Toxocariasis

Image shown is of a patient with toxocariasis. Toxocariasis is a roundworm that is commonly found in the feces of cats and dogs. It has been targeted by the CDC as a neglected parasitic infection. Majority of individuals are asymptomatic however some may develop visceral toxocariasis aka visceral larva migrans. This occurs when second stage larvae migrate to internal organs such as the liver, lungs, skin and central nervous system. In a smaller number of patients the larvae may migrate to the optic nerve and eye. This is called ocular larvae migrans and can result in blindness.

Life Cycle:

See chart below from the CDC. Eggs are excreted in the feces of animals including cats and dogs. Eggs can then spread vertically to puppies or kittens as well as be ingested by other hosts including humans. Humans are Paratenic hosts. This means the larvae can survive and migrate but do not mature passed their L2 stage. In humans infective eggs are typically accidentally ingested via undercooked food. The eggs hatch and progress through the intestinal wall. They are then spread to a variety of other organs where they cause damage via abundance or larvae or by immune system reaction to the roundworm.

Diagnosis:

Diagnosis largely based on symptoms and risk for exposure. Antibody tests are available however they do not differentiate from current or past infection. Serological testing via ELISA and PCR is available and clinicians can consider looking at rises in antibody level overtime to help in diagnosis an active infection. We were lucky enough to catch a larvae on colonoscopy and sent it for pathology!

Treatment:

Treat with Albendazole or Mebendazole. Treatment can be confined with steroids as the killing of large volumes of larvae can result in a severe inflammatory reaction.

Source: Centers of Disease Control and Prevention: Division of Parasitic Diseases and Malaria: https://www.cdc.gov/dpdx/toxocariasis/index.html