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Witness FeLV

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

Witness FeLV

This treatment applies to the following species:
Manufacturer: Zoetis


I. General Information

Feline Leukemia Virus (FeLV) is a contagious retrovirus from the Mammalian Type-C group, which is endemic in many areas of the world. The prevalence of FeLV is particularly high among dense populations. Transmission occurs essentially by contact, mainly through saliva or nasal secretions and by biting or licking.

Clinically healthy persistent viremic cats are known as a major source of the virus. Infection is characterized by the development of a viremia which can be followed by seroconversion with elimination of the pathogen. Infected cats may also present a chronic, persistent viremia which will lead to the development of both proliferative syndromes like lymphosarcoma or leukemia and non-proliferative syndromes such as anemia or immunosuppression, followed by death at short or middle term.

Diagnosis of FeLV infection is generally performed by the detection of a viral antigen from the core protein, p27, which is produced in high quantities in viremic cats. WITNESS™ FeLV test is indicated for use when history and/or clinical signs may suggest an infection by feline retroviruses. It will also be particularly recommended prior to an FeLV vaccination, especially in cats belonging to an at risk population.

Ii. Test Principles

WITNESS™ FeLV test is based on Rapid Immuno Migration (RIM)™ technology. FeLV antigen is detected using antibodies directed against the circulating p27 capside protein. Sensitized colloidal gold particles will form a complex with the p27 antigen (FeLV) present in the sample.

The formed complex migrates along the strip. The complex is then captured on a sensitized reaction line where its accumulation causes the formation of a clearly visible pink/red band. Control bands located at the end of the reading window (3) ensure that the test was performed correctly.


● The test can be performed on unclotted, whole blood, anticoagulated with EDTA or heparin, serum or plasma.

● Samples should always be collected with a sterile needle and syringe.

● Hemolysis does not significantly interfere with the test, but strongly hemolyzed samples may partly obscure a weak positive band.

Iv. Specimen Storage

Fresh anticoagulated whole blood samples should preferably be tested immediately after collection but not longer than 4 hours after collection, if stored at room temperature. If testing is further delayed, samples should be kept refrigerated (+2°C and 8°C) for up to 4 days. For prolonged storage, samples (serum and plasma only) should be kept frozen (-20°C).


● 10 pouches, each containing 1 test device and desiccant.

● 10 pipettes.

● 1 buffer dropper bottles (2.2 mL).

● Instructions for use.


1. Do not use components after expiration date.

2. Store the test kit at +2°C - 25°C. Do not freeze.

3. Use the test immediately after opening the sealed pouch (within 10 minutes).

4. Avoid touching or damaging membrane at windows (1), (2), (3).

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

6. Use a separate pipette for each sample.

7. Hold pipette and buffer bottle vertically when dispensing sample and buffer respectively.

8. Handle all reagents and samples as biohazardous material.

9. Saline Buffer contains sodium azide as a preservative.

10. For veterinary use only.

Test Procedure And Results

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


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

● Holding the provided pipette vertically, transfer one drop of sample to the sample well (1).


● Check that the sample has fully absorbed into the membrane.

● Remove the cap from the buffer bottle, hold it vertically and add two drops of buffer to the sample well (1)

● Leave the test device flat during migration of sample/reagent complex through the reading window.


After 10 minutes, observe the presence or absence of pink/red bands in reading windows (2) and (3).


● It is possible to read the test before 10 minutes if two pink/red bands (respectively in (2) and (3)) are clearly visible.

● The presence of only one band in reading window (3), prior to the end of the development time (10 min), does not mean that the test is complete, as weak samples may appear slower than the control band.



Test is validated if a pink/purple band is present in the reading window (3).


● No band in reading window (2), with one band in window (3): sample is negative for FeLV antigen.

● One band in reading window (2), with one band in window (3): sample is positive for FeLV antigen.


No band in control window (3): invalid test.

A test result should always be interpreted in the context of all available clinical information and history for the cat being tested.

Symbol Descriptions

Zoetis Inc., Kalamazoo, MI 49007, USA

U.S. Vet. License No. 190



NAC No.: 1115047.6

Telephone:   269-359-4414
Customer Service:   888-963-8471
Every effort has been made to ensure the accuracy of the Witness FeLV 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