Blood draw
Toxocara (IgG toxocariasis)
Toxocara IgG; parasitic exposure.
€ 35,00
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Infections · Blood
Toxocara IgG
Antibodies against the roundworm of dogs and cats; many people have them without ever having been ill.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
Toxocara IgG: what is measured?
Toxocara is the roundworm of dogs (Toxocara canis) and cats (Toxocara cati). The eggs end up in sand and soil with the feces and remain infectious there for years. People take them in through the mouth, for example while gardening, playing in a sandbox or from unwashed vegetables. The larvae cannot grow into adult worms, but migrate through the body and become encapsulated. This test measures IgG antibodies against substances that the larvae release.
What can it detect?
- A past or existing infection with the roundworm larva of dogs or cats
- Support for the investigation of unexplained eosinophilia (a raised number of a certain type of white blood cell), especially in children
- Support for the investigation of inflammation in the eye whose cause is unclear
Result
What does the result mean?
Positive result
A positive result means that your immune system has had contact with Toxocara larvae. This is common: in the Netherlands, about 16 in 100 people have these antibodies, usually without ever having had symptoms. The larvae can survive in the body for up to about ten years, so the result does not say when the infection took place. The result only becomes meaningful with matching symptoms, such as unexplained eosinophilia with abdominal pain and coughing, or an eye inflammation. Cross-reaction with other worms, such as Ascaris, occurs and is ruled out with an additional blot.
Negative result
A negative result makes a Toxocara infection less likely, but does not rule it out. With inflammation in the eye caused by a larva, there are sometimes no or hardly any antibodies to be found in the blood: according to the guideline on uveitis, a negative Toxocara serology does not rule out ocular toxocariasis. In that situation, the ophthalmologist can test fluid from the eye itself.
After an abnormal result
With a positive result and matching symptoms, the GP assesses the blood count and liver values and refers to the hospital if needed; with eye symptoms, treatment goes through the ophthalmologist. Most people with antibodies are not treated, because the larvae become encapsulated on their own. Toxocariasis is not notifiable in the Netherlands.
Reliability
How reliable is the test?
What a positive result means in people without symptoms has been little studied. The test is an ELISA for substances that the larva releases; to rule out cross-reactions with other worms, the result can be confirmed with a blot. The RIVM (Dutch National Institute for Public Health and the Environment) states that there are no clear criteria and no standardized testing agreements for toxocariasis, so results between laboratories and studies are not easy to compare. Because about 16 in 100 people in the Netherlands have antibodies, a positive result without matching symptoms is usually not an explanation for those symptoms.
What can affect the result?
- Antibodies remain detectable for years; the larvae can survive in the body for up to about ten years.
- Cross-reactions with other worms, such as Ascaris, occur; confirmation with a blot is then needed.
- There are no standardized criteria or cut-off values, so results from different laboratories cannot simply be compared.
- A negative result does not rule out inflammation in the eye caused by a Toxocara larva.
Who it is for
Who is the test useful for?
Useful for
Can be useful with unexplained eosinophilia, especially in children with recurring abdominal pain, headache or coughing, and with inflammation in the eye whose cause is unclear. Not useful as a general check in people without symptoms, not even if you have a dog or cat at home or garden a lot: antibodies are then often present without disease, and a positive result does not change the approach.
How common is it?
In the Netherlands, about 16 in 100 people have antibodies against Toxocara; in other European countries this ranges from about 2.5 in 100 in Germany and Denmark to higher figures elsewhere. Disease caused by Toxocara is much rarer than carrying antibodies and mainly affects children aged 1 to 3, who come into contact with sand and soil more often. Roundworm eggs were found in an average of 20 in 100 sandboxes and parks tested in the Netherlands.
RIVM, Infectious Diseases Bulletin 2018
Drawbacks and risks
- About 16 in 100 people in the Netherlands have antibodies without being ill; a positive result is therefore easily seen as an explanation for symptoms that have another cause.
- Because there are no standardized criteria, a positive result can lead to unnecessary further tests or a treatment that does more harm than good.
Get tested
Toxocara IgG: test panels
Toxocara IgG is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
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