How dogs get it and protecting against it

By Dr. Roger Krogstad, DVM

Wildwood Animal Hospital and Clinic LLC

The mosquitoes are hummin’, so heartworm is a-comin’. There are over 20 mosquito varieties in Wisconsin, and most can be the vector to transmit the microscopic microfilaria — heartworm larvae — from one dog to another. In some cases wild canids likes foxes or coyotes may be the source and not the neighbor’s untreated dog returning home from a Florida vacation.

In early 1980 there were concentrations of heartworm disease along the gulf coast into Florida and, interestingly, in Wisconsin and Minnesota. The reason for this strange geographical distribution was the motor home. More dogs were conveniently going with their owners on the southern vacations to get away from the winter cold of the upper Midwest.

At that time daily preventive was the norm but was seldom used as the heartworm established itself in unprotected dogs. Heartworm is not a new disease, being first diagnosed in the late 1970s.

What is canine heartworm disease? It is the presence of parasitic worms in the chambers of the heart. Instead of laying eggs, these worms produce live microscopic larvae that circulate throughout the body.

Mosquitoes ingest the larvae and then pass them on through a bite to another dog. In six months the larvae complete their migration to the heart and mature into the adult worms, ready to produce another generation of infective microfilaria.

The health issues are many. If high numbers of heartworms are present, there can be blood flow restriction and heart valve impairment. Some dogs may have a cough due to pulmonary artery changes from the presence of adult worms. Others may show kidney disease due to dead microfilaria in the filtering mechanism. Early on, many dogs show no symptoms at all and may be the source of infection for entire neighborhoods.

What can a pet owner do to protect against this potentially deadly and debilitating disease?

Ask your veterinarian about the best protection plan to fit you and your pet’s needs. Oral, topical, and now injectable medications are available for prevention. Any missed treatments create a 30-day window of possible infection. To be prepared for the early spring or late fall mosquitoes and to protect against the mosquitoes that linger indoors all year, consistent treatment for all 12 months is recommended. One way to prevent missed doses is to take advantage of injectable preventives like Proheart 6, which provides consistent protection for six months.

Heartworm is real and has been in our area for years. Last year there was an increase in positive cases. Is your pet protected? Call your veterinarian to schedule the annual blood screening test and begin preventive medication.

Wildwood Animal Hospital and Clinic LLC is located at 210 Airpark Road in Marshfield and online at wildwoodanimalhospital.net.