Why I no longer believe any positive FIV/FeLV test result unless I see it with my own eyes.
I know, I know – I’ve written about this before: one test on one day cannot diagnose a cat with FIV or FeLV. (Missed out on these? Read here. And here. And probably here and here too, for good measure.) Yeah, I’m a little obsessive about FIV and FeLV testing, but with good reason. Here’s the latest story.
A request came in to the main Calvin’s Paws email line to take a cat that had tested positive for feline leukemia. Beautiful cat – young male Maine Coon mix. The finders really wanted to keep him, but didn’t want to put their current cat at risk. So I gave them my standard initial advice:
- Have the cat retested. Ideally do another in-house test to rule out test error and if that is still positive, have an IFA test done.
- It’s really OK to mix FeLV+ cats with adult, vaccinated, negative cats if you’re OK with a small amount of risk (like, 2% under lab settings with a good vaccine – the whole inactivated ones, not the recombinant subunit crap, but I digress).
- Read more about FeLV here and let me know how the cat retests.
The finder was grateful for my advice and made an appointment to take the cat to his vet to be retested. They decided that if the cat was still positive, they didn’t want to take the risk, and asked if I would take the cat if needed. I agreed.
The day of retesting came, and they went to their vet. That night, the finder emailed me and explained that the vet had told them that it wasn’t worth redoing the test now because he would have to be quarantined for another three months and retested again regardless of the results. So no retest at all. Not even an in-house test to rule out test error. Yay.
At this point, I told the finder he could just bring the cat to me. I’m the medical coordinator for the rescue, and so I have the tools (and skills) on hand to do a blood draw and run the in-house test while he waited. Because really, I am a testing freak, and I will test any cat anytime for anyone. If the cat was positive, I would keep the cat. If the cat was negative, he would take the cat home with him and keep him. Deal? Deal.
So the day came, and the finders brought the cat (named Bowie) over to my house. They brought him in a carrier covered in a blanket, which my own personal (negative) cat promptly assumed was for him and sat on top of the carrier, trying to see inside. The finders seemed a little nervous at my cats coming so close, but I explained that they were vaccinated against FeLV, and it took prolonged close contact to spread anyway, so I really wasn’t concerned. They relaxed.
The first thing I did was look through the medical records they had brought with them. It turns out that Bowie had initially been tested at Banfield (not always my favorite place) with an IDEXX Triple Test (definitely not my favorite test). The finder started to tell me the full story of how she found him – he showed up at her old apartment right as she was about to move, so she took him in, took him to Banfield right at the end of the night before they closed, and they tested him and did initial care. The vet initially came in and told her that Bowie had tested positive for FIV, but then came back in the room 20 minutes later and told her that he had actually tested positive for FeLV, so understandably the finder was very suspicious already and anxious to have him retested. Yeah, me too.
I drew blood on Bowie and ran two tests – one was the fairly standard IDEXX Combo SNAP test that tests for FIV and FeLV (NOT the Triple Test). The other was a newer test – the Witness FIV/FeLV test made by Zoetis. When we have a cat that has tested positive before, I typically run both tests – just another way to help rule out test error. The Witness test typically comes up faster than the SNAP test, and guess what? So far, Bowie was NOT FeLV+, he was FIV+! The Witness tests are clearly labeled – one strip for FIV, one for FeLV, and it was the FIV strip that was showing up positive (and faint at that). We still had to wait for the IDEXX test to come up, but the finders were already ecstatic. Considering how Banfield had initially flip-flopped on the diagnosis, we felt pretty confident that this was a case of “mistaken identity” (to put it nicely anyway – personally I think a vet’s office should be able to read a SNAP test, but hey, maybe that’s just me). Sure enough, when the SNAP test came up, it showed the same thing – FIV+, FeLV negative. I even pulled up the package insert, just to be absolutely sure we were reading it correctly (it’s really not that hard). So with two tests both saying the same thing (and one previous test that probably actually said the same thing), we called it – Bowie has FIV, NOT FeLV!
