The heartworm is a parasitic roundworm that affects animals as well as humans. Dogs are the most vulnerable animals to heartworm infection. The heartworm looks like a thin, filamentous and translucent thread. In medical terms, heartworms are referred to as Dirofilaria immitis.
The heartworm generally tends to reside in the right side of the heart in addition to the lungs as well as the pulmonary arteries. Heartworms enter the body of dogs through the bites of infected mosquitoes, generally in the area where the skin is the thinnest. Once the larvae are inside the body, they tunnel through and enter the veins and finally reach the heart. The life cycle of heartworms is six to seven months in a dog and the emergence of adult worms takes about three to four months. The heartworms can reach lengths up to twelve inches and can survive for about five years in a dog’s heart.
The adult heartworms mate and reproduce millions of offspring known as microfilaria that tend to clog up the blood vessels. The blockage of blood flow can lead to serious abnormalities of the lungs and the liver in dogs. When mosquitoes bite the infected dogs, they tend to swallow the offspring along with the blood. The microfilaria then develop into larvae inside the mosquito and can be transferred to another dog or other animals with a bite of the infected mosquito.
Symptoms of heartworms in dogs
Most dogs do not show any symptoms during the initial stages of heartworm infection. It is only during the advanced stages that an infected dog will elicit any symptom. Dogs in the age group of three to eight years generally tend to get infected by heartworms though in some regions dogs as young as one year may get infected by heartworms.
The number of heartworms that can be found in infected dogs can vary from fifty to around two hundred and fifty. The severity of heartworm infection in dogs depends on several factors such as the duration of infection, the number of worms, the dog’s immune system response to the infection as well the locations of heartworm infections.
Some of the symptoms of heartworms infection in dogs are listed below:
- Instances of fainting after exercise
- The sputum as well as fecal material may contain blood
- Easy tiredness and fatigue
- Breathing problems such as shortness of breath
- Loss of appetite resulting in weight loss
- Blood disorders such as anemia
- Nervousness and listlessness
- Swollen abdomen
- The coat condition tends to deteriorate and become poor
As the disease progresses it may show signs and symptoms such as:
- Dogs at rest may have labored breathing
- Ribs that become prominent and more visible
- Visible bulging of the chest
- Advanced stages of the disease in dogs may lead to pulmonary clotting and cardiac failure that result in collapse and eventual fatality
Causes of heartworms in dogs
- Dogs are infected by heartworms through the bite of infected mosquitoes.
- Heartworms infections in dogs are present throughout the United States in all the fifty states. Hence it is necessary to take the preventive measures to avoid heartworm infection in dogs
Treatment of heartworms in dogs
The treatment of heartworm infections in dogs is a dangerous, expensive and complex process. It is essential that the dog is healthy enough to begin treatment, so that any organ damage can be treated at the very beginning.
The treatment of heartworm infection in dogs involves the following two stages:
- The first step involves the adulticide therapy wherein the adult heartworms in dogs are killed. Adulticide therapy involves the intravenous or intramuscular administration of either of the two very strong arsenic compounds. They are melarsomine dihydrochloride and thiacetarsamide sodium. The success of the drugs leads to blockage of blood circulation by dead worms as well as other side effects such as vomiting, jaundice, fever, cough and loss of appetite. The dog that has responded to adulticide therapy should be prevented from any exercise because of the blockage and clotting of circulation.
- The second step involves the killing and removal of the offspring or microfilaria infestation in the dog. This step is called the filaricide therapy and is usually conducted four to six weeks after adulticide therapy.
- The second stage involves the intake of medications such as milbemycin and ivermectin. Dogs that undergo the second step of treatment may have severe side effects such as coma or death and hence their hospitalization is absolutely essential. A third drug called levamisole may also be prescribed, but it has adverse side effects. It is also necessary to note that Collie mixes and Collies should not be given ivermectin as it can lead to extreme side effects.
- In rare cases where the dog is critically diseased, surgery may be required to remove the heartworms.
A prevention program is absolutely essential as soon as dogs reach the age of six months or more. Some preventive measures include a daily dosage of DEC or diethylcarbamazine tablets while others include a monthly dose of Ivermectin. Individuals with pets who live in areas which are more likely to have mosquito infestation have to take extra precaution to prevent