Heartworm Disease III

Very sensitive to antigen, high risk of death via anaphylaxis

Why should you not perform surgical extraction for caval syndrome in cats unless they are severely affected by the presence of the worm in the heart?

Anaphylaxis risk high

Why shouldn't you give high dose ivermectin to kill off microfilaria rapidly?

Progressive pulmonary pathology occurs during long kill period (30 months), very prolonged exercise restriction

Why would relying on the preventative dose of ivermectin for slow kill of adult worms be an unacceptable approach?

False (some dogs require sedation or analgesia, which is fine)

True or false: you should never give sedation or analgesia when administering melarsomine, it may interact with the adulticide therapy

Selamectin, moxidectin

What HW preventative drugs can be used in cats and are easier to use because they are topical?

Exercise restriction, doxycycline, ivermectin, corticosteroids, anticoagulants, phosphodiesterase inhibitors, RCHF therapy

What are 7 important ancillary therapies in HW treatment?

Ivermectin, milbemycin, selamectin, moxidectin

What are four examples of macrocyclic lactones used for HWD prevention?

Pulmonary artery enlargement, bronchointerstitial pattern

What are some possible radiographic findings consistent with feline HWD?

Local pain, inflammation, malaise, GI signs, reversible paralysis or neuro signs, pulmonary edema, renal or hepatic tox, PTE, death

What are some possible side effects of adulticide therapy?

Pleural effusion (echo free space outside the cardiac wall)

What are the arrows pointing to?

Lengthier exercise restriction, increased cost of extra dose, increased total arsenical dose

What are the cons of using the split dosing protocol for adulticide treatment?

Double line structure in PA or R heart, RV enlargement, septal flattening, effusions, evidence of PHT

What are the echo findings consistent with HWD?

Enlarged RV, pleural effusion

What are the findings on this echo?

1. Kill Wolbachia, 2. Eliminate MF 3. Kill adult worms (not at all once) 4. minimize pulmonary parenchymal and arterial pathology, treat RCHF and PHT is present

What are the goals of HW treatment? 4

Cough, hemoptysis, fever, dyspnea, sudden death

What are the signs of PTE in dogs following adulticide treatment?

1. Confirm diagnosis 2. Give doxy 10mg/kg BID and monthly HW preventative for 1 month 3. Give melarsomine after 2 months

What are the three general recommendations for HW treatment?

Correct dose, needle size for body weight, change needle, deep IM epaxial injection between L3-L5, firm pressure for 5 minutes at injection site

What aspects of giving melarsomine are extremely important to follow?

Trifexis, interceptor, sentinel

What brandname HW preventative have milbemycin oxime as the main ingredient?

Advantage multi, proheart 6

What brandname HW preventative have moxidectin as the main ingredient?

Revolution

What brandname HW preventative have selamectin as the main ingredient?

PHT increases RV pressure, flattens septum

What causes septal flattening on echo?

Severity of PHT, caval syndrome, cor pulmonale, parasite burden, concurrent heart disease

What characteristics are you checking for when performing an echo on a dog with HWD as supplemental diagnostic?

Asthma

What disease is often confused for feline HWD based on radiographs and signs?

50mg/kg

What dose of ivermectin can be used extalabel to RAPIDLY kill microfilaria?

Doxycycline

What drug can be paired with ivermectin to expedite the slow kill process for microfilaria control?

Macrocyclic lactones

What drug class is the mainstay of HWD prevention?

Ishihara

What forceps are used for HW extraction?

Susceptibility gap

What is decreased by pretreating with macrocyclic lactones before adulticide treatment?

Doxycycline 10-20mg/kg/day

What is given in combination with preventative doses of ivermectin in the slow kill approach to HW treatment?

Arsenical compound

What is is melarsomine made of?

Jugular venotomy, sedation or anesthesia, local block

What is required to surgically extract HWs in caval syndrome?

Cor pulmonale

What is seen here?

L3 and L4 target stages are around for more than a month, so when a single dose is missed, they can be killed with the next month dose

What is the "reachback" effect referring to in HW prevention?

HW

What is the arrow pointing to?

HWs

What is the arrow pointing to?

Controlled, staged killing, lungs have time to recover before 2 doses, kills 98%+ of worms

What is the benefit of the split dosing protocol for HW adulticide treatment?

Enlarged PA

What is the cursor pointing to?

Primary diagnostic tool to confirm diagnosis

What is the diagnostic importance of performing an echo in a cat to diagnose HWD?

Supplemental to serology (optional)

What is the diagnostic importance of performing an echo in a dog to diagnose HWD?

Sterile, no larvae produced

What is the effects of macrocyclic lactones of the reproduction of adult female worms?

10-20% (still more common than FeLV or FIV)

What is the feline infection rate of HW in endemic areas compared to that of dogs?

Septal flattening (huge RV)

What is the finding on echo?

Melarsomine

What is the mainstay of adulticide therapy for treatment of HW?

Corticosteroids (like asthma)

What is the mainstay of treatment is a cat symptomatic from HW infection?

Moxidectin/imidacloprid (Advantage multi)

What is the preventative of choice to use with doxycycline in the slow kill approach?

Kill L3 to L4 stage

What is the purpose of administering monthly HW preventative for 1-2 months before adulticide treatment?

