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Training module II - Heartworm Testing

Training module II - Heartworm Testing



Principles of heartworm testing in dogs presented for veterinary hospital employees

Principles of heartworm testing in dogs presented for veterinary hospital employees



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    Training module II - Heartworm Testing Training module II - Heartworm Testing Presentation Transcript

    • Training Module II
      The Heartworm Test and
      Heartworm Preventatives
    • Who needs a heartworm test?
      Wellness testing
      Heartworm testing in dogs over six months old is done routinely as a part of wellness testing in most parts of the U.S. In most practices, it is incorporated into the annual physical exam and/or along with routine immunizations.
      Sick dogs
      Dogs who have never had preventative or whose owners have lapsed in administering heartworm preventatives
      Why? It’s rare, but administering preventative to a positive dog can cause death. We had one this year—owner gave pill and his dog died in under 2 hours!
      Rarely, we will test cats, but it’s too complicated for this presentation.
    • Patient Selection
      Screening test for dogs and puppies over 6 months old
      Required for prescribing heartworm preventative prescriptions
      Recommended yearly by American Heartworm Society
      In our clinic, we allow dogs with a purchase history consistent with giving the pills monthly to be tested every other year. Some vets require a test yearly, and some are downright lax about testing.
      Coughing dogs
      Dogs with labored breathing
      Dogs with syncope (fainting)
      Dogs with ascites (swollen, fluid-filled abdomen)
      Outdoor dogs with vague clinical signs
      Dogs with stroke-like signs
    • Heartworm PREVENTATIVES
      Oral monthly
      Heartgard Plus
      Iverheart Plus
      Tri-Heart Plus
      Iverheart Max
      • Topical Monthly
      • Advantage Multi
      • Revolution
      • Proheart Injection
      Every six months
    • We can never truly tell if a client is faithfully giving the pill, or if their dog is actually taking the pill (as opposed to burying it in the sofa cushions or in the yard).
      But we do have a purchase history regarding heartworm preventatives
      If a client purchases the product, we assume they are administering the medication
      But, always ask anyway! Sometimes they will admit that they didn’t give them all
      Heartworm Preventative & Compliance-Is the dog actually taking the medicine?
    • What if they “missed a few months?”
      If the client missed one month, we tell them to give the pill and their dog needs to be retested 6-7 months after the dose was missed.
      We can manually insert a retest date into the Electronic Medical Record
      If the client missed more than a month, we require a retest before we will refill the heartworm preventative, and we also recommend retesting the patient during their next annual exam
      • Transferred records here from another vet with record of negative test within the last 12 months and record of consistent purchase history
      • Regular Patient here but buys Heartworm Rx from On-line Pharmacy?
      We have no record of purchase history because they buy their heartworm preventative elsewhere
      “Traveling vet” or mobile vets
      On-line Pharmacies
      We require a heartworm test every 12 months. If they buy it from us, we let them go 2 years.
      We will not fill Rx here or approve prescriptions to outside pharmacies without a test
      If they are a patient of record here, we will fill Rx
      Inconsistent Preventative Purchase History?
    • Four types of in-house tests:
      Heartworm Antigen Test
      Direct Blood Smear
      Modified Knott’s Test (“Filter test”)
      Canine Wellness Profile on the Abaxis machine
      Hasn’t proven totally accurate! Recently, we ran an Abaxis heartworm test with every Canine Wellness Profile to confirm discrepancies—after 25 tests there were none
      Blood Tests for Canine Heartworm Infection
    • Products we prescribe/endorse here
      Advantage Multi
      Tri-Heart Plus
    • Heartworm Antigen Test
      Our mainstay heartworm test
      Many manufacturers
      We use Abaxis here
      Occasionally, due to a really great deal, we may have a different test kit, but most of them are similar
      Industry standard
      Tests for a protein in the blood that is associated with adult female heartworms
      All male infections may test negative
      Immature infections may test negative
      Most dogs do not test positive unless they have been infected for at least 5 to 6 months
    • Conducting the Test
      “Wet the needle” of a TB syringe with heparin before drawing blood
      (prevents clotting)
      Draw some heparin into the syringe and then shoot it all back up into the bottle
    • Open the heartworm test kit
      Write patient name or room number on test
      Add 1 drop of heparinized whole blood, serum or plasma to the test well on the left (arrow)
      Add 2 drops of conjugate to the test well on the left
