Diagnosis of a Baylisascaris infection is difficult because symptoms depend on the number of infecting larvae and location in the body. Ocular larva migrans, when the larvae migrate to the eye, can cause sensitivity to light, inflammation of the eye, and blindness. Symptoms of visceral larva migrans, when the larvae travel to organs, depend on which organs are affected. For example, an invasion of the liver may cause hepatomegaly (inflammation and enlargement of the liver), while an invasion of the lung may cause pulmonary symptoms such as cough or chest pain. Larvae rarely end up in the nervous system but the most severe cases are neural larva migrans, when the larvae migrate into the brain and cause it to swell (encephalitis).

The incubation period (time from exposure to symptoms) of the infection is usually 1 to 4 weeks. If present, signs and symptoms can include:

• Nausea
• Tiredness
• Liver enlargement
• Loss of coordination
• Lack of attention to people and surroundings
• Loss of muscle control
• Blindness
• Coma