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Animal Medical Hospital
Choosing a Tick & Flea Preventive
Not only have we been seeing increasing numbers of ticks over the last few years, we do not seem to have much of a tick “season” any more. At the clinic we have now seen dogs with ticks attached in every month of the year. The peak times are early spring (March, April) and in the fall (late September to late November), but they are out there in moderate numbers year round. There is a great Canadian site that has graphics and maps of tick distribution in our fair country.
Ticks are problematic because they carry disease that can infect dogs, such as Lyme disease and Ehrlichia. The easiest way to prevent your dog from getting these diseases from ticks is to prevent the ticks from infesting your dog in the first place. There are many new options for tick prevention that have emerged in the last few years as the problem of exploding tick populations has become more widespread.
The three general categories of tick preventives (tick preventives also prevent fleas, as a bonus) are topical insecticides, topical medications, and oral medications. Each has its pros and cons.
Topical insecticides (such as Preventic) are applied to the skin in a liquid form. The hair is parted and a dose of the preventive is applied right to the skin. The product spreads on the lipid (oil) layer on the surface of the skin, so as the dog moves around the product is distributed over the entire body and will sit in the superficial layer of the skin. As the cells in this superficial layer naturally slough off and are replaced, the product is gradually lost and will need to be replenished after a month.
Pros: These products are generally safe, very effective, easy to apply, and kill fleas and ticks without the need for the pet to be bitten first.
Cons: It takes about 24 hours for the product to spread around after application, so there will be an oily spot in the hair where it was applied. There is also alcohol in the product. This alcohol is harmless to the pet (like diluted rubbing alcohol) but it can discolor leather furniture and sometimes even hardwood floor finishes, so you need to take some care where your pet is lying down for 24 hours after application. If your pet is bathed a lot some of the product will inevitably be lost and it might not be as effective later in the month. The same is true if your pets swims frequently, so water-lovers should be given a different preventive. There have been reports of focal hair loss where the product is applied, but this is rare.
Topical medications (selamectin is the only one in this class) are also applied to the skin, but they are almost immediately absorbed through the skin into the bloodstream where they persist for variable amounts of time. When the parasite (flea or tick) bites your pet it gets a dose of the drug and is killed.
Pros: Selamectin is easy to apply and generally safe. The residue from the application is mainly alcohol and does not leave a greasy spot. Residual product can be safely washed off after an hour.
Cons: It does require that the parasite bites the pet before it will die. It is not as effective against some of the ticks that carry Lyme disease as many of the other products. Available by prescription.
Oral medications are mainly comprised of the isoxazoline class preventives. These are relatively new products that, while all in the same class of preventives, all act in slightly different ways. One, for example, will last for 3 months, while others last only one month.
Pros: Generally safe. Very effective against the local species of ticks that carry Lyme disease. Starts to kill fleas and ticks within 2 hours of administration. Easy to administer (tablets are quite palatable and are in the form of a flavored chew). Administration is once monthly or once every 3 months, depending on the product. Also very effective in treating mites (Sarcoptes, Demodex).
Cons: They do require that the parasite bites the pet before it will die. As with any oral medication, the main adverse effects seen with these products is gastrointestinal upset (vomiting and diarrhea) that is self-limiting. There have been very rare reports of neurological events such as seizures in dogs after being given isoxazolines. Dogs with a history of seizures (or that are of a seizure-prone breed) should be given a different preventive option. Available by prescription. The minimum age for the monthly products is 8 weeks; the minimum age for the every-3-months product is 6 months of age.
Examples of isoxazoline class preventives
Bravecto (fluralaner) tablets for dogs- lasts 3 months (minimum age 6 months)
Credelio (lotilaner) tablets for dogs and cats - lasts 1 month
Nexgard (afoxalaner) tablets for dogs- lasts 1 month
Nexgard Spectra (afoxalaner and milbemycin) tablets for dogs (milbemycin is a dewormer) - lasts 1 month
Simparica (sarolaner) tablets for dogs- lasts 1 month
Simparica Trio (sarolaner, moxidectin and pyrantel) tablets for dogs (milbemycin and pyrantel are dewormers) - lasts 1 month
Revolution (selamectin) for dogs and cats - lasts 1 month
Dolmectin (selamectin) for dogs and cats - lasts 1 month
Permethrin-based topical preventives