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 98.86 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 39.54 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 19.77 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 18-20 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
20:353-367; 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
https://www.heartwormsociety.org/images/pdf/2014-AHS-CanineGuidelines.pdf
• Plumb, Donald C. Plumb's Veternary Drug Handbook. 7th ed. Stockholm:
Pharma Vet, 2011.
• Tickborne Diseases of the U.S. (2014, July 14). Retrieved October 3, 2014,
from http://www.cdc.gov/ticks/diseases/