My Dog Is Pregnant. Do I Worm and Flea Her?

Trent Webb

We get asked this a lot. You want them and their pups to clear of parasites but are worried that the flea and worm treatments may harm either mum or the babies. So how can you flea and worm pregnant dogs?

Think of the little ones

Most importantly as soon as you know your dog is pregnant you should change your anti-parasitic treatment routine. It will still need doing because worms and fleas don’t give two hoots that your dog’s expecting. They can still irritate and feast on mum sapping away her strength just when she (and the puppies) need it most.

So first off, work out where they are in their current flea treatment and worm cycle, as you will need to change when you next use a spot on. You will then have to adjust the frequency and possibly the wormer used too. This may mean that she goes for a week or so without out worm cover.

While for fleas you can implement other methods to break the ‘flea cycle’.

A different sort of worming

You’re going to have get used to a different way of worming. Rather than one big dose every 12 weeks the approach for pregnant dogs shifts to little and often, with small doses given daily as the pregnancy hits mid-term all the way through until after the puppies have been born. This keeps any individual dose down, but keeps the active ingredients pumping around their systems – so keeping them worm free.

Worm infestation can be passed from mum to pups in womb. So if you want the pups to have the very healthiest start, keep mum wormed. Due to the little and often approach then your regular worming tablets are not suitable as they can’t be broken down into small enough pieces accurately. In this situation, only really Panacur offers the right level accuracy as it comes in granules and suspension which allow you to give small doses.

40 days and 40 nights

Well you don’t need to do the whole wilderness thing. What you have to do is work out when it is the 40th day of their pregnancy. This is when you’re advised to start worming your dog in preparation. Now sometimes you won’t precisely know when, but your vet will be able to give you a pretty good idea of when. And it doesn’t really matter if it is actually day 39 or day 41, you just need to start around this time.

Weigh of a time

You’ll need to know what your dog now weighs, as this is the key determinant in how much wormer to give. It is easier (it really is) to do this in Kilos, so nip your dog down to the vets and use their walk-on scales (they really won’t mind) to get an accurate reading, as they will weigh more with pups on-board.

Every 4kg of body weight requires 1ml of Panacur Suspension daily from Day 40 through to 2 days post whelping. That will be approximately 25 days.

Panacur Suspension dosing guide

The alternate formulation Panacur Granules is much the same, just there are three different strength sachets – 1g, 1.8g and 4.5g. For pregnant dogs, the packaging recommends “administer 25mg fenbendazole per 1kg” which is precise but far from clear. In reality, they mean…

worming a pregnant dog - Dosing with Panacur Granules

Now not all dogs are helpful and weigh 8, 16 or 40kg precisely. In this case you’ll need to mix sachet strength and numbers to get a good near match weight (and err under rather than over as you’ve only an 8 kg window). So for example a 25kg dog would get 1 x 1g sachet (8kg) and 1 x 1.8g sachet (16kg), while a 50kg dog would need 1 x 4.5g sachet (40kg) and 1 x 1g sachet (8kg).


For all the regular health and comfort reasons you want to keep your dog clear of fleas while they’re pregnant – imagine the regular bump discomfort and having a constant itch on your back you can’t scratch!  But this does mean there are some tricky decisions to make.

Unlike wormers, where the variable dosing available through Panacur offers a “little and often” approach, spot ons are still “all or nothing”. Non-prescription flea treatments such as Frontline Plus and Frontline Spot On state it “can be used during pregnancy and lactation”. Advantage is less equivocal (due to limited studies) and says “evidence so far suggests that no adverse effects are to be expected”. While Effipro and Flevox are the most circumspect with “use only accordingly to the benefit/risk assessment by the responsible veterinarian”.

Which sort of paints the picture. So don’t just plough in with your regular flea routine while they’re pregnant. Take the time to read the leaflet carefully and if you’re unsure about what to do, talk to your vet – as they also have prescription flea treatments available which they may think better suited to your dog and her condition.

Worms are usually last thing on your mind when you find out there is a litter on the way, but they can have a major health impact on both mum and pups
John Campbell, Head Vet of Pet Drugs Online

It is nearly time

So make sure your keep your dog as healthy as possible during her pregnancy. This means she will be in peak condition for the rigours of whelping (pups can be demanding little buggers).

This post is an opinion and should only be used as a guide. You should discuss any change to your pet’s care or lifestyle thoroughly with your vet before starting any program or treatment.

If in doubt contact your veterinary practice

And always keep your vet's phone number handy - just in case!