takin’ it to the heart: new insights on managing heartworm ... · …heartworm-positive dogs with...

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Takin’ It To The Heart: New Insights on Managing

Heartworm Disease in Shelter Animals

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© 2019 ASPCA®. All Rights Reserved.© 2019 ASPCA®. All Rights Reserved.

Brian A. DiGangi, DVM, MSDiplomate, ABVP (Canine & Feline Practice, Shelter Medicine Practice)

Senior Director, Shelter MedicineShelter Outreach, ASPCA

Takin’ it to the heart:New insights on managing heartworm disease in shelter animals

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When should spay-neuter surgery be performed?How should we prepare dogs for relocation?

What does “activity restriction” mean and is it really that important?

What are the long-term effects of HW infection?When will a treated dog be cleared?

Frequently Asked Questions…

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• All dogs, cats and ferrets are at risk• Administer preventives year-round

Part 1

Review

Test for antigen and microfilaria• On intake• Annually

Treat with 3 doses of melarsomine• Safest• Most effective• Most cost-effective

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I currently have several heartworm positive dogs in my rescue. They are

all in various stages of treatment.

Some of the vets involve want to spay before injections. Others refuse

surgery until after treatment.

What is your recommendation?

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Peterson et al., 2014• 15 HW + mixed breed dogs• No or mild clinical signs• Cardiovascular-sparing anesthesia• No clinically relevant complications • 24 hours • 7-10 days post-op

Heartworm Treatment & Spay-Neuter

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Heartworm Treatment & Spay-Neuter

12.6%

44.9%

20.2%

5.6%7.6% 8.1%

Prior to diagnosis After diagnosis, prior totreatment

After beginningdoxycycline

After completingdoxycycline

After melarsomine Other

When is spay-neuter performed in relation to adulticidal therapy?

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Heartworm Treatment & Spay-Neuter

12.6%

44.9%

20.2%

5.6%7.6% 8.1%

Prior to diagnosis After diagnosis, prior totreatment

After beginningdoxycycline

After completingdoxycycline

After melarsomine Other

When is spay-neuter performed in relation to adulticidal therapy?

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But what happens when…

I am fostering a Yorkie that came in with heartworms 4 months ago

which have now been treated. She needs to be spayed, she has 3 mammary gland tumors that need

to be removed and needs a dental.

When can we start to get this all taken care of?

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Peterson et al., 2014…heartworm-positive dogs with an ASA patient classification score greater than 2 were treated for their heartworm disease, including a minimum 4-week convalescent period prior to re-evaluation and surgical sterilization.

AHS, 2018Surgery can then be performed 6 months after adulticidal treatment if the dog has recovered sufficiently.

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Hirano, 1992• 4 weeks after dead HW insertion…• Pulmonary arterial pressure (PAP) recovered• Blood flow between thromboemboli recovered• Effects depended on severity of lesions before insertion

•In HW + dogs….•Clinical signs and laboratory findings worsened until week 4

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What 2 components of the life cycle are needed for transmission?

WisconsinDept. of Agriculture Trade and Consumer Protection

Heartworm positive dogs are generally not eligible for import.

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Minimizing Transmission During Relocation

Microfilaria Status Treatment Rationale

NegativeAdminister heartworm preventive Prevent mf development

Begin doxycycline Inhibit mf developmentRepeat mf test in 7 days Confirm lack of circulating mf

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Minimizing Transmission During Relocation

Microfilaria Status Treatment Rationale

Positive or Unknown

Apply topical moxidectin ORAdminister heartworm preventive

+Apply topical insecticide

Eliminate most mfPrevent infection of mosquitoes & larval transmission

Begin doxycycline Inhibit mf development, render L3 non-infective

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Do we need to exercise restrict non-treated heartworm positive dogs? The issue then is

that staff is still exercise restricting these untreated dogs by keeping them out of play

group.

What about exercise right after heartworm treatment is completed? I have a dog that

wants to run.

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• Delays onset and extent of clinical disease

Rest and Recovery

Right heart failure

Increased cardiac

workloadCapillary damage

Increased blood flow

Aerobic

activ

ity

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• Provide safe physical and mental stimulation• Meet needs for socialization• Reduce stress and anxiety

Rest and Recovery

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• Begin upon diagnosis• Clinical signs ≈ restriction

• Greatest risk 7-10 days after injection• Crate, small room, leash walks

• Continue for 6-8 weeks

Rest and Recovery

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My sister, a vet tech, heard that I was planning to adopt a dog who had heartworm, and she told me it was a huge

mistake.

She told me that even if caught and treated early, the dead heartworms still wreak havoc on the dog’s heart and lungs. She told me “It’s not a matter of ‘if’ the dog

experiences complications, it’s ‘when.’”

She went on to say that dogs living a full life after having heartworm is the exception, not the rule, and that she

could almost guarantee me that any dog with heartworm, even after being treated, will have a short life and a sudden death. She told me that a year from

now, I could be taking her out to go to the bathroom and she could just drop dead. She told me it was very likely.

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Long-term Effects

Right heart failure

Increased cardiac

workloadCapillary damage

Increased blood flow

Blood clots (PTE)

Worm death +

Inflamma-tion

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Even if caught and treated early?

S. Jones

S. JonesNormal pulmonary artery <6 mos. after experimental infection

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Number of worms+

Duration of infection≈

Significant pathology+

Clinical diseaseS. Jones

Mummified adult worm remnants

S. Jones

Scarring

Irreversible chronic obstructive disease

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Duck, ~1.5 year old MN Pittie, presented to me after newly being adopted. He was

transported from South Carolina to a rescue in Pennsylvania. In South Carolina, Duck tested positive for HW disease, was started on doxycycline and treated with

melarsomine on 10/8/18 and 10/9/18. He has been on monthly HW prevention since

then. We retested Duck 3/16/19 and he remains positive.

Should I retreat this dog?

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• Antigen tests can’t distinguish between dead and living worms

• Melarsomine only affects adult stages• Preventives + doxycycline mask detection

• Worms may continue to die for >1 month

Should I re-treat?

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Give 2 doses melarsomine

• Antigen test 9 months after last injection

Should I re-treat?

Positive

Re-test in 6 months

Negative

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Should I re-treat?

X X=

X=

X=https://cheezburger.com/7826984448

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Should I re-treat?

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https://cheezburger.com/7826984448

X

X= XX= XX

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Hoerauf 2003• >95% loss of Wolbachia and

microfilaremia after 12 months(Humans, 200 mg/day x 6 wks)

Rossi 2010• Wolbachia and microfilaria numbers

remain low for 12 months (Dogs, 10 mg/kg/day x 21 days, every 6 mos)

Should I repeat doxycycline?

McCall 2014

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Hoerauf 2003• >95% loss of Wolbachia and

microfilaremia after 12 months(Humans, 200 mg/day x 6 wks)

Rossi 2010• Wolbachia and microfilaria numbers

remain low for 12 months (Dogs, 10 mg/kg/day x 21 days, every 6 mos)

Should I repeat doxycycline?

McCall 2014

To prevent rebound of Wolbachia populations, the course of doxycycline should be repeated every 12 months.

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When are they “negative”?

9 mos. 6 mos. 6 mos.

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When are they “negative”?

9 mos. 6 mos. 6 mos.

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Key Resource

https://www.sheltervet.org/assets/docs/ASV.Heartworm%20Management.pdf

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brian.digangi@aspca.orgsheltermedicine@aspca.org

Thank you!