Dangers of Heartworm Pills for Cats

Heartworms are caused by the parasite Dirofilaria immitis, which is carried by mosquitoes. When an infected mosquito bites your cat, it leaves the larvae of the parasite behind. The larvae penetrates your cat's skin and then begins to migrate through the tissues until it finds its way to the heart and lungs. Once the larvae has taken up residence in the heart and lungs it will form into a worm-like parasite called microfilariae. Heartworms develop inside your cats heart and lungs, causing severe damage and even sudden death. Symptoms of heartworm disease in cats are intense coughing fits, breathing difficulties, general lethargy, sudden weight loss and seizures.

Geography

The parasite that causes heartworm disease in cats is carried by mosquitoes, so it is more likely for cats living in warm and humid climates to be affected by the disease. Heartworm disease is less likely to occur in indoor cats than outdoor cats because indoor cats have exponentially less contact with mosquitoes. It is, however, still possible for indoor cats to contract heartworms. Heartworm disease is more common in dogs than it is in cats, but is much more dangerous when contracted by a cat and less easy to diagnose. In warm and moist climates, where mosquito populations are more prevalent and intense like the deep South and East Coast of the United States, heartworm disease cases in cats will increase. In high-risk areas it is estimated that 10 percent of outdoor cats and 3 percent of indoor cats will contract heartworm disease.

Types

There are two different types of preventative medication that can be administered to your cat. One pill is formulated to be given daily, while the other is a monthly pill that must be given on the same day every month in order to be effective. Daily pill administration is an older method of prevention and can be found in generic forms of diethycarbamazine, or DEC. Monthly heartworm pills are normally a chewy tablet that simulates a treat. The most common ingredients in current heartworm pills are invermectin and milbemycin oxime. Both ingredients and types of of pills are effective and safe. Heartworm pills can be administered seasonally though veterinarians recommend giving them year-round to be safe and to keep the medication in the feline's system at all times.

Warning

If your cat already has heartworm disease with circulating microfilariae, administering a preventative medication like ivermectin, diethylcarbamazine or milbemycin can be life-threatening. While the medications are safe at preventing heartworms, they can be fatal when used to treat a pre-existing infection. Diethylcarbamazine is proven to increase the die-off rate of microfilariae and this rapid die-off can cause a deadly anaphylactic reaction in your cat. Another risk with preventative medication occurs if you miss a dosage. Missing just one dose can allow for dirofilaria immitis larvae to infect your cat. Have your veterinarian test for heartworms before starting a preventative treatment program and be sure to stay up-to-date with your dosages.

Expert Insight

Veterinarians who specialize in feline cardiology remove heartworms from cats in one of two ways. In the first case, the worms are removed through the jugular vein. In the second, the veterinarian will make an incision in the right atrium and perform a thoractomy to remove the worms. Because of the rarity and the cost of these types of specialized surgeries, the risks are high. Cats who have contracted a heartworm also may be treated through prescription medication. One drug or a cocktail of drugs -- Prednisone, Aminophylline and Furosemidemay being the most popular -- may be administered through injection by a veterinarian. Heartworm-removal medication contains arsenic, a poison, which may be dangerous to your cat's health.

Considerations

While many argue that heartworm pills for felines are dangerous to their health, this is not the case. The mistake comes from the dangers of the medication that is given to a cat once they have already contracted heartworms or if heartworm preventative pills are given to a cat that already has heartworms. If you're considering starting your cat on a heartworm prevention regimen, make sure that they have been prescreened for heartworms. In the recorded cases where cats got heartworms, the symptoms and illnesses that develop along with the treatment plans and surgery involved in removing them far outweigh the dangers of preventative medication.

Resources

• American Heartworm Society