      Set timer for 10 minutes
      Conducting the test
    • Reading the test
      Negative test:
      No Color on the left side
      Within 10 minutes.
      Only the Positive control
      on the right side
      develops color
      Positive Test
      Color develops
      On the left side
      Within 10 minutes
      Positive Control
    • Invalid Test/Quality Control
      Positive control stripe fails to develop color—means the test is invalid and must be repeated.
      Entire test window is opaque and bloody
      Blood and conjugate do not flow across the test window within 2 minutes
      Sometimes it helps to elevate the left side of the test by leaning it against the syringe containing the blood sample
      Sometimes happens if the sample clots
    • Questionable Results?
      Sometimes results are questionable!
      Very weak or almost no color development on the test stripe
      Clinical signs are not consistent with test results
      The vet thinks it’s a positive and it tests negative
      The vet thinks it’s a negative and it tests positive
    • What the vet may want done if results are questionable
      Run a direct blood smear
      If live microfilaria are seen, it confirms Heartworm Positive.
      If no microfilaria are seen, it does not confirm negative status. Further testing is needed.
      Do chest x-rays
      Send a serum sample to AViD Labs
      Wait and retest in 1 month
    • Direct Blood Smear
      Not accurate enough to be a used-alone test!!!
      1 drop of heparinized whole blood on a slide
      Put cover slip on
      Tech or Vet read slide looking for living, moving microfilaria
      100% accurate if microfilaria are seen
      If no microfilaria are seen, it still could be a positive
    • Modified Knott’s Test or Difil Test
      Obsolete—we no longer use this
      Used to concentrate microfilaria and trap them in a filter and is read by a tech under the microscope
    • Samples Sent to AViD Labs
      For questionable tests
      Is an antigen test similar to ours
      Run on serum
      Collect blood in a Vacuutainer serum separator (red top) tube
      Spin down the tube
      Transfer serum into a transfer tube
      Fill out AViD submission form,
      Call AviD for courier pickup
      Place sample in AViD box outside
      Sometimes even this is questionable!
    • The Abaxis Canine Wellness Test
      We have gotten some questionable results with this test
      Sometimes they test positive on an antigen test and negative on the Wellness rotor
      Sometimes they test negative on the antigen test and positive on the Wellness rotor.
      Recently Abaxis asked us to run one of their Antigen test kits on each patient we are doing a Canine Wellness on. We did this 25 times
      All of our tests agreed
      But we remember no test is perfect
    • Quiz
      The industry standard heartworm test is
      a. AViD Laboratories
      b. Direct blood smear
      c. Antigen test
      d. Modified Knott’s test
      We run all of the following heartworm tests except
      a. Modified Knott’s tests
      b. Abaxis Canine Wellness Profiles
      c. Direct blood smear
      d. Antigen tests
    • Quiz, continued
      Our heartworm antigen tests do all except
      a. Are semi-quantitative and tell how many heartworms the pet has
      b. Have built-in quality control
      c. Can be run on one drop of whole blood
      d. Take only 10 minutes
      Heartworm antigen tests checks for
      a. Heartworm microfilaria
      b. A protein secreted by adult female heartworms
      c. Heartworm ova
      d. Adult heartworms in the blood stream
    • Quiz, continued
      Minimum age for heartworm testing is
      5 to 6 months
      One and one-half years old
      3 weeks old
      False negative tests can occur
      If there is an all female worm infection
      If there is an all male worm infection
      If pet has been infected less than five to six months ago
      If the owner is giving heartworm preventative
      B & C
      We require a heartworm test before prescribing heartworm preventative on all dogs over 6 months old
    • Quiz, continued
      If the positive control fails to turn pink
      You didn’t put enough buffer. Add another drop or two
      Tilt the left side of the test device up by leaning it against the TB syringe you took the blood in
      There is something intrinsically wrong with the test kit
      It’s ok, sometimes they do that
      A Direct blood smear
      Is 100 % accurate all of the time
      Is 100% accurate if moving microfilaria are seen
      If no microfilaria are seen, it’s definitely negative
      Is so easy and cheap we should do it more
    • Quiz, continued
      10. If the test results are questionable, the vet may
      Want you to take a chest x-ray
      Sent some serum out to Antech Labs
      Send the pet to Upstate Veterinary Specialists for a cardiac ultrasound
      A & B
      None of the above
    • Slide Presentation By
      Jacquelyn H. Burns, DVM
      Holmes Veterinary Hospital
      1001 Church Street Laurens, SC 29360
      (864) 984-2365
      Copyright © Jacquelyn H. Burns, 2011