Spotted Fever.

Feline roundworms can also cause disease in humans. Eggs from this parasite are excreted in cat feces. After two weeks in the open they can become infectious to humans! If accidentally ingested, the worms can migrate to organs such as the liver, lungs, brain or eyes, where the human body generates an immune response to try to wall them off and prevent them moving any further.

The disease in humans is known as visceral larva migrans, or if in the eye, ocular larva migrans. The symptoms of this disease vary. If the worms migrate to the eye, permanent loss of vision can result, while a cough or asthma-like signs indicate they are in the lungs. Some people display no symptoms at all. Children are at a higher risk of infection due to their playing habits, such as eating dirt, their attraction to pets and their reluctance to their wash hands before eating.

"Humans are an abnormal host for feline parasites, so the parasites become lost and confused in a human body and do some unusual things when they cannot find their way to a target feline organ."

Humans can also be infected with feline hookworms. As with roundworms, eggs are excreted in the feces of infected cats. These become infectious after five to 10 days in the environment, when they have developed in to larvae or juvenile worms capable of penetrating the skin by eating their way in.

They migrate under the skin leaving intensely itchy, red, swollen winding tracks in their wake. This is known as cutaneous larva migrans.

Some feline tapeworms can be transmitted to humans. The most common tapeworm in cats is the flea tapeworm, but this species is not readily transmitted to humans as it is necessary to swallow an infected flea to contract the disease. Infection is more commonly seen in children and the symptoms, similar to those in cats, include segments of tapeworms, (resembling grains of rice), being passed in the feces and sticking to the anal area.

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Tapeworms of the Taenia and Echinococcus species can also be contracted by humans via accidental ingestion of cat feces containing infectious tapeworm eggs. The only form of Echinococcus transmissable by cats is that causing alveolar echinococcus. Hydatid disease is another form of Echinococcus, but this form is only transmitted by dogs.

Alveolar echinococcus is more common in the central northern states and Alaska, and causes solid masses in the liver, lungs, brain or other organs which can sometimes be confused with tumors. The masses normally require surgical removal.

Cats contract tapeworms by eating raw meat infected with juvenile stages of the tapeworm. Preventing your kitty dining on wild animals such as rats and mice will help to reduce the likelihood of it contracting the infection and potentially passing it on to humans.

Another parasite which can be passed to humans via cat feces is a tiny single-celled parasite called Toxoplasma gondii. Millions of Americans have already been infected with this parasite. Normally, infection causes no problems in humans who develop immunity to the disease and cannot be reinfected. Likewise, infected cats generally display no symptoms, which makes it very difficult to diagnose them.

Cutaneous larva migrans. Image:www.nlm.nih.gov

However, on rare occasions, Toxoplasmosis can result in damage to the eyes, brain or other organs. This outcome is more likely in people with weakened immune systems or when a pregnant woman is infected for the first time. In this case, miscarriage, stillbirth, blindness or brain damage to the baby can result.

Cats and humans contract the disease from raw meat, which includes wild animals. Kittens are more susceptible to the disease than adult cats. To avoid the risk of a cat becoming infected, do not feed it raw meat. Commercial foods or cooked meat will ensure that this parasite is not transmitted to the cat. Pregnant women should avoid handling raw meat where possible, and where necessary should always their wash hands thoroughly afterwards. In addition, someone else should be responsible for changing the kitty litter at least once a day. It is possible to have a blood test to confirm whether you have immunity to this disease, so many doctors will recommend this when a patient with a cat becomes pregnant.

"Toxoplasmosis can result in damage to the eyes, brain or other organs. This outcome is more likely in people with weakened immune systems or when a pregnant woman is infected for the first time."

Prevention of infections in cats through regular worming and flea control will go a long way to stopping most of these diseases being transmitted to humans. Your veterinarian can advise on the most appropriate treatment for your cat.

When playing with the family cat, people should always wash their hands after contact, avoid kissing the cat and not allow it to lick them on the face. Preventing the cat from defecating in the back yard, especially around play areas such as sandboxes, is advisable. Wild cats can be prevented from entering your property and doing their business in the garden or lawn by fences and deterrents such as sprinklers.

Wear gloves when gardening to avoid contact with any feces which may be present. Most cats can be trained to use a litter box which can be changed daily and the contents disposed of. However, pregnant women should not handle cat feces at all, so this task should be assigned to another family member while Mom is expecting.

Encouraging young children not to eat dirt or sand may seem nearly impossible, but it will reduce the likelihood of them contracting a nasty disease.

If you are concerned that you or your family may have contracted a disease from your pet, consult your family doctor.

References
Fact Sheet: Toxocariasis, Roundworm Infection. Centers for Disease Control and Prevention, Division of Parasitic Diseases. http://www.cdc.gov/ncidod/dpd/parasites/toxocara/factsht_toxocara.htm
Fact Sheet: Hookworm Infection. Centers for Disease Control and Prevention, Division of Parasitic Diseases. http://www.cdc.gov/ncidod/dpd/parasites/hookworm/factsht_hookworm.htm
Fact Sheet: Dipylidium Infection, cat and Cat Flea Tapeworm. Centers for Disease Control and Prevention, Division of Parasitic Diseases. http://www.cdc.gov/ncidod/dpd/parasites/dipylidium/factsht_dipylidium.htm
Fact Sheet: Alveolar Echinococcosis. Centers for Disease Control and Prevention, Division of Parasitic Diseases. http://www.cdc.gov/ncidod/dpd/parasites/alveolarechinococcosis/factsht_alveolarechinococcosis.htm
Fact Sheet: Toxoplasma Infection. Centers for Disease Control and Prevention, Division of Parasitic Diseases. http://www.cdc.gov/ncidod/dpd/parasites/toxoplasmosis/2004_PDF_Toxoplasmosis.pdf