How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014 Brian A. DiGangi, DVM, MS, DABVP (Canine/Feline) Clinical Assistant Professor Veterinary Community Outreach Program College of Veterinary Medicine, University of Florida August 28, 2014 A Maddie’s Institute webcast Practical Management of Canine Heartworm Disease in Animal Shelters ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Outline • Heartworm disease overview – Epidemiology, life cycle, practice guidelines • Current practices – Results from an AHS-ASV survey • Practical management strategies for shelters – Prevention, diagnosis, treatment ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Canine Heartworm Disease I’m a first time dog owner. I recently adopted a dog…and was told he was healthy…. The dog was never tested for heartworm…. So, my poor boy has heartworm…. I don’t understand why they are giving out a lot of potentially sick dogs when they could test them and let the adopting party know what kind of experience and vet bills they will have. I’m so frustrated with the rescue group. ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Brian A. DiGangi, DVM, MS, DABVP (Canine/Feline)
Clinical Assistant Professor
Veterinary Community Outreach Program
College of Veterinary Medicine, University of Florida
August 28, 2014
A Maddie’s Institute webcast
Practical Management of
Canine Heartworm Disease in Animal
Shelters
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Outline
• Heartworm disease overview
– Epidemiology, life cycle, practice guidelines
• Current practices– Results from an AHS-ASV survey
• Practical management strategies for shelters
– Prevention, diagnosis, treatment
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Canine Heartworm Disease
I’m a first time dog owner. I recently adopted a dog…and was told he was healthy…. The dog was never tested for
heartworm…. So, my poor boy has heartworm…. I don’t understand why they are giving out a lot of potentially sick dogs
when they could test them and let the adopting party know what kind of experience and vet bills they will have.
I’m so frustrated with the rescue group.
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Learning Outcomes
• Recall characteristics pertinent to clinical management of canine heartworm disease
• Understand current practices and challenges to standard guidelines in the shelter setting
• Design management protocols feasible in the shelter setting in light of their risks and benefits
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Canine Heartworm Disease
• Prevalence of positive test results– Private practice
– Animal shelters• 15% shelter dogs in Florida
Region Mean Percent
Northeast <1%
Midwest <1%
Southeast 4%
West 1%
Overall 1%
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Canine Heartworm Disease
• Heartworms are endemic in the U.S.
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Canine Heartworm Disease
• Heartworms are endemic in the U.S.
– Transport of positive dogs
– Expansion of wild canid territory
– Environmental changes• New water sources
• Urban “heat islands”
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Canine Heartworm Disease
• Other factors– Some mosquito species survive over winter
– Live and breed for 1-5 months
Risk of transmission is always present!
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L3L2
Microfilaria
Canine Heartworm Disease
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
L4 2 to 3 months
ImmatureAdult
3 to 4 months
MatureAdult
Canine Heartworm Disease
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Canine Heartworm Disease
Who? Where? When?
L1 L2 L3 Mosquito 10-14 days
L3L4
Soft tissue3-12 days
2-3 months
Immature adultMature adult
Heart & lungs3-4 months
3-7 years
• Remember…
• We can only test for microfilaria & mature adults
• Treatment options & protocols vary by life stage
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Canine Heartworm Disease
• Prevention
• Diagnosis
• Treatment
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Canine Heartworm Disease
• Prevention
– Monthly oral or topical preventive OR
– Bi-annual injectable preventive
• Diagnosis
– Annual antigen testing
• Testing prior to changing preventives
• Following lapse in preventive
• Tandem mf testing
– X-rays, echocardiography as indicated
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Canine Heartworm Disease
• Treatment
– Days 0-59
• Exercise restriction
• 4-week course of steroids if symptomatic
• Monthly preventive
• 4-week course of doxycycline
– Days 60-91• Adulticidal treatment with melarsomine (Days 60, 90, 91)
• 4-week course of steroids
• Limit activity to cage rest & leash walks
– Continued exercise restriction for 6-8 weeks
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Current Practices & Challenges
• AHS-ASV working group– Identify current practices and needs of shelter veterinarians
– Create practical guidelines and resources
• February 2014– Online survey administered to ASV membership
– 105 responses
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Current Practices & Challenges
0
10
20
30
40
50
60
70
% S
he
lte
rs
Shelter Type
Model Response %
Open Admission 61%
Limited Admission 36%
Adoption Guarantee 25%
Other 10%
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Current Practices & Challenges
20%12%
32%
15%
2%
• Annual Canine Intake
– Max: 16,000
– Min: 10
– Average: 4,000
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Current Practices & Challenges
20%12%
32%
15%
2%
• Shelter HW Prevalence– Max: 70%
– Min: 1%
– Average: 9%
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Current Practices & Challenges
• Prevention
– 66% of shelters provide monthly heartworm preventive
– 65% shelters use oral ivermectin products on-label
010203040506070
Pe
rce
nt
Preventive Agents
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Current Practices & Challenges
• Prevention
– 66% of shelters provide monthly heartworm preventive
– 65% shelters use oral ivermectin products on-label
010203040506070
Pe
rce
nt
Preventive Agents
• Other
• Injectable IVM
• Whatever is donated
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Current Practices & Challenges
• Diagnostic practices
Yes, 42.2%
No, 9.8%
Some, 48%
Are dogs tested for heartworm infection?
