Dogs are prone to get infected with different forms of worms as they are exposed to infections due to tapeworms, hookworms, roundworms, and heartworms are common. This infection is asymptomatic until the completion of the first six months since the date of disease. As the worms grow and mature into adults, the health of your dog is remarkably at stake which may take the very life of your dog. So early diagnosis and timely treatment of heartworm disease in dogs is the most critical factor in saving the life of your pet.
What is Heartworm Disease in Dogs?
Heartworms are called as Dirofilariaimmitis. Being parasitic worms, not only dogs but also do not even spare foxes, wolves, and sea lions. Humans are also susceptible to this infection occasionally. It’s a vector-borne disease similar to filarial that is transmitted by mosquitoes. Dogs are the host wherein the parasites grow and mature including the completion of the reproductive cycle. The larvae of worms are equipped in the mosquito to turn infective as soon as it enters the host/dog. Mosquito is an excellent habitat for heart-worm larvae to develop into an infective agent.
Infected Dog Heart – The White Stringy Things are Worms:
Let us not be carried away with the presumption that heartworms affect the heart alone, but in fact, the lungs are also damaged by heartworm disease. The pulmonary blood vessels especially the arteries are more susceptible as the heartworms spend the best part of their life over there. The adult heartworms may have a choice to live on the right side of the heart of the infected dog thus affecting the veins therein.
How do Heartworms Infect Dogs?
Heartworms are carried by mosquitoes through which they manage to enter the dog’s physiology. When the larvae turn into adults, the offspring are released into the bloodstream of dogs by the females called as microfilaria. A mosquito bite on an infected dog is enough for this vector to get infested with those off-springs/microfilariae from the dog bitten by it. The microfilariae thus plagued turned to be an infective agent within a short period.
A valid point to remember is that microfilariae could not become infective unless they pass through the mosquito. A healthy dog gets infected with a bite of a mosquito as larvae transgress through the wound. Within 6-7 months of gaining entry into a dog’s bloodstream, the heartworm larvae develop into an adult.
When heartworms attain maturity, mating and reproducing take place in the dog wherein the female parasites release the offspring into the dog’s bloodstream, thus completing the life cycle. When these offspring are picked up by a mosquito over a bite, then other dogs are prone to get infected by transmission. Though not a contagious disease, heartworms are easily transmitted by a mosquito bite.
It’s not just the infection that would be sufficient to bring out symptoms, but it’s the number of worms that cause this problem and the pace of their multiplication within the host dogs which arouses the signs of disease. Proper food for allergies is best for one’s dog.
The infection is reflected by the gradual in-activeness of dogs, a decrease in the dog’s size and weight. Organ failure including heart, liver, lungs, and kidneys, and also the tissues around blood vessels is common when a dog is attacked by such a virus.
In the acute stage, dogs are asymptomatic as they lead a healthy life. But when the dog is active or as the bacteria progress or as the larvae grow and multiply in the host/dog, the signs of heartworm disease in dogs tend to start showing up.
The stages of infection as things get aggravated from the initial phase of the disease are as follows:
- Stage I
The immediate onset of this disease is when there are little or unnoticeable signs or even no signs. Occasionally mild cough by your dog is a tip of an iceberg prompting you to should visit your vet for a medical examination.
- Stage II
In this stage, mild to moderate signs and symptoms are apparent. As the worms increase in number, coughing and decreased physical activity by your dog are familiar.
- Stage III
A clear-cut symptom of the heart is seen in this stage. Frequent coughing, weight loss, physical inactivity, and a dog lying idle most of the time as it gets fatigued even due to minimal exertion. Breathing difficulty and progressive heart failure are common. Increased worm burden may worsen the condition and a chest-x-ray to examine the damage to the heart and lungs may be required.
- Stage IV
This stage is chronic, and the heart-worm infection is more severe in dogs. The blood vessels including the vena cava are affected, and this is called caval syndrome. Worm burden is such that blood vessels are blocked by these worms obstructing to flow of blood back to the heart. Surgical intervention is required to remove the worms mechanically. Caval syndrome proves fatal to most dogs. However, some dogs do not develop caval syndrome by chance.
Severe infection is associated with the symptoms like enlargement of the liver, damage to the lungs, and abnormal sounds over the chest during inhalation and exhalation. Poor circulation of blood due to blockage of blood vessels by worms leads to an ischemic brain that results in fainting and a transient unconscious state of the host dog.
Further, the symptoms of chronic heartworm disease include abnormal heart sounds and the accumulation of fluid in the abdominal cavity. If not attended, then it may lead to the death of the host dog.
