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A One Health guide to preventatives

Through a One Health lens, we evaluate the use of regular year-long preventives in dogs and cats, highlighting various available drug classes and options.

April 10, 2025

By Erica Tramuta-Drobnis, VMD, MPH, CPH

A brown Labrador standing in grasslands.
GettyImages/Christina Arnado

A key component of a well-rounded preventative program includes ensuring our clients receive proper education on preventing infectious (including zoonotic) diseases in their pets. We have a duty to our patients and to preserve the human-animal bond (HAB), but more than that, to the global One Health of our environment. We must ensure pet parents understand the reasoning behind regular preventatives, the options available to them, why products may be recommended, and risks, side effects, and benefits. Through a One Health lens, we will evaluate the use of regular year-long preventives in dogs and cats, highlighting various available drug classes and options.

Weeding through the pharmaceuticals

Weeding through what seems like zillions of heartworm, flea/tick, and intestinal parasite preventatives out there can be daunting. New products seem to pop up all the time. Some of these medications are regulated by the U.S. Environmental Protection Agency (EPA) (non-heartworm preventatives, generally topical or collars), while others are regulated by the U.S. Food and Drug Administration (FDA) (Isoxazoline class parasiticides and heartworm preventatives).

Further, when educating our clients, we need to discuss these prevention options as heartworm prevention or flea/tick blockers in the context of One Health. This means we must emphasize the protection some, though not all, provide against various intestinal parasites and even lice and mites, including several of the zoonotic ones of concern.

The American Heartworm Society (AHS) recommends (regardless of where a pet resides) routine year-round prevention measures against pathogenic parasitic infections, including zoonotic and heartworm disease in dogs and cats.1–5

Drug classes

Drug classes used in common flea, tick, heartworm, and intestinal parasite products include the following:6,7

  1. Isoxazolines parasiticides, the newest oral and topical parasiticide class. FDA-regulated (e.g. fluralaner, sarolaner, lotilaner, afoxolaner, esafoxolaner)
  2. Neonicotinoids insecticides, EPA-regulated (e.g. nitenpyram, imidacloprid)
  3. Macrocyclic lactones. FDA-regulated (e.g. moxidectin, selamectin, ivermectin, milbemycin oxime, eprinomectin)
  4. Biorational insecticides. EPA-regulated (e.g. pyriproxyfen)
  5. Pyrethroids and pyrethrins. EPA-regulated (e.g. permethrin, flumethrin, cypermethrin)
  6. Pediculicides. EPA-regulated (e.g. spinosad works against mites and lice)
  7. Phenylpyrazole insecticides. EPA-regulated (e.g. fipronil)
  8. Insect growth regulators (IGRs): EPA-regulated (e.g. (S)-methoprene, lufenuron)
  9. Cholinesterase inhibitors, which include carbamates and organophosphates, EPA-regulated but rarely used now in small animal preventatives because of a low margin of safety)
  10. Formamidines. EPA-regulated (e.g. amitraz, only for use in dogs)
  11. Oxadiazine insecticides. EPA-regulated (e.g. indoxacarb)
  12. Spinosyns. EPA-regulated (e.g. Spinosad)

Check out Table 1 for a summary of many American options, active ingredients, dosing intervals, formulations, prevention labels, species, and minimum starting age and weights.2,8–34 It does not represent an all-encompassing list of available products and does not include straight dewormers. However, it is a comprehensive, broad representation covering most of the classes above.

