Canine heartworm is caused by the bite of mosquitoes carrying the larva of the parasites. Dogs are one of the most pampered pets. Dogs are not only allowed to live with the family inside temperature controlled homes. These very lucky animals are allowed to sleep with the master and provided with all imaginable comforts. Does your pooch receive the same cosseting from you? Dont you ever allow your pet to set foot outside your spotless and pest free home? Are you sure that with this kind of environment you wont need to administer heartworm preventives?
Short of keeping the pet in a glass case, mosquito bites can never be prevented. You may have a mosquito free home but when you take the pet out to do its business there will always be a chance that pet would be the source of the mosquitos dinner. Dogs have the inclination to roam. A door that was left open will be a golden opportunity for the dog to wander. Guess what will happen to a dog that has wandered to a dark and dirty alley. Dogs are hardy animals. The dog may or may not be bitten by heartworm larva carrying mosquito. However, to be on the safe side dont you think it would be wise to administer heartworm preventive especially if you are living in the country side or in a rural area where there are many mosquitoes?
Heartworm or Dirofilaria immitis is a very dangerous parasite that can kill your dog. 
Many other animal species are affected by this parasite but it seems that dogs are the perfect hosts as heartworm disease is more prevalent in dogs. For heartworm disease to proliferate there has to be an established number of susceptible hosts, a secure reservoir of the disease, enough numbers of vectors and a climate that will ideally support the life cycle of the parasite. Dogs that are the most common hosts of these parasites became an established reservoir when treatments are not administered. Mosquitoes are the vectors. A temperature of above 80 degrees is ideal for the development of the larva which is also called microfilariae.
When a heartworm carrying mosquito bites a dog, the larva will be injected into the bloodstream. It would take some time before the microfilariae grow into adult female and male worms that are capable of reproduction. The reproduction will result to the tiny microfilariae that will be released into the dogs blood stream. When a mosquito bites the dog, the blood along with the microfilariae will be sipped. The mosquito will serve as an incubator that will harbor the microfilariea until the larval stage is reached where it will be transferred to dogs and other animals. An adult heartworm that is about 12 inches in length will travel through a vein and infest the right chamber of the heart and the lungs arteries. The worms would enter the liver. Worsening cough, coughing blood, weakness and weight loss are the signs of severe heartworm infestation.
Although challenging, canine heartworm disease can be prevented. Preventives can be in the form of oral meds or injections that are given monthly especially during the peak season of the disease. A lot of dogs have died from heartworm. Treatment is only possible if the disease has not gone too far. This parasite would affect not only the heart and the lungs of your pet but would also hamper the proper functioning of the liver and the veins. Protect your dog from heartworm. Administer the appropriate preventive measure that will save your pet from this disease.