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Feline viral disease screening
FeLV and FIV: understanding the tests and what the results truly mean for your cat
A first positive test is not a verdict. FeLV and FIV often require confirmation. Read this page, then call your clinic: that is the next step, not the last.
FeLV and FIV: two viruses, two very different realities
They are often tested together - yet these two retroviruses have almost nothing in common, neither in how they spread nor in what they mean for your cat.
| Feature | FeLV | FIV |
|---|---|---|
| Transmission | Gentle contact (grooming, bowls) | Deep bite wounds mainly |
| Most affected age | Kittens, young adults | Adults (especially outdoor males) |
| Survival untreated | < 3 years if progressive (see the 3 outcomes below) | Often normal with monitoring |
| Vaccine available | Yes (recommended) | Not offered in Canada |
| Transmissible to humans | No | No |
When and why to test your cat?
Viral screening is part of the standard workup in several situations. Knowing your cat's status protects them - and any other cats in your household.
New cat or kitten
Any adopted cat should be tested before joining a household with other cats, even if they appear healthy. A negative result obtained too soon after exposure can give false reassurance.
Sick cat with no clear cause
Unexplained weight loss, repeated infections, anemia, chronic digestive issues: these signs warrant viral screening even in an indoor cat.
Outdoor or stray cat
Cats with outdoor access, especially unneutered males, have a higher FIV risk. Annual screening is recommended.
Before vaccination
Knowing FeLV/FIV status before vaccinating allows the protocol to be adjusted and avoids unknowingly vaccinating an already-positive cat.
Before adoption or rehoming
Shelters test routinely. If adopting from a private individual, ask that the cat be tested, or have it done upon arrival.
Understanding your test result
The SNAP test (rapid blood or serum test) is the initial screening tool. It detects either antibodies, the defenses the cat itself makes (for FIV), or antigens, pieces of the virus itself (for FeLV). A first result, positive or negative, is never definitive in certain contexts.
Reassuring, but not absolute
- Your cat was probably not infected at the time of testing.
- If exposure was recent (under 60 days), retest later.
- If the cat goes outdoors: annual screening recommended.
Confirm before concluding
- A single positive test is not enough for a definitive diagnosis.
- A confirmatory test (IFA, meaning immunofluorescence, or PCR) is recommended, especially if the cat appears healthy.
- Three possible outcomes: see the dedicated section below.
Beware of false positives
- The SNAP FIV test detects antibodies, not the virus itself.
- Kittens under 6 months can be false positives (maternal antibodies).
- Confirm with a second antibody test (different method); PCR can help, but a negative PCR does not rule out FIV.
Dual infection: close monitoring needed
- Possible but uncommon.
- Confirmation of both viruses recommended.
- Increased veterinary monitoring required.
Rapid tests are excellent for screening, but they have a margin of error. A positive result in a cat without symptoms or risk factors always warrants confirmation. Confirmation is not a challenge to the test - it is good medical practice.
The 3 possible outcomes of FeLV infection
Contrary to common belief, a cat exposed to FeLV does not automatically become a permanent carrier. The outcome depends on several factors, including age at exposure and viral load.
FIV and kittens: the maternal antibody issue
A positive FIV result in a kitten almost never means it is truly infected. This is one of the most common - and anxiety-inducing - sources of confusion in feline medicine.
The kitten receives the mother's antibodies via milk (or in utero). If the mother is FIV+, the kitten will carry her antibodies.
Maternal antibodies are still present in the blood. A SNAP test will be positive - but these are the mother's antibodies, not a sign of active infection.
Maternal antibodies have disappeared. If the test is still positive at this age, the kitten is likely truly infected.
A FIV-positive cat can give birth to healthy kittens. The virus does not spread easily from mother to kittens in utero or through milk (unlike FeLV). Neutering and indoor living considerably limit transmission risk.
Living with a FeLV+ or FIV+ cat
A positive diagnosis is not the end. Thousands of cats across Canada live happy years with one or the other of these viruses, with appropriate monitoring.
Indoor life required
A positive cat should not go outdoors unsupervised. This protects them from opportunistic infections and protects neighboring cats. Have them microchipped: if the cat escapes, permanent ID keeps a positive test from leading to euthanasia at a shelter.
Cohabitation with other cats
FIV: possible if cats are non-aggressive. FeLV: real risk of transmission with close cohabitation. Your veterinarian will guide you based on your specific situation.
Veterinary check-up every 6 months
Blood work, weight, oral exam, signs of secondary infection. The goal is to catch complications early, not wait until they become serious.
Adapted vaccines
Core vaccines (calicivirus, panleukopenia, rhinotracheitis) remain important for an immunocompromised cat; killed (inactivated) vaccines are then preferred over modified-live ones. Discuss the protocol with your veterinarian.
Quality of life first
Quality nutrition, environmental enrichment, minimal stress: these elements have a real impact on disease progression. A happy cat is a cat that fights better.
Do I need to separate my cats?
Home care
When to seek emergency care
Some signs cannot wait: in a cat with a weakened immune system, a complication can worsen within hours.
- Difficulty breathing, rapid breathing, or open-mouth breathing
- Very pale or white gums (a sign of severe anemia)
- Collapse, extreme weakness, or loss of consciousness
- Complete refusal to eat or drink for more than 24 hours
Daily priorities
- High-quality diet (digestible protein, low carbohydrates)
- Avoid raw or undercooked meat (higher infection risk in an immunocompromised cat)
- Fresh water always available - fountain recommended
- Clean litter box, scooped 1-2 times daily
- Minimize stress: stable routine, multiple rest areas
- Monitor appetite, weight, and stools
Warning signs to watch for
- Loss of appetite lasting more than 24-48 hours
- Sudden or unusual lethargy
- Fever (very warm ears, shivering)
- Difficulty breathing
- Persistent diarrhea or vomiting
- Pale gums
When to call the clinic
- Any warning sign listed above
- Progressive weight loss (even slow)
- Unexplained behavior change
- Before any new medication or supplement
- When in doubt - better to call
Frequently asked questions
Can my FIV+ cat transmit the virus to my children or me?
My FeLV+ cat looks perfectly healthy. Is that possible?
Should a FeLV or FIV positive cat be euthanized?
Do human antiviral medications (like HIV antiretrovirals) work in cats?
Can I adopt another cat if I already have a FIV+ cat?
Is there a vaccine against FIV?
My cat tested negative but lived with a FeLV+ cat. What should I do?
Further reading
Let's talk about your cat's result
A positive test deserves a consultation, not an online anxiety spiral. Our team can explain the next steps, interpret the results, and build a monitoring plan suited to your cat.