imagescah7i43hSince the mosquito is sometimes considered Minnesota’s State Bird, we wanted to highlight some important points about heartworm disease which is spread by mosquitoes. Dogs are especially prone to contracting heartworm disease from mosquito bites. Cats can be affected too, though not as commonly. Heartworm disease is a severe, and often life-threatening infection that is easily prevented in your pet.

Heartworm disease causes parasitic worms to grow in your pet’s heart and blood vessels. The infection is spread from one infected pet to another through a mosquito. A dog with heartworm infection has male and female worms that reproduce baby heartworms, called microfilaria, inside the blood vessels. When a mosquito bites an infected dog, it ingests these microscopic baby worms. The baby heartworms mature inside of the mosquito and when the mosquito finds another dog or cat to bite, the baby heartworms are transmitted to that pet. All it takes for a heartworm infection to begin developing is a single mosquito bite from an infected mosquito.

Fortunately, the cold weather during Minnesota winters decreases some of the infected mosquitoes looking for their next lunch. However, since many dogs are now being adopted from shelters in the Southern part of the US, the number of infected dogs here is increasing. Many dogs also travel with their owners to other parts of the country where heartworm infection rates are higher. A single infected mosquito can travel for up to 7 miles looking for its next meal. This means that a single heartworm infected dog can increase heartworm rates within a 7 mile radius.

Even pets that spend most of their time indoors, including cats are at risk for heartworm infections. How many times have you heard a mosquito buzzing around your house at night? Sleeping indoor cats make a perfect snack for a mosquito looking for a meal.

How do I know if my pet has a heartworm infection?

Pet’s with heartworm infections usually don’t have any signs of heartworm infection until it is very advanced. The baby heartworms can live in the bloodstream for months to years before they grow into adults. Adult heartworms cause inflammation of the lungs which results in a cough. As the infection progresses, the worms, which can grow up to 14 inches in length, can cause blockage of the blood moving through the heart and blood vessels which leads to decreased energy levels, reluctance to exercise, fatigue, decreased appetite and eventually trouble breathing. Pet’s that aren’t diagnosed until the advanced stages of the disease often don’t survive the treatment.

Early infections are easily diagnosed with a simple annual blood test. All dogs should be tested once a year for exposure to heartworm infection. Some veterinarians will even do routine internal organ testing as part of the heartworm testing for an overall screen of internal health. For cats, any sign of coughing or respiratory issues is an indication for heartworm infection screening.

How can I prevent a heartworm infection in my pet?

Heartworm infections are easily preventable in pets. While we can’t prevent a mosquito from biting pets, we can prevent the infection from taking hold inside the blood vessels. Heartworm preventative, like Sentinel and Revolution are given monthly to treat any baby heartworms that might have found their way to your pet. These medications are very safe and easily administered to prevent heartworm infections. Most medications also have intestinal dewormer medication and flea prevention in addition to heartworm prevention. The medications are inexpensive compared to the cost of heartworm treatment.

Can heartworm infections be treated?

Heartworm disease can be treated, however, the treatment can be expensive and risky. The first step once a pet has been diagnosed with a heartworm infection is to stage the disease, or determine how advanced the infection is. This typically includes x-rays of the lungs and complete blood and urine testing. Dogs that are diagnosed in the early stages of the infection have a much better chance of complete recovery. Those diagnosed with advanced heartworm infections can have long-term, and often life-threatening complications from the infection and the treatment. Treatment involves giving injections of a medication called Immiticide to slowly kill the adult heartworms in the heart and vessels while the dog is hospitalized for observation. The medication is given over a period of several months and dogs need to remain inactive during the entire treatment period.

Prevention is key to keeping dogs free from heartworm infections. Not only is the treatment of heartworm disease expensive, but there has been a shortage of the only medication available for treatment. Immiticide was off the market and being rationed out to only the most severely affected dogs. It has recently been brought back on the market but in limited supplies.

Heartworm treatment for cats is much more difficult because there is no approved medication that can be used to clear the infection. Often, the only option for cats is to surgically remove the heartworm from the heart which is very expensive and risky. Again, prevention is key to keeping cats healthy and heartworm free.

Heartworm infections are a real risk for pets living in Minnesota. Help keep your pet healthy and heartworm-free by following your veterinarian’s heartworm testing and prevention recommendations. For additional questions about heartworm disease in pets, call Northwest Animal Hospital in Plymouth  at 763-475-2448 or email