Electric Burns
There are two types of electric currents: a direct current and an alternating current. Alternating currents are found in businesses and residential structures, and direct currents are more common in batteries. A direct current travels in one direction, whereas an alternating current frequently changes direction away from and toward its origin. In the United States most structural wall sockets are 110 volts unless for appliances and larger devices, which are usually 220 volts. A direct current (DC) is less dangerous than an alternating current (AC). A current of 50-80 mA (AC) can be fatal within seconds, in comparison to 250 mA DC for a similar time period, which is often survived in humans. In humans, an AC is more likely to cause cardiac arrhythmias (Saukko & Knight, 2016).
An electric current pulsing through tissue can cause skin lesions, organ damage, and death; this is referred to as electrocution (Saukko & Knight, 2016). The degree of damage is dependent on the current, voltage, generation of heat, and the time the animal victim is in contact with the electrical source (Merck & Miller, 2013; Schulze et al., 2016). The current is the quantity of electricity traveling through a wire and is measured in milliamps (mA). The damage to tissue is proportional to the amount of electricity flowing through it. Voltage is another factor; the higher the amount, the more electricity that passes through the tissue. The longer a current passes through a body, the higher the degree of damage produced. A low current exposed to the body for a long period of time can cause more damage than exposure to a higher current for a short period of time. Heat is generated from the electric current, causing thermal injury (Saukko & Knight, 2016). Due to the deep extension of generated heat, tissue damage can be severe. Death may result from respiratory paralysis or ventricular fibrillation (Hedlund, 2002) (Figure 12.4a-c).
When an electrical current enters a body, it will travel the shortest route from the origin of contact to a point of grounding or exit (Saukko & Knight, 2016). Tissue resistance to an electric current from greatest to least is bone, fat, tendon, skin, muscle, blood, and nerves. A current’s flow along a path of minimal resistance includes blood vessels, nerves, and wet tissue (Hedlund, 2002; Merck & Miller, 2013; Saukko & Knight, 2016). A current will concentrate in tissue of greater resistance such as bone, causing the generation of increased thermal energy (Hedlund, 2002).
Animal victims of electricity may be found still in contact with an electrical source that caused the injury. The majority of electrical injuries in animals are accidental (Merck & Miller, 2013). In animal abuse cases electricity can be used as a form of torture or to kill an animal (Merck & Miller 2013). According to Chris Schindler, Animal Cruelty and Fighting Director, for the Humane Society of the United States, pit bulls are routinely culled by their owners using electricity after losing an event or if the owner just wants to get rid of them. A method known as "plugging” is used. This makes use of an electric extension cord that can be plugged into a wall socket or a portable jump box (for charging a car battery) (Figure 12.5). There are two electrode devices usually with alligator clips and a cord to be plugged into an outlet. The animal has a clip applied to an ear and the tail or anus and then then the device is plugged in, killing the dog (Schindler, personal communication, 2018). A similar method has been used in show and racehorses to kill them for insurance fraud (Schindler, personal communication, 2018). According to Detective Mike Duffey, Animal Cruelty Investigator for the Humane Society of Southern Arizona, another method of electrocution used in these dogs is using a metal roofing sheet and a hand-operated toy electric train "transformer” with wires attached to the piece of metal. The dog’s feet are made wet and
Figures 12.4 (a-c) Magpie electrocution. (Photo courtesy Dr. J.D. Struthers.)
Figure 12.5 Simulated photo of the "clip" device used to electrocute fighting dogs; the device is attached to the lip and flank areas and plugged into a wall socket. Can be mistaken for utility cord at the scene. (Photo courtesy L. Siemens.)
the dog is placed on the metal sheet. The current is applied, killing the dog (Duffey, personal communication, 2018).
Electrocution by these methods may show external burns, such as pad injuries; however, the use of the alligator clips, especially in the anus region, may leave subtle if any electric marks and will need to be looked for during the necropsy on these animals. An animal injured from electricity might be found in a tonic state from prolonged contraction of striated muscles. There may also be evidence of vomiting or diarrhea (Merck & Miller, 2013). In humans this can lead to bone fractures (DiMaio & DiMaio, 2001). Lower amperage electrocution will cause muscle tremors, painful muscle contractions, and loss of consciousness. The animal may develop ventricular fibrillation or respiratory paralysis, causing damage. There may be decreased thermal damage to aqueous internal tissue, with evidence of pulmonary edema. If an animal survives when an electric source is removed, there will be generalized weakness and ataxia followed by secondary pulmonary edema. Electric burns can cause the release of vasoactive substances and vasoactive thrombosis, causing tissue necrosis. The tissue may appear charred, tan, or pale gray. Tissue edema may be observed in 1-2 days post injury. Local tissue ischemia can develop in 3-5 days. The full extent of the injury may take 2-3 weeks to be recognized (Hedlund, 2002; Merck & Miller, 2013).
Low-voltage electrical burns are called electrical marks and can be found in the area of electrical contact. These types of burns are generally small or appear as a chalky white lesion with an indented crater with raised borders or erythema (blistering) (Merck & Miller, 2013; Saukko & Knight, 2016). Some lesions have hyperemic borders surrounding a pale area or reddening within the zone. Burns may have yellow or black discoloration caused by heat (Saukko & Knight, 2016). Histologically, there may be disruption of the epidermal surface. There may be particles of metal deposits if a metal device such as a clip was used as a conduction surface. A pattern of calcification of collagen fibers both superficially and deeply in the skin within a zone of viable tissue in close proximity to necrotic tissue may be consistent with an electrically induced lesion. In experiments with pig skin using alternating currents and direct currents, these have been observed (Danielson et al., 1991).
High-voltage electric burns can result in charring of body tissue resulting in third-degree burns at the contact site. Multiple small burn wounds caused by arcing of the current can cause a crocodileskin effect observed in humans (Saukko & Knight, 2016). If the electric current is obtained through a tertiary object, the resulting electrical burns can be large and irregular. The actual burns consist of a chalky white crater with raised borders, with the heat producing a yellow or black discoloration at the burn sites. In humans, massive tissue destruction from high voltage along with loss of extremities and organ rupture have been noted (DiMaio & DiMaio, 2001). Death usually results from cardiac arrest. There may be high voltage thermal damage to the respiratory center of the brainstem resulting in respiratory arrest (DiMaio & DiMaio, 2001).
