17 Jul Dog Heartworm Disease (Dirofilariasis) ; Diagnosis, treatment, prevention (part 1)

Heartworm (dirofilariasis) in dogs is a significant disease that, if left untreated, usually causes the dog’s death. Therefore, it’s necessary to know as much as possible about this dog disease. So you can do the vital work to keep your dear dog healthy and cure him. In this article, we discuss heartworm’s causes, examine the way to prevent and treat them.

What is heartworm disease?

The cause of this disease is a type of parasite called “Dirofilaria immitis” that lives in the animals’ blood. It’s easy to prevent dog heartworm, but it’s challenging and expensive to treat. Adult Dirofilaria immitis worms are found inside the heart, pulmonary and large arteries, or sometimes inside other parts of the animal’s circulatory system.

Adult female worms are about 15 to 35 cm long and about 3 mm wide. Male worms are about half the size of females. Sometimes there may even be up to 300 heartworms in an animal. Usually, small dogs can’t tolerate the disease and its drugs as much as their large dogs. Because their arteries and hearts are smaller, few worms cause their arteries to clog. Adult worms can live up to five years. Female worms lay millions of eggs, and worm larvae (called microfilariae) live mostly in small vessels. Only one mosquito bite infected with worm larvae can cause heartworm disease in dogs.

How do dogs get this parasitic disease?

The only way to get dog heartworm is for an infected mosquito to bite the animal. One bite of a mosquito-infested with larvae worms is enough to sick the dog. At least 70 species of mosquitoes can transmit heartworm. When a female mosquito bites an infected dog, the microfilariae enter her body.

Microfilariae grow in the mosquito’s intestine for 10 to 30 days and then enter his mouth. So mosquito bites make healthy dogs sick. After biting, it takes about seven months for the larvae to become adult worms and begin to reproduce, easily endangering the dog’s health. 

Symptoms of heartworm in dogs 

Unfortunately, most dog heartworm symptoms usually appear when the disease is fully developed and has reached an acute stage. Symptoms of dog heartworm depend on the number of adult worms in the body, the location of the worms, how long the worms are in the dog, the reaction of the dog’s immune system, and the amount of damage to the heart, lungs, liver, and kidneys.

Worms can clog arteries and damage cells that don’t reach the bloodstream. Destruction of lung cells causes coughing. The animal can no longer function as much as before. He gets tired sooner and suffocates. Liver damage causes liver cirrhosis and jaundice, anaemia and general weakness. Kidney damage also causes toxins to accumulate in the body. The most important clinical signs of dog heartworm disease are:

• Soft and dry cough
• gasping
• Weakness and lethargy
• Loss of energy and endurance of the animal
• Lack of proper growth, difficulty breathing
• Blue or purple skin or gums
• Nose Bleeding 
• Blood vomiting

These symptoms are more common after physical activity. Some dogs may even become dizzy or faint because the blood doesn’t reach the brain. In advanced cases, heart failure or clogged arteries may cause fluid to build up and swelling in the abdomen and legs. Weight loss and anaemia are other symptoms of dog heartworm. Animals that become severely infected may die while running or excited.

Note that the severity of the symptoms also depends on the amount of activity the animal has. Dogs that are more active show more severe symptoms. Conversely, even if they have many heartworms, sedentary dogs may not show any symptoms or no symptoms at all. 

How is heartworm detected in dogs?

Veterinarians often use blood tests to diagnose dog heartworm. The easiest, best and most accurate dog heartworm test is the blood antigen test; But the antigen can only detect adult female worms. So your veterinarian usually recommends having this test every year.

Other methods, such as echocardiography (a type of heart ultrasound), blood tests, and chest x-rays, may be used by your veterinarian based on your dog’s history of taking anti-inflammatory drugs and his general health.

What are some ways to treat dog heartworm (dirofilariasis)?

Before treating a dog with heartworm, your veterinarian will ask you questions, and you will need to have some tests done; Because the choice of the most appropriate treatment depends on many factors (including whether the animal has another disease or not, how many worms are in the body, and how much damage has been done to the organs). If the illness is severe, vet my other medications such as antibiotics and painkillers, special diets, diuretics, or heart-strengthening medications before killing the worms. In most cases, dogs are given heartworm medications before injecting melarsomine.

Some dogs may even need certain medications for the rest of their lives after the worms are killed, such as:

• Diuretics
• Cardiac drugs (such as inhibitors ACE, Cardiac beta-blockers or glycosides)
• Lung drugs
• Special low-salt diets

Treatment of this disease has risks and, in some rare cases, may cause the death of the animal—treatment options for dog heartworm disease range. Previously, the only drug available to treat adult heartworms was a toxin called arsenic, which causes many side effects in dogs.

A new drug for dirofilariasis’ treatments, which is also the most common anticonvulsant for dogs, is melarsomine dihydrochloride. This drug also has arsenic, but its side effects are much less. Melarsomine injections aren’t dangerous if you follow the veterinarian’s instructions correctly. It can treat more than 95% of dogs.

Two treatments for treating dog heartworm

There are two methods for treating dog worms: the 2-injection and the 3-injection method. In both methods, the drug is injected deep into the muscles behind the dog (each time to one side). About one-third of dogs develop local pain, swelling, and sometimes abscesses at the injection site. This injection involves 2 injections of the drug at 24-hour intervals. In the 3-injection method, one injection is given first, and then the animal is rested for 30 days; Then, they give two more injections at 24-hour intervals.

The veterinarian determines the treatment plan according to the dog’s condition, But most dog owners use the 3-injection method; because it’s both less dangerous for the dog and can better eliminate all the worms. Most dogs are also given antibiotics (usually doxycycline) because a type of germ lives in the worms’ bodies and may have caused an infection. Antibiotics also kill germs (microfilariae) and reduce pulmonary problems caused by melarsomine injections. Heartworm medications can also kill baby worms. There’s another drug called corticosteroids that can reduce the inflammation associated with killed worms. Make sure the veterinarian’s instructions are followed exactly.

Can this parasite be transmitted from dog to human?

Fortunately, dog heartworms aren’t usually transmitted to humans. These worms only infect dogs, cats, rats and some other mammals. Of course, some sporadic cases of human infection with dirofilariasis (due to mosquito bites) have been reported, but the life cycle of these worms in our body isn’t complete. The worm can only go to the lungs and create a round lesion that looks like a tumour.

Is it possible to treat heartworms with ivermectin for dogs?

Research has shown that if you give your dog ivermectin every month, most worm babies will die after about two years. But the problem is that the worms cause damage to the heart and arteries that are incurable until then. But still, if there’s no cure for you at all, using ivermectin is better than nothing.