Thursday, March 19, 2009

Protect dogs from heartworm disease with perventative screening

I found this article in the Toronto Community News and thought I'd send you the reminder since it's that time of year where the weather is warming and vacation time is nearing. Let's keep our fur-kids healthy!

Protect dogs from heartworm disease with preventative screening
March 18, 2009 3:43 PM

Dear UrbanAnimal

Each spring I receive a letter from my vet clinic reminding me about heartworm prevention for my three dogs and two cats. And every spring I wonder why I'm spending the money. How
prevalent is this disease in this part of the world?


There were 272 heartworm-positive dogs reported in Ontario in 2006. A small number considering the cost of prevention, isn't it? It's important to keep in mind, however, this number was reported by only one blood diagnostic laboratory and, currently, only 25 per cent of owners choose to have their dogs tested for this deadly disease.

While I was unable to find more current statistics based on results from all the labs in Ontario, it's that 25 per cent that keeps leaping out at me. Heartworm disease was first reported in the U.S. in the late 1800s and now, more than 100 years later, it's almost an epidemic in some southern states. Even with all of our knowledge about this disease, only one out of four dogs in the U.S. is tested. Although I couldn't find similar statistics for Canada, it's probable the same ratio applies here. Cats are susceptible to heartworm disease, too. Feline heartworm infection is thought to be at a rate of five to 15 per cent of the dog population.

According to the Ontario Veterinary Medical Association (OVMA), heartworms are large roundworms that live in the right side of the heart and the blood vessels that supply the lungs, surviving on nutrients they steal from the dog's bloodstream. They can grow to a length of 15 to 30 centimetres and in a severe case, a dog may be infested with hundreds of worms.

Heartworm is transmitted via mosquito, which is why pet owners in southern Ontario receive a heartworm blood test in early spring when mosquitoes begin hatching. A preventive treatment is administered at the start of the season and ends when cooler weather causes mosquitoes to die off. In warmer climates, dogs are kept on heartworm prevention throughout the year. It's extremely dangerous to give heartworm preventive products to an animal who is already infected. That's why Ontario veterinarians screen each animal for existing heartworm prior to administering the preventive medication.

Heartworm larvae are picked up by a mosquito that bites an infected animal. It then bites an unaffected animal, effectively depositing the larvae directly into its bloodstream. Newly affected animals will not show signs of the disease until the larvae grows to its adult stage and enters the animal's pulmonary artery and right side of the heart. Initial symptoms include: persistent cough, lethargy, reduced appetite and weight loss. Advanced symptoms include: enlargement of the liver, abnormal heart rhythm, excessive fluid in the abdominal cavity and loss of consciousness. Affected animals can be treated, but unfortunately, complications from the cure can be toxic. Yes, the treatment can be as deadly as the disease, which is why veterinarians insist pre-screening be performed.

Your veterinarian will send your pet's blood sample to a veterinary laboratory to screen for existing heartworm. If nothing is found, your vet will choose the best preventive product to suit your pet's age, weight and any pre-existing medical conditions. There are several products available and all are administered by the owner at home at specific intervals. Take caution. These meds are prescribed according to the animals' weight and type. Sharing isn't allowed. Your veterinarian will label each product to be given to each animal in your household. Another note of caution is a small number of animals who have been on these products have tested positive for heartworm on their next annual blood screening. One reason is that no product can be 100 per cent effective, but the main reason may be owner error in administration. Read the package instructions carefully and if you have any questions, contact your veterinarian.
Call me paranoid, Gene, but regardless of the reportedly small number of heartworm cases in Ontario (and I suspect the real number is much larger), I'll always opt for preventive measures. It's the 'pay now or pay later' scenario that causes me to have all my animals tested annually and preventive action taken as soon as that first mosquito hatches each spring.