Eating a slug in itself is not dangerous to your dog. However, slugs and snails are often infected with the parasite Angiostrongylus Vasorum, sometimes referred to as lung worm or French heart worm. This parasite is capable of causing serious, even fatal infections. Fortunately, treatment is available, and infected dogs can be cured.
The first thing to do if you believe your dog has eaten a slug is to call your veterinarian and schedule an appointment for the dog to be seen. The vet can perform a simple test to find out if your dog is infested with lung worm.
Lung worms can be killed with a number of prescription medicines, including Advocate, a formulation made by Bayer. Over-the-counter wormers given in recommended doses are typically not sufficient to eradicate lung worm.
Although treatment should eradicate the larvae of the parasite, keep an eye on your dog for any symptoms, just in case. If the dog develops a cough or shortness of breath, begins to tire more easily than before or bleeds excessively from any cut or wound, it needs to be evaluated by a veterinarian again. Sometimes a second dose of medication is needed to completely destroy lung worms.
The parasite Angiostrongylus Vasorum lives in the blood vessels around an infected dog's lungs. When the dog coughs, it swallows the eggs of the parasite, which are then eliminated in the stool. From there, they are passed on to snails and slugs, who scavenge dog waste for food. Thus, a good way to prevent the spread of lung worm is to ensure that all dog waste is promptly cleaned up.