Every year thousands of animals worldwide succumb to lightning injuries. Animals are particularly vulnerable as they are usually placed outside during severe storm events. Animals that have a large separation between their front and back legs (such as cattle) are vulnerable to receive lightning strike injuries due to the dangerous potential differences that built up between those feet during lightning strike events.1
A case of presumed lightning strike has been described in the Central West region.2 Elsewhere, since 1943, there have been 22 reported incidents involving animals and lightning strike events.1 Lightning strike is viewed as a relatively uncommon cause of trauma in domesticated animals, however heavy mortalities can occur where a number of animals have congregated near a tree or water source.3
Over the course of 2 months in September, and October 2014, 2 separate cases of lightning strike were reported and investigated in the Young area. The following case report aims to further the reader's knowledge in the topic of lightning strike in production animals.
In early September a landholder from the Young area called to inquire about sudden deaths in 2 steers out of a mob of 140.
The animal was described as having blood emanating from its nostrils, eyes and anus. Both animals died within a few meters from one another and were located close to a creek bed. The day before there were storms in the area.
Anthrax, suspected because blood exuded from the orifices and decomposition was rapid, was ruled out using an ICT field test. Confirmatory samples via an impression blood smear and a piece of ear were taken and sent to EMAI for verification.
Evidence of singe marks were observed towards the lateral aspect of the right hock. Unchewed food was also found on examination of the oral cavity.
A producer called about undertaking an insurance claim in regards to a presumed lightning strike post another storm event in the region. As with the animal was reported as bleeding from all orifices and this animal and the herd were fed close to an oak tree.
This animal was necropsied. Unclotted blood was found in the lumen of the while petechial hemorrhages were found on the serosal surface of the trachea. Superficial singing of the hair was again observed in this animal.
Peer-reviewed scientific literature in relation to animals and lightning strikes is scarce. Many of the reports of lightning strike events are mentioned in popular media are compiled by authors of a non-scientific background, with the facts distorted to enhance audience's attention.1
Human cases of lightning strike have been described both from a medical and engineering perspective. The permanent or temporary damage that ensues from a lightning strike, depends, among other factors, on the mechanism of interaction (described below) through which the body is exposed to a lightning strike and the path and the strength of the electric current passing through the body. 4
In livestock, cases have been reported in swine, cattle, horses and sheep. Vestibular disease and other neurological conditions have been described as a common sequel in horses.6 Two cases of ocular lesions have been described in cattle and horses.5/6 Pigs have been found dead, paralysed and with broken bones.8/9 Wildlife such as elephants, giraffes and deer have also been found dead near trees and open water sources following electrical storms.
Mechanisms of lightning strike injury include a direct strike, side flashes, step potential and touch potential. A direct strike is where enormous quantities of energy pass through the body very quickly causing resultant burns, organ damage and damage to the flesh and bones.1 Side flashes are where animals underneath a large tree or pole receive a side flash if the tree is hit by lightning.1 Touch potential is where a partial current may pass through the body of an animal if part of the animals body comes into contact with higher elevation of a lightning struck object while the other parts of the animal remain in contact with ground.1 Step potential is the most common lightning injury amongst animals. "When the feet of an animal are separated in the direction of increasing potential, a partial current may pass through the body in contact with the ground align in the direction of potential gradient developed due to the injection of current into the Earth from a nearby lightning strike". 1
In human beings the effects post a lightning strike are usually evident from the history of the case or from the physical surroundings. This may not always be the case in animals.
To diagnose lightning strike, there should be a history of exposure and evidence of sudden death or injury. Half-chewed food might be found in the oral cavity of dead animals. Singe marks, scorching of the grass and tearing of the bark of nearby trees are also clues that lightning strike may be the primary cause of death or injury. In case 2, an insurance claim was to be made in relation to the death of the animal and the diagnosis of lightning strike. Best (1967) and Brightwell (1968) discussed the examination of animals/carcasses with relation to a diagnosis of lightning strike. In order to minimize the conflict and any potential future repercussions that could occur from lightning strike insurance claims, it is best to have a representative present at the time of the autopsy to ensure that all sides are in agreement at the time of the diagnosis.3 If this is not possible, appropriate communication with the insurance company should be maintained to ensure that all procedures are followed in relation to submitting a claim.
It is difficult to prevent prevent lightning strike in animals that graze in herds in large fields. It is natural behavior of herding animals to move towards fences or take shelter under trees as a storm approaches. Gomes et al (2012) mentioned a number of ways to minimize stock losses from lightning strikes by amending current fence structures and trees that animals might utilize as shelter(s). This unfortunately, will not prove to be feasible for most producers, but they are methods worth considering for those with valuable livestock and/or those that frequently experience lightning.