A dog with worms is an unhappy, unfulfilled and potentially very poorly dog. You won't be surprised to learn that one of the more common queries we receive is from dog owners who want to know how often should I worm my dog because the frequency of worming your dog is something that requires some further analysis. It's not quite as simple as a number. You'll see why when you read on.
Dog worms used to be considered as 'just something you have to accept'. Not any more. We know that dogs can actually pass on nasty illnesses to humans as a result of worm infection and if that's not enough to motivate the average dog owner to keep their dog free of worms, the very fact that a worm infestation can actually prove fatal should really do the trick.
Worms generally tend to be more prevalent in younger animals, but there is a common misconception that by simply treating worms in puppies the dog won't require regular worming as he or she grows. The fact is, a dog can be infected and reinfected with worms at any time. So even a dog who has been wormed very recently can still reinfect themselves within days, let alone weeks.
Zoonotic diseases are those that can be passed on by animals to humans. They can be very serious, in extreme cases can even cause blindness.
To find out more about the most common types of dog worms and how they can affect a dog's health, we spoke with Dr Sue Huggett, who holds a PhD in parasitic worms and is the Business Manager for Beaphar UK, a pet healthcare and pharmaceutical manufacturer whose product range includes wormers, fleas treatments and other healthcare products for cats, dogs, small animals and birds.
The two most common types of dog worms explained
Dr Huggett tells us that the most common canine intestinal worms are roundworms and tapeworms and shares their symptoms.
“Roundworms are slender with ‘spaghetti-like’, cylindrical bodies. They are prolific egg-layers and just a few worms can produce large numbers of eggs. These eggs are passed with the dog’s faeces and can infect other dogs or remain dormant in the environment for years.
“Symptoms of a roundworm infestation vary, with many animals not showing any signs at all. Signs can include a pot-bellied appearance, changes in appetite, weight loss, dull coat, vomiting or diarrhoea, scooting and on occasion, visible worms in faeces or vomit. However, absence of these symptoms does NOT mean your dog doesn’t have worms.”
“Tapeworms are flat worms formed of multiple segments. In addition to your dog, tapeworms require a second intermediate host to complete their life cycle, which, depending on the species of tapeworm could be a sheep, rabbit, small rodent or a flea. The most common type of tapeworm, Dyplidium caninum, is mainly spread by fleas. Cats and dogs ingest the infected flea (containing a tapeworm larva) whilst grooming, which is then released into the host’s stomach where it continues its life cycle.
“Symptoms of a Dyplidium caninum tapeworm infestation often include seeing white segments, which can resemble grains of rice, around your dog’s bottom or in their faeces. Shed Taenia tapeworm segments will look like a small section of a tape measure.”
Rising concerns about lungworm
A parasite many dog owners fear, a lungworm (Angiostrongylus vasorum) infection is much less common than round or tapeworm, but can be very serious or even fatal. It can cause varied signs such as coughing, weight loss and bleeding disorders. Any dog owner concerned that their dog may have lungworm should speak with their vet immediately.
How do dogs get worms?
Most responsible dog owners know that they should be worming their dog but there are many myths regarding how often to worm dogs and what to worm with.
Here are the facts:
Why worm your dog?
Worms are masters of multiplication and survival so there are plenty of worms out there waiting to infect your dog.
Dr Huggett reminds us that there are several ways your dog can become infested with worms.
“Infested dogs shed worm eggs back into the environment via their faeces. If the faeces are not picked up immediately, worm eggs can lay dormant in the environment for months and even years. This means dogs can become infected long after the previous host has shed the eggs. Roundworm eggs are particularly sticky, often becoming caught on pet’s fur, paws or noses and then ingested while grooming.”
Scavenging or eating infected raw meat
“Birds, sheep, cattle and small mammals act as an intermediate host for different types of parasitic worms. Cats, dogs and even people can become infected by eating an infested intermediate host. This is either in the form of uncooked meat or offal (kidneys, liver and lungs) or by catching and eating prey that is infected with the developmental stages of a worm.”
“Fleas act as an intermediate host to the most common type of tapeworm, Dipylidium caninum, and are often ingested while grooming. If the ingested flea is carrying a tapeworm larva, your dog will become infected with tapeworms too. Even if your dog is regularly treated for fleas, it's still very likely they will have come into contact with another pet or place where fleas are present.”
During pregnancy and/or during nursing
“In healthy adult dogs, many of the roundworm larvae travel to other areas within the body, especially the muscles, where they form harmless, dormant cysts, which can remain inactive for many years.
"However, during pregnancy, when the body’s immune response is compromised, roundworm larvae are released from the cysts and become active again. The larvae then migrate across the placenta in the womb to the unborn puppies. Roundworms are also passed through the mother’s milk during nursing. Therefore, regular worming of newborn puppies is essential.”
How to tell if your dog has worms
It can be difficult to know if your dog is infected with worms.
