Heartworms, Their Diagnosis and Treatment, and How to Prevent Them By: Ashley Wheelock, Aubrey McMahan, Christine Siebeneicher, Sarah Zavala

Immiticide Melarsomine (Immiticide) is indicated for the treatment of Class I, II, and III heartworm disease in dogs. – It is an adulticide, meaning that it kills immature (4 month old, stage L5) to mature adult heartworms. Monthly heartworm preventions are microfilariocides, meaning that they kill heartworm larvae before they can migrate to the heart and pulmonary vessels and develop into adults. – Immiticide is given deep IM in the lumbar epaxial muscle (L3-L5), alternate sides should be used for subsequent injections. A 23g 1 inch needle is recommended for dogs under 10 kg, and a 22g 1.5 inch needle is recommended for dogs over 10kg.

Reconstitution To reconstitute a drug means to turn a powdered drug back into a liquid. – If 2 mL of sterile saline is added to 50 mg of powdered drug, the new concentration is 25 mg/mL.

Immiticide Dosing His total dose is mg (3.95 mL) per injection. So he would get 4 mL (2 vials) the first day, then another 4 mL the second day – The patient would receive 4 vials total

Prednisone According to the American Heartworm Society, “Administration of diminishing anti-inflammatory doses of glucocorticosteroids helps control signs of pulmonary embolism.” – The current recommended dosing protocol for prednisone is 0.5 mg/kg PO BID for the first week, then 0.5 mg/kg PO SID for the second week, followed by 0.5 mg/kg every other day for 1 to 2 weeks. There is no current recommendation for short term steroid use after melarsomine is administered. – Should the vet still want to prescribe steroids as the original script, 1 mg/kg PO SID x 3 days, then the pet would get mg (40 mg) PO SID for 3 days, so we would script out: “Prednisone 20 mg tabs #6, Give 2 tabs PO SID”. – W can only assume this is being considered as a burst therapy to help with inflammation. Given this consideration I would speak with my veterinarian about alternatively scripting out a NSAID such as Rimadyl, to help with pain and inflammation at the injection site, especially since the vet diagnosed the pet with Class I heartworm disease.

Prophylactic Medications Prophylactic: means preventative or protective of disease. –Diphenhydramine is classified as an antihistamine (Plumb, pg. 384)

Aspirin Therapy Aspirin has been previously used as an antithrombotic or to help reduce pulmonary arteritis. According to the American Heartworm Society, “The empirical use of aspirin for its antithrombotic effect or to reduce pulmonary arteritis is not recommended for heartworm infected dogs. Convincing evidence of clinical benefit is lacking and there is some research suggesting that aspirin may be contraindicated.” Again, instead of prednisone and aspirin, I would speak to my veterinarian and recommend an NSAID such as Rimadyl, Metacam, Previcox, or Deramaxx for post injection pain and inflammation. If pain is a large concern, oral dosing of tramadol could also be considered At 0.5 mg/kg PO BID, our patient (39.5kg) would get mg of aspirin twice daily. The script would be 81 mg Aspirin #10.5 tabs, Give ¼ tablet PO BID.

Selamactin (Revolution) “Topical selamectin (Revolution® - Pfizer) is indicated for flea infestations (Ctenocephalides felis), prevention of heartworm disease (Dirofilaria immitis), and for ear mites (Otodectes cynotis) in both dogs and cats. Additionally in dogs, it is indicated for sarcoptic mange (Sarcoptes scabeii), and tick infestations (Dermacentor variabilis).” (Plumb) The selamectin is being prescribed as a heartworm preventative (microfilariacide) to prevent further heartworm infection.

Fleas It is possible and very common for fleas to be transmitted from pet to pet. The owner needs to treat the environment as well as any animal that may have fleas and any bedding that might have been exposed to fleas or flea larvae. Topical treatment with frontline or advantage or oral administration with Capstar if the flea infestation is severe. – The environment would need to be treated otherwise the Capstar will be rendered ineffective as soon as new fleas infest the pet.

“Flea Dirt” “Flea Dirt” is actually flea feces, it presence on pets is due to a flea infestation. The most common type of flea found on dogs is Ctenocephalides felis also known as the cat flea.

Ticks Ticks can be manually removed from a pet using tweezers or hemostats, it is very important to grasp the tick as close to the head as possible so the head is removed with the body and doesn’t remain in the skin. Ticks can also be removed by applying Vaseline, this suffocates the tick and will cause them to pull their head out of the skin, and they can then be grasped with tweezers. It is very important that you do not remove a tick with your fingers because ticks transmit diseases such as Anaplasmosis, Babesiosis, Borrelia miyamotoi, Colorado tick fever, Ehrlichiosis, Heartland virus, Lyme disease, Powassan disease, Rickettsia perkeri rickettsiosis, Rocky mountain fever, STARI ( Southern tick-associated rash illness), TBRF (Tickborne relapsing fever), Tularemia, and 364D rickettsiosis (CDC)

Tick Prevention The topical preventatives for ticks are Frontline, Revolution, and Vectra 3D. Frontline also comes in a topical spray that works when applied but will not work monthly. Oral prevention of ticks is also available in the form of a tablet called NexGard. Pesticides can be used to treat the environment, just use caution as to not expose pets to pesticide treatments.

Why Test for Heartworms? Oral and topical medications for heartworm prevention are antiparisitic drugs. These preventatives have an on label use for dogs that have tested heartworm negative. Many preventatives can cause side effects if given to heartworm positive dogs. If the pet is debilitated or has a heavy load of heartworms, some preventions can cause death. For the safety of our patients, our clinic requires a negative heartworm a minimum of every year to continue to refill heartworm prevention. If there have been doses missed, retesting for heartworms is recommended in 6 months.

SLUDDE SLUDDE stands for: Salivation, Lacrimation, Urination, Defecation, Dyspnea, Emesis

Chlorpyrifos Chlorpyrifos is an organophosphate. According to the ASPCA Animal Poison Control Center, "Animals exposed to chlorpyrifos may present with typical muscarinic SLUDDE signs (salivation, lacrimation, urination, defecation, dyspnea, emesis) and bradycardia. Very large exposures may result in tremors, coma, seizures and death. Chlorpyrifos is also reported to cause a delayed neuropathy syndrome that can be seen days post exposure and is characterized by ataxia, hypermetria, and hindlimb CP deficits. (Fikes, 1992) Chlorpyrifos causes non-typical signs in cats. With acute toxicity, predominant neurologic signs are tremors, (especially of the back, top of head, and neck), ataxia, depression, and seizures. Other signs include anorexia, ventroflexion of neck, change in personality, hyperesthesia, and hyperactivity. Mydriasis and miosis occur with the same frequency. Depression, anorexia, and tremors can persist for 2-4 weeks. (Fikes, 1992)"

Work Cited Fikes JD: Organophosphorus and carbamate insecticides. VCNA:SA 20: ; 1990 Nelson DVM, C., & McCall DVM, J. (2014, July). Current Canine Guidelines for the Prevention, Diagnosis, and Management of Heartworm (Dirofilaria immitis) Infection in Dogs (D. Carithers DVM, Ed.). Retrieved September 13, 2014, from Guidelines.pdf Plumb, Donald C. Plumb's Veternary Drug Handbook. 7th ed. Stockholm: Pharma Vet, Tickborne Diseases of the U.S. (2014, July 14). Retrieved October 3, 2014, from