Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract only
Publication Acceptance Date: 8/12/2003
Publication Date: 10/10/2003
Citation: Alverson, J., Bender, S., Herrmann, L.M., Orourke, K.I. 2003. Third eyelid lymphoid tissue biopsy in sheep is aided by histamine [abstract]. Proceedings of the American Association of Veterinary Laboratory Diagnosticians 46th Annual Conference. 41: 212. Interpretive Summary:
Technical Abstract: Ovine scrapie is a member of a heterogeneous family of fatal neurologic disorders known as transmissible spongiform encephalopathies characterized by deposition of prion proteins (PrPSc) in the central nervous system and lymphoid tissues. Diagnosis of ovine scrapie by third eyelid lymphoid tissue biopsy and PrPSc immunohistochemistry (IHC) assay has been described. One of the biggest drawbacks to implementing routine field use of the third eyelid test has been obtaining adequate numbers of lymphoid follicles in each tissue biopsy for disease diagnosis. We will describe a technique for enhancing third eyelid lymphoid tissue using histamine eyedrops that improved biopsy collection of third eyelid tissue with increased numbers of lymphoid follicles and did not interfere with PrPSc detection by IHC assay. An eyedrop formulation of 1 % histamine and 0.5 % proparacaine hydrochloride in an aqueous base was applied approximately 6 min prior to third eyelid lymphoid tissue biopsy by an established protocol. The technique has been used in the field in over 400 sheep to date, and has improved the success rate for obtaining third eyelid biopsy samples with sufficient lymphoid follicles for scrapie diagnosis from approximately 60 % to over 90 %. The left and right third eyelids of five sheep from a scrapie positive research flock were biopsied after using the histamine eyedrop preparation in the right eyelids and proparacaine eyedrops without histamine in the left eyelids to test the histamine eyedrop formulation for interference with PrPSc detection. Four of the five sheep tested positive for PrPSc in both eyelids while the fifth sheep was negative for PrPSc in both eyelids indicating that the histamine eyedrop preparation did not interfere with detection of PrPSc by IHC. Therefore, the addition of histamine eyedrops to the regular third eyelid testing protocol will be useful in consistently obtaining biopsy samples of sufficient quality for diagnosis of preclinical scrapie in third eyelid tissue.