Parasite Prevention for Dogs

Dogs can truly make a house a home. They’re excellent door-greeters and couch-snugglers, but unfortunately they also make very hospitable hosts for a variety of unwelcome parasites!

Not only do parasites affect our furry family members’ quality of life, but the ones that target our canine companions can also carry risks that affect our whole families. Fortunately, we can keep these dangerous critters at bay with a personalized parasite prevention plan.

These parasites are here in London:

These are the parasites that we are concerned about in our area. Preventative products are available, but they’re not one-size-fits-all.

Your veterinarian can work with you to create your pet’s personalized prevention plan, taking into account their medical history, the other pets in the household, and their risk factors. We’ll help you find the best product, or combinations of products, to keep your little one safe.


Parasite: Transmitted by: Risk: Who is affected?
Heartworm Infected mosquitos Lives in and around the heart, causing heart failure and damage to other organs

Dogs (can be fatal if untreated)

Note: Rare in cats, but risk is increasing

Intestinal worms (hookworm, roundworm, whipworm)

Ingesting the eggs containing larvae

(Often through consuming infected feces)

They rob the body of nutrients causing GI symptoms, anaemia and even death.

Dogs, cats

Note: Can be transmitted to humans

Fleas Other animals/ picked up outside or in infested areas (ex. apartments) Extreme discomfort from bites, anaemia. Can also carry intestinal parasites (ex. tapeworm).

Cats, Dogs

Note: Will bite humans

(Most commonly the American Dog Tick, Blacklegged/deer tick, Lonestar tick, Brown dog/wood tick, and Gulf Coast tick)

Picked up outside or in infested areas, burrows in skin to feed where it can then transmit disease

Depending on the species of tick:
– Lyme disease (lameness, pain in joints)
– Ehrlichiosis (Fever, weight loss, respiratory distress)
– Anaplasmosis (joint pain, fever, lethargy)


Cats can carry ticks but have a very low risk of developing tick-borne diseases

(Sarcoptic Mange/ scabies,
Demodectic Mange/ red mange/ demodex)
Skin disease caused by mites. Picked up from other animals/infested areas Extreme itchiness, rash, infection, hair loss

Dogs, cats

Note: some forms are transmissible to humans

When temperatures become milder, hungry parasites emerge from their dormant states. Around this time, your veterinarian will likely emphasize the importance of coming in for your furry family member’s annual parasite prevention and heartworm test. But what is that “heartworm test” exactly, and why is it so important?

More accurately called a “parasite screening test”, this test also typically screens for common tick-borne diseases such as Ehrlichiosis, Lyme, and Anaplasmosis. A drop of your dog’s blood is placed on a test strip, which will indicate if they have antigen to heartworm disease or antibodies to one of the tick-borne diseases.

Heartworm is transmitted by mosquitoes. These parasites live in and around the heart, causing heart failure and damage to other organs. Lyme disease symptoms include lameness and pain in the joints, while Ehrlichiosis includes fever, weight loss, and respiratory distress. Anaplasmosis involves joint pain, fever, and lethargy.

Annual testing for parasite-borne diseases allows early diagnosis and treatment before symptoms become severe, and a positive test result would affect your pet’s prevention and treatment plan. It is recommended in the spring because it must be performed a minimum of five months after the last possible mosquito bite.

As with any prescription, your pet must have had an exam recently enough for the doctor to be familiar with their health. Some parasite preventatives are not recommended for heartworm-positive pets, so in those cases, a parasite screening test may also be required. Your veterinarian will use their discretion to determine the safest way to proceed, based on product requirements, your dog’s age, and medical history.

Cats should still be on parasite prevention for their wellbeing as well as their families’. However, they are significantly less likely to contract heartworm or tick-borne diseases themselves, therefore, they typically do not undergo parasite screening.

As with many things in life, an ounce of prevention is worth a pound of cure. By preventing, testing, and treating the diseases carried by mosquitoes, fleas, ticks, and internal parasites, we can prevent illness and discomfort for our furry family members while protecting our families and our communities too.

Q: Why is seasonal parasite prevention important?

A: Most parasites tend to lay dormant in the cold weather and become active during the warmer months. These parasites can transmit diseases to your pet that can make them ill and in some cases even be fatal.

There are many types of parasites and different products protect against different parasites. Talk to your veterinarian or a veterinary technician to determine which product is best for your pet’s lifestyle and risk factors.

Q: My dog hardly, or never, goes outdoors. Should they still receive parasite prevention?

Yes. Ticks can hitch a ride indoors on other members of the family and one kind can even live in your baseboards. Mosquitoes, which transmit heartworm, can easily access a balcony, front porch, or come inside the home. Additionally, fleas and other parasites can actually infest indoor areas, especially apartments and shared buildings.