Table 1. Created by Erica Tramuta-Drobnis, VMD, MPH, CPH
Disclaimer: This is not an all-inclusive list of products but represents the commonly used, known, and recommended products in the U.S. as of February 2025
Brand Name Active Ingredients/Drug class Dosing interval Formulation Labeled Prevention Species Min. Age/Wt Misc
Advantage Multi®, ImoxiTM, ParasedgeTM Multi, MidamoxTM Moxidectin + imidacloprid Q Monthly Topical Dogs: Whips, Hooks, Rounds, Fleas
Cats: Ear mites, Hooks, Rounds, Fleas		 Dogs/Cats 7 W Puppies, 9 W Kittens
Advantage® Imidacloprid (neonicotinoid insecticide) Q Monthly Topical Flea adulticide +/- larvacide Cats, Rabbits, Dogs 8 weeks and up for dogs and cats and 10 weeks for rabbits
K9 Advantix® II Imidacloprid, permethrin and pyriproxyfen Q Monthly Topical Per product label: Prevention/treatment of Fleas, Ticks, Mosquitoes, Lice and Biting flies Dogs 4 lbs or more and 7 weeks of age or older
Bravecto® Chews Fluralaner Q 12 weeks except for lone star tick Q 8 weeks Oral chewable Kills and prevents fleas and kills ticks Dogs 8 weeks/4.4 pounds Not considered effective vs. A. americanum  in those < 6 months
Bravecto Plus® Fluralaner and moxidectin Q 2 months Topical Heartworm, fleas, ticks, hooks, & rounds Cats 6 months/2.6 Pounds
Bravecto Topical® Canine Fluralaner topical solution Q 8 to 12 weeks Topical Fleas/ticks Dogs 6 months/4.4 Pounds *** Resists swimming/bathing for the duration
Bravecto 1-month chews® Fluralaner Q 8 to 12 weeks Oral chewable Fleas/ticks Dogs 8 weeks and 4.4 pounds
Bravecto® Topical Cats Fluralaner (isoxazoline class) Q 8 to 12 weeks Topical Per drug label: fleas, prevents flea infestations, and kills ticks (black-legged tick and Asian longhorned tick) for 12 weeks; American Dog ticks for 8 weeks Cats 6 months/2.6 Pounds
Capstar® Nitenpyram (neonicotinoids insecticide) Q 24 hours for live fleas Non-chewable tablet Flea adulticide Dogs/Cats Per label: dogs, puppies, cats and kittens 2 pounds of body weight or greater and 4 weeks of age and older.
Comfortis® Spinosad Q Monthly Oral chewable Fleas Dogs/Cats 14 weeks dogs, 5 pounds dogs/14 weeks cats/4.1 Pounds cats
Credelio QuattroTM Lotilaner, moxidectin, praziquantel, and pyrantel Q Monthly Oral chewable Heartworm, rounds, hooks, fleas, ticks, and tapeworms Dogs 8 weeks/3.3 pounds Newest on the market as of 2/205
Credelio® Dog Lotilaner Q Monthly Oral chewable Fleas, ticks Dogs 8 weeks/4.4 Pounds dogs
Credelio® Cat Lotilaner Q Monthly Oral chewable Fleas, ticks Cats 8 Weeks/2 pounds
Frontline Plus® Dog and Cat options Fipronil and (S)-methoprene Q Monthly Topical Fleas, ticks, chewing lice Dogs/cats 8 weeks (dogs/cats)/ 5 pounds dogs/1.5 Pounds cats
Heartgard® Cats Ivermectin Q Monthly Oral chewable Heartworm, Hookworms Cats 6 weeks
Heartgard® Dogs Ivermectin Q Monthly Oral chewable Heartworm Dogs 6 weeks
Heartgard® Plus, Tri-Heart® Plus, Iverhart Plus® Ivermectin, pyrantel pamoate (Iverhart Max also praziquantel) Q Monthly Oral chewable Heartworm, hooks, rounds, and Iverhart Max - Tapeworms Dogs 6 weeks
Interceptor® Plus Milbemycin oxime/praziquantel Q Monthly Oral chewable Heartworm, rounds, tapeworms, whips, adult hooks Dogs 6 weeks/2 pounds
Interceptor®, MilbeGuard®, MilbehartTM Milbemycin Oxime Q Monthly Oral chewable Heartworm, hooks, rounds, whips Dogs, cats 4 weeks puppies, 6 weeks kittens
Iverheart Max®, Imectro® Ivermectin, pyrantel pamoate/praziquantel Q Monthly Oral chewable Heartworms, hooks, rounds, tapeworms Dogs 8 weeks/6 pounds
Nexgard® Afoxolaner Q Monthly Oral chewable Fleas/ticks Dogs 8 weeks/4 pounds
Nexgard® Plus Afoxolaner, moxidectin, and pyrantel Q Monthly Oral chewable Heartworm, ticks, fleas, rounds, hooks Dogs 8 weeks/4 pounds
Nexgard Combo® Esafoxolaner, eprinomectin, and praziquantel Q monthly Topical Fleas, ticks, heartworm, rounds, hooks, tapes Cats 8 weeks/1.6 Pounds
Proheart® 6 Moxidectin Q 6 months Inectable Heartworm Dogs 6 months Not safe to give in heartworm positive dogs
Proheart® SR12 Injection Moxidectin Q 12 months Inectable Heartworm Dogs 12 months Not safe to give in heartworm positive dogs
Revolution®, Paradyne®, SenergyTM, SelaridTM, RevoltTM Selamectin Q monthly Topical Heartworm, adult fleas, flea infestations, ear mite treatment/control, sarcoptic mange tx/control, and Dermacenter variabilis (only tick) Cats/dogs (though not all brands may be for both species) 6 weeks, no age limit (Revolution)
Revolution® Plus Selamectin and sarolaner Q Monthly Topical Heartworm, adult fleas, flea infestations, various ticks, ear mites, rounds, hooks Cats 2.8 pounds, 8 weeks
Sentinel Spectrum® Milbemycin oxime+lufenuron+praziquantel Q monthly Oral chewable Heartworm, tapes, hooks, rounds, whips, fleas and prevents flea eggs from hatching Dogs 6 weeks, 2 pounds
Sentinel® Milbemycin oxime & Lufenuron Q monthly Oral chewable Heartworm, hooks, Rounds, whips, immature fleas (prevents egg hatching) Dogs 4 weeks/2 pounds
Seresto® Flumethrin and imidocloprid Q 8 months Collar Fleas/ticks Dogs/cats 10 weeks
Simparica Trio® Sarolaner, moxidectin and pyrantel Q monthly Oral chewable Heartworm, ticks, fleas, rounds, hooks Dogs 8 weeks/2.8 pounds
Simparica® Sarolaner Q monthly Oral chewable Fleas, ticks and specifically mentions prevention of Lyme disease on label Dogs 6 months/2.8 pounds
Trifexis® Spinosad + milbemycin oxime Q monthly Oral chewable Prevents heartworm, treats/controls adult hooks, whips, and roundworms, and kills/prevents flea infestation per label Dogs 8  weeks/5 pounds

