Know the facts about heartworm disease

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What is canine heartworm disease?

Heartworm or dirofilariasis is a potentially fatal disease that affects cats, dogs and almost thirty other animal species. The causative agent is a blood-borne parasite known as Dirofilariaimmitis that live in heart, lungs and associated blood vessels of affected pets causing severe lung disease, heart failure and ultimately death.

How is heartworm disease transmitted from one animal to another?

“The parasite requires mosquitoes as an intermediate host”

The parasite is transmitted from one pet to another by mosquitoes which act as a vector.  In the bloodstream of an infected animal, adult female heartworms are present, they reproduce within the host. The lifecycle of the heartworm is complicated, the parasite requires mosquito as an intermediate host to complete its lifecycle in the host animal. Over thirty species of mosquitoes can transmit heartworms.

What is the lifecycle of heartworm?

When a female mosquito bites an animal infected with dog heartworm snap test, it ingests microfilariae during that blood meal, further, development occurs within the gut of mosquito and after about 10-30 days, they reach the oral region of mosquito. At this stage, microfilariae become infective larvae and are capable of causing infection. When the mosquito bites a healthy animal, larvae enter into the bloodstream and after completing their maturation phase, they mate and reproduce within 6-7 months and cause infection.

What are the symptoms of heartworm disease?

The parasite remains dormant for a few days within the host’s body. The disease is mostly diagnosed in two to eight years old dog. The disease cannot be diagnosed in dogs less than one year of age since microfilariae take five to seven months for maturation.

Adult heartworms cause disease by blocking major blood vessels of the body which ultimately reduces the blood supply to the vital organs particularly lungs, liver, and kidneys resulting in tissue necrosis and organ malfunctioning.

The symptoms of heartworm disease depend upon the number of adult worms present, location, incubation period and degree of damage sustained by the vital organs. The most obvious clinical signs are a soft and dry cough, shortness of breath, list nesses, loss of stamina, general body weakness and shortness of breath. Symptoms become severe after exercise and animal may even faint or get disoriented. Veternity doctors may notice abnormal lung and heart sounds with a stethoscope. In severe cases, swelling from fluid accumulation may occur in abdomen and legs, weight loss, pale skin, and anemia. Immature heartworms circulate throughout the animal’s body but primarily remain localized in the blood vessels, their width is similar to that of body’s vessels so they may block the blood flow.

Dirofilariasis has affected dogs and cats across all the fifty states of America and is a major cause of parasite-related deaths in pet animals. Keep in mind that heartworm is a treatable and preventable disease so preventive measures should be taken seriously. Infected animals show no clinical signs in the early stages.

How is heartworm disease diagnosed?

A simple blood test can lead to the diagnosis of heartworm disease. A positive test requires further laboratory procedures for confirmation of the disease and to determine the type of treatment.

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Blood test for microfilariae (Knott’s test)

 Blood sample is collected from the animal’s body and then it is centrifuged in the laboratory. After centrifugation, it is examined for the presence of microfilaria under a microscope; the number of microfilariae present per mL of blood indicates the severity of the infection. According to a recent report, 20% of dogs do not test positive even though the parasites are present in their bodies, this is because in initial stages, the immune system of the body has the ability to destroy the parasite. There will be a greater number of microfilariae in summers, for these reasons, antigen test is preferred for diagnosis.

Canine heartworm antigen test kit at home

Canine heartworm antigen kit uses the concept of antigen-antibody complex to detect the presence of larvae in the animal’s blood. Highly specific and purified antibodies produced by biotechnology are used for detection and capture of heartworm antigens. This technique has the following benefits over trivial methods.

•    It is a small device which is simple and easy to use.

•    Provides instant result within 5 minutes.

•    It can be stored at room temperature (20-30 degree Celsius).

•    It is widely used for its high sensitivity and specificity.

•    It provides 100% accurate results.

•    It requires a small volume of blood for sampling.

•    It can be used on serum, plasma or whole blood.

Radiography, electrocardiography (ECG), echocardiography (ultrasound of the heart) and blood tests may also be required for complete diagnosis.

Treatment of heartworm disease

Generally, injectible drugs are used to kill adult heartworms in the heart and adjacent vessels. The dose is suggested as per the severity of the condition. Complete rest is essentially required during treatment and pets should be kept as quiet as possible, any form of exercise is strictly prohibited for almost one month following treatment.


Today, safe and affordable heartworm preventives are available in the market, take care of your beloved pets and don’t let them suffer from this terrible disease. Prevention is always better than cure, so make sure that your pets are vaccinated against heartworms infection, no pet should ever suffer from this dreadful disease!

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