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Infectious Disease and Microbiology - Larva migrans syndromes
Larva migrans syndromes represent a group of conditions caused by the migration of helminth larvae through human tissues, affecting the skin, internal organs, or eyes. These syndromes include cutaneous, visceral, and ocular forms, depending on where the larvae migrate. Humans are accidental hosts, and the parasites are unable to complete their life cycle, leading instead to tissue inflammation and damage.
The condition is seen worldwide but is more common in tropical and subtropical regions. Infections are particularly frequent in children, especially those under 6 years old. Cutaneous larva migrans is the most common tropical dermatosis, often acquired from contaminated beaches or soil. Visceral and ocular forms are most commonly caused by Toxocara canis and, less frequently, Toxocara cati, with a significant proportion of the population showing evidence of past infection.
Risk factors include contact with soil contaminated by dog or cat feces, poor hand hygiene, and geophagia. Children who play in contaminated environments are particularly at risk. Prevention focuses on avoiding direct contact with contaminated soil, wearing protective footwear, maintaining good hygiene, and regular deworming of pets.
The pathophysiology varies by form. In visceral larva migrans, eggs are ingested and hatch in the intestine, after which larvae migrate via the bloodstream to organs such as the liver, lungs, and central nervous system. These larvae may persist for years, causing chronic inflammation. In cutaneous larva migrans, larvae penetrate the skin but remain confined to the epidermis, migrating and forming characteristic tracks.
Cutaneous larva migrans, commonly caused by Ancylostoma braziliense, presents with intensely itchy, serpiginous, erythematous skin lesions that slowly advance over time. These lesions are most often found on the feet, legs, or areas exposed to contaminated ground. Visceral larva migrans may present with fever, fatigue, abdominal pain, cough, and hepatomegaly, while ocular larva migrans may cause visual disturbances, floaters, or even unilateral blindness due to retinal inflammation.
Physical examination findings vary with the syndrome. Cutaneous disease shows a creeping eruption on the skin, while visceral disease may show hepatomegaly, wheezing, or lymphadenopathy. Ocular disease may reveal retinal granulomas, uveitis, or optic nerve involvement on funduscopic examination.
Laboratory findings in visceral disease often include marked eosinophilia, leukocytosis, and elevated IgE levels. Serologic testing such as ELISA can support the diagnosis. Imaging studies may reveal hepatic or pulmonary lesions, while ocular disease is diagnosed primarily through ophthalmologic examination. Larvae are rarely identified directly in tissue samples.
Treatment depends on the clinical form. Cutaneous larva migrans is treated with antiparasitic agents such as albendazole or ivermectin, and symptoms usually resolve as the larvae die. Visceral larva migrans may not require treatment in mild cases, but severe disease is managed with albendazole or mebendazole. Ocular disease may also require antiparasitic therapy, often combined with corticosteroids to reduce inflammation, although treatment must be carefully managed to avoid worsening ocular damage.
Prognosis is generally good for cutaneous and most visceral cases, with spontaneous resolution common. However, ocular larva migrans carries a risk of permanent vision loss. Complications may include secondary bacterial infection in cutaneous disease, and in severe visceral cases, involvement of the brain, heart, or lungs.
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