Not all preventatives are equal

canine heartworm

This article is sponsored content brought to you by Zoetis.

Deadly heartworm disease

Canine heartworm (Dirofilaria immitis) infection has been detected in all mainland Australian states.1,2 Infection is characterised by the presence of adult worms in the pulmonary arteries which can lead to right heart and pulmonary artery enlargement, with resulting congestive heart failure, hypertension, and potentially caval syndrome over time.3,4

Heartworm preventatives were considered 100% efficacious all around the world if used according to the label. This has changed with the emergence of resistance to the macrocyclic lactones (MLs) in heartworm in the USA. 

Heartworm Prevention

Prevention of heartworm for the last 30 years has relied almost solely on the use of MLs. They are thought to target recent infections by interfering with the parasite’s ability to suppress the dog’s immune response to the infective and developing larvae.5 Many veterinarians consider all MLs to be equivalent, but moxidectin has unique characteristics that differentiate it from other MLs. 

Lipophilicity – Moxidectin’s higher lipophilicity, tissue distribution and longer elimination half life may play a role in its increased potency as a heartworm preventative.5,6

Receptor Binding – Moxidectin has different binding to structural targets on the parasite. These differences may be a contributing factor to the higher potency and slower development of parasite resistance to moxidectin.5,6

Potency – Moxidectin has been shown to be 100% effective when dosed 60 days post infection at only 0.5 μg/kg orally, which is a much lower dose than is required for either ivermectin or milbemycin.5-7

canine heartworm

Gold Standard in Heartworm Prevention Compliance and Efficacy

Compliance failure is the major reason for dogs contracting heartworm.2 The unique and innovative formulation of ProHeart® SR-12 reliably and predictably delivers protective concentrations of moxidectin for 12 months. 

It provides safe and reliable heartworm prevention without owners having to comply with monthly administration. 

ProHeart® SR-12 allows Australian veterinarians to ensure owner compliance, with full confidence in its efficacy, using a product from the trusted and proven manufacturer of this complex technology. ProHeart® SR-12 remains a vet-only heartworm preventative in Australia and is Zoetis’ first choice recommendation for heartworm prevention in this country.

The Optimal Choice for Monthly Oral Heartworm Prevention Efficacy

Simparica Trio®, delivering a minimum of 24 μg/kg of moxidectin in addition to sarolaner and pyrantel, has demonstrated 100% efficacy and robust safety in both US and Australian heartworm field trials.8-10 Simparica Trio has been shown to be superior to both milbemycin oxime and ivermectin against ML-resistant USA heartworm isolates.5 This allows vets to recommend Simparica Trio with confidence in its efficacy as a heartworm preventative, as well as providing protection against fleas, ticks, mites, and intestinal worms. Simparica Trio is ideal for clients who prefer a palatable chewable monthly oral combination parasiticide for their dog while retaining the benefits of moxidectin. We recommend veterinarians re-engage with their clients and choose the moxidectin-based preventative that is the most suitable for their patients.

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  1. Power, R.I., Slapeta, J., (2022). Exploration of the sensitivity to macrocyclic lactones in the canine heartworm (Dirofilaria immitis) in Australia using phenotypic and genotypic approaches, International Journal for Parasitology: Drugs and Drug Resistance
  2. Nguyen et al. (2016). Mosquito-borne heartworm Dirofilaria immitis in dogs from Australia Parasites & Vectors 9:535. 
  3. Rawlings CA, Losonsky JM, Lewis RE, McCall JW. (1981) Development and resolution of radiographic lesions in canine heartworm disease. J Am Vet Med Assoc. 178(11):1172–7. 
  4. McCracken MD, Patton S. (1993). Pulmonary arterial changes in feline dirofilariasis. Vet Pathol. 30(1):64–9. 
  5. Savadelis et al. (2022) Moxidectin: heartworm disease prevention in dogs in the face of emerging macrocyclic lactone resistance Parasites & Vectors 15:82. 
  6. Prichard RK, Geary TG. (2019). Perspectives on the utility of moxidectin for the control of parasitic nematodes in the face of developing anthelmintic resistance. Int J Parasitol Drugs Drug Resist. 10:69–83. 
  7. Kaminsky R, Geary TG (2023) Human and Animal Filariases : Landscape, Challenges, and Control. 
  8. Kryda et al. (2019) Laboratory and field studies to investigate the efficacy of a novel, orally administered combination product containing moxidectin, sarolaner and pyrantel for the prevention of heartworm disease (Dirofilaria immitis) in dogs. Parasites & Vectors 12:445. 
  9. Zoetis data on file. Study Report No. A161C-AU-16-754. 
  10. Zoetis data on file. Study Report No. A161C-AU-16-755.

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