Heartworm is a parasite that has made huge inroads into our canine and feline population in the past years causing serious health concerns for pets across the nation. The most unfortunate aspect of canine and feline heartworm infestations is that they are almost completely preventable. I will discuss the history of heartworms, infection, clinical signs, treatments, and most importantly, prevention.
In dogs heartworm was first reported in the United States about 100 years ago and in cats the first reported case was in 19201. Since then the parasite has spread across the United States and has currently been diagnosed in all 50 states1. Heartworms can infest “dogs, cats and other species of mammals, including wolves, foxes, ferrets, sea lions and (in rare instances) humans1.”
Heartworms are spread by mosquito. Female worms living in the heart of an infected animal produce larva. When a misquote bites the infected animal it will ingest the larval worms in the blood meal. These larva then mature in the mosquito for 10-14 days. This time when the mosquito bites a susceptible host the infective larval are injected into the skin. The larva then borrow into the blood stream where they remain for six to seven months in dogs, and seven to eight months in cats. After this time the worms migrate to the heart and blood vessels in the lungs. Adult worms can live for as long as seven years in dogs and three years in cats1.
Early cases will go unnoticed as they usually don’t cause any clinical signs. As the heartworm burden increases however, dogs show typical signs of heart failure such as; coughing, weakness, loss of appetite, and weight loss. Cats may show no other clinical signs than coughing, which mimics feline asthma1.
Initial diagnosis is accomplished by testing the blood for proteins to the adult worms. If your pet tests positive your veterinarian will recommend additional testing to confirm the diagnosis.
There is no approved treatment for heartworm disease in cats. There is an approved treatment for dogs, but complications are possible and vary in severity depending on the number of worms with which your dog is infected.
Prevention is definitely the best approach to heartworm management in both dogs and cats. Since all heartworm infestations are a result of mosquito bites, mosquito control should be at the forefront of any preventative program. I have discussed mosquito control in depth in my previous article on Malaria.
Bayer Animal Health has developed a medication for dogs called Advantix that is labeled to kill fleas, ticks, and is a mosquito repellant. It is applied once a month, but is not safe for cats. There are also a variety of oral and topical heartworm preventatives for dogs and cats that are very safe and effective. Most of these also treat or prevent a number of other serious parasites.
There is little reason to allow your pet to suffer from this considerable health threat. Our arsenal for thwarting heartworm infection leaves us with little excuse for not preventing this significant parasite.
1. American Heartworm Society