Q: When can my puppy have parasite prevention?

Most products are designed for puppies over eight weeks of age. However, with growing pets, we recommend that they come in monthly to be weighed so that we know we are giving them the correct dosage for their size. We will dispense their prescriptions month-to-month based on their weights.

Q: Does my puppy need a heartworm (4DX) test?

A: If your puppy was born in the winter, they should not need a heartworm/4DX test, since it is unlikely that they were exposed to mosquitos during the cold months. Additionally, it takes a minimum of 5 months from the time a dog is bitten by an infected mosquito until a positive 4DX test can result. That is why we do most heartworm testing in the spring – 5 months after the last possible mosquito bite.

Your puppy should be on parasite prevention starting in the spring. For some preventatives, a negative heartworm test will be required prior to starting prevention. Because your puppy will be growing his dosing will change and we will want to conduct monthly weigh-ins and dispense preventatives on a month-to-month basis.

Q: How much is a heartworm (4DX) test?

A: The test is around $50, but you may want to consider bundling it with Wellness Bloodwork. The company we use for external labs and diagnostics, IDEXX, often has a seasonal sale this time of year (March 1 – July 31) on blood profiles that include the 4DX test. These panels look at some common parameters in your dog’s blood, which gives us an overall indication of organ function and establishes a baseline to compare any future bloodwork.

Q: Which products are available for parasite prevention?

A: For dogs, we typically recommend Nexgard Spectra or Simparica Trio to protect against fleas, tick, heartworm, and other parasites from June-November. Sometimes we will use Multi-Duo. These are all broad-spectrum products from different companies. We will help you find the best option for your household.

Throughout the rest of the year, but especially in April and May, we still recommend protecting against fleas and ticks. Products with a tick-focus may include regular Nexgard or Simparica.

If you have any cats in the household, they will also need to be on prevention in order for the products to be effective at keeping parasites out of the home. For cats, we typically recommend Revolution Plus.

We also stock Bravecto, Capstar, Profender, Milbemax, Interceptor and Advantage.

Q: How do I know which prevention is right for my furry family member?

A: Every pet is unique and parasite prevention isn’t one-size-fits-all, so your veterinarian or veterinary technician is always the best resource to find the ideal prevention for your pet’s lifestyle while considering the other pets in the household and their medical history.

Typically, prevention for dogs is divided into two categories by preference: topical or oral.

• Some families prefer an oral preventative (looks like a treat) such as Nexgard Spectra or Simparica Trio
• For topical (a tube of liquid administered behind the shoulders), we typically go to Multi-Duo but it cannot be used if there are cats in the house

Note: Revolution (a topical preventative) was once the go-to parasite prevention for dogs, however, it is no longer the best choice as it does not provide adequate tick protection as more tick species become endemic to our area. We recommend a product by the same manufacturer, called Simparica Trio.

As always, a veterinarian is the best source of information and may have other recommendations based on your pet’s needs.

Q: How much are these products?

For most, the prices vary quite a bit by weight category. Bigger Pet = Bigger Price.

If you have an idea of what your pet’s weight is, we can help you find the corresponding cost. For the cost-conscious dog owners, Multi-Duo generally has the lowest price, but all forms of prevention are quite comparable across the different brands.

Most products are packaged to cover a 6 month treatment window with treatments being given once monthly. For each product, you usually have the option to buy one month’s treatment at a time instead of buying the whole 6 month supply. The cost works out to be the same per treatment, however, there is a $5 dispensing fee every time. Therefore there is better value to buy a full pack and only pay the dispensing fee once.

For dogs, there are two product options that “do it all” to be given from June-November: Nexgard Spectra or Simparica Trio. In the past, we would have to use two products combined to do what each product can do individually (i.e. Nexgard + Heartgard or Simparica + Revolution). It is a bit more cost-effective to buy the all-in-one product than to buy its two corresponding combo products individually.

We recommend tick protection outside of the June-November window, though, and especially in April and May when temperatures are consistently mild. Heartworm is not so much of a concern during this time, so for a tick-focused protection such as regular Simparica or Nexgard, it’s usually about half the price of the cost of prevention for the summer months. The exact cost will vary depending on your dog’s size, though.

Q: When should I give my dog his or her prevention?

The most important time to have your dog on parasite prevention is between June and November, as this is when heartworm is a concern.

Ticks become active in mild temperatures, as low as 0-4 degrees celsius, so we also recommend flea and tick protection in the milder months, especially April and May.

