Aleutian Disease - Treatment Differences
THE DIFFERENCES BETWEEN THE CEP IFA AND PCR ALEUTIAN TESTS
BY JERRY MURRAY DVM
Recently there has been some questions about the different tests and what do they mean, so I will try to explain the 4 different tests, in simple terms .
1) The CEP test is the most common test. It is the one that United Vaccines runs. A similar test is run by Dr Bloom at the NIH, and by the lab in the UK. It is actually a test for the ferrets response (antibodies) to exposure to the AD virus. Thus when a ferret or mink is exposed to the virus it will produce antibodies to the virus, which results in a positive CEP test.
2) The IFA test is another test that is testing for exposure to the virus (antibodies). This test is able to detect even smaller amounts of the antibody than the CEP test. This means a test may be negative by CEP but positive by the IFA test if there is only a small amount of antibody present (i.e. areal low titer). This test is what most lab animal centers were using to screen their ferrets. This test WAS available through Dr Fox's lab at MIT, but it is no longer available! MIT now uses the CEP test from United Vaccine to screen their lab ferrets.
3) The PCR test is actually testing for the virus (antigen). This test will likely be positive when they are exposed, but it will likely become negative with time. For instance in mink viremia (virus in the blood) often peaks at 10 days postinfection. [The antibody response (CEP) takes a couple of weeks
to become positive after infection.] In chronic cases you would expect a positive antibody test (CEP), and you would expect a negative antigen test (PCR). Thus the CEP test is the more accurate test. The good news about a negative PCR test is the ferret is not likely to be shedding the virus, but it does not mean he will not become sick or die in the future from AD.
4) The ELISA test is what the group at the U of Georgia (Drs. Ritchie and Stevenson) hopes to develop in the near future. It would be slightly more specific than the CEP test (i.e. there would be no false positives). Another test that is used to diagnosis AD is the percent gamma globulin compared to the total protein. If the percent of gamma globulin is 20% or more of the total protein (hypergammaglobulinemia) than AD is the likely cause. The case I had (that died on 5/19) had a gammaglobulin of 32%. The higher the gammaglobulin level means a high antibody response, and the worse the lesions will be in the organs. Not all cases will produce a high gammaglobulin level, but when it is present it is likely from AD. In simple terms, if the CEP test is positive then the ferret has been exposed and will either become sick, or become sick and die, or will become a carrier. We cannot predict the future outcome due to the multiple variables involved in this disease (i.e. which strain of the virus, how old the ferret is, what the ferret's immune response will be, what stress the ferret is under, etc, etc). Now to try to answer some of the questions about the 2 different research groups.
1) The University of Georgia's vet school group is led by Drs Ritchie and Stevenson. Bran Ritchie DVM, Ph.D. is famous for his work with 2 bird viruses (polyoma virus, and the beak and feather virus). He developed a vaccine for the avian polyoma virus. He is a well know viral researcher as well as an expert in avian and exotic medicine. He is the current editor of the exotics section of one of the top veterinary magazines. M.A. Stevenson DVM, Ph.D. did her pH work with mink AD at the NIH (in Dr Bloom's lab). She is an expert with this disease in mink. Plus she is also a board certified surgeon. This group already has a CEP test, and a PCR test. They are working on an ELISA test also. In the future they want to study the virus in ferrets and develop a vaccine for AD.
2) The University of Penn's vet school group is led by Dr Karen Rosenthal.
She is well know for her column in FERRETS magazine and for her parts in the textbook FERRETS, RABBITS, and RODENTS. She was at the AMC in New York City when she did a lot of the clinical work with ferret adrenal gland disease. Then she went to work for Antech Labs in NY. From there
she went to the University of Penn. where she is the head of the special species medicine department. She is an expert in ferret, rabbit, and reptile medicine. I do not know what experience she has in viral research or what her goals are for her AD research project at this time.
Jerry Murray, DVM
Animal Clinic of Farmers Branch
Dallas, Texas