- by Dr Azeemulla H R Neha Veterinary Clinic
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- Nov 21 2017
What causes Heartworm diseases in dogs?
Heartworm disease or dirofilariasis is a serious and potentially fatal disease. These are worm-like parasites that can reach up to a foot in length. Dogs are the main target of heartworms. These are transmitted by mosquitoes, who leave a larval form of them behind after bites. Adult heartworms travel to the pet's lungs. If left untreated, they can cause death.
When a mosquito bites a dog with heartworm, it ingests the microfilaria, or baby heartworms, along with the dog’s blood. These microfilariae mature over the course of about a week within the mosquito, transforming into a larval form of the heartworm. After the larval form is achieved, the mosquito passes it along to other dogs that it bites. Because of the parasite’s reliance on mosquitoes, the disease spreads particularly rapidly during the summertime, when a temperature is warmer.
In early stages of heartworm disease, there are virtually no symptoms.
- Coughing may be most noticeable after exercise and may end with fainting. Even light exercise can cause fainting.
- Tiredness and finding difficulty to be active even when performing small tasks.
- Weight loss or anorexia
- Breathing problems occur when inhabiting the lungs and surrounding veins.
- The ribs seem to protrude, and the chest has a bulging appearance as a result of adult heartworm infection.
- Blockage of blood flow.
- Secondary pneumonia
- Increased blood pressure
- Excessive sleeping
The complete physical exam is done, chest X-rays and routine blood chemistry tests. The definitive diagnosis is usually made through the use of a heartworm antigen test. Whole blood is drawn from the dog, stabilized so it will not clot, and tested for the presence of a protein shed by the female worm as she passes microfilaria. Knots test or modified knots test is done. A urine sample is evaluated to determine the impact of the heartworm infection on the dog’s health.
The dog will be staged for heartworm disease as part of the evaluation. It assists the veterinarian in choosing the best method of treatment for eliminating the heartworms:
Stage I: Lowest risk, young healthy dogs with minimal heartworm disease evident on X-rays and all other tests are normal.
Stage II: Moderately affected dogs, some coughing is noticed, some difficulty in breathing, changes are seen on X-rays, and blood test may reveal some kidney or liver damage.
Stage III: Severely affected dogs, the patient has weight loss, coughing, difficulty breathing, more damage visible on X-rays, and blood test shows kidney or liver damage.
Stage IV: Vena Cava Syndrome or Caval Syndrome, the dog is collapsing in shock, all of the above abnormalities are moderate and intense and the dog is dying.
Treatment varies from dog to dog. It involves two basic areas:
1. Patient evaluation and stabilizing of the treatment procedure.
2. Elimination of all forms of the heartworm parasite.
The most common preventatives kill the immature heartworm larvae before they molt to the L5 stage. As long as they are given to the dog every month, they are very effective in preventing heartworm infection and subsequent development of heartworm disease.
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