Evaluation of an Enzyme-Linked Immunosorbent Assay (ELISA) for Pregnancy Detection in Okapi (Okapia johnstoni) and Gerenuk (Litocranius walleri)
Accurate and timely pregnancy diagnosis is crucial for population management of captive and wild ruminants. Pregnancy-associated glycoproteins (PAGs) are a large family of glycoproteins that are conserved across species and have been detected in domestic and wild bovids, ovids, caprids, and cervids.1-8 PAGs are produced by placental trophoblasts and can reach detectable levels in maternal blood. This study evaluated the use of a commercially available, visual enzyme-linked immunosorbent assay (ELISA; IDEXX Rapid Visual Pregnancy Test, IDEXX Laboratories, Inc., Westbrook, ME) for diagnosis of pregnancy in okapi (Okapia johnstoni) and gerenuk (Litocranius walleri). This assay has been validated for use in domestic cattle, sheep, goats, and water buffalo. Unlike other blood-based PAG detection methods, this assay does not require sophisticated laboratory equipment for detection or interpretation, and can therefore be utilized in many settings. Banked serum samples from gerenuk (n=11) and okapi (n=3) were tested, and a pregnant and non-pregnant sample from each individual was included. The ELISA showed 100% sensitivity and specificity in the gerenuk samples, and 0% sensitivity in okapi. In gerenuk, the earliest detected pregnancy was at approximately 7–8 weeks gestation. These results are consistent with previous studies that were able to accurately detect pregnancy in other members of the family Bovidae,2,6 but it is possible that PAGs present in okapi are too structurally dissimilar for detection using this test. This ELISA appears to be an accurate, rapid, and inexpensive method of point-of-care pregnancy diagnosis in gerenuk, but not okapi. Additional studies should be pursued to investigate the validity of this test in other non-domestic ruminant species.
The authors thank Melissa Meyer, CVT, as well as all of the staff at White Oak Conservation for their technical assistance. The authors thank White Oak Conservation for providing the funding for this project.
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