Medicines for Toxocariasis

What it is

Toxocariasis is a rare infection caused by the larvae (immature form) of a type of roundworm (Toxocara) that lives in the intestines of dogs and cats. Infected animals pass the worm’s eggs in their faeces, and the eggs can then contaminate soil, sand, or the environment. People — often children — can become infected by accidentally swallowing these tiny eggs, for example from contaminated soil, sand, or surfaces (such as by putting unwashed hands or objects in the mouth after contact with contaminated ground, or from unwashed contaminated food). It is not spread directly from person to person, or directly from stroking a pet (the eggs need time in the environment to become infectious). Once swallowed, the larvae can travel through the body, but humans are not the worm’s natural host, so the larvae do not develop into adult worms; instead, they may migrate through the tissues and eventually die, sometimes causing inflammation. Most people who are infected have no symptoms or only mild, non-specific symptoms, and the infection often causes no lasting problems. However, in some cases, toxocariasis can cause illness, and there are particular forms: one form (covert or common toxocariasis) may cause mild, non-specific symptoms such as tiredness, tummy discomfort, cough, or a rash; another form (visceral larva migrans) occurs when larvae migrate through internal organs and can cause symptoms such as fever, tiredness, tummy pain, cough or wheezing, and, sometimes, effects on the liver or other organs, more often in young children with heavy exposure; and, importantly, another form (ocular toxocariasis) occurs when a larva affects the eye, which can cause eye problems and, in some cases, damage to vision, usually affecting one eye — this is uncommon but can be serious for the eye. Toxocariasis is diagnosed based on the symptoms and tests (such as blood tests, and, for eye involvement, eye examination). Treatment depends on the form and severity: many mild cases may need no specific treatment, while symptomatic cases are treated with anti-worm medicines and, where relevant (such as for eye involvement), other treatment, guided by specialists. Because toxocariasis is caught from environments contaminated by dog and cat faeces, prevention through good hygiene and responsible pet care is key. The key messages are that toxocariasis is a rare infection caught from worm eggs in soil contaminated by dog or cat faeces, that it usually causes no or mild symptoms but can occasionally affect the eye or other areas, and that it is preventable by good hygiene.

How it is treated

Toxocariasis is managed according to the form and severity — many mild cases need no specific treatment, while symptomatic cases (including eye involvement) are treated with anti-worm medicines and other treatment as needed; prevention through hygiene and responsible pet care is key. Because toxocariasis is uncommon and its symptoms are often mild and non-specific, it may be considered where there are suggestive symptoms and relevant exposure, and is diagnosed with the help of tests — such as blood tests (which can show the body’s response to the infection), and, for suspected eye involvement, an eye examination by an eye specialist. The approach depends on the form and severity. Many people with no symptoms, or only mild ones, may not need specific treatment, as the infection often resolves without lasting problems. For symptomatic toxocariasis — such as the form where larvae migrate through internal organs (visceral larva migrans), causing symptoms like fever, tummy pain, cough, or effects on organs — treatment with anti-worm (antiparasitic) medicines is used to treat the infection, sometimes along with other treatment (such as medicines to reduce inflammation) depending on the severity and which organs are affected, guided by specialists. For ocular toxocariasis (affecting the eye), which can threaten vision, treatment is managed by eye specialists and may include anti-worm treatment and treatment to control the inflammation in the eye (such as steroids), and other measures as needed, to protect the eye and vision — this form needs specialist eye care. Managing symptoms and any complications is part of care. Because most toxocariasis is caught from environments contaminated with dog and cat faeces, prevention is the key practical message, and is achieved through good hygiene and responsible pet care: washing hands well, particularly after contact with soil, sand, or animals, and before eating; washing fruit and vegetables; supervising young children to reduce them putting soil, sand, or dirty hands or objects in their mouths, and covering sandpits when not in use; regularly worming pet dogs and cats (as advised by a vet) to reduce the worm eggs they pass; and cleaning up and disposing of dog and cat faeces promptly and hygienically, and not letting dogs foul public areas, particularly where children play. These measures greatly reduce the risk. The reassuring messages are that toxocariasis is rare, usually causes no or only mild symptoms, and often resolves without lasting problems, that symptomatic cases (including the occasional eye involvement) are treated with anti-worm medicines and other treatment as needed, and that good hygiene and responsible pet care effectively prevent it; so prevention through hygiene and pet care, and treatment where symptoms occur (with specialist eye care for eye involvement), are the keys to managing toxocariasis.