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Well March has arrived. I like the month, it sits between winter and spring and keeps us guessing while at the same time hoping and dreaming of warmer days. A month full of contrasts, March for me is optimistic even though my birthday lies in wait in the middle of the month, a reminder that time is passing so I’d better get on and actually do something!
Like most professions, we have an official monthly journal, the “Veterinary Record” which comments on current veterinary affairs and serves up a helping of relevant political issues and research. I cannot say it makes an entertaining read. However, once in a blue moon an edition is published that contains an article of real relevance to vets in general practice and the general public. Last month was an example. The front cover pictured three pet dogs being walked in a park with the question, “How prevalent are Toxocara eggs in UK park soil?” A summarised version of the research paper behind this headline made for interesting and scary reading with direct relevance to everyone who owns a dog or cat. The perfect subject for a Sherborne Times article, thinks I, with the bonus of a link to last month.
So, off I go on a detailed description of the science behind the life-cycle of the all-too-common intestinal roundworm of dogs and cats, called “Toxocara”. Oh, the temptation to wallow in the fascinating details of this parasite was irresistible until I realised, not for the first time, that writing about science should not be full of impenetrable scientific jargon. For anyone who wants more detail, just Google “Toxocara canis life cycle”.
Let’s get back to the question; is our environment contaminated with parasite eggs from dogs and cats? Answer, Yes! Does this matter? Answer, Yes! So let’s have a closer look at the findings of the research. Soil samples were taken from public parks and recreational areas across the UK and in almost 90% of the areas sampled Toxocara eggs were found in just 50g samples of topsoil. Am I surprised? Yes! So where have all these parasite eggs come from and do they pose a hazard to public health, children in particular? I’ll answer the first question in that sentence as the second is rhetorical, although I will elaborate on this later.
There are more than 13 million dogs in the UK and about the same number of cats. It’s likely that up to 75% of these 25 million or so animals are not treated for roundworms as often as they should be, so a reasonable estimate is that at any one time, around 19 million are capable of excreting roundworm (Toxocara) eggs in their faeces. The eggs are microscopic so obviously cannot be seen with the naked eye, a factor that contributes to some owners thinking their pet does not have a worm burden. As the eggs are almost indestructible, they survive long after the organic matter of the faeces has disappeared, laying dormant in the soil or being washed into water courses. It’s true that foxes carry Toxocara and so shed eggs in their faeces but fox numbers are inconsequential compared to our pet dogs and cats.
Can roundworms harm dogs and cats? The short answer is yes, particularly puppies and kittens, although these days heavy infestations are rare. The vast majority of puppies are wormed several times by breeders which helps to limit Toxocara numbers but most semi-feral cats who give birth receive little or no worming treatment and nor do their kittens.
The message behind the research article is one of public health and a real wake-up call to all of us, owners and vets alike. The reason is simple, Toxocara in humans has been greatly unrecognised and undiagnosed for years, mainly because the larvae are tiny and can hide in any organ of the human body. Only recently has medical science been able to demonstrate Toxocara larvae in a range of human conditions, from ocular impairment, epilepsy, cognitive dysfunction and asthma. Ingestion of soil or water contaminated with Toxocara eggs, passed in the faeces of dogs and cats is the primary source of human infection.
So, what can we do about it? I am sure most readers of the Sherborne Times worm their pets regularly (at least 4 times per year for cats and 8 times for dogs) but we can be sure plenty of owners are not so responsible. The importance of collecting dog faeces and disposing of it properly cannot be emphasised enough, as wild birds and mammals can spread the eggs, as can earthworms. Chucking dog faeces in the hedge may hide the evidence but it won’t stop the eggs contaminating the environment, as the research in public parks has demonstrated. We don’t have data from the countryside to compare with the urban parks in the study but as egg numbers correlated well with perceived levels of dog fouling, most of us are aware of these areas.
There is probably very little we can do with the Toxocara eggs already in our soil as they are resistant to extreme temperatures and disinfectants, not as though use of either is practical on large areas of land. What we can do is ensure our pets are treated against roundworms every 1-2 months and pick up after our dogs. Never be without a poo-bag!