Conservation science in a terrorist age: the impact of airport security screening on the viability and DNA integrity of frozen felid spermatozoa.

In response to growing terrorism concerns, the Transportation Security Administration now requires that all checked baggage at U.S. airports be scanned through a cabinet x-ray system, which may increase risk of radiation damage to transported biologic samples and other sensitive genetic material. The objective of this study was to investigate the effect of these new airport security regulations on the viability and DNA integrity of frozen felid spermatozoa. Semen was collected from two domestic cats (Felis silvestris catus) and one fishing cat (Prionailurus viverrinus), cryopreserved in plastic freezing straws, and transferred into liquid nitrogen dry shippers for security screening. Treatment groups included frozen samples from each male scanned once or three times using a Transportation Security Administration-operated cabinet x-ray system, in addition to non-scanned samples (i.e., negative control) and samples previously scanned three times and exposed to five additional high-intensity x-ray bursts (i.e., positive control). Dosimeters placed in empty dry shippers were used to quantify radiation exposure. Following treatment, straws were thawed and spermatozoa analyzed for post-thaw motility (percentage motile and rate of progressive movement), acrosome status, and DNA integrity using single-cell gel electrophoresis (i.e., the comet assay). Dosimeter measurements determined that each airport screening procedure produced approximately 16 mrem of radiation exposure. Our results indicated that all levels of radiation exposure adversely affected (P < 0.05) post-thaw sperm motility, but the percentage of acrosome-intact spermatozoa did not differ (P > 0.05) among treatment groups. Results also showed that the amount of double-stranded DNA damage was greater (P < 0.05) in sperm samples from both cat species scanned three times compared to samples scanned once or negative controls. Findings suggest that new airport security measures may cause radiation-induced damage to frozen spermatozoa and other valuable biologic samples transported on passenger aircraft and that alternative modes of sample transportation should be used whenever possible.