The finders were fairly knowledgeable about cats and after discussing FIV and what that meant for Bowie (hint: not a big deal, and he can live just fine with other negative cats), they decided to take him home and keep him. Since Calvin’s Paws had already tested him, we offered to continue his care and handle his neutering, retest him again at that time, and then the finders could just pay our adoption fee to help cover the costs of care. They happily agreed, and by the next day I got an email saying that Bowie was already becoming friends with his new kitty housemate, who’s about the same age as him.
THIS is why I am such a freak about testing. THIS is why I am so adamant that ONE test on ONE day does not a diagnosis make. Aside from the fact that human error is always a factor to consider (because really, you can’t take the time to double check which spot is which?), all tests have a known false positive rate, and so any positive test should ALWAYS be repeated no matter what. Here is what Calvin’s Paws does any time a cat tests positive:
- Stop and repeat the test immediately. (Swearing while repeating the test is acceptable, especially if you’re the FeLV foster home and you know your husband is going to be quite displeased if you bring another one home.)
- If that test is positive, and the cat is an adult, make an appointment to send off an IFA test. If that’s positive, then the cat is considered positive. If the IFA is negative, then repeat the in-house tests and IFA test in a month or so.
- If the in house test is positive and the cat is a kitten, repeat the test in a month. IFA tests will usually be negative on kittens, so we don’t usually do them until the kitten has tested positive for several months, or until the kitten is about 6+ months old. If the kitten is with its mother and the mother is positive, separate the kitten from mom as soon as it is safely possible to minimize any potential exposure.
- TAKE A PICTURE of the test and attach it to a record of any positive test. Our database allows us to upload files to a cat’s profile, so that’s how we keep track, but you can do it however you want. If you’re at the vet and the vet comes in the room and says your cat has tested positive, ask to see the test. Then take a picture.
So at this point you might be thinking, “OK, I get that this is a crazy testing story, but really, how often does this really happen?” More often than you might think. Calvin’s Paws has taken in countless cats over the years with wonky testing stories. Consider Cremesicle for instance. He’s one of our current fosters who came to us in the summer of 2012 when his owners lost their home. His owners stated at the time that he was double positive, meaning he had both FIV and FeLV, and we took their word for it. He went to the foster that had our FeLV+ cats at the time, and there he stayed until I took him in December 2014. The first thing I did when I got the FeLV cats in the program was retest them – just for a new baseline (because I am all about data). To our great surprise, Cremesicle only tested positive for FIV. He was FeLV negative. He’s been living with FeLV+ cats for almost 4 years now, but now we have no idea if he actually has the virus or not. Sure his owners said he did, but that’s not what my tests say. We tested him again this year, and same results – FIV+ only. So now we’re in a bit of a tricky situation with him because we don’t have access to those initial testing records. Did he ever really test positive for FeLV? Did he initially test positive for both FIV and FeLV and later clear the FeLV from his system completely? Is the FeLV just suppressed by his immune system, hiding out deep in his bone marrow somewhere waiting to become active again if he ever becomes immunosuppressed? We literally have no idea. Frankly, this could be the case with any cat with an unknown history that tests negative – just because a cat tests negative doesn’t mean they don’t have FeLV (read more here), but with Cremesicle, because we were told he was positive, we have to treat him like a positive and disclose that potential risk to adopters. How would knowing what previous tests were done help us now? Well, in a perfect world, he would have had an IFA test done back when he was first diagnosed with his original owners. If that IFA test was positive, then he’s probably harboring the virus somewhere, and his immune system just has it under wraps. If that IFA test was negative, then there’s a pretty good chance that he cleared the virus completely, and is a FeLV negative (but immune) cat living with FeLV+ cats and struggling to be adopted because of it.
These are just two examples of the LUCKY ones. Imagine what it’s like in overcrowded, underfunded, public shelters. Many shelters still euthanize positive cats, based solely on one test. They simply can’t afford to do more testing, and one positive test is enough to condemn a cat in many places. Based on just my own personal experience with testing, I truly can’t even imagine how many healthy, loving cats that weren’t actually positive at all, get euthanized every year in shelters across the country. I bet the number is staggering.
Calvin’s Paws is a 501(c)(3) rescue. We work through a network of foster homes throughout the Triangle area to save homeless cats and dogs. We are a dedicated group of volunteers with common goals: rescuing animals (both positives and non-infected felines), finding the best fitting homes for each animal, and educating the public on animal health and responsible pet ownership.