Toxocariasis is a zoonosis caused by the larvae of toxocara canis and toxocara cati. The disease is transmitted when humans, especially children, accidentally consume soil contaminated with the eggs present in cat or dog feces. The eggs release larvae which spread through the human body causing inflammation and symptoms of toxocariasis. The disease can manifest as visceral larva migrans or ocular toxocariasis or may be covert.
Toxocariasis is a tropical disease caused by the roundworm, toxocara. It is transmitted to humans with the accidental consumption of soil contaminated with the eggs of the parasite excreted in cat or dog feces . The eggs release larvae which puncture the intestinal wall and migrate through the circulatory system to various organs of the human body (brain, eyes, heart, liver, lungs and muscle) where they cause inflammation leading to symptoms of toxocariasis.
The clinical presentation of toxocariasis depends upon the organ system involved and can be classified as:
VLM affects mainly children under the age of five  who present with fever, pain in abdomen, hepatosplenomegaly, eosinophilia, bronchospasm, seizures, neuropsychiatric or cognitive symptoms or encephalopathy depending on the organ system involved.
OLM, on the other hand, affects children in the five to ten year age group and is associated with unilateral visual impairment and, strabismus . In severe cases of OLM, there may be retinal invasion with granuloma formation in the posterior pole, heteropia and macular detachment . There may also be endophthalmitis, papillitis followed secondarily by glaucoma and blindness.
The diagnosis of the disease is based mainly on the history and symptoms of multi-organ or ocular involvement. Serological testing and biopsy or autopsy specimens showing larvae help to confirm the diagnosis.
Toxocariasis should be suspected in a child with a history of pica, contact with dogs or cats, clinical signs of unexplained febrile illness with hepatosplenomegaly, eosinophilia or ocular symptoms. A complete blood count will reveal eosinophilia, although it may be absent in some cases of OLM and covert toxocariasis.
Confirmation of the diagnosis relies on the laboratory demonstration of specific anti-toxocara antibodies in either the serum or aqueous or vitreous fluid of the infected individual. The enzyme-linked immunosorbent assay (ELISA) test which uses antigens from the second stage larva is the best indirect test for the diagnosis of toxocariasis. Although histopathology of tissue samples with the identification of larvae or the detection of larval DNA in tissues is definitive, it is difficult to obtain such infected tissue samples  .
The diagnosis of OLM is based on clinical criteria and ophthalmic examination as immunodiagnostic tests are not as reliable as for VLM . Neuroimaging, especially magnetic resonance imaging (MRI) is recommended to detect granulomas in the cortical or subcortical layers of the brain in patients with neuropsychiatric symptoms. MRI findings combined with cerebrospinal detection of eosinophil is indicative of toxocara infection.