Providing year-round protection

The benefits of regular prevention, though frequency varies with the products selected, benefit pets, pet parents, and the environment. Year-round benefits include:1,3–5,35–40

    • All 50 states have had confirmed cases of heartworm disease. Due to ever-changing climate conditions, wildlife carriers, and mosquitoes' ability to come indoors, pets are potentially at risk year-round. Fluctuations in conditions vary yearly, not only state-wide but also in smaller communities. One never knows. Thus, the AHS recommends monthly heartworm prevention (or 12 months of prevention in the case of the 12-month ProHeart injection. See Table 1 for further guidance from the author.).
    • Further, for those combination products that help protect against key intestinal parasites and potentially other organisms, year-round protection protects against all remains key.
    • If some organisms have developed resistance and any fourth-stage larvae mature, this could lead to patent infections with microfilariae production. Thus, year-round prevention lessens this likelihood.
    • Several products protect against infectious and zoonotic pathogens, thus protecting humans, animals, and the environment.
    • We improve compliance with routine regularity. Thanks to smartphone reminders, hopefully, people will not be as forgetful about missed doses, but life can get in the way. Busy lifestyles, children, careers, and more can increase the risk of missed doses. Remembering to administer may be more manageable when given the same day every month (or every 12 weeks forsome products).
    • With inadvertent missed doses, many products have a retroactive effect (for heartworm prevention); so, missing a few days should not interfere with efficacy. However, underdosing or missing a preventative dose can contribute to developing antimicrobial resistance (AMR). Starting and stopping products may also increase the risk of AMR development. This represents a key One Health concern, and the practice of proper antimicrobial stewardship comes into play.
    • While reach back is present for heartworm prevention, it does not hold for many other parasites that many products protect against. Thus, regular administration remains crucial.
    • Prevention always supersedes the need for treatment or a cure. The adage "An ounce of prevention is worth a pound of cure." has validity in numerous aspects of veterinary medicine.

While some may argue not all regions of the U.S. have the same rates of exposure and risk to various intestinal parasites, heartworm disease, and fleas/ticks/mites/lice, the AHS and other experts still recommend year-long preventatives. The above reasons drive home many of these intentions. Because many of the preventives can protect against zoonotic potential (from hookworms to roundworms to scabies to tickborne diseases) by using them regularly, we keep pets (who act as sentinels) and pet families safe while ensuring minimal environmental contamination.

When Banfield practices instituted year-round heartworm prevention programs in 2023, they noticed prevalence decreases of greater than 10 percent nationwide despite the upward trend in overall heartworm in the U.S.41 Thus, it stands to reason that regular, consistent preventatives can help mitigate this increasing trend.42,43 However, again, our goal is to prevent heartworm disease and protect our pets from ectoparasites and intestinal organisms, especially those with zoonotic potential.

Compliance

We can only recommend certain products based on our clinic's goals, product selection, and regional concerns. We must consider the ability of a client to administer a specific preventative to a pet. Chewables may not be an option for some pets, especially those with food allergies or chronic enteropathies. Topicals may be less desirable for owners, especially with small children, but may be necessary for those with allergies/GI ailments. In addition to considering the product, parasites it may protect against/treat, and other factors, recognizing that not all pets will readily accept all formulations and that we must consider flavoring in some pets remains crucial to compliance and efficacy.

Year-round preventives

The myriad products available can make it daunting for a client to choose, let alone navigate the preventative world. One of our duties as veterinarians is educating clients on the available products. Further, we must ensure pet parents understand the parasites, various products they protect against, the types of disease, clinical signs, risks these organisms have, a pet's overall risk level, and the safety of the recommended medication.

Providing the risks and benefits of various options and stressing that prevention beats trying to treat many conditions, some of which can be fatal, is paramount. To do this, however, we must ensure we understand the available products, classes of parasiticides, and recommendations of the experts, e.g. AHS, and think more globally, not just about the individual animal, but also, about the environment (prevent shedding and environmental contamination by preventing parasite infestations), lessen the risk of AMR with consistent dosing, and preserve the HAB by keeping pets happy and healthy.

Erica Tramuta-Drobnis, VMD, MPH, CPH, is the CEO and founder of ELTD One Health Consulting, LLC. Dr. Tramuta-Drobnis works as a public health professional, emergency veterinarian, freelance writer, consultant, and researcher. She is passionate about One Health issues and believes pet health, food safety, agricultural health, and more can address the interconnection of human, animal, and environmental health.

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