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       When possible, collect whole blood, serum, plasma, and urine before death for routine clinicopathologic tests; this helps to delineate pathophysiologic processes, which aids in refining an initial differential list.

      Other Laboratory Tests

       In addition to samples collected for clinicopathologic testing, other samples for toxicologic analysis include stomach contents, urine, liver, kidney, brain, eyeball, and heart blood. Given the delay in the possible incorporation of a chemical into hair, hair samples are not generally useful for testing.

       With any suspicion of an injection site, obtain tissue from around that site.

       Collect representative feed and water samples.

       Submit plants for identification if necessary (submit fresh whole plants, wrap plant [at least the base of the plant] in moistened paper towels, place in a plastic bag and keep chilled; representative samples of hay can also be collected for identification of contamination).

       Because of medicolegal considerations, handle all samples under chain‐of‐custody procedures. These records specifically identify each specimen, document their condition and container in which they are packaged, time and date of both transfer and receipt of samples, and all individuals involved in their handling, transfer, or receipt.

       Testing can be targeted or non‐targeted depending on whether there are known exposures or unknown exposures. Mass spectrometry is a powerful technique for broad‐based targeted testing. However, there is no one or two analytical procedures that can rule out all possible chemical exposures.

      Pathological Findings

       Conduct a complete and thorough postmortem examination.

       Consider transporting the animal to a veterinary diagnostic facility as soon as possible. If this is not an option, conduct a thorough field postmortem examination, and record any actual or suspected abnormalities.

       If an animal cannot be taken to a veterinary diagnostic facility, consultation with a veterinary pathologist or toxicologist might be warranted to ensure collection and appropriate preservation of useful samples in sufficient quantities.

       Carefully examine stomach and GI tract contents for evidence of toxic plant fragments or unexpected grain or forage ingestion.

       Collect formalin‐fixed samples from all major organ systems and any gross lesions, and submit these samples to a veterinary pathologist for histopathologic examination.

THERAPEUTICS

       In many situations, treatment is not possible; however, if the animal is alive, direct treatment toward stabilization of vital organ systems – establish and maintain an open airway, control seizures, correct life‐threatening cardiac dysrhythmias, and begin fluid administration.

       Once the animal is stabilized, initiate oral and dermal decontamination.

      Detoxification

       AC (1–4 g/kg PO in water slurry [1 g of AC in 5 mL of water]).

       One dose of cathartic PO with AC if no diarrhea or ileus – 70% sorbitol (3 mL/kg) or sodium or magnesium sulfate (250–500 mg/kg).

       Administration of other drugs depending on the individual situation.

      Appropriate Health Care

      Appropriate monitoring and follow‐up depend on the specific toxicant under suspicion or analytically confirmed.

      Antidotes

       Antidotes are not available for most toxicants, but fortunately, many animals survive with timely decontamination and appropriate symptomatic and supportive care.

       If an antidote is available, consider giving it first before further treatment.

COMMENTS

      Prevention/Avoidance

       Routinely inspect the immediate environment of an animal and note any unusual human activity.

       Routinely inspect feed and water for any foreign material.

       Encourage clients to know sources of feeds and forages.

       To minimize malicious poisoning opportunities, camera surveillance can be considered, particularly for valuable animals.

      Possible Complications

       Potential complications depend on the specific toxicant involved.

      Expected Course and Prognosis

       Variable depending on the chemical.

      See Also

      Necropsy Analysis

      Other specific toxicant topics

      Abbreviations

      See Appendix 1 for a complete list.

Suggested Reading

      1 Haliburton JC, Edwards WC. Medicolegal investigation of the sudden or unexpected equine death: toxicologic implications. In: Robinson, NE, ed. Current Therapy in Equine Medicine 4. Philadelphia: WB Saunders, 1997; pp. 657–659.

      2 Johnson BJ. Handling forensic necropsy cases. Vet Clin N Am: Equine Practice 2001; 17(3):411–418.

      3 Poppenga RH. Toxicology. In: Southwood LL, Wilkins PA, eds. Equine Emergency and Critical Care. Boca Raton: CRC Press, 2015.

      Author: Robert H. Poppenga DVM, PhD, DABVT

      Consulting Editor: Robert H. Poppenga DVM, PhD, DABVT

Chapter 2 Necropsy Analysis

      

DEFINITION/OVERVIEW

       The key components of a diagnostic toxicology work‐up include history, clinical signs, clinical chemistry, analytical toxicology, and, if animals die, a postmortem examination (necropsy).

       The first goal of a postmortem examination is to determine the cause of death, circumstances surrounding the death, and/or the extent of disease.

       Systematic gross and microscopic inspections of all organ systems after death are indispensable diagnostic tools that can help the clinician gain clues about what the physical findings likely represent and are important should litigation become an issue.

       The second goal is to collect appropriate specimens for analytical toxicology testing. Samples typically collected for toxicology testing include stomach contents, liver, kidney, fat and brain.