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Witness Heartworm

This page contains information on Witness Heartworm for veterinary use.
The information provided typically includes the following:
  • Witness Heartworm Indications
  • Warnings and cautions for Witness Heartworm
  • Direction and dosage information for Witness Heartworm

Witness Heartworm

This treatment applies to the following species:
Manufacturer: Zoetis


For the detection of canine and feline heartworm infection

I. Heartworm Disease

Heartworm disease is caused by Dirofilaria immitis, a filarial nematode whose immature stages are transmitted by mosquitoes. In dogs, the adult heartworms live in the heart and adjacent large blood vessels. In cats, heartworms affect primarily the lungs and lead to Heartworm Associated Respiratory Disease (HARD). Although primarily a disease of dogs, the parasite can also infect ferrets and other mammals, such as the red fox and the coyote.

WITNESS™ Heartworm tests for the detection of the soluble antigen D. immitis and is recommended for use when clinical history and/or signs suggest heartworm disease or where a rapid verification of heartworm infection is required.

Ii. Test Principles

WITNESS™ Heartworm test is based on rapid immunomigration (RIM)® technology, which detects the presence of adult D. immitis antigens in dog or cat blood. Sensitized particles bound to heartworm antigens present within the specimen (whole blood, serum or plasma) migrate along a nitrocellulose strip. The complex is then captured on a sensitized reaction zone where its accumulation causes the formation of a clearly visible pink/purple band. A pink/purple band in the control window ensures that the test is being performed correctly.

Iii. Specimen Information

50 uL (0.05 mL) of anticoagulated (EDTA or heparin) whole blood, plasma or serum is required. Hemolysis does not significantly interfere with the test, but strongly hemolyzed specimens may partly obscure a weak positive band.

Iv. Specimen Storage

Fresh, anticoagulated whole blood should be tested within 4 hours. Anticoagulated whole blood may be refrigerated for up to 24 hours. Serum or plasma may be refrigerated (2° to 7°C; 35° to 45°F) for up to 7 days or frozen (-20°C) if even longer storage is required.


● 10 or 25 pouches, each containing 1 test device.

● 10 or 25 disposable pipettes.

● 1 buffer dropper bottle (5.0 mL).

● Instructions for use.


● Do not use components after expiration date.

● Refrigeration not required. Store the test kit at 2° to 25°C (35° to 77°F). Do not freeze.

● Use the test within 30 minutes after opening the sealed pouch.

● Avoid touching or damaging membrane at windows #1, #2, #3.

● The WITNESS™ device should be placed on a flat, horizontal surface while performing the test.

● Use a separate pipette for each specimen.

● Hold pipette and buffer bottle vertically when dispensing specimen and buffer.

● Do not mix components of different serials.

● Saline Buffer contains sodium azide as a preservative.

● For veterinary use only.

Witness™ Heartworm Test Procedure And Results

Important: Allow specimen and buffer drops to fall onto membrane at window #1. Do not touch pipette tip, specimen or buffer drops, or buffer bottle tip directly to the membrane.


● Tear open the pouch provided and place the test device on a flat horizontal surface.

● Squeeze the provided pipette near the sealed end. Insert the open end of the pipette into an anticoagulated whole blood, serum, or plasma specimen. Release the pressure slightly to draw up a small amount of specimen into the pipette.

● Holding the pipette vertically, transfer one drop of specimen to the specimen well, window #1. Allow specimen to be completely absorbed.


● Remove the cap from the buffer bottle, hold it vertically and add two drops of buffer to the specimen well.


● Wait 10 minutes. Observe the presence or absence of pink/purple bands in reading windows #2 and #3.

● Specimen results are read in window #2. The control band is read in window #3.

Notes: The test is complete and may be read before 10 minutes if pink/purple bands are visible in both windows #2 and #3.

The presence of a pink/purple band only in window #3 before 10 minutes does not mean that the test is complete. A pink/purple band in window #2 may develop slower than the control pink/purple band in window #3.



● Test is validated if a pink/purple band is present in reading window #3.


● Negative for HW antigen: No band in reading window #2, with one pink/purple band in window #3.

● Positive for HW antigen: One pink/purple band in reading window #2, with one pink/purple band in window #3.

Invalid Test

● Invalid test: No pink/purple band in control window #3.

Note: A test result should always be interpreted in the context of all available clinical information and history for the dog or cat. Cats testing negative for heartworm antigen may benefit from other diagnostic tests, including heartworm antibody assays.

Symbol Descriptions

Zoetis Inc., Kalamazoo, MI 49007, USA

U.S. Vet. License No. 190


Licensed under U.S. Pat. No. 4,839,275; Canadian Pat. No. 1,232,849; and Australian Pat. No. 582,129.

Effective Date 06-2015


NAC No.: 1115048.7

Telephone:   269-359-4414
Customer Service:   888-963-8471
Every effort has been made to ensure the accuracy of the Witness Heartworm information published above. However, it remains the responsibility of the readers to familiarize themselves with the product information contained on the US product label or package insert.

Copyright © 2018 Animalytix LLC. Updated: 2018-10-31