Worming and Giardia in Dogs

Hardly any topic accompanies a dog's life as steadily as worming – and precisely because it is so taken for granted, it is often underestimated. Yet worms are extremely common in dogs, some can pass to humans, and in Switzerland the fox tapeworm adds a parasite that is worth knowing about. And then there are the giardia – tiny lodgers that are constantly mentioned in the same breath as worms, yet have nothing to do with them at all.

A note up front: this article is general orientation, not a substitute for veterinary advice. Which worming schedule suits your dog and what a treatment looks like in an individual case is always decided by the vet, who knows your dog and its way of life. Side by side with vaccinations, worming is one of the two pillars of routine preventive care.

Why Worming Matters at All

Worms are not a sign of neglect but part of a dog's life: while sniffing, licking and eating out and about, a dog almost inevitably picks up worm eggs or larvae. Many go unnoticed for a long time, because a healthy adult dog copes well with a light infestation. It becomes problematic from two directions: heavy worm burdens can harm the dog – especially puppies with their still immature immune system – and some worm species are zoonotic, that is, they pass from animal to human.

The most prominent are the roundworms (Toxocara canis). Their eggs reach the environment in the faeces and can be picked up by humans via dirty hands or contaminated soil. Children are particularly at risk, because they play in the sand and put their hands in their mouths. Worming is therefore never just a question of the dog's health, but always also a piece of family hygiene.

One misconception stubbornly persists: that a wormed dog is now 'protected'. Unfortunately that is not the case. Worming does not work preventively – it only clears out the worms present at the moment of treatment; the very next day the dog can be reinfected. That is precisely why it has to be repeated regularly or replaced by regular testing.

Which Worms Affect Dogs

Behind the word worms lies a whole group of parasites that can be roughly divided into two families: roundworms and tapeworms.

The roundworms include the common roundworm (Toxocara) already mentioned, above all an issue in puppies, the hookworms, which anchor themselves in the intestinal lining and suck blood, as well as the whipworms in the large intestine. They all shed their eggs in the faeces, from where the cycle begins anew.

The second group is the tapeworms. They are usually taken up via an intermediate host – via fleas, raw meat or small animals caught as prey. Among them are two species that deserve particular attention in Switzerland: the fox tapeworm (Echinococcus multilocularis) and the dog tapeworm (Echinococcus granulosus). Both are significant for humans as well – we devote a separate section to the fox tapeworm below.

The Worming Schedule: Puppies and Adult Dogs

How often a dog should be wormed depends on age and way of life. The schedule is densest in the first stage of life.

In puppies, worming begins astonishingly early: as soon as around two weeks they are treated against roundworms, then every two weeks until about two weeks after weaning. Because the mother's milk is a source of infection, the nursing mother is treated at the same time. After that it continues regularly – often monthly up to around the sixth month of life. The exact plan is set by the vet practice; more on this in our guide for puppies.

In the adult dog, everything depends on the risk. The European specialist body ESCCAP explicitly states that once or twice a year is not enough for most dogs. If the individual risk cannot be assessed, treatment at least around four times a year is regarded as a sensible basic rule.

Depending on the way of life, this frequency rises. Dogs that roam freely, hunt or eat prey and carrion should be treated against tapeworms monthly; for raw-fed dogs (BARF), about every six weeks applies. A quiet apartment dog simply has a different risk from a young hunting dog – which is why there is no single plan for all.

Testing Instead of Treating

Not everyone wants to treat their dog by a fixed calendar without knowing whether there are any worms present at all. For this there is an equivalent alternative: testing instead of treating.

Here the faeces are examined in the laboratory at the same intervals – treatment follows only if something is actually found. A meaningful sample is important: because worms do not shed their eggs evenly, the faeces are ideally collected over three days (a few grams each time), so that a single 'clean' day does not give a false picture.

Both routes – treating regularly or testing regularly – are defensible and have their own advantages and disadvantages. Which one suits better is best discussed with your vet; an overview of practices near you is offered by our list of vets. For both routes the same holds: a single test or a single treatment is not enough – what counts is regularity.

The Fox Tapeworm in Switzerland

One parasite deserves particular attention in Switzerland: the fox tapeworm (Echinococcus multilocularis). It is endemic here, that is, it occurs across the region in the fox population. Dogs become infected by eating infected wild rodents – above all mice. A dog that likes to hunt mice is therefore a classic candidate.

It is tricky because of its significance for humans. It is zoonotic: if a person takes up the tiny eggs, larvae can develop that slowly damage organs over years – above all the liver. The disease, alveolar echinococcosis, is serious. For dogs that hunt or scavenge, regular tapeworm treatment is therefore especially important – hand in hand with good hygiene: consistently pick up faeces, then wash your hands.

Travel plays a part too: for leaving the country and re-entering, a tapeworm treatment within a set time window is often required. The rules differ from country to country and sometimes change – check them in good time. More on this in the guide to travelling with a dog.

Giardia: A Different Problem

And now to giardia, which are often mentioned in the same breath as worms but are in truth something quite different. Giardia are single-celled parasites (protozoa) – precisely not worms. This has an important consequence: an ordinary worming product does not reliably remove them. Anyone who simply reaches for a worming treatment in the case of digestive problems misses the target here.

Giardia are common, especially in puppies and wherever many dogs come together. Typical is a recurring or fluctuating diarrhoea, sometimes slimy or foul-smelling; in puppies growth can suffer as well. At the same time, some dogs carry giardia without ever showing symptoms. Because diarrhoea has many causes, it is worth a look at our article on diarrhoea in dogs – but the diagnosis itself belongs in expert hands.

Giardia are detected through a faecal examination; sometimes several samples are needed, because the pathogens are not shed continuously. If the suspicion is confirmed, the vet prescribes a targeted medication – always together with thorough hygiene. This is decisive, because the hardy cysts survive in the environment, so that without cleaning the dog keeps reinfecting itself again and again. This includes washing the dog bed and blankets hot, wiping down surfaces, bathing the dog (especially the hindquarters, where cysts cling to the coat) and picking up faeces immediately. If several dogs live in the household, usually all of them are treated together, often with a follow-up check afterwards. For healthy people the risk is generally low – but a little hand hygiene is nonetheless wise. In the case of persistent complaints, the way leads to the vet practice; you should not try anything with human medicines on your own initiative here.

Hygiene: Half the Battle

Whether worms or giardia: a large part of the success lies not in the tablet but in everyday life. Picking up and disposing of faeces is the most effective single measure, because it breaks the cycle of shedding and reinfection – for your own dog as well as for all the others on the meadow. Then the plain classics: wash your hands after the walk and before eating, keep bowls clean, clean the resting place regularly.

One may be especially careful where children and dogs live together. Because small children are often on the floor and put their hands in their mouths, it is precisely they who benefit from the hygiene surrounding worming. How a relaxed coexistence succeeds from the start, we describe in the article dogs and babies.

In the end, worming shows how unruffled routine and a little knowledge achieve a great deal: a suitable plan – whether treating or testing – a watchful eye on the fox tapeworm and giardia, and everyday hygiene. You settle the individual schedule and every treatment with your vet; this guide does not replace personal advice but helps you ask the right questions. That way your dog stays healthy – and your family right along with it.