Kill Wolbachia

What is the purpose of giving doxy for a month before adulticide treatment?

Initial single injection following in 1-3 months by 2 doses 24 hours apart

What is the recommended adulticide therapy protocol (split dosing protocol)?

Doxycycline and macrocyclic lactones

What is the recommended treatment for HW before adulticide is used?

Surgical extraction prior to melarsomine

What is the recommended treatment for dogs with caval syndrome?

Symptomatic dogs

What is the split dosing protocol required to treat?

Juvenile HW stage that isn't susceptible to either preventative or adulticide (days 60-180)

What is the susceptibility gap in HW treatment?

Caval syndrome (when image plays, you can see the mass of worms moving between the RA and RV)

What is this finding?

L4, early L5 due to susceptibility gap

What life stage of HW is NOT susceptible to melarsomine? Why?

L5, adults

What life stages does melarsomine target?

Moxidectin

What macrocyclic lactone is available as a 6 month slow release injectable?

96%

What percentage of adult worms were kills after doxy and Moxidectin/imidacloprid use for 10 months?

10-20%

What percentage of cats may die suddenly from HW infection?

HW test

What should you with a cat that presents with coughing before diagnosing it with asthma?

Caval syndrome (stage 4)

What stage of HWD can you NOT use adulticide treatment for in dogs?

Heartgard, Triheart, iverhart

What three brandname HW preventatives have ivermectin as the main ingredient?

Geriatric, dogs with severe systemic disease, or adverse reaction to melarsomine

What three types of canine patients are good candidates for the slow kill approach to HW treatment?

Severe systemic disease, RCHF, pneumonitis

What three types of patient animals must be stabilized before adulticide treatment?

L3 & L4

What two stages of the HW lifecycle are targeted by macrocyclic lactones?

Severe renal or hepatic disease

What underlying diseases should you use caution in when giving adulticide treatment?

Prevent transmission

Why is it important to eliminate microfilaria during HW treatment?

High die off increases risk of side effect, 10% may still remain

Why is the original dosing recommendation of 2 injections 24 hours apart no longer recommended?

Worm toxicity confined to L3 to L4 molt, had to give daily, could cause shock

Why isn't DEC used as a HW preventative anymore?

Rapidly microfilaricidal, may result in shock

Why isn't milbemycin oxime (interceptor, trifexis) recommended in microfilaremic dogs?

False (variable radiographic signs make it harder to diagnose)

True or false: Feline HWD presents consistently with the same radiographic findings

True

True or false: Melarsomine is safer and more effective than Na carparsolate, but there are still severe side effects

False (not all dogs are good candidates, some owners not interested)

True or false: in practice, adulticide is a good option for all HW positive dogs and most owners are on board for treatment

False (NOT protective)

True or false: indoor only status is protective against HW in cats, so no prevention is required

False (NEVER use any adulticide in a cat, it will kill them)

True or false: only certain adulticide treatments for HW can be used in cats

8 weeks

At what age should you start a HW preventative in dogs?

False (ALL animals always get PTE accompanying worm die off, which is why we need to minimize risk)

True or false: only some animals get PTE as a result of worm death

True

True or false: rapidly microfilaricidal drugs, such as high dose ivermectin, should only be given to dogs that are known microfilaria negative

False (the low dose is safe for any dog or any breed)

True or false: the HW prevention dose of ivermectin is only safe in breeds without the MDR1 mutation

True

True or false: the HW prevention dose of ivermectin is safe for use in all dogs regardless of HW or microfilaria status, but the owner should monitor for the first 24 hours to look for signs of anaphylaxis

False (risk of inflammation is greater, so steroids are used)

True or false: the risk of hypercoagulability is greater than the risk of inflammation in HW, so corticosteroids are avoided

False (melarsomine is still considered the best option and slow kill is not recommended)

True or false: the slow kill approach to adulticide treatment of HW is the standard of care recommended by the AHS

False (required for symptomatic dogs, recommended for all dogs needing adulticide)

True or false: the split dosing protocol is only recommended for symptomatic dogs

False (it's really only dogs that we call caval syndrome, we don't always see the severe signs we see in caval syndrome with dogs)

True or false: we always call HWs in the R heart caval syndrome when in the cat

Exercise restriction, corticosteroids for pneumonitis

How can we minimize pulmonary parenchymal and arterial pathology in HW treatment?

Cage rest for 6-8 weeks post treatment, tapering course of prednisone

How can we minimize risk associated with worm die off after adulticide treatment?

Allows time for juvenile to become susceptible as adults, no new juveniles develop

How does giving macrocyclic lactones for 2 months before adulticide treatment decrease the susceptibility gap?

6 months

How long after HW adulticide treatment should we administer another antigen test?

9-12 months

How long does the slow kill approach using ivermectin and doxycycline take to reduce the adult worm burden by 80-95%?

Monthly

How often should you given macrocyclic lactones?

21 days

How soon is after starting slow kill treatment is doxy combined with Moxidectin/imidacloprid microfilaricidal?

Give 1 month before anticipated HW season, continue for 3 months after transmission ends

If an owner only wants to give HW preventative seasonally, how should you give it?

False - 8 weeks

T/F EVERY dog over 24 weeks of age in endemic area should be on HW preventative