Dear Dr. Z,
I was watching the news last night. They ran a special on heartworm disease in pets and the potential for transmission to people. I thought only animals got heartworm disease? I thought we didn't have heartworm in California?
There have been instances of heartworm infection in people. Instead of migrating to the heart, the larvae migrate to the lungs in humans. There the larvae can block vessels causing a blockage. At the site of the blockage, a nodule develops which can be seen on radiographs. Usually, the person has few, if any signs of infection. Surgical removal of the nodule is sometimes necessary.
Many people are surprised to hear that we have heartworm in California, especially San Diego, which has fewer mosquitoes then other areas of the state. Many people hear "worm" and think the dog must eat something to become infested. This is not the case for heartworm, which is actually transmitted by the Culex mosquito. The mosquito must feed off an animal with active heartworm disease (microfilaria circulating in the blood). Most dogs with heartworm infection do not show signs of disease. Some dogs may show decreased appetite, loss of weight, and listlessness. Often, the first sign of the disease is a cough. This disease can only truly be diagnosed by a blood test that your veterinarian can perform.
The best program for prevention of heartworm infection includes using preventives, performing routine heartworm testing, and reducing exposure to mosquitoes.
Monthly heartworm preventives have activity against intestinal parasites, which inadvertently infect millions of people every year. These preventives protect pets and people. A preventive should be given to all dogs. Remember that mosquitoes can get indoors, so even though your dog may not go outside, the dog is still susceptible. All adult dogs being started on a heartworm preventive for the first time should be tested. In addition, all dogs should be tested annually for heartworm infection.
Dr. Dustin Zimmer works for Bonita Pet Hospital in Bonita.