As the days get shorter and temperatures cool, many people assume that giving the monthly heartworm and flea preventives for their pets is unnecessary. However a number of bothersome and potential life threatening infections are still a concern throughout the fall and winter months and year-round protection in needed.

Heartworm disease is a blood parasite that is spread by mosquitoes and infects dogs and cats. The tiny worms settle in the arteries of the lungs and mature into larger adults. Over time the inflammation in the lungs blocks blood flow and eventually heart failure develops. Early in the course of the disease most dogs and cats do not have significant symptoms but are a source of infection to other animals. Later coughing and wheezing may be noticed and untreated the disease will ultimately be fatal. Cats can have a wide range of symptoms and in some cases sudden death may occur.

Unfortunately the treatment for heartworm disease is in very short supply, which means that dogs that are diagnosed may not be able to be treated until a more consistent supply of the medicine is available. The resulting damage from the untreated infection will invariably shorten the lives of infected dogs. This means that prevention is even more important in light of the shortage.

The monthly prescription tablets also serve double duty by protecting your dog and cat against the most common intestinal parasites. Some of these parasites can also be contagious to people and children are most often affected. The eggs are spread through contact with infected feces or eggs that remain in the environment. Hookworms can lead to anemia in dogs, cats and people while roundworms have more serious effects. The parasite migrates through the body and can damage organs, most commonly the eye in humans. During the hard winter months I tell people the intestinal parasite protection provided by the monthly preventives is probably more important than the heartworm benefits.

The fall months are also peak season for fleas. The fleas live on your pets through the warm, wet summer months and now the populations are the highest they have been all year. This coupled with the fact that people stop giving pets preventives when the days get cooler and you have optimum conditions for the little pests. Some seasons I see very active flea infestations through the holidays. For pets that are allergic to the flea bites, which the vast majority are, they can scratch and chew themselves raw. These can lead to skin infections and make your pets miserable. Fleas carry some diseases as well. Tapeworms have part of their life cycle in the flea and cats can contract a very serious blood disease that can cause life-threating anemia.

The good news is that these conditions are easily prevented and the preventives cost less than a cup of coffee a week. So as the snows start to fly, remember your pet still needs to be protected against parasites that can infect your pets and your family. Ask your veterinarian what is best for your pet's lifestyle and risk factors.

Questions for Dr. Gary Thompson can be emailed to askthevet@theblade.com or mailed to The Blade, Attn. Ask the Vet, 541 North Superior St., Toledo, OH 43660. Dr. Thompson regrets that he cannot answer individual letters.

First Published October 9, 2011, 4:15 a.m.