Wednesday, April 6, 2011

Neglected Infections of Poverty - Toxocariasis

From Centers for Disease Control and Prevention (CDC): Expert Commentary

LCDR Paul T. Cantey, MD

I'm Paul Cantey, a Medical Epidemiologist with CDC's Division of Parasitic Diseases and Malaria. Today, I'm here to speak with you as part of the CDC Expert Video Commentary Series on Medscape. I'll be talking about one of the neglected infections of poverty, which are infections that disproportionately affect minorities, women, and disadvantaged groups in the United States.
Often clinicians do not receive sufficient training in the diagnosis and treatment of these infections, which include, but are not limited to, Chagas disease, congenital cytomegalovirus infection, cysticercosis, toxocariasis, toxoplasmosis, and trichomoniasis.

Today, we'll discuss the clinical aspects of just 1 of these infections -- toxocariasis.
Toxocariasis is a human disease caused by infection with the larval stages of the dog or cat roundworm.
Humans become infected by ingesting embryonated eggs in soil or food or encysted larvae in raw tissues from cows, sheep, or chickens.
The seroprevalence of infection with Toxocara is 14% in the United States, and the highest prevalence is in the southern United States.
Risk factors include poverty, low education levels, and dog ownership.
Soil contamination is common; areas of particular concern are sandboxes and places in yards and public parks where animals defecate.

There are 3 clinical forms of Toxocara infection.
The first is called mild toxocariasis. Although it may be asymptomatic, children may present with fever, headache, behavioral and sleep disturbances, cough, anorexia, abdominal pain, hepatomegaly, nausea, and vomiting. Peripheral eosinophilia may also be present.
In adults, mild toxocariasis can be associated with chronic dyspnea, weakness, rash, pruritus, and abdominal pain. Eosinophilia is much more likely to be present in adults.
Mild toxocariasis is often undiagnosed because the patient is not sick enough to seek medical attention.

The 2 more severe forms of the disease are visceral toxocariasis, also known as visceral larva migrans, and ocular toxocariasis, known as ocular larva migrans. Visceral toxocariasis typically occurs in children, although it can infect persons of any age.
Signs and symptoms include fever, lower respiratory symptoms, hepatomegaly, abdominal pain, and anorexia. The skin, heart, kidney, or central nervous system can also be affected. Symptoms are usually severe enough for the patient to seek medical attention. Eosinophils are usually markedly elevated.

Ocular toxocariasis typically occurs in 5- to 10-year-olds, but up to 20% of cases occur in people over the age of 16. Usually only 1 eye is affected, and manifestations can include strabismus, unilateral decreased vision, and leukorrhea. Eye exam may show peripheral posterior polar retinal granuloma and endophthalmitis, with a vitreous band on ultrasound. Eosinophils are often not elevated.

Diagnosis of mild and visceral toxocariasis is made using an enzyme-linked immunosorbent assay (ELISA).
Ocular disease is diagnosed on the basis of clinical criteria because many patients do not develop an antibody response.
Diagnosis cannot be made with stool ova and parasite testing because Toxocara does not reproduce in humans.

Treatment of toxocariasis varies depending on the type of infection.
Mild toxocariasis may not need to be treated.
Visceral toxocariasis is treated with a 5-day course of albendazole.
Ocular toxocariasis requires a 2- to 4-week course of treatment with albendazole, along with corticosteroids to control inflammation. Surgery may also be needed.

For more information on toxocariasis, please see the resources listed on this page. Thank you.

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