Why might a dog have worms even if they are wormed regularly?

It is not usually obvious if a dog is infested with worms unless the infestation is very heavy and the worms are obvious in your dog’s stools, or if the infestation is causing systemic symptoms like weight loss and an insatiable appetite – which is why it is so important to worm your dog regularly and keep to an appropriate schedule, even if you have no reason to believe that your dog actually has worms at all.

However, if you do treat your dog for worms on a regular basis, it can be confusing and worrying to find out that your dog has worms, or that they seem to keep getting worms despite your treatment regime.

Dogs can pick up intestinal worms in a whole variety of different ways, and your dog may be exposed to worms, worm eggs and worm larvae every day when they come into contact with other dogs, or even simply when you take them out walking on public land.

Understanding how dog wormers work and how dogs can get exposed to worms can help you to gain an insight into why your dog has worms, and so, get a better handle on resolving the issue.

In this article, we will explain some of the most common causes behind why a dog that is wormed regularly may still have worms. Read on to learn more.

Wormers are designed to eradicate worms, not prevent them

First of all, it is important to understand that wormers for dogs don’t work in the same way as flea treatments – flea treatments are designed to protect your dog from further flea infestations up until the date of their next due treatment, while most dog wormers are designed to kill worms already in the body, but do nothing to provide protection against future infestations.

This means that your dog might pick up worms again within a couple of days of a treatment cycle -but the treatment cycles for wormers are designed to ensure that even if this does occur, the next dosage will resolve the issue before a serious infestation sets in.

The wormer is ineffective

Not all wormers are equally effective or good quality – tablets that you can pick up in the supermarket from the regular shelves along with your dog’s food are widely considered to be highly ineffective, and so, unlikely to eradicate worms, even if you are vigilant about using them.

Talk to your vet about the best type of wormer for your dog, and you will find this much more effective.

The dosage is wrong

In order to eradicate worms from your dog effectively, it is important to get the dosage right. Over-worming by means of giving too much wormer for your dog’s size can lead to digestive upsets and diarrhoea, but if the dosage is too low, it won’t be fully effective.

Again, your vet can help you to determine the right dosage for your dog’s weight and size.

The wormer isn’t designed to treat the type of worms your dog has

Most good quality dog wormers are designed to tackle the most common types of intestinal worms that affect dogs, but there are a variety of different types of worms that can infest dogs, and not all wormers treat all of them.

For instance, if your dog’s wormer is only designed to treat tapeworms and roundworms, it won’t be effective against hookworms and flatworms, so if you’re not sure or find that the wormer doesn’t seem to be working, you may want to ask your vet to examine a stool sample from your dog to help you to choose the right wormer.

The wormer causes a digestive upset in your dog

Providing that your give your dog an appropriate wormer and get the dosage right, they shouldn’t suffer from any ill effects of taking their medicine – but as with any medicine, wormers can cause digestive upsets in dogs, such as vomiting and/or diarrhoea.

This may mean that the wormer isn’t digested properly and so, proves ineffective – so if your dog tends to get sick for a day or so after worming, let your vet know and try an alternative product.

Your dog is exposed to other dogs with worms

Contact with other dogs can cause worms to spread, in the form of adult worms and their virtually invisible eggs and larvae. If your dog plays with other dogs with worms or that are not wormed regularly, the canine population can pass the infestation from dog to dog with ease, which can lead in re-infestation soon after worming.

Your dog scavenges and eats dead wildlife or stools

Most forms of wildlife like rodents, foxes, squirrels and so on are infested with worms, often heavily. If your dog thinks that animal carcasses, roadkill, mouldering wildlife and fox poo are delicious gourmet snacks, they are highly likely to pick up worms along the way.

If your dog is an adept scavenger, you may want to muzzle them to prevent this, and ask your vet if your dog may need to be wormed more often than is normal to counteract this.

Worm infestations can be picked up from the ground

Certain type of worms – like hookworms – can thrive in the soil, and attach themselves to your dog’s paw pads and enter the body to cause an infestation. Infected land is usually land that a lot of dogs use and more so, land where dog poop isn’t cleared up promptly.

If you find that your dog keeps getting worms and can’t find another obvious cause, it may be worth considering where you usually take them for walks and trying a new route, in case the land in question is the source of infestation.