Re: [Felvtalk] Immunity to Felv once exposed then test neg?
Nina, I haven't done a recent search on the persistence of felv but judging from the quote you had in your email, I can tell you what it sounds like they think. PCR is a very senstive test for DNA or RNA. Basically you have a probe that attaches to the DNA or RNA of interest. You then amplify this region over and over again until you can detect it. Molecular (genetic) tests are somewhat new and so their interpretation is not always understood. By having a positive PCR test, the only thing that you can say is that the portion of DNA you put in a probe for is present in your sample. This DNA does not mean there is a virus present in your blood (by virus I mean a particle that has DNA or RNA that is surrounded by a capsule - this particle is infectious). It only means that the DNA is present. Viral DNA implants itself into your cat's DNA - when it is sitting there, it is not doing any damage. When it starts to proliferate, it uses your cats own cells to make more of it's particles (DNA surrounded by a capsule). It makes thousands of viral particles that then rupture the cat's cells and they go on to infect other cells. What I am trying to say is that if you can detect felv DNA or RNA - it can either be active viral particles or it can be the single strand of DNA in your cat's cells just doing nothing. felv is a retrovirus, however, so when in it's particle form it should have RNA rather than DNA. They change the RNA to DNA and then implant in your cat's cells DNA. They could potentially use this difference as a way to differentiate between viral particles and latent viral DNA in your cat's cells. I don't know if this has been looked at yet. When they talk about antigen negative, that is basically a negative snap test or IFA. Both of these tests are looking for specific antigens on the felv capsule. If it comes up positive, that mean that the test is detecting presence of the viral capsule - this means the viral particles are present. I really hope this makes sense. If it were me and the second test came back negative (are you doing a repeat snap (ELISA) or IFA - I would be more inclined to believe an IFA) my guess would be that you had an initial false positive. If this were the case, I would not mix the kitten with a felv positive until she was a year and a half and had been vaccinated (then I would consider it). Kittens are the ones that have the most difficulty with this disease and die early. To be honest, if you believe the first test, now would be the time to try and treat the cat as you may be able to clear the virus at this point - that is a very debatable statement). Kittens have an immature immune system and it has been found that felv positive kittens have thymic hypoplasia (very small thymus - thymus is responsible for making T-cells, a very important part of the immune response in this virus). It appears that the virus can actually inhibit the activity of the thymus. LTCI injections appear to attempt to halt and reverse this process. Hope this helps and good luck. God bless. Jenny On Fri, Oct 1, 2010 at 5:52 PM, vixen...@verizon.net wrote: Hi Sharyl, I'm sorry for your loss. I can relate to the heartbreak. My first experience with felv was with tiny babies too. Happily one of the 6 kittens was neg, so I got to keep my special Timmy boy with me, (he's over six yrs old and sitting on my lap as I type this). The person who is fostering Sally has no idea what has become of her Momma or her littermates. I asked that question too. I'm hoping if Sally's test was a true pos and her subsequent test is neg, she might be safe from felv in a home with another pos kitten. I called a veterinary Internist I have used and asked the question. I'll let everyone know what they have to say when they get back to me. Nina Fri, 01 Oct 2010 13:41:31 -0700 Nina, I don't want to give you any false hope. It is more likely that an adult cat will throw off the virus than a kitten. There is always a chance the test result was an error. Do you know what became of Sally's littermates. My experience with kittens is that all in the litter tested positive at 4 weeks of age and remained positive. The Momma cat was also positive. It's great that you have a home lined up for Sally if she remains positive. My four positive babies were adorable and I loved every day I had with them. Sharyl ___ Felvtalk mailing list Felvtalk@felineleukemia.org http://felineleukemia.org/mailman/listinfo/felvtalk_felineleukemia.org ___ Felvtalk mailing list Felvtalk@felineleukemia.org http://felineleukemia.org/mailman/listinfo/felvtalk_felineleukemia.org
Re: [Felvtalk] Immunity to Felv once exposed then test neg?
