Explaining Heartworm

Mosquitoes have become recognised as carriers of disease. Humans in tropical climates must receive vaccinations to prevent falling sick to a mosquito transmitted illness. Animals are also at risk of contracting diseases from mosquitoes. One such disease is caused by the parasite Dirofilaria immitis– you may know this parasite simply as the heartworm.

The relationship between heartworm and mosquitoes seems to go deeper than simply as a method to transport from one host to another, however. Observations have shown that heartworms seem to actually rely on the mosquito for the initial stages of their life cycle.

When the worms inside an infected dog┬ámate, they give birth to microfilariae- the very first stage of heartworm development. These microfilariae circulate throughout the blood system of the dog until they become lodged in the smaller capillaries towards the surface of the dog’s skin. When the mosquito feeds on the infected dog, it ingests these micro heartworms.

At this stage of the heartworm’s life, it is apparent that it is dependent on two things:

  • It needs the mosquito. If mosquitoes were wiped out, heartworms would need to adapt to find a new vector or risk extinction.
  • I requires ideal temperatures. If temperatures drop below 57 degrees Fahrenheit, the development of the heartworm will be halted.

Presuming all goes well, the microfilariae develop into heartworm larvae. The next time the mosquito feeds, the larval heartworms enter the victim’s body, coming to a rest just under the surface of the skin.

Not all hosts are ideal for heartworms to thrive. While they can potentially cause damage to any warm-blooded creature, their preferred host is the canine. It is this ‘environment’ that is least likely to fight their presence.

When the heartworm larvae develop into immature heartworms, they make their way into the bloodstream, eventually coming to reside in the dog’s heart (specifically, the right ventricle) and the pulmonary arteries. This is their ideal environment. Here, the heartworms reach full maturity, mate, and begin the life cycle again.

Heartworms are a physical obstruction in a crucial part of the dog’s body. Simply the presence of heartworms can result in reduced blood flow, blockages and even heart failure. Heartworm disease is a very serious condition indeed.

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