Roger Salmon column: The risks to human health of voracious Toxocara parasite

Roger Salmon
Roger Salmon

A common parasite of pet cats and dogs,, worms reside in the gut of pets and lay eggs that are passed in the faeces.

One mature female adult worm can produce up to 84,000 eggs per day. These eggs are not immediately infective, instead taking around two weeks or more to mature, and can persist in the environment long after animal waste has been washed away or decomposed. Accidental ingestion of infected eggs found in animal faeces is the main route of infection for humans.

Studies have shown that children who make a habit of eating soil (geophagia) are significantly more likely to become infected with Toxocara. Heavy worm burdens in young pet animals can cause loss of condition and the typical “pot bellied” appearance of a worm infested puppy. In humans, where migration of the larval stages of the parasite is the cause of disease there are three disease presentations:

nVisceral larval migrans.

This where the human ingests a large number of eggs that cause severe ,acute illness

nOcular larval migrans where small numbers of larvae migrate to the retina (film at the back of the eye), causing damage and affecting vision, sometimes years after initial infection.

*Covert toxocariasis: caused coughs, allergies and asthma.

Vets advise owners to regularly(at least four times a year) worm pets with an effective anthelmintic. Start from a young age (two weeks of age for puppies and three weeks of age for kittens), remembering that transfer of the parasite to puppies before birth is a feature of the parasite life cycle. Reducing pet’s access to raw food can also reduce pet infection.