Toxocariasis is a rare infection caused by roundworm parasites (Toxocara). It is spread from animals to humans via their infected faeces.
The roundworm parasites live in the digestive system of dogs, foxes and cats. The worms range from 4cm to 12cm in length (1.5-5 inches).
The worms produce eggs, which are released in the faeces of infected animals and contaminate soil.
If someone accidently eats small particles of contaminated soil, they may develop toxocariasis. See Toxocariasis - causes for more information.
Types of toxocariasis
The symptoms of toxocariasis can vary depending on where in the body the infection occurs. There are three main types of toxocariasis:
- covert toxocariasis
- visceral larva migrans
- ocular larva migrans
Covert toxocariasis
Covert toxocariasis is the most common and mildest form of toxocariasis. Symptoms of covert toxocariasis include abdominal pain, a cough and headache.
Visceral larva migrans
Visceral larva migrans develops when large numbers of parasites spread through different organs of the body, such as the lungs, liver and heart.
The main symptoms of visceral larva migrans are fever, abdominal pain and shortness of breath.
Ocular larva migrans
Ocular larva migrans is the least common but potentially most serious type of toxocariasis. The condition can develop if the roundworm parasites move into the eyes.
The main symptoms of ocular larva migrans are blurred or cloudy vision and irritation of the eyes. Left untreated, ocular larva migrans can result in permanent vision loss, although only one eye is usually affected.
How common is toxocariasis?
Toxocariasis is an uncommon condition in this country. It is hard to estimate exactly how many cases of toxocariasis occur every year as the covert toxocariasis and visceral larva migrans forms of the condition often are misdiagnosed (or undiagnosed).
One researcher estimates that there are around 50 -100 cases of the ocular form of the condition each year in the UK.
However, many people have toxocara antibodies in their blood, which indicates that they have been exposed to the parasites.
Toxocariasis usually affects children aged between one and four years old. However, cases have been reported in people of all ages.
Young children are particularly at risk of getting toxicariasis because their play habits make them more likely to come into contact with contaminated soil, and many young children have a habit of eating soil.
Outlook
Treatment involves taking medication to kill the parasites. Most people will quickly make a full recovery and won't experience any long-term complications. See Toxocariasis - treatment for more information.
Due to advances in treatment, the potential risk of blindness is now a very rare complication of toxocariasis.
