Toxocara - IVD Research, Inc.

Almost 14% of the US population is infected with Toxocara. Toxocariasis is a worldwide infection. It is a zoonotic (animal to human) infection caused by parasitic roundworms commonly found in the intestines of dogs and cats.

You or your children can become infected after accidentally ingesting (swallowing) infective Toxocara eggs in soil or other contaminated surfaces. The larval form is visible only under a microscope. The larvae penetrate the bowel wall and migrate through vessels to the muscles, liver, and lung and sometimes to the eye and brain.

Toxocariasis is almost always a benign, asymptomatic, and self-limiting disease, although brain involvement can cause severe morbidity. Brain involvement can provoke meningitis, encephalitis, or epilepsy.

The most severe cases are rare, but are more likely to occur in young children, who often play in dirt, or eat dirt (pica) contaminated by dog or cat stool, or owners of dogs and cats.

There are two major forms of toxocariasis:

1) Ocular larva migrans (OLM):

Infections with Toxocara can cause OLM, an eye disease that can cause blindness. It happens when a microscopic worm enters the eye; resulting in inflammation and formation of a scar on the retina. Each year more than 700 people infected with Toxocara experience permanent partial loss of vision.

2) Visceral larva migrans (VLM):

Heavier, or repeated Toxocara, while rare, can cause VLM, a disease that causes swelling of the body's organs or central nervous system. Symptoms of VLM, which are caused by the movement of the worms through the body, include fever, coughing, asthma, or pneumonia.

VLM is treated with antiparasitic drugs, usually in combination with anti-inflammatory medications. Treatment of OLM is more difficult and usually consists of measures to prevent progressive damage to the eye.

Disease severity depends not only on the number of larvae ingested but also on the degree of the allergic reaction.

Diagnosis

Symptoms during the acute phase may include the following:

Abdominal pain
Decreased appetite
Restlessness
Fever
Coughing
Wheezing
Hives
History of seizures

Ocular involvement - Decreased visual acuity, seeing floaters or bubblelike images
Clinical diagnosis depends on serologic testing (eg, ELISA, immunoblot). ELISA with aqueous fluid is therefore useful when ocular toxocariasis is suspected. The encapsulated larvae can be found in the liver, lung, brain, and/or enucleated eye. The larvae occur in a matrix of epithelioid cells surrounded by a fibrous capsule with weak inflammatory reactions. In ocular toxocariasis, a mobile larva can be directly observed under the retina.

Treatment

Chemotherapy is the treatment of choice in most patients with liver, lung, or eye involvement. Occasionally, ocular involvement requires ocular surgery.
Treatment also includes mebendazole or thiabendazole and specific organ treatment. Severe toxocariasis involving the lungs, eye, or other important organs may be treated with antiparasitic drugs to kill the larvae. For severe lung toxocariasis, doctors sometimes also prescribe anti-inflammatory drugs.The prognosis of toxocariasis is generally favorable.
For liver or lung involvement, no surgical care is required.
For ocular involvement with retinal detachment, laser treatment may be considered

Prevention

Regularly have your veterinarian treat your dogs and cats, especially young animals, for worms.
Wash your hands well with soap and water after playing with your pets and after outdoor activities, especially before you eat. Teach children to always wash their hands after playing with dogs and cats and after playing outdoors.
Do not allow children to play in areas that are soiled with pet or other animal stool.
Clean your pet's living area at least once a week. Feces should be either buried or bagged and disposed of in the trash.
Teach children that it is dangerous to eat dirt or soil.

If you are moving into a new household inquire about pets in the home. Ask if children play in a sandbox. Ask about pica and handwashing practices and determine if hygiene practices are poor.