Testing Passive Transfer of Antibodies

Q. In an article about the newborn foal’s care, Christina Cable, DVM, talks about the CITE test as one of the most frequently used tests for foal antibodies in her area. Could you please give me more information about this test?


A. The CITE test was one of several “foal-side” or field screening tests developed for assessing passive transfer of antibodies in the foal. These tests can be performed on the foal at the farm and require only minutes to obtain relatively accurate results on the amount of IgG (immunoglobulin G) present in the bloodstream. The most accurate test is the RID (radial immunodiffusion)—however, it must be performed in the laboratory, and results can take up to 24 hours. A delay in the treatment of failure of passive transfer can result in a septic foal. So, the “foal-side” tests have a great advantage in that they can give rapid, fairly accurate results on the farm, so that treatment can be started immediately if needed. The tests are usually performed between 12 and 24 hours of age, when there should be close to peak levels of IgG present.

There are several types and brands of field screening tests available. The CITE test, an Elisa (enzyme-linked immunosorbent assay) based test, however, is no longer available. IDEXX Laboratories, who manufactured the test, replaced the CITE test this year with a Snap-test, which is another type of Elisa test. This test uses a color spot with calibration standards, so that you can see if the foal has less than 400 mg/dL or greater than 800 mg/dL of IgG present. IgG levels greater than 800 mg/dL are considered optimal in the newborn foal.

Other field screening tests available are the glutaraldehyde clot test, the zinc sulfate turbidity test, and the latex agglutination test. These tests all come in commercial kits that are available to your veterinarian.

About the Author

Christina S. Cable, DVM, Dipl. ACVS

Christina S. Cable, DVM, Dipl. ACVS, owns Early Winter Equine in Lansing, New York. The practice focuses on primary care of mares and foals and performance horse problems.

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