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I continue to share about parasites today and I will be talking about heartworm disease which is a serious one that has the ability to affect our pets. Heartworm disease can lead to organ damage, serious lung disease, heart failure, and eventual death. 

The disease is caused by a parasitic worm with the name *Dirofilaria immitis*, these worms are spread when there is a mosquito bite, and dogs happen to be the definitive host. Being a definitive host means that, the worms mature into an adult size, mate, and produce offspring even while living in the dog. The name heartworm was coined because the worm lives in the lungs, heart, and other associated blood vessels of an affected animal.

Heartworm is a large worm that takes up to 6-7 months to complete its lifecycle, it can live in the heart and pulmonary vessels of the animal for several years. How severe an infection gets depends greatly on the number of worms present, the immune system of the dog affected, the duration of the infection, and the activity level of the animal. 

With heartworms in the vessels serving the lungs and heart, it would cause irritation, and inflammation of the heart chamber or affected vessels. In response to a dead worm, the immune system of the dog does further damage to the blood vessels. The symptoms of heartworm include; exercise intolerance, cough, lethargy, collapse, difficulty breathing, and weight loss, and if the condition is left untreated, it could extend to causing a right-sided heart failure.

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#### How the infection happens.

During a mosquito bite, blood is taken from an infected host, which they ingest, circulate microfilariae, or young immature heartworms. Right inside the mosquito, the microfilariae undergoes three stages of larval development. L1,L2, and L3. During the process of biting another animal, the same mosquitoe deposits L3 onto the skin of the dog which further migrates into the body of the dog and develops into an L4 level.

At the L5 level, it begins to migrate all through the tissues and bloodstream of the dog, winding up in the heart where it would take up residence as an adult. This entire process takes around 4 months to complete. At the age of 7 months, the adult female becomes sexually mature, mates, and produces microfilariae.

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By the time a dog gets diagnosed with heartworm disease, it must have gotten to the advanced stage, at this stage, the heartworm has been present for a long time that it has already caused a significant level of damage to the lung, blood vessels, liver, kidneys, and heart. In cases of serious advancement, experts believe it is safer to treat organ damage and still keep the dog comfortable than to take the risk and negative influences that heartworm diseases come with.

Treating an adult heartworm requires an injectable drug, which will kill the adult heartworms found in the heart and adjacent vessels, the drugs are administered through a series of injections. Within a few days, the heartworm begins to decompose, they are carried to the lungs where they lodge in the small blood vessels and eventually, they get reabsorbed by the body.

The process of reabsorption can take several weeks to months, most complications of post-treatment are caused by the leftover fragments of dead heartworm. This period is considered a very dangerous one, so dogs are advised to be kept quiet and not allowed to exercise while other doses of injections are still administered. Limiting the exposure our dog has to mosquitoes will protect them a lot from heartworm, a preventive heartworm medication can also be taken.  Even after a dog has been treated for heartworm, there is still a chance of reinfection, thankfully, due to the available preventive options, our pets can be protected against this dangerous disease.

#### <center>References.</center>

[fda.gov/animal-veterinary](https://www.fda.gov/animal-veterinary/animal-health-literacy/keep-worms-out-your-pets-heart-facts-about-heartworm-disease)

]vcahospitals.com/know-your-pet](https://vcahospitals.com/know-your-pet/heartworm-disease-in-dogs)

[veterinarypartner.vin.com](https://veterinarypartner.vin.com/default.aspx?pid=19239&id=11942142)

[heartwormsociety.org/heartworms](https://www.heartwormsociety.org/heartworms-in-dogs)

[msdvetmanual.com/dog-owners](https://www.msdvetmanual.com/dog-owners/heart-and-blood-vessel-disorders-of-dogs/heartworm-disease-in-dogs#Treatment_v39120909)

[vdci.net/vector-borne-diseases](https://www.vdci.net/vector-borne-diseases/heartworm-disease-dog-and-cat-education-and-integrated-mosquito-management-to-protect-public-health/)

[petmd.com/dog/conditions/infectious-parasitic](https://www.petmd.com/dog/conditions/infectious-parasitic/heartworm-disease-in-dogs)