Your dog can appear totally healthy and may not pass worms in their faeces as is often thought or may display symptoms of worm infection, such as scooting their bottom on the ground, vomiting, diarrhoea and even weight loss. In addition to this, a dog with worms poses a health risk to other animals and humans.
Dr Huggett says, “Symptoms of both roundworms and tapeworms are often hard to spot, making a regular worming regime the only way to be sure your pet remains worm-free. For more information, speak to your specialist pet retailer.”
How often should I worm my dog?
“The frequency of a worming routine can depend on several factors, including the dog’s age, geographic location and lifestyle (for example, if they live outside, are working dogs, scavengers etc) and the type of wormer you use.
“As a general rule, when using a broad-spectrum wormer to treat intestinal roundworms and tapeworms, we recommend worming adult dogs every three months,” Dr Huggett tells us.
Does a dog’s age change how often they should be wormed?
Here's what you need to know about how often you should be worming your dog, whatever their age, according to Dr Huggett.
“Worms can cause serious harm to dogs of all ages but puppies are considered to be most at risk. This is due to an underdeveloped immune system, the likelihood of reinfection from their mother and because the damage caused by worms can severely affect their development.
“Nursing bitches and puppies should be wormed every two weeks until the puppies are 8 weeks old. Once the puppies are 12 weeks old and the bitch is no longer nursing, they can all be wormed once every three months. As young dogs are still growing and developing, some vets recommend you worm once a month between the ages of 12 weeks and six months, and then move onto a three monthly routine. Pregnant bitches should only be wormed following a risk-benefit assessment by a veterinary surgeon. Most adult dogs should be wormed every three months.
“Always read your chosen product’s leaflet and packaging carefully to ensure you are treating your dog or puppy correctly.”
Some experts advocate treating older dogs less often due to chemicals. Do you still need to worm older dogs as often?
“Yes, it is very important to continue to worm older dogs. Some argue that older dogs don’t need to be wormed as often because they are often less mobile, and so people feel they are less likely to be exposed to worms.
“However, roundworms that have formed harmless cysts in a dog’s soft tissues, such as muscles, throughout the dog’s life can reactive when their immune system begins to fail in old age. The released larvae can then complete their life cycle and produce a worm burden causing discomfort and even illness in elderly dogs.
“In addition, the most common type of tapeworm is spread by fleas, which puts dogs of all ages at risk. For more information, speak to your specialist pet retailer,” says Dr Huggett.
What are the main differences - if any - between over-the-counter and prescription worming treatments?
There are many types of dog wormers. As an expert in the field, we asked Dr Huggett to explain some of the differences.
“The main difference is that over-the-counter wormers have been proven to be sufficiently safe and easy to use that they don’t require the added advice of a veterinary professional. Any medicine, regardless of whether it’s sold over-the-counter or prescribed by a vet, has to go through the same stringent testing for efficacy and safety to be granted a licence for sale.
“You can tell if a product is a licenced medicine by looking on the pack for a number preceded by the letters ‘Vm’. Over-the-counter veterinary medicines will also bear an AVM-GSL symbol, like the one pictured. All licenced medicines are proven to do what the label says. Therefore, if an over-the-counter wormer says it will kill intestinal roundworms and tapeworms, then that’s exactly what it will do. If you are unsure of the most suitable product for your dog, speak to your specialist pet retailer or vet.”
Is it true dogs can be reinfected soon after being treated?
Something we have wondered about with our own dogs, we took the opportunity to ask Dr Huggett if this is true.
“Yes, this is true. Wormers are only effective on the parasites present at the time of dosing and don’t have any residual effect. This means a dog could become infected again within days of being dosed.
“By following a regular worming routine you can prevent a worm burden building up to the point where an infestation causes clinical problems. This is why it is so important to limit the contamination of worm eggs into the environment by picking up your dog’s faeces and adopting a regular worming routine to keep your pets and family safe.”
Are dog worms seasonal?
Something many dog owners have asked us, we asked Dr Huggett for her expert advice.
“No, dogs can pick up worms at any time of year. It is important to follow a regular worming routine all year round and best practice is to always pick up after your dog.”
What are the health implications to dogs if not treated for worms (whether at all or regularly)?
Dr Huggett shares some of the biggest risks to a dog’s health through lack of worming.
“Health complications of a worm infestation can vary greatly depending on the dog’s age, life stage and overall health, as well as the number and type of worm that the dog is infested with.
“As a worm burden increases, the worms will start to take a disproportionate amount of nutrients from the dog’s intestines. This can damage the gut, stunt growth, cause diarrhoea, dehydration, anaemia and put dogs off their food, leading to severe weight loss and a general lack of condition. In rare occasions, worms can cause an intestinal obstruction and may even prove fatal.
“Additionally, certain worms are capable of being transmitted from animals to humans; such worms are said to have ‘zoonotic potential’. The dog roundworm, Toxocara canis, and cat roundworm, Toxocara cati, are probably the best known of these.
“Occasionally, roundworm infestations have been linked to blindness and asthma in children. So by regular worming, you are not only helping to keep your pet healthy but you are also protecting your family from any health implications.”