April Showers bring Mosquitoes! Here Comes Heartworm Season!

Everyone knows the little annoying bug that buzzes around, bites you, feeds on your blood, and goes around to its next victim. Yup, its a mosquito! Did you know those annoying bugs spread heartworm disease to your pets? It's true! Let's discuss what heartworm disease is, how it is spread, heartworm disease symptoms, and prevention. 

Heartworms in a heart

What is Heartworm Disease? 

Heartworm disease is a serious worldwide disease affecting dogs, cats, ferrets, wolves, coyotes, foxes, and sea lions. Heartworms are foot-long worms that live in the heart, lungs, and blood vessels. These worms cause damage to organs in the animal's body specifically the heart and lungs. If heartworm disease is left untreated it can be fatal to animals as it can block blood vessels, disrupt heart function, and decrease circulation to the lungs. 

Where do Mosquito's Play into this? 

As we discussed earlier, mosquitos bite animals to obtain blood. Did you know when a mosquito bites you, it also transfers a small amount of saliva to you? Mosquitos use their saliva laced with an anticoagulant enzyme to keep blood from clotting. If a mosquito were to feed on an animal infected with heartworms, the mosquito would pick up microfilaria with the blood. Microfilaria are baby heartworms produced by adult female heartworms. ​These baby worms then take 10 to 14 days to mature into larvae, an infective stage. Once they have reached an infective stage the infected mosquito can bite another susceptible animal and infect that animal with the larvae through their saliva.

​The larvae are deposited on the animal's skin and enter the bloodstream through the tiny wound created by the mosquito. Once the larvae reach the bloodstream, it takes about 6 months for them to sexually mature to adult heartworms. Mature heartworms (Dirofilaria immitis) can live for years and produce new microfilaria. These microfilariae then wait for a mosquito to come along and transfer them to their new home. Mosquitos play a large roll in the transmission of heartworm disease across the world.

Heartworm life cycle

Fun Fact: Microfilaria can be transferred from mother to offspring through milk

Symptoms of Heartworm Disease

​These worms are transferred by mosquitos, what is the big deal? Once heartworms are mature, they will grow throughout the animal's bloodstream, major arteries and veins, and eventually to the heart and lungs. Most dogs do not show symptoms at first. The longer the worms are in the bloodstream, the more they grow potentially causing health issues and symptoms. Symptoms of heartworm disease may include a mild cough, exercise reluctance, fatigue, decreased appetite, vomiting, weight loss, seizures, heart murmur, and respiratory issues. In severe cases, dogs can have sudden blockages in the blood flow in the heart leading to cardiovascular collapse. Few dogs live from a cardiovascular collapse without immediate surgical removal of the worms from the blockage. Heartworms can kill an animal. Animals need blood and good circulation throughout the body, without that, issues arise.

Preventing this Fatal Disease

​Preventing heartworm disease is your pet's safest option as heartworm disease is a worldwide battle. 
The detection of heartworm disease is a simple blood test. For dogs, we can draw the blood, test the blood, and have results in less than 10 minutes at our clinic. Since heartworms take 6 months to mature into adults, it can take 6 months from when your pet was infected with heartworms to show a positive test result. Therefore, we recommend any dog over a year of age should have a heartworm test done before receiving heartworm prevention for one year. Dogs under a year of age can be prescribed heartworm prevention as it can take 6 months to develop adult heartworms. 

A 4DX Snap test for heartworm and tick disease test done in clinic.

​​Once your dog has tested negative for heartworms, we can give your pet heartworm preventatives. These heartworm preventatives are given on a monthly basis to kill microfilaria and larvae in your dog's bloodstream. Heartworm preventatives do not kill adult worms. If your dog has heartworms in their bloodstream and receives heartworm preventatives, the adult worms will remain in the bloodstream. Also, if your dog is positive for heartworms and is given heartworm prevention if too many microfilaria and larvae are suddenly killed it could send your dog into shock and kill your dog.

Our variety of heartworm preventatives: Interceptor Plus, Heartgard, and Revolution Plus

 We recommend annual heartworm testing for all dogs even if they are on heartworm preventatives year-round as heartworm preventatives are not 100 percent effective. However, companies that create these preventatives have a customer satisfaction guarantee. These guarantees state that if your dog has been on heartworm preventatives year-round, have your dog tested annually, and tests positive for heartworm disease; the company will provide assistance in treating your dog for heartworm disease. 

If you have noticed I have not mentioned cats yet, there is a reason. Luckily cats are not the preferred host for heartworms making heartworm disease in cats rare. Dogs are the preferred host for heartworms. Also, there are no easy blood tests to identify heartworm disease in cats like there is for dogs. To diagnose a cat with heartworm disease, a serious of physicals exams, x-rays, and blood tests would need to be completed. Cats are not as easily diagnosed as dogs. There are heartworm preventives for cats out there to prevent heartworms in cats. ​

Treating Heartworm Disease

​We have discussed what heartworm disease is, how it is transmitted, symptoms, and prevention. We have yet to discuss what happens if your dog is positive for heartworm disease. I would like to assure you that heartworm disease is not a death sentence. Dogs that are tested heartworm positive can be treated and go on to live a full life. Treatment can be costly and tough on any dog(s) being treated which is why veterinary practices highly recommend preventing the disease. Treating heartworm disease can range from $500 to $4,000 depending on the dog's size, the severity of the disease, and how long treatment is necessary.
The first step to the treatment of heartworm disease is to confirm the diagnosis with a different type of test. For example, most veterinary practices use an antigen test in house. To confirm the dog has heartworm disease and treatment is necessary we would send a blood sample to a specialized lab for them to run a different type of test. Once the diagnosis is confirmed, the restriction of activity needs to take place. You might wonder why, but the more active your dog is the more blood flows through your dog's body. Meaning the more activity your dog has, the more heartworms are able to cause damage to your pet's heart and lungs. The next step is to create a treatment plan with the veterinary team for your dog and start the dog on it. The treatment plan would depend on the severity of the disease, symptoms, and the dog. Once the treatment regimen is complete, you will monitor your dog for 6 months. After 6 months a veterinarian will complete another test for heartworm disease to confirm the heartworms are no longer present. Once this test is negative we as a veterinary team highly recommend keeping your dog on heartworm preventatives year-round and retesting annually for the rest of their life. This is to prevent your dog from becoming infected with heartworms again.

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In summary, it is in your pet's best interest to stay on heartworm preventatives year-round to protect them against heartworm disease. If you decide not to protect your pet year-round, you may be bargaining with heartworms. This is a lot of information, some of the information can be scary. If you have questions feel free to give us a call to discuss heartworm disease and prevention. We are happy to help keep your pet healthy! 

For more information about heartworms go to  www.heartwormsociety.org

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Give us a call to discuss your pet's heartworm prevention needs. 
​(605) 697-5252

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Heartworm on a blood smear