Feline Antibody Heartworm Test Information

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Feline Antibody Heartworm Test Information

Test Code: FABH
Test Name: Feline Antibody Heartworm Test

Contact Name: Dr. Mani Lejeune
Contact Telephone: 607-253-3581
E-mail: ml872@cornell.edu

Test Method: Lateral flow immunoassay
Sample Required: 0.5 ml of serum or plasma
Collection container: red-top tube or blood tube with anticoagulant
Transport: Ship on cold packs
Test Day: Tuesday and Friday
Lag Time: 1-4 days
Species: Cat
Results Format: Positive or Negative


The HESKA feline heartworm antibody test is a lateral flow immunoassay for the detection of IgG antibodies to Dirofilaria immitis (heartworm) antigen in feline serum or plasma. This antigen is present in male and female heartworms. This test detects antibodies resulting from heartworm infections in cats including immature worms, adult male and female worms and single sex male or female infections.

Results of the antibody test may be interpreted as follows

Antibody Positive (antibodies are present)

  • Adult heartworms are present in the heart and/or pulmonary arteries
  • Cat is infected with late L4 or adult worms
  • Heartworm infection has been cleared, but antibodies are still present
  • Ectopic heartworm infection may be present.

Antibody Negative (no antibodies are present)

  • Cat not infected with heartworm
  • Cat was infected less than 60 days prior to collection of the sample 

If negative result and clinical signs are present, a retest in 2-3 months is recommended. Additional tests need to be run to rule out other causes of the clinical signs

For a more complete evaluation of the Dirofilaria status in a cat, it is recommended that an occult serological test and a microfilarial test be done at the same time. If both techniques are done the results may be interpreted as follows:

Antigen Positive and Microfilaria Negative

  • single sex infection
  • immature adult worms (5-6 months postinfection)
  • immune mediated clearance of microfilariae
  • animal on monthly preventives, or after microfilaricide treatment

Antigen Negative and Microfilaria Positive

  • microfilariae are not Dirofilaria immitis
  • heartworm antigen not present, or present in levels too low to detect
  • adult worms dead and antigen cleared, but microfilariae still present
  • microfilarial contamination of lysing solution, dye or filter chamber
  • animal transfused with microfilaremic blood
  • prenatal transfer of microfilariae
  • immune mediated clearance of antigen-antibody complexes
  • antigen destroyed due to improper storage or treatment of sample

If both a microfilarial test and an occult serological test produce inconclusive results, then other diagnostic tests may be conducted, such as thoracic radiographs, electrocardiogram, blood chemistry, and urinalysis. If the animal is clinically normal, follow up testing in six months with an occult serological test is recommended if the initial testing is inconclusive. In a positive animal that has been treated, heartworm antigen can persist for up to four months. Repeat testing must be done after that time to confirm that treatment has been effective.