An unsavoury problem – dog faeces parasite most commonly found at park entrances and playgrounds

Posted on: 27 March 2025

While unsavoury, the findings do pinpoint these locations for targeted interventions to reduce the risk of human infection.

The roundworms of dogs (Toxocara canis) and cats (Toxocara cati) can cause hard-to-diagnose disease in people. While most people do not become ill after coming in to contact with them, the worms can spread to parts of the body such as the liver, lungs or eyes, where they can occasionally cause serious problems like difficulty breathing or loss of vision. Other research has also linked asthma, epilepsy and cognitive decline to this parasite.

The new research – just published in international journal PLOS Neglected Tropical Diseases – sought to identify the levels of contamination (numbers of roundworm eggs) in the soils of 12 Dublin parks; the most common species (indicating whether dog or cat faeces was to blame); and the hotspot locations.

The key results included:

Eggs were found in 9/12 (75%) parks that were sampled

Most eggs were located at park entrances, with playgrounds the next-most common hotspot

The majority of eggs were potentially infective

Most were identified as Toxocara canis, linking their origins to dog (rather than cat) faeces

Dr Jason Keegan, from Trinity’s School of Natural Sciences, is first author of the published research article. He said:

“Toxocara is one of the most common parasitic infections across the globe and while there are many potential routes of infection, it is widely believed that the most common one for people is coming into contact with soil containing infective eggs and then accidentally ingesting them.

“This new research specifically pinpoints the hotspots in Dublin’s public parks where egg counts are highest in soil samples, and that tells us where we need to target our intervention efforts. By providing more signage, bins and a means to clean up after dogs in these locations, we could reduce the level of contamination – and that’s the next step in the research.

“With that in mind, it is important to underline that many dog-fouling reduction interventions are not assessed for their effectiveness after implementation, so it’s imperative that such an assessment is built into any plan in the future. Of the assessments that have been completed, we know posters made by schoolchildren can be useful, perhaps underlining that involving the local communities most impacted by dog faeces in their recreational areas could be an opportunity worth exploring.”

The research was funded by Research Ireland (formerly by the Irish Research Council).

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