1. Which are the animals affected by heartworm disease?
Heartworm disease affects:
– Other mammal species: wolves, coyotes, foxes, sea lions and in rare occasions humans
Dogs are the natural host for heartworms. This means that heartworms that infect and live inside the dog mature into adult stage, mate and produce descendants.
If this disease is untreated or not diagnosed, worm’s number can increase, and dogs have been known to port several hundred worms in their hearts and lungs.
Heartworm disease causes permanent damage to the heart, lungs and arteries. Thus it can affect the dog’s health and quality of life after parasites are eliminated. For this reason, prevention is the best option, and treatment should be administered as early in the course of the disease as possible.
2. How is heartworm disease transmitted?
The mosquito plays a vital role in the heartworm life cycle.
Adult female heartworms living in an infected canine produce microscopic worms called microfilaria that flow in the bloodstream. When a mosquito takes a blood meal from an infected animal, it eats the “baby worms”, which develop and mature into “infective stage” larvae in 10 to 14 days.
Then the infected mosquito bites another susceptible animal and the infective larvae are deposited onto the surface of the animal’s skin and move into the new host through the mosquito’s bite wound.
Once inside a new host, it takes about 6 months for the larvae to mature into adult heartworms. Once mature, heartworms can live for 5 to 7 years in dogs.
3. What are the clinical signs of heartworm disease?
In the initial stages of the disease, dogs present few symptoms or are asymptomatic. The longer the infection persists, the more symptoms will appear.
Signs of heartworm disease include:
- Mild persistent cough
- Lack of enthusiasm to exercise
- Low energy after moderate activity
- Decreased appetite
- Weight loss
As heartworm disease advances, dogs may develop heart failure and the presence of an enlarged belly due to extra fluid in the abdomen. Dogs with large numbers of heartworms can develop abrupt blockages of blood flow within the heart leading to cardiovascular collapse.
This is known as Caval Syndrome, and consists of sudden onset of difficult breathing, pale gums, and coffee-colored urine. The treatment is surgical removal of the heartworm blockage. A small number of dogs survive.
4. Why do dogs die from heartworm disease?
Heartworm disease is very complex. It can upset many vital organs, such as the heart, lungs, kidneys, and liver. When there is a massive infection or a prolonged infection these organs can start to shut down.
The adult worms induce inflammation of the blood vessels and can block passage of blood leading to the formation of clots in the lungs and heart failure. In some dogs, heartworm disease can also lead to liver or kidney failure.
There are animals that live for a long time with only a few adult heartworms and show no clinical signs except faced with an environmental change, such as a heat stroke, or another significant health problem.