Tick prevention pros and cons | boulder vet clinic

May 30, 2023

Tick prevention pros and cons | boulder vet clinic

We are seeing a disgusting number of ticks right now on the Front Range of Colorado.  Not a day passes that we don’t randomly spot them on a dog in-hospital for their annual exam.  A couple weeks ago my wife pulled 11 ticks off my own dogs in one day.  We live rural and have a large pasture, but still.  That’s as many ticks as we’ve found on our dogs in the last two years combined.  For those of you from the East Coast these numbers may sound paltry, but we hardly ever found ticks 10 years prior.  I don’t know what’s going on in an ecological sense, but I don’t’ like it.

To honor the influx of these disease spreading vectors, below is a summary of the primary tick-borne diseases of dogs along with Colorado testing statistics.  A positive test does not necessarily mean a dog was clinically ill from the disease.  It can simply mean antibodies are present in the circulation (i.e., exposure to the disease).  That said, a fair cross section of dogs testing positive likely had some degree of illness, and there are unknown numbers of dogs with the disease(es) that go un-tested.  These numbers are brought to you by the Companion Animal Parasite Council (CAPC), an organization that is “dedicated to increasing awareness of the threat parasites present to pets and family members. By generating and disseminating credible, accurate and timely information for the diagnosis, treatment, prevention and control of parasitic infections, CAPC works to educate pet owners and veterinary professionals.”  They’re not big fans of parasites (but who is…gross).

Here’s the 2022 stats from Colorado:

1) Lyme Disease: 1 in 200 dogs tested positive.  Lyme disease can lead to joint pain, neurological issues, cardiac issues, and kidney disease.  Approximately 1-2% of dogs with Lyme disease develop “Lyme nephritis” (kidney disease) which is bad news and often fatal.

2) Anaplasmosis:  1 in 100 dogs tested positive.  Complications include both white blood cell abnormalities (really bad for the immune system) and thrombocytopenia (low platelet counts which means blood can’t clot properly…also bad)

3) Ehrlichiosis:  1 in 50 dogs tested positive.  This disease is like anaplasmosis regarding how it impacts the body (it invades white blood cells and platelets) and can also include occasional respiratory and neurologic complications.  Dogs battling any of the above diseases can display a wide range of symptoms including fever, lethargy, loss of appetite, weight loss, enlarged lymph nodes, joint pain, bruising, etc.

4) Tick Paralysis:  We don’t have stats on this one, primarily because there are no blood tests available for the disease.  It’s basically what it sounds like – paralysis from a tick.  There’s a host of toxins ticks can carry in their saliva, and some of these can cause paralysis.  The paralysis usually begins after a tick has been engorged for several days.  The amazing thing is that all you need to do for treatment is find the tick and remove it.  About 6-12 hours later, the dog will be right as rain.  However, if for some reason a person was completely neglectful or you could not find the tick, the affected dog could die.  At Rise, we’ve had three patients with tick paralysis in the past 10 months.  Prior to this, I’d only seen it once in the past 11 years.

For me, the best solution is prescription tick preventatives.  There’s a variety of options – NexGard, Simparica, Bravecto, Frontline, Seresto (collar), etc.  As most of you know they come in oral tablets, topical applications for the skin, or a collar.  These medications target receptors in an insect’s nervous system, killing the tick when they bite.

We get occasional questions regarding the safety of flea and tick preventatives.   The first thing I want clients to know is that I use it for my own dogs.  Nothing in medicine though is 100% free and clear of any potential side effects, including IV fluids.  While it’s near impossible to predict which animal will have a negative response to a certain medication, I always try to weigh the risks of giving it vs. not giving it.

***CHOOSE YOUR OWN ADVENTURE…If you want a bunch of sciencey-stuff, continue on.  If not, skip it and take a short cut to the clearly marked section 12 paragraphs below***

Here’s the list of adverse reactions from a study of 615 dogs (415 administered NexGard, 200 administered active control).  Note in some cases there were greater numbers of adverse events noted in the control group than in those administered NexGard:

Dogs: vomiting (4.1% vs. 12.5% in controls), dry/flaky skin (3.1% vs. 1% controls), diarrhea (3.1% vs. 3.5% controls), lethargy (1.7% vs. 2% controls), anorexia (1.2% vs. 4.5% controls); one treated dog with history of seizures experienced seizure on same day after receiving first dose, on same day after receiving second dose, and 1 week after 3rd dose; another dog with history of seizures experienced seizure 19 d after 3rd dose; another dog with history of seizures experienced no seizures throughout study Click here for a link to the study.

Another study administered NexGard at 5 times the recommended dosage for multiple administrations.  Three doses were administered at 28-day intervals (Days 0, 28, and 56), followed by three additional doses administered with 14-day intervals (Days 84, 98, and 112).  The conclusion showed it to be safe, even at a much higher dose.  Click here for a link to this study.