Jenny, I haven't heard back from my specialty vet yet. Something tells me they don't have a definitive answer, probably no one does. It was so kind of you to break down what they are saying on the website I found. You've got me thinking, if Sally tests neg on her second test, it is not worth taking any chances, no matter what. If Sally really is negative, she as a kitten, is too vulnerable to this insidious disease. It's just not worth exposing her if she can find a loving home in a negative environment. I don't know which test the rescue is planning to use for the re-test. I will strongly recommend an IFA vs another ELISA. I have no real influence here, but I'll throw my two cents in and pray for the highest good. Thank you again, Nina Mon, 04 Oct 2010 10:43:01 -0700 Nina, I haven't done a recent search on the persistence of felv but judging from the quote you had in your email, I can tell you what it sounds like they think. PCR is a very senstive test for DNA or RNA. Basically you have a probe that attaches to the DNA or RNA of interest. You then amplify this region over and over again until you can detect it. Molecular (genetic) tests are somewhat new and so their interpretation is not always understood. By having a positive PCR test, the only thing that you can say is that the portion of DNA you put in a probe for is present in your sample. This DNA does not mean there is a virus present in your blood (by virus I mean a particle that has DNA or RNA that is surrounded by a capsule - this particle is infectious). It only means that the DNA is present. Viral DNA implants itself into your cat's DNA - when it is sitting there, it is not doing any damage. When it starts to proliferate, it uses your cats own cells to make more of it's particles (DNA surrounded by a capsule). It makes thousands of viral particles that then rupture the cat's cells and they go on to infect other cells. What I am trying to say is that if you can detect felv DNA or RNA - it can either be active viral particles or it can be the single strand of DNA in your cat's cells just doing nothing. felv is a retrovirus, however, so when in it's particle form it should have RNA rather than DNA. They change the RNA to DNA and then implant in your cat's cells DNA. They could potentially use this difference as a way to differentiate between viral particles and latent viral DNA in your cat's cells. I don't know if this has been looked at yet. When they talk about antigen negative, that is basically a negative snap test or IFA. Both of these tests are looking for specific antigens on the felv capsule. If it comes up positive, that mean that the test is detecting presence of the viral capsule - this means the viral particles are present. I really hope this makes sense. If it were me and the second test came back negative (are you doing a repeat snap (ELISA) or IFA - I would be more inclined to believe an IFA) my guess would be that you had an initial false positive. If this were the case, I would not mix the kitten with a felv positive until she was a year and a half and had been vaccinated (then I would consider it). Kittens are the ones that have the most difficulty with this disease and die early. To be honest, if you believe the first test, now would be the time to try and treat the cat as you may be able to clear the virus at this point - that is a very debatable statement). Kittens have an immature immune system and it has been found that felv positive kittens have thymic hypoplasia (very small thymus - thymus is responsible for making T-cells, a very important part of the immune response in this virus). It appears that the virus can actually inhibit the activity of the thymus. LTCI injections appear to attempt to halt and reverse this process. Hope this helps and good luck. God bless. Jenny ___ Felvtalk mailing list Felvtalk@felineleukemia.org http://felineleukemia.org/mailman/listinfo/felvtalk_felineleukemia.org
Re: [Felvtalk] Immunity to Felv once exposed then test neg?
Nina, I don't want to give you any false hope. It is more likely that an adult cat will throw off the virus than a kitten. There is always a chance the test result was an error. Do you know what became of Sally's littermates. My experience with kittens is that all in the litter tested positive at 4 weeks of age and remained positive. The Momma cat was also positive. It's great that you have a home lined up for Sally if she remains positive. My four positive babies were adorable and I loved every day I had with them. Sharyl --- On Fri, 10/1/10, vixen...@verizon.net vixen...@verizon.net wrote: From: vixen...@verizon.net vixen...@verizon.net Subject: [Felvtalk] Immunity to Felv once exposed then test neg? To: felvtalk@felineleukemia.org Date: Friday, October 1, 2010, 1:54 PM Hello All, This question is for a foster kitten I know of that tested felv+. Her name is Sally and she is only 6 weeks old. Happily the rescue that Sally is with knows enough to test again and Sally is being fostered in the meantime. I'm wondering this, if Sally has tested pos once, (assuming it was a true pos), then that means she has been exposed to the disease. If she later tests neg, does that mean she would be immune to felv in the same way she would had she been vaccinated against it? The reason I ask is Sally has a potential adopter waiting for her based on her next test result. This woman already has an felv+ kitty. I'm wondering if there have been any studies done indicating a cat previously testing pos, then throwing the virus and testing neg, is less susceptible to contracting felv when exposed to known positive cats. Nina ___ Felvtalk mailing list Felvtalk@felineleukemia.org http://felineleukemia.org/mailman/listinfo/felvtalk_felineleukemia.org ___ Felvtalk mailing list Felvtalk@felineleukemia.org http://felineleukemia.org/mailman/listinfo/felvtalk_felineleukemia.org
Re: [Felvtalk] Immunity to Felv once exposed then test neg?
Hi Sharyl, I'm sorry for your loss. I can relate to the heartbreak. My first experience with felv was with tiny babies too. Happily one of the 6 kittens was neg, so I got to keep my special Timmy boy with me, (he's over six yrs old and sitting on my lap as I type this). The person who is fostering Sally has no idea what has become of her Momma or her littermates. I asked that question too. I'm hoping if Sally's test was a true pos and her subsequent test is neg, she might be safe from felv in a home with another pos kitten. I called a veterinary Internist I have used and asked the question. I'll let everyone know what they have to say when they get back to me. Nina Fri, 01 Oct 2010 13:41:31 -0700 Nina, I don't want to give you any false hope. It is more likely that an adult cat will throw off the virus than a kitten. There is always a chance the test result was an error. Do you know what became of Sally's littermates. My experience with kittens is that all in the litter tested positive at 4 weeks of age and remained positive. The Momma cat was also positive. It's great that you have a home lined up for Sally if she remains positive. My four positive babies were adorable and I loved every day I had with them. Sharyl ___ Felvtalk mailing list Felvtalk@felineleukemia.org http://felineleukemia.org/mailman/listinfo/felvtalk_felineleukemia.org
