Toxocariasis is an illness of humans caused by the dog roundworm (Toxocara canis) and, less frequently, the cat roundworm (Toxocara cati). These are the most common intestinal roundworms of dogs, coyotes, wolves and foxes and domestic cats, respectively. Humans are among the many "accidental" or paratenic hosts of these roundworms. While this zoonotic infection is usually asymptomatic, it may cause severe disease. There are three distinct syndromes of toxocariasis: covert toxocariasis is a relatively mild illness very similar to Löffler's syndrome. It is characterized by fever, eosinophilia, urticaria, enlarged lymph nodes, cough, bronchospasm, wheezing, abdominal pain, headaches, and/or hepatosplenomegaly. Visceral larva migrans (VLM) is a more severe form of the disease; signs and symptoms depend on the specific organ system(s) involved. Lung involvement may manifest as shortness of breath, interstitial lung disease, pleural effusion, and even respiratory failure. Brain involvement may manifest as meningitis, encephalitis, or epileptic seizures. Cardiac involvement may manifest as myocarditis. Ocular larva migrans (OLM) is the third syndrome, manifesting as uveitis, endophthalmitis, visual impairment or even blindness in the affected eye. Signs and symptoms Physiological reactions to Toxocara infection depend on the host's immune response and the parasitic load. Most cases of Toxocara infection are asymptomatic, especially in adults. When symptoms do occur, they are the result of migration of second stage Toxocara larvae through the body. Covert toxocariasis is the least serious of the three syndromes and is believed to be due to chronic exposure. Signs and symptoms of covert toxocariasis are coughing, fever, abdominal pain, headaches, and changes in behavior and ability to sleep. Upon medical examination, wheezing, hepatomegaly, and lymphadenitis are often noted. High parasitic loads or repeated infection can lead to visceral larva migrans (VLM). VLM is primarily diagnosed in young children, because they are more prone to exposure and ingestion of infective eggs. Toxocara infection commonly resolves itself within weeks, but chronic eosinophilia may result. In VLM, larvae migration incites inflammation of internal organs and sometimes the central nervous system. Symptoms depend on the organs affected. Patients can present with pallor, fatigue, weight loss, anorexia, fever, headache, skin rash, cough, asthma, chest tightness, increased irritability, abdominal pain, nausea, and vomiting. Sometimes the subcutaneous migration tracks of the larvae can be seen. Patients are commonly diagnosed with pneumonia, bronchospasms, chronic pulmonary inflammation, hypereosinophilia, hepatomegaly, hypergammaglobulinaemia (IgM, IgG, and IgE classes), leukocytosis, and elevated anti-A and anti-B isohaemagglutinins. Severe cases have occurred in