You may wish to consider year-round prevention anyway, especially with our fluctuating temperatures and if you plan any travel with your dog during the winter months.

Parasite prevention should typically be given on the same day each month to ensure its effectiveness, but for the details of your dog’s specific products, please confirm with your veterinarian.

Q: Why do I need to pay for an examination to buy these products?

A: These are prescription medications, and just like any prescription, a veterinarian must ensure that the patient is in good enough health to receive them. For efficacy and your pet’s safety, they will also determine the best type of medication and dosage.

However, if your pet has had an examination in the last year (and is in good health and not growing/changing weight), your veterinarian may use their discretion to dispense the prescription without another examination. They may also request a recent weigh-in or a heartworm test before dispensing.

Q: What are the differences between the products my veterinarian carries and the ones in the pet store/online?

A: Pet store preventative products are not recommended as they are not as safe as the medications available through your veterinarian. Some pet store products may be effective against some parasites (ex. fleas) but do not protect against heartworm or the ticks that we are concerned about in our area. Other risks may vary. Some products have caused extreme reactions and chemical burns, while others may be dangerous and even fatal for other pets in your household.

Additionally, many convincing knock-off brands are available online that look almost identical to the brands available through your veterinarian, but may not be licensed for use in Canada or may contain different ingredients altogether. The products that your veterinarian sources have been rigorously tested and provide guarantees of effectiveness when used properly. This level of support and safety cannot be matched by retail stores and online pharmacies.

As always, though, we are your partner in your furry family member’s care. If you choose to use any pet store or knock-off versions (or even any prescription prevention that has not been prescribed specifically for your pet this season – ex. for another pet or from a previous year), we strongly encourage you to let us know before use so that we may record it in your pet’s medical records and be prepared for any adverse reactions.

Parasite prevention is not one-size-fits all. There are many considerations to be made including your dog’s history, the other pets in your household, and which species of parasites your dog is most likely to encounter. For the safest and most effective prevention, your veterinarian is always your best resource.

Q: I found a tick on my dog. What should I do?

A: The tick should be removed by grasping it near the head with a pair of tweezers and with steady even upward pressure, withdrawing the mouth parts from where they are buried in the skin. We have a special tick removal tool available for this purpose. Remember to wash your hands afterwards, and if you must use your bare hands, always wear gloves.

The removed tick should be disposed of as soon as possible to reduce the likelihood of transmitting disease, or you may wish to preserve it in rubbing alcohol and bring it to us for identification of the tick species and the associated risks.

If you are not comfortable removing the tick yourself, a veterinary technician will help you. It is important to get the whole tick out and to monitor the site for any signs of irritation or infection afterward, then contact your veterinarian for next steps.

We always recommend doing a 4DX test on any dog 4 weeks following a confirmed tick bite for a dog that is not on prevention.

Q: I found a flea/tick on my dog, but it’s on prevention! Why isn’t it working?

A: Most products require the parasites to bite in order to kill them. The tick will die within a few hours and fall off.

Q: My pet vomited after receiving its oral dose. What should I do?

A: It’s always best to check with a veterinarian. Typically, if your dog vomited within two hours post-administration, redosing is required. In most cases, the company will replace the lost dose.

Q: Why can’t I just give Revolution to my dog? That’s what I always used to use.

A: Five to ten years ago, ticks just weren’t as prevalent in our area as they are now. Now, every year, we see tick-borne diseases in our furry friends who were not on adequate tick prevention the year before.

Revolution was fine at one point for heartworm coverage and some internal parasites, but it only protects against one type of tick, and does not protect against the black-legged/deer tick, which transmits Lyme disease. Canine Revolution is no longer considered adequate parasite prevention on its own.

We now recommend switching to Simparica Trio, which is made by the same company as Revolution. It is an all-in-one chewable tablet that protects against fleas, heartworm, internal parasites, and many ticks, including the one that carries Lyme disease. We recommend giving it from June-November.

Outside of that window, heartworm is less of a concern, but ticks are still active. You may wish to consider additional tick protection in the early spring and milder winter months, such as giving regular Simparica (tick protection only) in April and May.

If you prefer a topical solution, a veterinary technician can discuss whether switching to another product line, such as K9 Advantix II and Advantage Multi, might be an option for your furry family member.

If you have any questions about your dog’s parasite prevention plan, or if you’re ready to protect your pet this season, we’re here to help!

Contact Us

Phone: 519-649-0080

In-Home Services
City of London
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Westmount Neighbourhood Pet Clinic

(corner of Wonderland Road South & Viscount Road)
851 Wonderland Road South
London, Ontario N6K 4T2
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North London Neighbourhood Pet Clinic

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