Diagnosis of Heartworms in a Dog
This virus is diagnosed by various tests like antigen tests, X-rays of the chest, and microfilaria concentration tests. Antigen test promises accuracy as the antigen produced by matured female larvae reflects the heart-worm infection. But antigen test is not fit for early diagnosis at the larval stage.
Even when adult heartworms are fewer in number or when there are male worms, they may misdirect the antigen test. The paltry sum of worms or worms at the larval stage does not cause a worm burden. So until the reproductive stage, there is not a worm burden, and hence the bacteria remain asymptomatic.
In the micro filarial concentration test, a microscopic view of the blood sample readily reveals the presence of microfilariae. Even when the test is negative, the infection could not be ruled out as the peripheral blood does not contain microfilariae in about 11-25 percent of dogs. In other words, the dogs infected by this virus have a more latent period to have the parasite migrate to peripheral blood.
In chronic and severe cases, chest X-ray shows damage to the lungs and the entire chest area. High worm burden blocks the pulmonary artery, and cardiomegaly or enlargement of ventricles in the heart is also seen in the chest x-ray.
The electrocardiogram-ECG easily shows the random wave graph due to arrhythmic heartbeat and pulse as well as enlargement of the right ventricle.
However, early diagnosis by identifying even occasional cough decreased physical activity, and fatigue due to the minimal exertion of your dog is better than the delayed diagnosis when the heart-worm burden has already reached its peak to cause detrimental effects.
Treatment Options Available for Dog Heartworm Infection
Treatment: the objective is to eliminate microfilariae and adult worms. The block caused by heart-worm burden and organ-specific treatment remains the top priority to minimize the severity of symptoms.
Weeding out dead worms and administration of drugs without further complications or side effects are factored in.
The FDA has approved these two drugs viz., thiacetarsamide and melarsomine to effectively counteract heart-worm infection. Melarsomine is sold under the brand name miticide. It is said to be safer than that thiacetarsamide which is sold under the market name – Caparsolate.
Your vet will opt for the right choice. Intravenous injection of the thiacetarsamide drug is effective. But jaundice, kidney failure, vomiting, and diarrhea are its adverse effects, and this toxicity may even be fatal.
The thiacetarsamide drug is disadvantageous to a certain extent as it does not destroy the larvae or immature heartworms, unlike the adults as the former resists the medication. Kidney problems, heart, and liver diseases are contraindications to the administration of capreolate as it may prove counterproductive.
But melarsomine or miticide is highly effective in killing 90 percent of worms, and the added advantage of this drug is that side effects are minimal it is also administered to dogs already reported to be affected by liver, kidney, or heart ailments. But supervision of vets is deserved to a greater extent.
Immiticide is usually administered via intramuscular injections, once a day for two days but the vet may decide on the dose based on the severity of the infection.
Surgical intervention is inevitable in severe forms of infection. The Vena cava syndrome is the result of acute disease and as such surgery may prevent the risk of chronic infection leading to kidney or liver failure. A surgical procedure may also prevent the thrombus to get disseminated into emboli and even the blockage of blood vessels other than thromboembolism such as worm burden.
Prognosis and follow-up of the treatment to ensure the extent of elimination of microfilariae is excellent. Even when the adult larvae have been killed the dog should have to be treated until the larvae are also eliminated. Microfilariae are treated with drugs like ivermectin which is used with minimal side effects.
To effectively fight this infection in your dog, you should zero in mosquito breeding control. Prevention of waterlogging or water stagnation and spraying of insecticides over yards tends to protect your dog from heart-worm disease.
By Chemically Treating Your Yard You Decrease the Likelihood of HeartWorms
To clear the root, you may spray your yard and waterlogged areas in your vicinity with insecticides to kill the mosquitoes at once. Removing stagnant water and applying pills to prevent the growth of this bacteria are precautionary measures to escape from this disease. Periodical check-ups and caring symptoms like an occasional cough may be a wise step to arrest the infiltration and proliferation of heartworms in the host/dog. So that such parasitic diseases in dogs can be kept at bay.
The crux of the disease is that the increasing number of worms in a dog causes the burden of infection to get aggravated. Around 250 worms are enough to deter the physical activity of a dog, and it’s the severe stage of the disease. The severity of the problem depends on how long the virus persists in a dog’s body and how the dog’s physiology responds to it. In the initial stage, the symptoms are occasional coughing, physical inactivity, and fatigue even after mild physical exertion.