On the other hand, there are a few sites online that will scare you half to death surrounding the use of flea and tick preventatives. These sites all point to one survey in common:

V. Palmieri et al.  Survey of canine use and safety of isoxazoline parasiticides. Veterinary Medicine and Science, June 2020.  From the Abstract (and for clarification, the most common anti-parasitics including NexGard are classified as isoxazolines):

“A veterinarian and pet owner survey (Project Jake) examined the use and safety of isoxazoline parasiticides given to dogs. Data were received during August 1-31, 2018 from a total of 2,751 survey responses. Forty-two percent (1,157) reported no flea treatment or adverse events (AE), while 58% (1594) had been treated with some parasiticide for flea control, and of those that received a parasiticide, the majority, or 83% (1,325), received an isooxazoline. When any flea treatment was given, AE were reported for 66.6% of respondents, with no apparent AE noted for 36.1%.” (note…remember those last two numbers)

The survey suggests between January 2013 and January 2017, the FDA found 1,728 reported seizures and 801 reported deaths caused by isoxazoline products. NexGard was said to have been indicated in 341 of those deaths.  But the authors of the paper go on to point out the errors in reporting…

-Since an AE may have been related to an underlying disease, use of other drugs at the same time, or other non‐drug related causes, these circumstances create uncertain causality between the adverse event and treatment with the drug (in other words they’re not really sure if there were other factors involved)

-Regulatory AE reporting systems as well as the Project Jake survey are all voluntarily reported with inherent biases weighted towards adverse effects, since few pet caregivers/owners or veterinarians have cause to report the absence of side effects. However, the Project Jake survey included questions and responses about drug treatment with or without the observation of AE, and thus it provided a population of responders registering treatment without AE. In fact, 36.1% of the Project Jake survey respondents indicated that they did not see any AEs and another 8.2% were unsure.  Also, because the FDA CVM and EMA ADE reporting systems depend upon the voluntary reporting of adverse clinical events by veterinarians and animal caregiver/owners, as well as the mandatory reporting of AE by manufacturers, aggregate AE reports potentially may include duplicative reported events(i.e. the numbers of adverse events are likely a lot lower than reported)

…data indicated that more than 60% of canine deaths and 55% of seizures were in dogs > 5 years of age, but information regarding concomitant disease or other treatments was unavailable.  Finally, no FDA or EMA data were available to determine whether most dogs that died also had preceding seizures, nor were we able to establish the time to death, and onset of or recovery from seizures.  (again, there’s no information about contributing factors or other potential causes of adverse events that may have been entirely unrelated to the medication)

You can find this survey referenced on multiple alternative pet websites.  And if you solely take small snippets of it such as “NexGard killed 341 dogs over a four-year period,” the alarm bells start going off.  As a veterinarian and a dog owner, I get it.  None of us want to give anything that would cause harm to our dogs.  The other side of that coin is “how much harm can the disease cause that I’m trying to prevent.”  For example, I mentioned about 1-2% of dogs with Lyme disease can develop Lyme nephritis, which has a grave prognosis.  In 2022, there were approximately 500,000 dogs that tested positive for Lyme disease in the U.S.  That means potentially 5,000-10,000 dogs succumbed to Lyme disease in one year alone.  And that’s only one aspect of Lyme disease.  Who knows how many dogs were euthanized due to complications from chronic arthritis?  Throw in complications from ehrlichiosis and anaplasmosis, and the number of dogs suffering from these diseases VASTLY outweighs the miniscule chance of a serious complication from administering an isoxazoline antiparasitic. This is enough to make me reach for the prevention.

Credit to the authors in pointing out the flaws in their own data collection.  On a side note, those two numbers I said to remember…66.6% reported and adverse event (AE) and 36.1% reported no apparent AE…66.6 + 36.1 = 102.7%, which it shouldn’t.  Those two numbers should equal 100%.  So, there’s a miscalculation in their numbers as well, but it’s also repeated at multiple points through the paper which is a bad look for an academic publication.


Lots of clients ask about the use of natural products for flea and tick prevention.  There are three common ones mentioned online:

1) Homemade repellent spays using peppermint, lavender, or lemon mists: All I can say is good luck.  After a day or two of spraying this on your dog’s coat, they won’t even want to come near you.  The smell is way too much for most dogs, and once they catch on, most of them will bolt as soon as you break out the spray bottle.  It’s not practical to think you’ll be putting this on your dog every day for 4-5 months.

2) Coconut Oil: Picture coconut oil, picture your house, then picture your dog covered in coconut oil for the duration of tick season.

3) Garlic (given orally): I’ve seen this mentioned more than once.  Garlic can cause hemolytic anemia in dogs (meaning it can destroy red blood cells).  It takes a pretty hefty dose, but you’re running a risk doing this every day for months on end.  Also, there’s no published data suggesting any benefit as an effective preventative therapy for dogs when it comes to ectoparasites.

If there was an effective and practical natural solution to tick prevention I’d be all in.  I just haven’t seen it.

One other tactic you can use is to simply give your dog a pat-down at the end of each day.  Ticks are usually easy to feel.  Make sure to look in your dog’s ears, groin, and under the tail as well.  On short-coated dogs they’re not hard to find.  For long coated dogs, it’s a little more difficult and you’re much more likely to miss them.  If your dog is a big shaggy creature and they’re out and about on hiking trails, I’d strongly consider prevention.  Come on in and we’ll get you taken care of.  

To sum it all up, there are way more ticks than usual.  I use tick prevention for my own dogs and feel very comfortable doing so.  Don’t let the internet scare you to death about preventatives.  Natural products leave a lot to be desired.  Check your dogs for ticks.  I think that about covers it.

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