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False Positive FeLV - Retested Negative ?

post #1 of 7
12/17/10 at 1:14pm
Thread Starter 
I posted about 2 weeks ago about a very young (5 wk) kitten that tested a faint positive for FeLeuk on a SNAP test. We don't typically test so young, but we are in need of getting him quickly into a foster home so a test was done.

The test was done in house, and when the positive was "faint" they decided to board him at the vet til a retest could be done. A second test was done, and while I'm not aware of what "kind" of test, it was sent out "to a lab", and today the results came back a nice clean negative.

I'm cautiously jumping for joy. Kitten is 7 weeks now. Which test is more reliable? Cuz this boy will be coming to MY house, so a negative result is very important. Is the lab-performed test on a slightly older kitten more reliable than an in house snap done on a 5 week old kitty?

Thanks.
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post #2 of 7
12/17/10 at 1:49pm
The test done in a vet's office is an ELISA (snap) test. The one sent out to a lab is an IFA (indirect immunofluorescent antibody assay) test, and is considered a confirmatory test. However, in cats that tested positive on the ELISA and negative on the IFA, it is recommended that they be retested after a minimum of 30 days.

The kitty is still with mom and siblings? Unless something happened to the kitty's family, 7 weeks is too young to be removed from the family. 12 weeks is normal.

http://www.peteducation.com/article....1+1316&aid=211

Here is info on FeLV testing from Pet Education:

Quote:
In 2008, The American Association of Feline Practitioners (AAFP) revised their guidelines for FeLV testing. They recommend that all cats be tested for FeLV. In addition, cats should be (re)tested:

* During sickness: Regardless of previous negative results. While many signs (such as fever, stomatitis, vomiting, and diarrhea) are obvious indicators of illness, other signs are subtle and may include changes in behavior, grooming, and eating habits.

* When being adopted/entering new home: Regardless of age and whether or not they will be entering a household with other cats. They should be tested prior to being introduced into the household.

* When living in multi-cat households in which another cat is infected with FeLV, or are otherwise at high risk (e.g., cats that go outdoors unsupervised).

* After potential exposures: When cats have had known or possible exposure to other cats who are infected or are of unknown infection status. If a negative test is obtained, the test should be repeated after a minimum of 30 days.

* Prior to initial FeLV vaccination: FeLV vaccine should not be given to FeLV infected cats.

In addition, it is important to note that:

* No test is 100% accurate. In populations of cats with low FeLV infection rates, many positive tests may be false positive.

* Any positive ELISA test should be repeated.

* In most cases, the ELISA test should be used as the screening test, and IFA as the confirmatory test.

* ELISA tests using tears or saliva are not recommended.

* All cats with a negative result but with the potential of having been exposed to FeLV should be retested after a minimum of 30 days.

* All cats with a suspected or known exposure should be tested.

* If the ELISA is positive but the IFA test is negative, the cat should be retested in 60 days and then annually until test results agree.

* The vaccine will not interfere with FeLV testing.
Hope this helps.
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post #3 of 7
12/17/10 at 1:54pm
Lab tests are always more reliable because the human error is taken out of the equation as much as possible with trained professionals. I'm tempted to say that even more because you described the positive as faint. At that young age you did the snap test, it could have been antibodies left over from its mother still.
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post #4 of 7
12/17/10 at 3:07pm
The office test (Elisa) will test for exposure to the virus. Once exposed, there is a period of time where the cat will try to fight off the virus, and that usually takes roughly 30-60 days. The IFA test will not show a positive until a cat has actually contracted full blown FeLV, and since that can take up to 60 days, the IFA test is useless in a kitten that young. The Elisa will continue to show positive if the kitten is trying to fight off the virus.

Like was previously pointed out, retest with the Elisa in roughly 30 days when the kitten is a bit older. If that comes out positive again, rerun the IFA in 60 days.

In the meantime, you won't really know for certain. Sending vibes that its just residual readings from its mom.
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post #5 of 7
12/17/10 at 4:13pm
Thread Starter 
Thanks, everyone..... The kitty is not coming here for a while. With 7 cats in our home (5 of my own, 2 current fosters) I am not comfortable bringing it here without proper quarantine (which I'm not currently able to provide) until we have a more definitive neg result. He will be retested in 30 days.

We do leave kittens with the mother until at least 10-12 weeks (sometimes longer just simply because they are not available for adoption until they are big enough for spay/neuter at 2.5-3 pounds anyway). This is a surrendered orphan that according to the 'finder' of the kitten, the mother was nowhere to be found for quite some time and she had been feeding it for a few days before contacting us. So it was a situation in which the mother was not available.

We don't typically test this young either, but this was a unique situation.
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post #6 of 7
12/17/10 at 5:46pm
Quote:
Originally Posted by Momofmany View Post
The office test (Elisa) will test for exposure to the virus. Once exposed, there is a period of time where the cat will try to fight off the virus, and that usually takes roughly 30-60 days. The IFA test will not show a positive until a cat has actually contracted full blown FeLV, and since that can take up to 60 days, the IFA test is useless in a kitten that young. The Elisa will continue to show positive if the kitten is trying to fight off the virus.

Like was previously pointed out, retest with the Elisa in roughly 30 days when the kitten is a bit older. If that comes out positive again, rerun the IFA in 60 days.

In the meantime, you won't really know for certain. Sending vibes that its just residual readings from its mom.
Actually, the FeLV test is different than the FIV test. With FIV, there is no point in testing kittens until they're at least 6 months old, because that test DOES check for antibodies, and the kittens can have them from mother's milk but not be infected. With FeLV, kittens can be tested at any age, because maternal immunity/exposure does not interfere with testing. Also vaccination for FeLV does not affect test results as it does with cats vaccinated for FIV, because the FeLV test looks for viral antigens, not antibodies.

More info is available here (Cat Fanciers Assoc): http://www.cfa.org/articles/health/FeLV.html
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post #7 of 7
12/19/10 at 6:12pm
Actually exposure can cause a positive, that is why they always retest to verify a positive cat is in fact positive. They re test past 12 weeks to verify that it wasn't just exposure to the virus via an infected mother and it see if the immune system managed to clear the virus. That is how mine(5 out of the 6, if Blue is infected it's from exposure to my cats when he was dumped here) became infected, they were infected before, during, or via nursing after birth.

I will say faint positives don't mean much. Attitude was a faint positive, she made it to 17 months. Nuts is also a faint positive and he couldn't be healthier. So the strength of the result doesn't always affect how sick it will make a cat.

Getting him retested at 12 weeks(of age) will give you what should be his lifelong leukemia status. Unless you get a negative test earlier have him retested at 12 weeks old.

Taryn
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