History
An accurate history is the starting point of any toxicologic investigation and, when done correctly, ensures that you have obtained the appropriate samples for further analysis. The investigation may vary from simple to complex but should always be done in a calm and ordered manner so that nothing is overlooked.
The history should be used to provide information on circumstances surrounding the problem and may or may not identify the toxicant itself. Again, the presence of a toxicant in the environment does not necessarily mean that it is the source of the problem. Finding a toxicant is simply a starting point, as it may or may not support the clinical findings. Many*Contributions to portions of this chapter in previous editions by Gary Osweiler are acknowledged. other factors, including the dose and degree of exposure, need to be considered because exposure to a nontoxic dose generally does not result in a worthwhile diagnosis.
Species, breed, age, sex, body weight, and body condition are important pieces of information that should be collected for all involved animals. Current and past medications used, vaccination history, reproductive status, and illnesses in other animals are other pieces of useful data. Species identification is particularly important because some toxins are species specific or have different toxicologic profiles for different species. In addition, absorption of some toxins in ruminants, horses, and swine varies due to their specific gastrointestinal (GI) tracts. Some individual breeds may have different metabolic pathways, resulting in delayed metabolism and excretion. The presence of a P-glycoprotein transporter in the MRD1 gene was recently identified in horses, and this may play a role in the development of breed-related toxicosis.3,4,5 Very young and very old animals are often at increased risk for developing signs of poisoning at much lower doses.
Neonatal animals absorb some metals and chemicals more readily than adults do, and nursing animals may receive toxic substances in the milk. Geriatric animals often have underlying deficiencies in liver metabolism and renal excretion that affect their ability to clear potential toxicants in a timely manner.Initial questions often revolve around whether a known toxicant is present in the animals' environment. There are literally hundreds of toxicants, but many people, when questioned appropriately, often know or are suspicious of which one(s) may be playing a role. Common questions include whether medications, pesticides, herbicides, or fertilizers have recently been used or are present on the property. Is rodent control used in barns and outbuildings? Are there old junk piles on the property? What farm equipment and automotive products have been used recently? Have any old buildings been moved or torn down? Are there any known poisonous plants on the property?
Recent changes in animal management should be investigated in detail. Animal handlers should be questioned about the introduction of any new feeds, either new bags or fresh batches from a feed mill, or a complete change in feed. Feed should be examined closely for mold and the presence of any foreign bodies. Samples of feed, both as purchased and as fed, should be obtained and stored for further analysis. Hay and pasture should be examined for the presence of blister beetles, clippings from plants such as yew or oleander, other poisonous plants and weeds, foreign bodies, and mold. Again, samples should be taken and saved for analysis. Water samples from the original
■ TABLE 54.1
Common Internet Websites
| Type | Organization | Web Address |
| Animal poison control centers | ASPCA Animal Poison Control Pet Poison Helpline | www.aspca.org/pet-care/animal-poison-control www.petpoisonhelpline.com |
| Diagnostic laboratories | American Association of Veterinary Laboratory Diagnosticians | www.aavld.org |
| General information | International Veterinary Information Service Veterinary Information Network | www.ivis.org www.vin.com |
| Literature search sites | MedlinePlus National Agricultural Library PubMed Google Scholar | http://medlineplus.gov/ http://agricola.nal.usda.gov www.ncbi.nlm.nih.gov/pubmed/medline.html https://scholar.google.com/ |
| Toxicology information | Extoxnet InChem MSDS Search Site Toxnet | http://extoxnet.orst.edu www.inchem.org www.msdssearch.com/ www.toxnet.nlm.nih.gov/ |
Refer to references 1 and 2 for a more complete listing of various toxicology information resources.
source and at the trough or stock tank should be taken and conserved in preserving jars for analysis if needed.