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Oops, I Forgot It Again: An Overview of Long-Acting Canine Parasite Preventatives

By Erin Turowski, DVM
Medical Director, Angell at Essex

Dr. Turowski oversees Angell at Essex, our clinic in Danvers, MA that provides primary care, spay/neuter, vaccine, dentistry and outpatient surgery service.


Parasite preventatives are an integral part of high quality veterinary medicine. Unfortunately, monthly preventatives are problematic in some cases: dogs in high risk areas for ticks and heartworm, dogs who are difficult to medicate, dogs with food allergies, dogs who swim or are bathed frequently, and dogs with forgetful owners (myself included – no shame here!) may all have trouble relying on standard monthly preventatives. With these hurdles in mind, pharmaceutical companies have developed several long-acting parasite preventatives for use in dogs to facilitate administration, improve efficacy, and provide owners with peace of mind that their dog has a much smaller chance of being exposed to a potentially dangerous vector-borne disease. This article will briefly review some long-acting canine parasite preventatives and some pros and cons of each.

Common canine ticks. Image credit CDC.

Bravecto (fluralaner) Bravecto for dogs is available as either a chewable oral pill or as a topical solution, effective at killing and preventing fleas and most ticks for twelve weeks (lone star ticks for eight weeks) in dogs aged six months and older. The chews are dosed incrementally based on body weight. Product labeling in the United States does not include efficacy against skin and ear mites, although Bravecto has been used successfully off-label in dogs to treat these parasites. The most common adverse effects include minor gastrointestinal signs and local skin irritation; however, there is evidence to suggest that Bravecto and related drugs should be used cautiously in dogs with a history of neurologic disease due to a possible link to seizures, tremors, and other neurologic adverse effects. The oral formulation is flavored with pork protein and may be contraindicated in some dogs with food allergies. In most cases, the benefits and efficacy outweigh the risks when used under veterinary guidance. Additionally, the off-label use against demodectic mange, which can be difficult to diagnose in dogs, makes Bravecto an attractive product for use in animals with atopic dermatitis and other allergic skin diseases, especially given the availability of the flavorless topical solution for use in dogs with food allergies.

Preventic (amitraz) Preventic collars are labeled for use in dogs over twelve weeks of age and come in two sizes: less than 60 lb (27 kg) and over 60 lb. They provide protection for up to 90 days, or until the collar is removed, whichever comes first. Some references discourage use in households with cats or small children who may ingest collar pieces or residue, although the risk for poisoning with casual indirect contact is unlikely. Ingestion of the collar by any animal species can cause poisoning; the antidote is yohimbine. Unfortunately, these collars do not protect against fleas, so an additional flea preventative (that does not contain amitraz) is necessary. Preventic collars are regarded as one of the most effective and long-lasting forms of tick prevention for dogs in high risk areas, especially dogs who cannot be treated with an oral preventative due to food sensitivity or other oral administration issues. There are conflicting reports as to whether or not Preventic collars can be used extralabel to treat demodex mites; they may be effective on a case-by-case basis, particularly in small dogs. Frequent water exposure may reduce the duration of action. The most common side effects are local irritation and sedation, either of which is usually relieved by removal of the collar.

ProHeart 6 and 12 (moxidectin) ProHeart has seen some tough times in the recent past. ProHeart 6 was voluntarily recalled by Fort Dodge in 2004 after it was tentatively linked to over 5,000 various adverse events in dogs, including several hundred deaths. Product testing suggested that solvent residues remaining from the production process may have contributed to allergic reactions after injection. A refined formulation of ProHeart 6 was introduced on a limited basis in 2008 under a risk minimization program that required veterinarians to complete a pre-purchase training program and have clients sign a consent form prior to injection. The program also discouraged use of the drug in dogs with pre-existing allergies, weight loss, or debilitating illness. Administration within one month of vaccines was also discouraged, and veterinarians were encouraged to report potential adverse effects more diligently. Interestingly, ProHeart 6 was the first veterinary drug to be released under this type of risk minimization and restricted distribution program. In 2013, these recommendations were relaxed somewhat, permitting the use of ProHeart 6 in healthy dogs six months to seven years of age, removing the requirement for a pre-injection consent form, and permitting administration by veterinary technicians or assistants.

Today, ProHeart 6 is labeled as safe for use in preventing heartworms for six months in dogs ages six months and older, with the additional benefit of possibly providing extralabel prevention against intestinal helminth parasites. ProHeart 6 is used heavily in heartworm-endemic areas of the United States, where a lapse in monthly prevention carries a very real risk of heartworm infection. In July 2019, the FDA approved an annual formulation called ProHeart 12 that provides twelve month prevention against heartworms and also treats existing hookworm infections, for use in dogs over one year old. Limited data on clinical use of ProHeart 12 are available, although the drug seems to be well-received thus far. Both formulations can cause gastrointestinal upset and possible anaphylactic reactions as potential adverse effects. ProHeart 6 and 12 should be used cautiously in dogs with allergic diseases and should not be used at all in debilitated or underweight dogs. Flea and tick preventatives are still required for dogs receiving ProHeart, as this drug does not prevent against ectoparasites. Overall, despite several issues in the past, ProHeart is used widely in southern areas of the United States because of its reliability in prevention of potentially fatal heartworm disease. In non-endemic areas, clinical judgment is necessary to evaluate the benefits versus potential risks of use. In Massachusetts, ProHeart may be especially useful in dogs who travel occasionally to areas where heartworm infection is common.

Activyl/Scalibor (deltamethrin) Deltamethrin collars are labeled for flea, tick, and mosquito prevention in all sizes of dogs over the age of twelve weeks. The collars are one-size-fits-all, trimmed to fit the circumference of the dog’s neck. They are water-resistant and take up to three weeks to reach effective protection levels, so they should be applied ten to fourteen days prior to arthropod exposure. These are the only products in this list labeled to repel mosquitoes, so they may be a good choice for dogs where diseases like heartworm infection and West Nile Virus are common. They have also been reported to decrease the incidence of Leishmania infection, a tropical blood parasite infection transmitted by sand flies. Deltamethrin collars are water-resistant for up to six months. The collars may cause local irritation. They should not be used in cats and should be regarded similarly to Preventic collars when evaluating use in cat-friendly households – casual contact is unlikely to cause a problem, but cats who groom “their” dogs frequently or ingest collar pieces may experience toxicosis.

Seresto (flumethrin/imidacloprid) Seresto collars repel and kill fleas and ticks for up to eight months and help control louse and mite infestations. They are labeled for use in dogs over the age of seven weeks and come in two sizes: less than 18 lb (8 kg) and greater than 18 lb. Seresto collars are also available for cats and contain the same ingredients as the canine product, so this product may be a better choice in households with young cats or cats who frequently groom dogs in the same household. These collars are generally well tolerated, and the most common side effects are an aversion to the odor from a fresh collar (the odor usually dissipates over a few days) or local irritation from the repellant, with occasional gastrointestinal effects.

Certifect (fipronil/methoprene/amitraz) is not included here because despite providing 90 days of flea prevention, it only provides 30 days of tick prevention, and is therefore of limited utility in most dogs in New England.

Conclusions Overall, it is recommended to consult with your veterinarian to see which, if any, of these products is best for your dog. When used appropriately, these products can greatly improve owner compliance and provide enhanced parasite prevention that may not be feasible with typical monthly preventatives, leading to a great increase in quality of care for pets that might otherwise be at a higher risk for vector-borne diseases.