Efficacy of a Novel Electrical Shock Trap for Pest Control Programs
An effective rodent pest control program is an important aspect of any animal care and use program. It ensures the SPF status of rodent colonies and also protects human safety as regards zoonoses prevention. According to the AVMA Guidelines for Euthanasia of Animals, kill traps do not always render a rapid or stress-free death, and thus, the use of live traps followed by euthanasia is preferred; however, they also state that, although newer technologies improve kill trap performance by assuring rapid loss of consciousness, individual testing of traps is recommended to ensure the device works properly. Here, we evaluated an electrical shock trap as an option for vermin control in animal facilities. We assessed the trap’s ability to quickly induce irreversible loss of consciousness and death with minimal pain and distress. This was performed by placing a modified trap (allowing visualization of the animal’s interaction within the trap) in a test chamber and allowing animals to freely interact with the trap. Assays were videotaped by an overhead and a side camera. We measured time to induce loss of consciousness and time to death using male (n = 10) and female (n = 10) Crl:CFW(SW) mice. A subset of electrical shock (n = 10) and CO2 (n = 4) euthanized animals were used for blinded comparative necropsy and histopathology. Our results indicate that the trap has a 100% kill rate. Mean time to unconsciousness was 7.35 ± 3.76 s, while mean time from unconsciousness to death was 25.62 ± 7.2 s. Histopathology revealed a 20% (2/10) occurrence of focal mild dermal lesions, indicative of perimortem burn injury, in the electrical shock animals. No other histologic changes associated with electrocution were identified. In conclusion, this system presents a viable alternative to current mouse traps, while improving animal welfare compared with other kill trap options, as well as allowing reduced labor investment associated with pest control management.
(A) Front view of the test chamber with the trap aligned along the long axis against the wall. The viewing window allowing for visualization of the interaction of the mouse with the trap. (B) Top down image of the electrical shock trap positioned for use in the test chamber. Trap is positioned to utilize the natural thigmotaxic behavior of the mouse.
(A) The modified tunnel portion of the electrical shock trap in the closed position with the viewing window installed. (B) Tunnel portion opened up with top laying at a 90° angle from the tunnel base. Yellow arrows denote location of the metal conduction plates of the trap. Grey arrows indicate the location of the baffles, which cause the mouse to contact the triggering plate and starting the high voltage electrical shock train.
Still images of a mouse’s interaction with the trap. (A) Entering the trap. (B) Initial reaction after triggering the trap with dorsalflexion of the head and neck, (C) head beginning to fall and body relaxation, (D) beginning of involuntary opening of the eyes, and (E) head ventral eyes open, interpreted as unconsciousness. (F) Death, ears in neutral resting position, eyes completely open, respiration stopped, and shock cycle over. This was sequence of events was consistent across all trials.
Results of the unpaired t test assuming equal variance between groups. (A) results comparing time from triggering the trap to unconsciousness between females and males showing no significant difference. t = 0.6462, df = 18, P = 0.5263. (B) Time to death between females and males. t = 0.9537, df = 18, P = 0.3529.
Photomicrograms of the hematoxylin and eosin stained slides from the 2 lesions found in electrical shock animals (2/10) submitted for necropsy and histology. A is 10× magnification of the focal lesion (red arrows) found on the abdominal skin approximately 3 mm in length. (B) 10× magnification of the focal lesion found on the muzzle (red arrows). Both are characterized by a loss of epidermal-dermal architecture with scattered pyknotic nuclei and a deep basophilic matrix, indicative of perimortem burn injury.
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