Diabetes mellitus is an illness caused by the body’s inability to either make or use insulin, which is a hormone produced and released by specialized cells in the pancreas. Insulin permits the body’s cells to take sugar (glucose) from the blood and use it for their metabolism and other functions. Diabetes mellitus develops when the pancreas doesn’t make enough insulin or when the body’s cells are unable to use available insulin to take glucose from the blood.

Obesity (the storage of excess fat) is usually caused by excessive food intake and insufficient exercise. According to estimates, 40% to 50% of dogs are overweight and 25% of dogs are obese. Obesity is more common in older, less active pets. Dogs that are fed homemade meals, table scraps, and snacks are more likely to be overweight than dogs that are fed only a commercial pet food.

Toxicosis is disease due to poisoning. Chocolate contains two ingredients that can be toxic to pets—caffeine, and a chemical called theobromine. While dogs and cats are both very sensitive to the effects of caffeine and theobromine, cats are usually not attracted to chocolate, so chocolate toxicosis tends to be less common in cats.

Dealing with an injured pet can be scary and frustrating. In many cases, you don’t know how bad the injury is, and your pet may not be acting normally. If your pet is injured, the first thing you need to do is try to remain calm. If possible, try to determine how severe the injury is, but remember that caution is extremely important when approaching an injured animal. Any pet, no matter how calm or friendly he or she may usually be, can bite or scratch when in pain.

West Nile virus (WNV)is a virus that causes encephalitis (brain inflammation). WNV is usually transmitted to dogs and cats through the bite of an infected mosquito. Some birds, including crows, jays, sparrows, finches, grackles, and robins, are competent reservoirs for the virus (meaning they are able to infect mosquitoes). Some infected birds can shed WNV in their feces and other body fluids. In theory, cats and dogs can become infected through ingestion of (or contact with) an infected bird, but mosquito bites remain the primary route of infection.