Visceral Larva Migrans

What is visceral larva migrans?

Visceral larva migrans is an infection caused by parasitic roundworms passed from animals to humans. It usually affects children. Most people with visceral larva migrans don’t need any treatment. If you do experience symptoms like pain or fatigue, you might need medication to treat the infection.

Visceral larva migrans is usually caused by a roundworm called Toxocara. There are four species of Toxocara roundworms:

• Toxocara canis found in dogs.
• Toxocara cati found in cats.
• Ascaris suum found in pigs.
• Baylisascaris procyonis found in raccoons.

What is toxocariasis?

Toxocariasis is the parasitic disease caused by the larvae of two species of Toxocara roundworms: Toxocara canis from dogs and, less commonly, Toxocara cati from cats.

Toxocariasis is the medical term for a Toxocara infection. The main presentations of toxocariasis include:

• Visceral larva migrans: Affects internal organs, including your liver, lungs and heart.
• Ocular larva migrans: May cause inflammation in your eyes and can lead to vision loss.
• Neurotoxocariasis: Affects your brain and spinal cord. It can cause severe inflammation, seizures and an altered mental state (encephalopathy). This type of infection is rare.

How is Toxocara transmitted from animals to humans?

Toxocara live in the intestines of the animals they infect. They lay eggs that are shed in the animal’s poop. Animal poop with Toxocara eggs in it can contaminate the soil where it lands. These infectious eggs can remain in the soil for several months.

You can become infected with Toxocara if you ingest soil contaminated with its eggs. This usually happens when kids play in contaminated dirt or if you eat fruits or vegetables grown in contaminated soil.

Toxocara don’t grow into adults and lay eggs in your intestines. But the eggs can hatch into immature roundworms called larvae in your digestive tract. The larvae burrow out of your intestines and into other tissues in your body where they eventually die. This damages your tissue and causes any symptoms you might experience.

What is the difference between visceral larva migrans and cutaneous larva migrans?

Although the names sound similar, they are separate conditions. Roundworm larvae that die in tissue throughout your body cause visceral larva migrans. Hookworms — another type of parasitic worm — cause cutaneous larva migrans. People with cutaneous larva migrans usually have an itchy, red rash on their skin.

How common is visceral larva migrans?

Around one in 10 people in the U.S. have been infected with Toxocara at some point. Most people never develop symptoms or know they’ve been infected.

People in some developing countries are more likely to be infected by Toxocara and develop visceral larva migrans.

How common is Toxocara in cats and dogs?

Toxocara can be found in any cat or dog, especially pets that go outside a lot. Studies have found that around 2% of dogs and 5% of cats in the U.S. have Toxocara in their intestines.

Who is affected by visceral larva migrans?

Children younger than six are more commonly infected with Toxocara that cause visceral larva migrans.

People who have cats and dogs are more likely to experience visceral larva migrans.

If you live in a warm climate, you’ll have a higher risk of ingesting Toxocara because their eggs can survive longer in infected soil when it’s hot.

What causes visceral larva migrans?

Toxocara larvae cause visceral larva migrans. After you’re infected, larvae burrow out of your intestines and into organs in your chest and abdomen.

It’s rarer, but larvae can also travel to your eyes, brain and spinal cord, too.

Your body responds to a Toxocara infection by producing extra immune cells in your blood. An increase in blood flow and immune cells to the affected area causes inflammation. Which symptoms you experience depends on how much inflammation your immune system creates in response to a Toxocara infection.

What are the symptoms of visceral larva migrans?

Most people infected with Toxocara don’t experience symptoms. If you do, they might include:

• Fatigue.
• Fever.
• Elevated levels of a type of white blood cell called an eosinophil (eosinophilia).
• Swollen lymph nodes (lymphadenopathy).
• Abdominal pain.
• Hives (urticaria).
• Cough.
• Wheezing.
• Enlarged liver (hepatomegaly).
• Enlarged spleen (splenomegaly).

How is visceral larva migrans diagnosed?

A healthcare provider will diagnose visceral larval migrans with a physical exam and blood tests. Be sure to let your provider know if you have pets or if you might have been exposed to contaminated dirt.

The main test for diagnosing toxocariasis is a blood test called an enzyme-linked immunosorbent assay (ELISA). This test determines whether you have Toxocara antibodies in your blood. It doesn’t confirm whether or not you’re currently infected with Toxocara. Instead, it checks your blood for signs that your immune system responded to an infection at some point in the recent past.

Your provider may recommend other tests to establish a diagnosis, including:

• Complete blood count to assess the amount of red blood cells, white blood cells, platelets and hemoglobin in your blood.
• Imaging tests, including ultrasound, CT scan or MRI to look for inflammation.
• Checking for evidence of parasites in your poop (a stool sample).
• A biopsy to look for larvae in the affected tissue.

How is visceral larva migrans treated?

Most people with visceral larva migrans don’t need any treatment other than rest and waiting for the inflammation to go away.

If you’re experiencing symptoms, your provider may recommend:

• Corticosteroids or nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation.
• Antihistamines to reduce your body’s immune response.

If your provider finds living larvae in your body, you might need an antiparasitic medication to destroy them. This can prevent live larvae from burrowing further and causing more damage, especially to your eyes, brain or spinal cord.

Can I prevent visceral larva migrans?

You can prevent visceral larva migrans with the following steps:

• Don’t eat food grown in dirt that might be contaminated with dog or cat poop.
• Keep an eye on your children when they’re playing outside. Don’t let them put dirt in their mouth.
• Wash fruits and vegetables before you eat them.
• Practice good hand washing techniques. Teach your children to wash their hands before they eat and after they play outside or touch pets.
• Restrict your pets to designated areas to poop and properly dispose of their bagged poop or litter.
• Take your pets to the vet regularly for parasite screenings and deworming.

What is the outlook for visceral larva migrans?

The infection usually goes away on its own.

It’s rare to have long-term complications. If you do they might include:

• Inflammation of the heart (myocarditis).
• Pneumonia.
• Scarring of lung tissue (pulmonary fibrosis).

People with ocular larva migrans and neurotoxocariasis can also experience severe complications, including:

• Blindness.
• Swelling in the brain and spinal cord (meningoencephalitis).

How do I take care of myself or my child?

If you or your child is diagnosed with visceral larva migrans, it’s important to find out how, so you can prevent future infections.

If you have a dog or cat, take them to the vet for testing and deworming regularly. Ask your vet about routine deworming, especially if your pet spends time on their own outside.

Toxocara eggs can live in soil for months. You can prevent infection by picking up pet poop right away.

A note from Cleveland Clinic

You might be surprised to find out that your beloved pet can be a source of infection for your family. Dogs and cats can carry the roundworms in their intestines that cause visceral larva migrans. If you have pets, take extra precautions when cleaning up their poop and take them to the vet regularly. Washing your hands regularly can also help protect you and your family from visceral larva migrans. Wash all your fruits and veggies before eating them.