Heartworm prevention crucial before summer

Spring has sprung, and the arrival of warm weather and spring rains mean our mosquito population is about to undergo its annual explosion.

This may be a difficult concept for some readers from colder states to grasp, but in the Deep South, we have some level of mosquito population active throughout the year. In the spring, eggs that have been dormant through the winter begin hatching en masse.

In the South and some areas of the western United States, dogs should be kept on heartworm preventive medication 12 months out of the year because it’s possible for them to be infected by a mosquito bites year-round.

However, we still see some pet owners who take their dogs off heartworm preventive medication during the winter in our area or just accidentally run out and don’t promptly refill their pet’s prescription. In colder areas of the country, dogs may be taken off prevention during the coldest winter months but should be put back on it before it gets warm enough for mosquito activity to start.

With the surge in mosquitoes that occurs this time of the year, any dog that is not on heartworm preventive needs to be tested to confirm a negative status and put back on prevention now.

If the dog has been infected with heartworms, it could have a serious or even fatal reaction to the medication, so a test is needed to assure the dog’s safety before resuming prevention. If the dog is found to be infected, treatment can be done before the warm summer months, when environmental conditions add a level of stress to the treatment process.

Infection by heartworms is almost guaranteed in the South for outdoor dogs who aren’t on a prevention program and is quite possible for those dogs who spend most of their time indoors. Even indoor dogs go outside to play occasionally, and mosquitoes will fly in through open doors and windows.

Contact your pet’s doctor now to get your dog back onto its preventive medication if it’s been off. Preventing heartworm disease is much better for your pet and your pocketbook than having to deal with an infection.


— Greg McGrath is a veterinarian at Cedar Lake Pet Hospital in Biloxi, Miss.