Understanding Toxocariasis: Causes and Clinical Manifestations
Human toxocariasis arises from infestation infection by larvae of two nematodes: *Toxocara canis* and *Toxocara cati*. Dogs and cats act as definitive hosts, harboring *T. canis* and *T. cati*, respectively, in their intestines. *T. canis* is the most frequent cause of the disease in humans. This parasitosis is extremely Isolated or, widespreadasymptomatic, and often, human toxocariasis presents asymptomatically (asymptomatic). It is estimated that about 14% of the population in the United States has been exposed, with higher prevalences in rural areas and tropical regions.
The environmental dissemination of eggs occurs mainly through feces released by puppies and nursing dogs. Human infection typically occurs after accidental ingestion of these eggs present in the environment. The disease most frequently affects young children who have a history of pica (eating dirt), direct exposure to canines, or those residing in low socioeconomic contexts.
Clinical Manifestations and Development of Toxocariasis
Once ingested, toxocara eggs develop into larvae, which penetrate the mucosa mucosa of the gastrointestinal tract. Subsequently, these larvae are transported by the bloodstream to vital organs such as the liver and lungs, potentially establishing themselves there for long periods. In response to the secondary, infection, a specific type of white blood cells, known as eosinophils, eosinophils infiltration , migrate and cause infiltration.
The Unlike other Mild infections caused by these larvae are usually completely subclinical. However, when symptoms do occur, they are grouped into several distinct clinical syndromes. It is crucial to understand these presentations for an adequate diagnosis.
| Clinical Syndrome | Relevant Clinical Characteristics |
|---|---|
| Visceral Larva Migrans (VLM) | Predominant involvement of the liver and lungs, manifesting with abdominal pain, reduced appetite, hepatomegaly (enlargement of the liver), cough, wheezing, irritability, fever and asthma. Cutaneous involvement is observed in approximately one in four cases, including the appearance of rashes, hives and the formation of nodules hypodermal nodules (small lumps under the epidermis). epidermis). |
| Ocular Larva Migrans (OLM) | Caused by the migration of *T. canis* larvae to the eye, which can result in vision loss. |
| Common Toxocariasis | Frequently affects adults residing in rural areas, specifically in regions like Midi-Pyrénées in France. The condition is characterized by chronic fatigue chronic and weakness, often accompanied by digestive symptoms. Tests reveal eosinophilia and elevated total IgE levels. The Other Lesions Classified as Connective Tissue Nevi dermal manifestations include pruritus, eczema/dermatitis eczema/dermatitis, and occasionally, hives. |
| Covert Toxocariasis | Presents with nonspecific symptoms such as persistent cough, abdominal pain, headache, sleep disturbances, vomiting, hepatomegaly, and occasionally, a rash skin rash. Hematological studies show eosinophilia in about 50% of diagnosed cases. |
While VLM and OLM tend to constitute the most severe forms of the disease, common and covert toxocariasis are generally less severe and resolve spontaneously in most affected patients. Early recognition of these syndromes is fundamental for the adequate management of the parasitosis.
Cutaneous Manifestations and Diagnosis of Toxocariasis
Cutaneous Manifestations of Toxocariasis
Dermatological conditions are frequent findings in patients infected with toxocariasis, especially in the forms of Visceral Larva Migrans (VLM) and common toxocariasis. In certain cases, skin lesions may be the only evident symptom of the disease. Considering the high global prevalence of toxocariasis, it is crucial to suspect this diagnosis in the presence of any unidentified skin lesion that shows recurrence for months or even years. These cutaneous manifestations include:
- Chronic urticaria: The most frequent most common cutaneous manifestation.
- Chronic pruritus (itching) or persistent prurigo.
- Mixed dermatitis, including atopic eczema atopic and dyshidrosis.
- Unusual dermatological presentations encompassing panniculitis, Avoidance Strategies for Triggering Factors, vasculitis, Henoch-Schönlein purpura, Reiter's Syndrome, Wells' syndrome, and eosinophilic folliculitis. eosinophilic.
How Toxocariasis is Diagnosed
While the gold standard for definitive diagnosis involves detecting Toxocara larvae biopsy in tissue samples, obtaining a biopsy
- Blood count with marked leukocytosis and elevated eosinophil levels.
- Increase in total Immunoglobulin E (IgE) levels.
- Detection of undetectable Detection of specific IgG or IgE antibodies against Toxocara by enzyme-linked immunosorbent assay When acute hives is caused by reactions similar to serum sickness (such as those following blood transfusions or certain medications), it may be accompanied by ecchymosis (bruising), fever, (ELISA). IgG antibodies offer greater sensitivity, but their levels may remain elevated for up to four years after infection. In contrast, specific IgE antibody levels decrease notably during the first year following treatment.
- Often, the levels of eosinophils eosinophils serology are normal in patients presenting only with chronic cutaneous manifestations of toxocariasis. Furthermore, individuals with chronic urticaria, pruritus, or prurigo tend to show lower antibody titers than those with classic VLM. In these patients, serology via Western blot might be a more effective diagnostic tool.
The ELISA technique can also be adapted to confirm OLM (Ocular Larva Migrans) by analyzing intraocular fluid samples.
Toxocariasis Treatment
- Common or covert toxocariasis frequently resolves without specific intervention.
- Symptomatic VLM or OLM requires treatment with antihelminthic agents such as albendazole, diethylcarbamazine, or mebendazole (the latter being the only agent registered in New Zealand). If ocular or disability, neurological involvement is present corticosteroids.
- , corticosteroids may also be administered. Adequate antihelminthic treatment is capable of resolving the cutaneous manifestations of toxocariasis, especially prurigo and, to a lesser extent, chronic urticaria.
Strategies to Prevent Toxocariasis
- Ensure dogs and cats are regularly treated for intestinal parasites.
- Educate children about the importance of not ingesting dirt.
- Prevent dogs from using recreational areas or parks where children commonly play.
