Hunting dogs are generally exposed to more toxins than house pets. The most common poisoning we see in hunting dogs involved "commercial anticoagulant rodenticides" or, more commonly called "warfarin poisoning".
These poisons are commonly used by homeowners and exterminators and our hunting dogs are better at finding something that smells good than most dogs. Almost all these poisonings come from ingesting the actual poison as opposed to eating a dead rodent. These chemicals are well absorbed with peak blood levels occurring within 12 hours after consumption.
These toxins interfere with normal blood clotting and death occurs from internal (or external) bleeding. Usually, signs of these poisonings don't show up for 24 to 36 hours after they eat the stuff and often times it may take 2-5 days for the signs to show up.
Non-specific signs are lethargy, depression, and failure to eat. Your veterinarian will often find pale gums, weakness, and a poor pulse quality. Many of these dogs vomit blood, pass blood in the stool, have difficulty breathing, and have bruises on the abdomen. When your vet takes blood from a vein, it will often bleed for a prolonged time.
Your veterinarian can diagnose the condition via laboratory tests that determine the "prothrombin time" and the "activated partial thromboplastin time".
The typical presentation we see with a hunting dog is "Doc, I think my dog ate some rat poison." but the dog appears quite normal. Typically, with these dogs, if the ingestion has been less than 3 hours, we make the dog vomit. Most of these poisons have a green color, so often we can see the remnants in the vomit.
The real antidote is Vitamin K-1. We like to give an injection first and send home some Vitamin K capsules. If the dog at one of the first generation rodenticides like D-Con, we will treat them for about 6 days. But, the newer rodenticides are much more potent containing a long-acting poison called bromadiolone, brodifacoum, diphacinone or chlorphacinone. These poisonings require 4 weeks of treatment! Ideally, the owner gives the Vitamin K with a high-fat meal to enchance the antidote's absorbtion.
If a dog presents with signs of bleeding already, the situation is much more dire. Then, we get into oxygen therapy, blood transfusions, and giving fresh-frozen plasma. These can be big cases.
The prognosis for dogs that do not have signs of active bleeding is excellent but if the dog is bleeding internally, the prognosis is guarded.