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Ask Dr. Michael Salkin Your Own Question
Dr. Michael Salkin
Dr. Michael Salkin, Veterinarian
Category: Cat Veterinary
Satisfied Customers: 25551
Experience:  University of California at Davis graduate veterinarian with 44 years of experience.
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1 year old female cat with corona titre. originally 1:1600,

Customer Question

1 year old female cat with corona titre. originally 1:1600, then sat at 1:400 for 4 months. Now IgG 1:320 (ANTECH LAB this time). New second number added on their test IgM <1:10. Can you explain what that number indicates. Do not want to put this cat with any cats in the home or use her for breeding if I risk them getting corona. (I understand this is not FIP, but my breeding cats are all negative). Also very odd on the IgM line it says CANINE. I wonder if they did the wrong test? Is there one for dogs/cats?
Submitted: 7 months ago.
Category: Cat Veterinary
Expert:  Rebecca replied 7 months ago.

Hello,

I am sorry to hear you are worried about your cat's titers for Corona. My name is Rebecca. I am a veterinarian and will do my best to help.

Your requested expert appears not to be online; can I be of help?

As you know, having a titer to Corona virus simply means she was exposed to a Corona virus, and made antibodies to the virus. I am glad you understand this does not mean she has FIP.

There are different types of antibodies. IgM is the antibody that is made immediately in response to a virus or other pathogen, giving quick but not long lasting immunity. Then IgG antibodies are made; they take longer to make, but last much longer. So if the IgM is low, that is not unusual; IgM wanes early on and the IgG continues working.

Her IgG titer is also going down, meaning that she is not being continually exposed to Corona virus.

It is odd it says IgM canine. There is a canine Corona virus; if they measured for those antibodies you are not getting an IgM for feline Corona virus.

Let me know if this helps, and what other questions I can answer. The immune system is complex and complicated!

Customer: replied 7 months ago.

I was hoping for a reply from "my vet option". I appreciate your explanation but wonder if he can reply or I need to request an answer again from him.

Expert:  Rebecca replied 7 months ago.

I will opt out and you can wait until he is online again.

Expert:  Dr. Michael Salkin replied 7 months ago.

Hi, Kathryn. Sorry for the delay; I was hiking in the middle of nowhere again. My dear colleague Rebecca gave you the straight scoop and I'm going to be even more direct. Assessment of IgG and IgM tell a breeder nothing. Because of the problems associated with serology, it's difficult to use FCoV (feline coronavirus virus) antibody testing to control or eliminate FIP in catteries. In most cases, it's not possible to interpret the results of FCoV testing cats in catteries. Most catteries with an active breeding program and having at least 6 cats will have endemic FECV (feline enteric coronavirus), and 50% or more of the cats will have FCoV titers of 1:100 or greater at any given time. Unfortunately, antibody titers don't provide the type of information the breeder requires, such as whether any cats have FIP, whether a particular cat will develop FIP, and which cats are shedding FECV.

You do need to ask about that "canine" coronavirus test but even if it were feline, it's worthless to you. It's good to have your breeders testing negative but a negative doesn't rule out FeCoV or FIP. Nice, huh?

Customer: replied 7 months ago.

Not the answer I was looking for. So should I just re home this cat rather than waiting for at least a negative titre to put her with my other cats because it may mean nothing, and she can infect my other cats that consistently (PCR stool test for corona) test negative (I pool test the other cats) who may in fact have corona, because all these tests are just a waste of my time and money and are not accurate. FIP is not the concern. I am concerned about enteric corona.

Expert:  Dr. Michael Salkin replied 7 months ago.

I believe that rehoming her will give you the most peace of mind. Yes, I'd like you to accept the futility of this type of testing. I want you to save your money...and send it to me on my birthday this July 14.

Customer: replied 7 months ago.

ARGGH, I am going to have to get a second opinion on this one. She is a great cat and if her titre(ever) is <1:25 and continues to have negative stools it will be hard for me to accept that at any given time the corona can begin to be shed again. And with your theory I should not even be believing my other cats are negative anyhow..But I'm not a vet so after more research and a few more tests... ;) I'll take her to your practice and with the mark up on these tests you'll be able to buy yourself a nice new pair of hiking boots.

Expert:  Dr. Michael Salkin replied 7 months ago.

Rats. I'm not in clinical practice at this time. I'm chained to my computer by evil gnomes. I'd like you to speak to a specialist veterinary internist. There's a good chance that you'll only need a phone consult. Check www.acvim.org for such a specialist near you.

Customer: replied 7 months ago.

lol, I put in my state and the #1 on the list was the vet I saw today for my abby that has lymphoma. We have the corona discussion today and every time I see him. He feels there is not any clear cut answer as there are too many unknowns about this disease (my words). Maybe I need to try to contact Dr Addy who probably has done the most research on the virus. But he does say i'm probably probably safest not to put her with my other cats if she has a positive titre.

Expert:  Dr. Michael Salkin replied 7 months ago.

He and I are on the same page. Dr. Addie isn't going to give you any demonstrably different current information but there may be yet unpublished research she knows about that I don't. The last published article of Dr. Addie's was in 2009.

Customer: replied 7 months ago.

you don't trust the reliability of a PCR stool sample? or your thinking is you just don't know when they can start shedding again if they have a IgG titre. The labs say a negative by them is confirmed after 4 weeks of negative PCR tests.

Expert:  Dr. Michael Salkin replied 7 months ago.

A positive PCR stool sample identifies coronavirus antigen in the GI tract but a negative PCR doesn't rule out coronavirus antigen which may not be shedding at the time of testing or is shedding below the level of detection of the PCR test. I can't relate shedding to a titre. We've had the discussion of what labs say - it's a reasonable assumption that 4 weeks of negative PCR tests truly identifies the lack of coronavirus in the GI tract but someone will need to show me proof that it also identifies the lack of coronavirus elsewhere in a cat.

Customer: replied 7 months ago.

And if it is "elsewhere" you think it is contagious to other cats, even if the titre returns to <1:25 which I think is as low any test goes. In which case in your theory all cats could be actually positive and I should re home all the cats, close shop, and spend my time hiking in the middle of nowhere.

Expert:  Dr. Michael Salkin replied 7 months ago.

All carriers can shed the virus - particularly in times of "stress" - and the titre doesn't tell us how likely shedding is. This virus is ubiquitous in the environment. It's found in up to 100% of some populations of cats. You don't have to close up shop but you should understand that maintaining negative titres in your cats may not be realistic. My latest middle of nowhere has been on the Pacific Crest trail made more famous lately by Reese Witherspoon in the movie Wild. She hiked the northern portion. I'm finishing up the portion between the Mexican border and and the Laguna Mountain Recreation Area - about 90 miles of trail. I found that hiking keeps my feet from swelling when chained to my computer by evil gnomes.