Toxicologic considerations for working dogs (Proceedings)

Veterinarians that care for service dogs such as police, military, and search and rescue dogs are entrusted in maintaining the health of animals that provide a vital service to man, especially during times of crisis such as the terrorist events of 2001, when the searching abilities of the these dogs were of paramount importance. Understanding the types of agents and environments to which these dogs may be exposed will aid the practitioner in providing the utmost of care to these valuable dogs, both during and after their exposure to disaster sites. Many of the concepts presented here are not restricted to dogs that are involved in terrorist attacks, but may also be applied to dogs that are present at natural disaster sites, such as earthquakes or floods.

Dogs working at disaster sites may be exposed to a variety of environments, from burning fires to areas flooded by rain or fire control water. Search and rescue dogs may enter areas deemed too hazardous for their human counterparts, risking hazards such as crush injury or exposure to undetected pockets of noxious gases. When humans enter disaster sites, they are frequently outfitted with equipment that protects them from dermal, ocular and inhaled toxicants. Unlike their human counterparts, the use of protectants such as "booties"' or goggles is not common, often due to the reluctance of handlers to use these products. This reluctance may be due to poor tolerance of these items on some dogs or the perception by the handler that these products impede performance in the dog (e.g. poor traction from booties). Because they rely on their olfactory sense to perform their duties, dogs that are searching disaster sites are continually exposed to the inhalation of a variety of potentially irritating and/or toxic agents.

Potential routes of exposure to toxic agents include skin, gastrointestinal tract, respiratory tract, and mucous membranes of the eye and oral cavity. Many of the breeds used for search and rescue (e.g. German shepherd, Labrador retriever) have dense coats that can protect much of the dog from dermal exposures. However, because the use of protective "boots" on dogs is not uniform, dogs may be at risk of exposure to physical (e.g. broken glass) and toxic (e.g. solvents) hazards that they walk through as they work disaster sites. Additionally, areas of skin with thinner hair coat protection (e.g. muzzle, ventral abdomen), may allow significant dermal exposure to potentially toxic agents.

Ingestion of potentially toxic agents is a significant concern in dogs that are working disaster sites. Dogs may lick from puddles, ingest agents that they find on the ground, or lick toxic agents off of their coats. Additionally, inhalation of large particulates results in these agents being moved up to the pharyngeal area by the mucociliatory escalator of the trachea, where they are subsequently swallowed.

Inhalation of large particulate matter may result in respiratory tract irritation and/or oral ingestion of particulates. Smaller particulate matter may reach the smaller airways or alveoli, where irritation and/or systemic absorption may occur. Inhalation of gases may result in almost immediate systemic absorption.

Ocular exposure to toxicants is not generally considered to be a significant source of systemic exposure, but the irritation from ocular irritants may cause sufficient ocular injury and inflammation as to force the retirement of a dog from a disaster site.

The types of agents to which dogs may be exposed during their work at a disaster site can roughly be categorized as solids (particulates), liquids, and gases. Explosive and compressive forces may release a variety of toxic agents (e.g. heavy metals, asbestos) that are normally safely contained. Many solid agents may be converted to particulates that may cause immediate or delayed injury. Particulate matter poses hazards as both respiratory and ocular irritants. Occasionally, a dog may swallow sufficient particulate matter as to cause gastrointestinal irritation and/or systemic absorption. Particulates of heavy metals, such as arsenic or lead, may result in significant systemic absorption and, potentially, toxicosis. Asbestos, which is normally trapped in concrete matrix, may be released in hazardous particulate form when explosive forces pulverize concrete. Asbestos may cause acute respiratory irritation but is more of a concern due to the potential for long-term injury, including pulmonary inflammation. Whether short-term exposure to asbestos is likely to cause pulmonary neoplasia in dogs has not yet been determined.

Liquids, depending on their physical characteristics, can pose both dermal and ingestion hazards. Solvents, such as ethylene glycol and acetone may leak from damaged equipment and containers. Many solvents will cause chemical burns to the skin upon contact, while agents such as ethylene glycol pose significant systemic hazards.

Gases have the potential to have significant and immediate systemic absorption from the lungs, with potentially lethal effects (e.g. hydrogen sulfide). Gases may be present due to release from ruptured containers, or they may be spontaneously formed due to mixing of spilled chemicals. For instance, highly toxic arsine gas is released when metallic arsenic is exposed to strong acids. Gases that are heavier than air, such as hydrogen sulfide, may accumulate in pockets in the ground below the level where gas detectors may be used, but still at levels where dogs may have access.

Unfortunately, very few diagnostic tests are available for on-site testing for exposure to toxic agents, and many agents have no specific diagnostic test that would detect their presence. Exceptions include agents such as heavy metals (lead, arsenic, cadmium, etc.) Ideally, prior to entering a disaster site, dog should have a blood sample drawn and stored for future use as a baseline in the event that exposure to a particular agent is suspected. Additionally, discussions between the veterinarian and the on-site human health authorities may clue the veterinarian into the types of toxicants that are considered high risk for that site. On-site veterinarians should remind those involved of detecting noxious gases with mechanical "sniffers"' that areas near ground level, where dogs will be working, should be closely monitored.

Much of the veterinary management of service dogs on-site is a matter of prevention and symptomatic care. Encouraging the handler to acclimate their dog to safety devices such as booties and goggles can result in decreased risk of physical or toxic injury to feet and eyes. However, the veterinarian should understand that some search and rescue groups discourage the use of these types of protective gear, as they feel that the equipment compromises the dog's ability to work at its best. On site treatment should include frequent eyewashes with sterile saline and baths using mild detergent and water.

In a situation where a dog is observed to drink from a puddle or ingest solid material, induction of emesis is recommended, unless the agent ingested is suspected as being corrosive in nature. If exposure to corrosive agents is suspected, immediate dilution with water or milk, monitoring for oral burns, and use of gastrointestinal protectants such as sucralfate are recommended. Activated charcoal may be recommended for ingestions of non-corrosive agents, with the caveat that activated charcoal is of minimal effectiveness against most heavy metals and many short-chain solvents.

Veterinarians that are involved in the life-long care of service dogs should attempt to educate themselves on what particular agents might have been present at a given disaster site. If the site was within the United States borders, discussion with local public health authorities and/or the Centers for Disease Control and Prevention (www.cdc.gov) may help the veterinarian determine what types of agents were considered human hazards at the site. Handlers of service dogs that have been exposed to disaster sites should be encouraged to have at least yearly physical examination, chemistry profiles and, ideally, thoracic radiography in an attempt to detect any potential problem that may develop. As the service dogs exposed to the disaster sites at Oklahoma City in 1995 and the World Trade Center in 2001 age, information on their overall health status may improve our understanding of the overall risks associated with working disaster sites.

References

Gwaltney-Brant SM, Murphy LA, Wismer TA, Albretsen JC. General toxicologic hazards and risks for search-and-rescue dogs responding to urban disasters. Journal of the American Veterinary Medical Association. Vol 222(3), 2003, in press.

Otto, CM, Franz MA, Kellogg, B, Lewis L, et.al. Field treatment of search dogs: lessons learned from the World Trade Center disaster. Journal of Veterinary Emergency and Critical Care, 12(1): 22-41, 2002.

Wismer, TA, Murphy LA, Gwaltney-Brant SM, Albretsen JC. Management and prevention of toxicoses in search-and-rescue dogs responding to urban disasters. Journal of the American Veterinary Medical Association. Vol 222(3), 2003, in press.