The results were discovered after researchers at the NMBU School of Veterinary Medicine had taken liver samples from dead dogs over an extended period of time.
The number of rat poison findings in these samples is so high that Professor Lars Moe at NMBU School of Veterinary Medicine considers it necessary to warn people about the dangers.
The rat poison is called superwarfarin. It acts as a blood thinner and disrupts the coagulation of blood, causing internal bleeding that can kill dogs. The University Animal Hospital at NMBU School of Veterinary Medicine has received several dogs with this type of poisoning in recent weeks. Of these, three have died as a result of the poisoning. Others are given long-term treatment using vitamin K.
Rescued by blood transfusion
Monsen, a 1.5 year old male Labrador retriever was poisoned by superwarfarin at the end of January 2015. He started bleeding of the gums and was very anaemic. Following blood transfusion, intravenous fluids and vitamin K treatment, he was soon back on his feet again.
The rat poison findings were a result of a long-term sampling project based on initiatives in multiple academic fields, including The University Animal Hospital and the autopsy department at NMBU School of Veterinary Medicine. The multiple veterinary students who have collected and analysed the liver specimens have been crucial to the project. The analyses have been conducted at the toxicology laboratory at the Norwegian Veterinary Institute.
These veterinary students have since graduated and currently work as vets. Like most dog owners they are concerned and surprised by the extent of the findings they have discovered.
"When we started the work we considered it an interesting subject but never believed that the incidence would be this high. We had anticipated only a few hits. We never imagined that it would be this widespread," said vet Jeanette Pedersen.
Pedersen is one of three former veterinary students who have been working on the above mentioned project. Other studies conducted in nature show that birds of prey consume a large amount of rat poison as a result of eating many mice and other rodents that have ingested the poison. They had no idea that one in five dogs had the same problem.
"It has been an interesting process. We have collected specimens and conducted physical assessments. We have done something completely new that could become very important," said vet Eiril Pettersen.
The long-term effects are unknown
So far the study has discovered only that this is a widespread and extensive problem that could have consequences for both animals and people. The researchers and vets now hope that the research will continue so that we can discover the potential long-term effects. Some unanswered questions include:
- Why is it so widespread in so many counties and municipalities?
- The source of the poison is rat poison that has been put down, but where does the individual dog ingest the poison?
- What could this mean for other pets and, not least, humans? How common is it here?
- Could ordinary food or water be a source?
- Is it generally widespread in nature or is it rapidly biodegraded in soil?
Children could also be exposed
Professor Lars Moe at NMBU School of Veterinary Medicine is concerned that dogs may ingest the poison by drinking from puddles of water in nature.
"We know that a lot of poison is used in apartment buildings to keep down the rat and mice populations. If it turns out that the poison ingested by dogs originates from natural drainage then it would be reasonable to assume that children may be exposed to the same. They like to taste things and put things in their mouths. It is important that we quickly determine what this means for animals and, not least, people. Let me add that we have recently found the same poison in a dead sow, but they do occasionally eat mice or rats. Dogs do not do so quite as often," the professor said, and questioned what the sources for the poison findings could be.
More dangerous than before
Superwarfarin is completely different to the old-fashioned "ordinary" warfarin, which was not as dangerous. The reason is that the old warfarin type was quickly separated by the body, whereas superwarfarin is not metabolised or separated from the body in the same way. It takes a very long time. In other words, the poison is stored in the body, presumably mostly in the liver.
"It takes a long time for the poison to break down in nature. The consequences must be researched further. We need to know what low concentrations of the poison do and how the body handles this. And we need to find out what small concentrations of the poison in the blood do over time. We know that it affects the coagulation factors and that the poison remains in the liver for months," said Moe.
The professor and the students behind the findings emphasise that more research is required.
"We need someone to confirm the study and investigate the sources. More research is needed," the former veterinary students stressed.
Vets urged to monitor
All vets should be attentive and alert when new patients come in.
"Vets must be on the lookout. If a lethargic, pale, sick dog is brought to their attention they should be prepared to run blood coagulation tests more frequently. There needs to be more awareness in the event of bleeding and anaemia. Poisoned dogs will get better if they are given vitamin K treatment and, if necessary, blood transfusions," said Moe.
He is still concerned that not enough is known about the long-term effects, since superwarfarin has an extremely long half-life. This could complicate other disease patterns.
"If the figures are correct then there is a great need for better diagnostics. A lot of everyday drugs that are used cause a slight reduction in blood coagulation. When more than 20% of dogs also have detectable amounts of superwarfarin in their liver, vets may have to take completely different and new things into consideration when treating the disease," the professor added.
All of the results and the complete thesis can be read in Norwegian in the appendix at the bottom of the Norwegian version of this article here.
Authors: Sara Olerud, Jeanette Pedersen, Eiril Pettersen
Supervisors: Lars Moe, Andreas Lervik, Gjermund Gunnes, Jens Børsum