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Current Practices & Challenges
• Diagnostic practices
– Which dogs are tested?• Adoption candidates
• Those from endemic areas
• Specific health concernsSome, 48%
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Current Practices & Challenges
• When does testing occur?
0 10 20 30 40 50 60
Other
Adoption
Transfer
Intake
Admission
Percent
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Current Practices & Challenges
• What type of screening test is used?
0 20 40 60 80 100
Serum antibody
Centrifugation microscopy
Direct microscopy
Lateral flow
ELISA
Percent
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Current Practices & Challenges
• Diagnostic practices
– 48% shelters do additional testing after a positive screening test
• Repeat screening test
• Bloodwork
• Chest x-rays
• Urinalysis
• Echocardiogram
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Current Practices & Challenges
• Treatment
– 85% of shelters treated at least some infected dogs
– Dogs not treated are• Euthanized
• Placed for adoption without treatment
• Transferred elsewhere for treatment
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Current Practices & Challenges
• Treatment
0 20 40 60
Other
Monthly IVM
2-doseMelarsomine
3-doseMelarsomine
What is the adulticide treatment protocol?
0 20 40 60 80 100
Other
None
NSAID
Mac. lactones
Prednisone
Doxycycline
Which adjunctive treatments are utilized?
Percent of Shelters
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Current Practices & Challenges
• 70% provided monthly preventive (vs. 66%)
• 60% used on-label IVM preventive (vs. 65%)
• 72% tested all dogs for infection (vs. 42%)
• 88% treated at least some infections (vs. 85%)
• 43% used 2-dose melarsomine (vs. 55% 3-dose)
Prevention
Diagnosis
Treatment
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Current Practices & Challenges
• Notable deviations from standard guidelines
– Prevention• Ivermectin is frequently used extra-label for prevention
– Diagnosis• Many shelters do not test dogs for infection
• A single screening test is frequently used for diagnosis
– Treatment• 2-dose melarsomine treatment protocol is frequently used
• Adjunctive treatments are inconsistent
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Designing Practical Protocols
• Why administer preventives?
– Infected dogs serve as reservoirs
– Assistance with other parasites
• Shelter concerns
• Ivermectin is frequently used extra-label for heartworm prevention
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Designing Practical Protocols
• Extra-label use of ivermectin
Cost Toxicity
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Designing Practical Protocols
• Understand the Concerns
– Gene mutation results in inability to move avermectins out of the brain
• Includes ivermectin, milbemycin, moxidectin, selamectin
– Toxic dose 4x higher than heartworm preventive dose
– Treatment• Prevent further absorption
• Supportive care
• Time (days to weeks)
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Designing Practical Protocols
• Mitigate the Risk
– Ensure accurate body weight measurements
– Dilute solution for more accurate dosing
– Create dosing chart to minimize human error
– Mutation most common in Collies, Australian Shepherds, Longhaired Whippets, Shetland Sheepdog
• Selectively avoid use in at-risk breeds
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How Animal Shelters Can Treat and Prevent Heartworm in Dogs August 28, 2014
Designing Practical Protocols
• Why obtain a diagnosis?– Infected dogs serve as reservoirs
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